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• 71. [Article] Interaction of crop plant population with weed competition in corn (Zea mays L.), bush snap beans (Phaseolus vulgaris L.), and onion (Allium cepa L.) at differing stages of development

  Yield reductions due to competition of weeds with crop plants can be extremely important. Early weed competition can be as important in reducing crop yield as weed competition for the entire season. The ...

  Citation × Citation Citation Abstract Copy Title: Interaction of crop plant population with weed competition in corn (Zea mays L.), bush snap beans (Phaseolus vulgaris L.), and onion (Allium cepa L.) at differing stages of development Author: Williams, Clarence Frank Yield reductions due to competition of weeds with crop plants can be extremely important. Early weed competition can be as important in reducing crop yield as weed competition for the entire season. The objectives of this study were (1) to determine the weed control achieved by narrow row-cropping patterns, (2) to measure the competitive effect achieved with narrow row-cropping patterns, with low photosynthetic capacity crop plants or with high photosynthetic capacity plants, in competition with high photosynthetic capacity weeds, (3) to determine at what time weed control becomes important and (4) to determine if the time at which competition begins could be determined by change in weight, sugar content, and/or nitrogen content of the commercial crop. Also, two greenhouse studies were made to evaluate the differential uptake of nitrogen by two competiting species, corn (Zea mays L.) and pigweed (Amaranthus rectroflexus L.), and to evaluate the effect of competition for soil and light between two broadleaf species, snap beans and pigweed. Yields of bush snap beans (Phaseolus vulgaris L.), corn (Zea mays L.), and onion (Allium cepa L.) were all decreased significantly by the presence of weed competition throughout the entire growing season. Reduction in total area occupied by an individual crop plant resulted in decreased effects on vegetative and reproductive parts due to weed competition and increased the effect of crop plant-to-plant competition. Early weed control was important in all crops. In 1969, yield reductions in corn and beans allowed, to compete with weeds for a period of five to six weeks after crop emergence were equal to those from plots with weed competition for the entire season. In 1970, corn required two weeks of cultivation after emergence and snap beans required three weeks of cultivation after emergence to decrease losses due to weed competition. Weed weight yields were significantly reduced in snap beans at the 5 x 5 inch spacing when compared to the 15 x 5 and 35 x 5 inch spacings. As measured by leaf fresh weight, competition was determined to begin between snap beans and redroot pigweed at 36 to 44 days after crop emergence at crop plant spacings of 35 x 5 and 15 x 5 inches. Significant weed competition did not develop after 51 days at crop plant spacings of 5 x 5 inches. Competition between corn and redroot developed 41 days after emergence for all plant spacings. This study indicated the time at which competition between crop and weeds could be determined by leaf fresh weight measurements or by measuring the leaf area of the crop plants. At a fertilizer rate of 77-101-64 pounds of N-P-K per acre, corn made greater gains in total green weight than did pigweed in the greenhouse. However, with the further addition of 300 pounds of ammonium nitrate per acre, pigweed continued to make gains while corn growth was unaffected. At all fertility rates, pigweed had higher levels of total leaf nitrogen than corn. When snap beans had emerged and become established before the emergence of pigweed, the total green and dry weight of pigweed was significantly reduced if growing in full competition or in competition for soil factors only. Title: Interaction of crop plant population with weed competition in corn (Zea mays L.), bush snap beans (Phaseolus vulgaris L.), and onion (Allium cepa L.) at differing stages of development Author: Williams, Clarence Frank Yield reductions due to competition of weeds with crop plants can be extremely important. Early weed competition can be as important in reducing crop yield as weed competition for the entire season. The objectives of this study were (1) to determine the weed control achieved by narrow row-cropping patterns, (2) to measure the competitive effect achieved with narrow row-cropping patterns, with low photosynthetic capacity crop plants or with high photosynthetic capacity plants, in competition with high photosynthetic capacity weeds, (3) to determine at what time weed control becomes important and (4) to determine if the time at which competition begins could be determined by change in weight, sugar content, and/or nitrogen content of the commercial crop. Also, two greenhouse studies were made to evaluate the differential uptake of nitrogen by two competiting species, corn (Zea mays L.) and pigweed (Amaranthus rectroflexus L.), and to evaluate the effect of competition for soil and light between two broadleaf species, snap beans and pigweed. Yields of bush snap beans (Phaseolus vulgaris L.), corn (Zea mays L.), and onion (Allium cepa L.) were all decreased significantly by the presence of weed competition throughout the entire growing season. Reduction in total area occupied by an individual crop plant resulted in decreased effects on vegetative and reproductive parts due to weed competition and increased the effect of crop plant-to-plant competition. Early weed control was important in all crops. In 1969, yield reductions in corn and beans allowed, to compete with weeds for a period of five to six weeks after crop emergence were equal to those from plots with weed competition for the entire season. In 1970, corn required two weeks of cultivation after emergence and snap beans required three weeks of cultivation after emergence to decrease losses due to weed competition. Weed weight yields were significantly reduced in snap beans at the 5 x 5 inch spacing when compared to the 15 x 5 and 35 x 5 inch spacings. As measured by leaf fresh weight, competition was determined to begin between snap beans and redroot pigweed at 36 to 44 days after crop emergence at crop plant spacings of 35 x 5 and 15 x 5 inches. Significant weed competition did not develop after 51 days at crop plant spacings of 5 x 5 inches. Competition between corn and redroot developed 41 days after emergence for all plant spacings. This study indicated the time at which competition between crop and weeds could be determined by leaf fresh weight measurements or by measuring the leaf area of the crop plants. At a fertilizer rate of 77-101-64 pounds of N-P-K per acre, corn made greater gains in total green weight than did pigweed in the greenhouse. However, with the further addition of 300 pounds of ammonium nitrate per acre, pigweed continued to make gains while corn growth was unaffected. At all fertility rates, pigweed had higher levels of total leaf nitrogen than corn. When snap beans had emerged and become established before the emergence of pigweed, the total green and dry weight of pigweed was significantly reduced if growing in full competition or in competition for soil factors only. Close

• 72. [Article] Estimation of genetic-parameters in the Oregon State University Hazelnut (Corylus avellana L.) breeding population

  Heritability in the narrow sense and in the broad sense, variance components and correlation coefficients are important genetic parameters in a breeding program. The estimates of these parameters can provide ...

  Citation × Citation Citation Abstract Copy Title: Estimation of genetic-parameters in the Oregon State University Hazelnut (Corylus avellana L.) breeding population Author: Yao, Qiang Heritability in the narrow sense and in the broad sense, variance components and correlation coefficients are important genetic parameters in a breeding program. The estimates of these parameters can provide important information for a breeder in the selection of parents, the most efficient design for evaluation of seedlings and advanced selections and the choice of selection strategy to improve many target traits simultaneously. In addition, histograms showing the distributions of the traits in offspring may provide additional information about parent combinations for the improvement of target traits. The Oregon State University hazelnut breeding program is developing improved varieties for the kernel market. Estimates of genetic parameters for most traits of interest are not available. Seventy seven trees representing 41 genotypes and 35 progenies were used to investigate midparent values and progeny means for 17 traits, including 13 kernel and nut traits, and 4 phenological traits, for three years. Estimates for heritability in the narrow sense are all high, ranging from 0.56 for amount of kernel fiber, and 0.58 for date of opening of female flowers to 0.87 for percent kernel, 0.88 for nut compression index and 0.89 for nut depth. Therefore, progeny means can be predicted from mid-parent values and response to selection is expected to be rapid for the improvement of all traits. The analysis of variance components revealed that genotypic variance accounted for most of the phenotypic variance. Although significant, the genotype X year interaction only accounted for a very small part of the phenotypic variance. It suggested one year's evaluation of genotypes for all traits should be sufficient except for nut weight, kernel weight, number of nuts per cluster, fiber amount, nut maturity, time of catkin elongation, and time of opening of female flowers. Genetic and phenotypic correlation coeficients were large and positive for nut size traits (nut length, width, depth, nut weight and kernel weight). Phenological traits (date of opening of female flowers, time of catkin elongation and time of leafing out) were also highly and positively correlated. But most other traits were uncorrelated with each other. Therefore, selection of parents with round nuts of medium size, high % kernel, easily-blanched kernels, and early nut maturity is expected to rapidly improve the population for all of these traits. Histograms show that all traits have continuous variation. Transgressive segregation is very common. For all traits except blanching ability, parent combinations may be based on midparent values. For the improvement of blanching ability, both parents should blanch easily. Because existing statistical packages do not allow easy calculation of genetic correlation coefficients for tree fruit and nut crops, the use of a spreadsheet to quickly estimate genetic correlation coefficients is demonstrated. Title: Estimation of genetic-parameters in the Oregon State University Hazelnut (Corylus avellana L.) breeding population Author: Yao, Qiang Heritability in the narrow sense and in the broad sense, variance components and correlation coefficients are important genetic parameters in a breeding program. The estimates of these parameters can provide important information for a breeder in the selection of parents, the most efficient design for evaluation of seedlings and advanced selections and the choice of selection strategy to improve many target traits simultaneously. In addition, histograms showing the distributions of the traits in offspring may provide additional information about parent combinations for the improvement of target traits. The Oregon State University hazelnut breeding program is developing improved varieties for the kernel market. Estimates of genetic parameters for most traits of interest are not available. Seventy seven trees representing 41 genotypes and 35 progenies were used to investigate midparent values and progeny means for 17 traits, including 13 kernel and nut traits, and 4 phenological traits, for three years. Estimates for heritability in the narrow sense are all high, ranging from 0.56 for amount of kernel fiber, and 0.58 for date of opening of female flowers to 0.87 for percent kernel, 0.88 for nut compression index and 0.89 for nut depth. Therefore, progeny means can be predicted from mid-parent values and response to selection is expected to be rapid for the improvement of all traits. The analysis of variance components revealed that genotypic variance accounted for most of the phenotypic variance. Although significant, the genotype X year interaction only accounted for a very small part of the phenotypic variance. It suggested one year's evaluation of genotypes for all traits should be sufficient except for nut weight, kernel weight, number of nuts per cluster, fiber amount, nut maturity, time of catkin elongation, and time of opening of female flowers. Genetic and phenotypic correlation coeficients were large and positive for nut size traits (nut length, width, depth, nut weight and kernel weight). Phenological traits (date of opening of female flowers, time of catkin elongation and time of leafing out) were also highly and positively correlated. But most other traits were uncorrelated with each other. Therefore, selection of parents with round nuts of medium size, high % kernel, easily-blanched kernels, and early nut maturity is expected to rapidly improve the population for all of these traits. Histograms show that all traits have continuous variation. Transgressive segregation is very common. For all traits except blanching ability, parent combinations may be based on midparent values. For the improvement of blanching ability, both parents should blanch easily. Because existing statistical packages do not allow easy calculation of genetic correlation coefficients for tree fruit and nut crops, the use of a spreadsheet to quickly estimate genetic correlation coefficients is demonstrated. Close

• 73. [Article] Biochemical evaluation of silage corn varieties

  Chemical and biological evaluations were conducted to provide chemical composition and digestibility information, in addition to yield data, for silage corn varieties produced on poorly drained Dayton ...

  Citation × Citation Citation Abstract Copy Title: Biochemical evaluation of silage corn varieties Author: Anderson, Daniel Craig Chemical and biological evaluations were conducted to provide chemical composition and digestibility information, in addition to yield data, for silage corn varieties produced on poorly drained Dayton soil series. Each variety was subjected to a Kjeldahl nitrogen, acid detergent fiber, acid detergent lignin, cell wall, and residual ash test. Subsequently cell contents, cellulose, and hemicellulose were calculated by difference. The objectives of this study were to determine if significant differences in nutrient composition and digestibility existed among silage corn varieties grown under similar cultural conditions, and whether such differences could be detected by the detergent analysis scheme in a non-pasture forage. Finally, a comparison of in vitro (artificial rumen) and summative equation digestibility coefficients would indicate the possibility of using the latter for estimating nutritive value in forage crop experimental work. In addition, grass and legume samples, varying widely in nutritive value, were subjected to detergent analysis to ascertain the systems capabilities for assessing differences in chemical composition between forage types. Statistical analysis of the data for chemical composition of the silage corn varieties showed that no significant differences among varieties existed at the five percent probability level. Biological availability of the nutrients of the silage corn varieties was measured by the in vitro (artificial rumen) technique. No significant differences were noted in the 24-hour trials. However, in the 12-hour trials varieties two and four gave coefficients that were significantly (P < .05) greater than varieties one, five, six, seven, or ten. Calculated correlations of the 12 and 24-hour in vitro (artificial rumen) dry matter digestibility and of coefficients estimated by the summative equation were not highly significant. Relationships of chemical constituent data of grass and legume samples from detergent analysis provided evidence that this feed-stuff fractionation accurately reflects differences in chemical composition between species. Hemicellulose values of the grass were four times as great as those of the alfalfa, but the cellulose content was similar for the two forage types. Comparison of silage corn data with that of the alfalfa gave a relationship analogous to that of the alfalfa-grass. Residual ash values of the grass were ten times larger than those of the alfalfa. However, it was not an important factor limiting nutritive value in either the alfalfa or the silage corn. Alfalfa cell wall level and its digestibility were lower than that of the grass. But cell wall material of the grass was twice the amount contained in the alfalfa, and its digestibility was also higher which reflects its lower degree of lignification. Title: Biochemical evaluation of silage corn varieties Author: Anderson, Daniel Craig Chemical and biological evaluations were conducted to provide chemical composition and digestibility information, in addition to yield data, for silage corn varieties produced on poorly drained Dayton soil series. Each variety was subjected to a Kjeldahl nitrogen, acid detergent fiber, acid detergent lignin, cell wall, and residual ash test. Subsequently cell contents, cellulose, and hemicellulose were calculated by difference. The objectives of this study were to determine if significant differences in nutrient composition and digestibility existed among silage corn varieties grown under similar cultural conditions, and whether such differences could be detected by the detergent analysis scheme in a non-pasture forage. Finally, a comparison of in vitro (artificial rumen) and summative equation digestibility coefficients would indicate the possibility of using the latter for estimating nutritive value in forage crop experimental work. In addition, grass and legume samples, varying widely in nutritive value, were subjected to detergent analysis to ascertain the systems capabilities for assessing differences in chemical composition between forage types. Statistical analysis of the data for chemical composition of the silage corn varieties showed that no significant differences among varieties existed at the five percent probability level. Biological availability of the nutrients of the silage corn varieties was measured by the in vitro (artificial rumen) technique. No significant differences were noted in the 24-hour trials. However, in the 12-hour trials varieties two and four gave coefficients that were significantly (P < .05) greater than varieties one, five, six, seven, or ten. Calculated correlations of the 12 and 24-hour in vitro (artificial rumen) dry matter digestibility and of coefficients estimated by the summative equation were not highly significant. Relationships of chemical constituent data of grass and legume samples from detergent analysis provided evidence that this feed-stuff fractionation accurately reflects differences in chemical composition between species. Hemicellulose values of the grass were four times as great as those of the alfalfa, but the cellulose content was similar for the two forage types. Comparison of silage corn data with that of the alfalfa gave a relationship analogous to that of the alfalfa-grass. Residual ash values of the grass were ten times larger than those of the alfalfa. However, it was not an important factor limiting nutritive value in either the alfalfa or the silage corn. Alfalfa cell wall level and its digestibility were lower than that of the grass. But cell wall material of the grass was twice the amount contained in the alfalfa, and its digestibility was also higher which reflects its lower degree of lignification. Close

• 74. [Article] Combining ability and associations of agronomic traits involving three sources of dwarfism in wheat (Triticum aestivum, L. em Thell)

  Three genetically different dwarf cultivars of spring wheat were evaluated as potential sources of short stature to use in a wheat improvement program. The study involved a five parent diallel cross which ...

  Citation × Citation Citation Abstract Copy Title: Combining ability and associations of agronomic traits involving three sources of dwarfism in wheat (Triticum aestivum, L. em Thell) Author: Maya de Leon, Jose Luis Three genetically different dwarf cultivars of spring wheat were evaluated as potential sources of short stature to use in a wheat improvement program. The study involved a five parent diallel cross which included a semidwarf, a standard height and three dwarf cultivars. The genetic sources of dwarfism included a Norma 10 derivative named Vicam 71, a derived line from Tom Thumb called Tordo, and Olesen dwarf. Experimental material consisted of parental lines, F₁, F₂, and both backcrosses to the parents space planted in a randomized block design. The agronomic characters measured on an individual plant basis were: (1) plant height, (2) days to heading, (3) number of tillers, (4) number of spikelets per spike, (5) head length, (6) days to maturity, (7) grain yield, (8) harvest index, (9) kernel weight, (10) number of kernels per spikelet, (11) rachis internode length, (12) grain filling period and, (13) head grain weight. Estimates of gene action were determined by heterosis, heterobeltiosis, broad and narrow sense heritabilities and combining ability analyses. Associations among traits were estimated by phenotypic, environmental, and genotypic correlations as well as path-coefficient analysis for grain yield and eight of the variables. There were significant differences among the parental lines, their crosses, and generations for all traits measured. Either partial dominance for tallness or no dominance was manifested for those crosses involving the dwarf cultivars Vicam 71 and Olesen. Tordo, when crossed to taller wheats showed dominance for short stature. All three genetic sources of dwarfism and their resulting progenies manifested desirable agronomic characteristics. Vicam 71 was a good parent in terms of grain yield and number of tillers per plant. Tordo was the best source for increasing the number of spikelets per spike, kernel weight and head grain weight. Olesen was a good progenitor for increasing number of kernels per spikelet. All three dwarf cultivars displayed some advantage(s) over the other two and all could be used to breed short statured wheats with a possibility of success. Plant height did not appear to have a direct effect on plant grain yield in any of the 10 crosses. With the exception of number of tillers per plant and grain yield, a major proportion of the phenotypic variability observed for all characters studied was due to genetic factors. A large portion of the total genetic variability associated with days to heading, maturity, height, rachis internode, spikelet number, kernels per spikelet, kernel weight, and harvest index was mainly a result of additive gene action. Both additive and non-additive genetic effects were involved in the expression of grain filling period and head weight. The nonadditive portion of the genetic variance associated with tiller number and grain yield per plant was relatively large when compared with the additive portion. Therefore, selection for increased expression of tillers and yield should be delayed until the F₄ or later generations where a large degree of homozygosity has been obtained. The genetic correlations for individual crosses indicated that only a few of the traits studied were associated in the same manner in most or all the 10 hybridizations. High positive genetic correlations were found between plant grain yield vs tiller number and kernels per spikelet, tiller number vs days to maturity, kernels per spikelet vs head grain weight, plant height vs head weight, and head length vs rachis internode length. High negative genetic correlations were found between kernel weight vs days to maturity, plant height vs harvest index, and days to heading vs grain filling period. Most correlations among agronomic traits were different in value and/or sign from one cross to another suggesting different gene associations in the parental cultivars. Genetic correlations between components of yield showed this type of inconsistency. Therefore, grain yield could be increased by a combined increase of more than one component of yield without compensatory oscillation among them because tiller number, spikelet number, kernels per spikelet and kernel weight were often not correlated between one another and sometimes were positively correlated. Path-coefficients analysis indicated that number of tiller per plant had a high direct effect on grain yield in all crosses. With the exception of two crosses, indirect effects of this trait were negligible. In the latter two crosses tiller number had a high negative indirect effect on plant grain yield via head grain weight. Kernels per spikelet and kernel weight had no direct effects on grain yield but their indirect effects via head weight were positive and significant. Large amounts of additive gene action were observed in the expression of plant height. This trait was also highly negatively correlated with harvest index; therefore, phenotypic selection for restricted plant height would be useful in obtaining lines with high grain to straw ratios. In general, crosses that showed high specific combining ability effects involved parents with low general combining ability. However, there were some exceptions to this rule. Crosses of high x high and high x low general combiners presented high specific combining ability effects, suggesting that some additive gene action may be involved in the superior performance of these combinations. Also the F ₂ generation did not differ from the F₁ in assessing general cornbining ability. A wheat breeder should be aware of those genetic associations between agronomic traits that could be used to select superior cultivars. However, the genetic correlations in this study suggested that each cross represented a different set of gene associations depending upon the parents involved. If some progress is to be made in using the genetic variability available in the crop, the breeder should not try to select exactly the same type of plant from every cross. Every hybridization is potentially a source of better lines if they are well planned and the reasons they were made are remembered during selection. It is very important to realize what are the contributions of each parental line in a cross and what are the most important trait associations present in each parent. Superior rural genetic variability existing in the crop. Title: Combining ability and associations of agronomic traits involving three sources of dwarfism in wheat (Triticum aestivum, L. em Thell) Author: Maya de Leon, Jose Luis Three genetically different dwarf cultivars of spring wheat were evaluated as potential sources of short stature to use in a wheat improvement program. The study involved a five parent diallel cross which included a semidwarf, a standard height and three dwarf cultivars. The genetic sources of dwarfism included a Norma 10 derivative named Vicam 71, a derived line from Tom Thumb called Tordo, and Olesen dwarf. Experimental material consisted of parental lines, F₁, F₂, and both backcrosses to the parents space planted in a randomized block design. The agronomic characters measured on an individual plant basis were: (1) plant height, (2) days to heading, (3) number of tillers, (4) number of spikelets per spike, (5) head length, (6) days to maturity, (7) grain yield, (8) harvest index, (9) kernel weight, (10) number of kernels per spikelet, (11) rachis internode length, (12) grain filling period and, (13) head grain weight. Estimates of gene action were determined by heterosis, heterobeltiosis, broad and narrow sense heritabilities and combining ability analyses. Associations among traits were estimated by phenotypic, environmental, and genotypic correlations as well as path-coefficient analysis for grain yield and eight of the variables. There were significant differences among the parental lines, their crosses, and generations for all traits measured. Either partial dominance for tallness or no dominance was manifested for those crosses involving the dwarf cultivars Vicam 71 and Olesen. Tordo, when crossed to taller wheats showed dominance for short stature. All three genetic sources of dwarfism and their resulting progenies manifested desirable agronomic characteristics. Vicam 71 was a good parent in terms of grain yield and number of tillers per plant. Tordo was the best source for increasing the number of spikelets per spike, kernel weight and head grain weight. Olesen was a good progenitor for increasing number of kernels per spikelet. All three dwarf cultivars displayed some advantage(s) over the other two and all could be used to breed short statured wheats with a possibility of success. Plant height did not appear to have a direct effect on plant grain yield in any of the 10 crosses. With the exception of number of tillers per plant and grain yield, a major proportion of the phenotypic variability observed for all characters studied was due to genetic factors. A large portion of the total genetic variability associated with days to heading, maturity, height, rachis internode, spikelet number, kernels per spikelet, kernel weight, and harvest index was mainly a result of additive gene action. Both additive and non-additive genetic effects were involved in the expression of grain filling period and head weight. The nonadditive portion of the genetic variance associated with tiller number and grain yield per plant was relatively large when compared with the additive portion. Therefore, selection for increased expression of tillers and yield should be delayed until the F₄ or later generations where a large degree of homozygosity has been obtained. The genetic correlations for individual crosses indicated that only a few of the traits studied were associated in the same manner in most or all the 10 hybridizations. High positive genetic correlations were found between plant grain yield vs tiller number and kernels per spikelet, tiller number vs days to maturity, kernels per spikelet vs head grain weight, plant height vs head weight, and head length vs rachis internode length. High negative genetic correlations were found between kernel weight vs days to maturity, plant height vs harvest index, and days to heading vs grain filling period. Most correlations among agronomic traits were different in value and/or sign from one cross to another suggesting different gene associations in the parental cultivars. Genetic correlations between components of yield showed this type of inconsistency. Therefore, grain yield could be increased by a combined increase of more than one component of yield without compensatory oscillation among them because tiller number, spikelet number, kernels per spikelet and kernel weight were often not correlated between one another and sometimes were positively correlated. Path-coefficients analysis indicated that number of tiller per plant had a high direct effect on grain yield in all crosses. With the exception of two crosses, indirect effects of this trait were negligible. In the latter two crosses tiller number had a high negative indirect effect on plant grain yield via head grain weight. Kernels per spikelet and kernel weight had no direct effects on grain yield but their indirect effects via head weight were positive and significant. Large amounts of additive gene action were observed in the expression of plant height. This trait was also highly negatively correlated with harvest index; therefore, phenotypic selection for restricted plant height would be useful in obtaining lines with high grain to straw ratios. In general, crosses that showed high specific combining ability effects involved parents with low general combining ability. However, there were some exceptions to this rule. Crosses of high x high and high x low general combiners presented high specific combining ability effects, suggesting that some additive gene action may be involved in the superior performance of these combinations. Also the F ₂ generation did not differ from the F₁ in assessing general cornbining ability. A wheat breeder should be aware of those genetic associations between agronomic traits that could be used to select superior cultivars. However, the genetic correlations in this study suggested that each cross represented a different set of gene associations depending upon the parents involved. If some progress is to be made in using the genetic variability available in the crop, the breeder should not try to select exactly the same type of plant from every cross. Every hybridization is potentially a source of better lines if they are well planned and the reasons they were made are remembered during selection. It is very important to realize what are the contributions of each parental line in a cross and what are the most important trait associations present in each parent. Superior rural genetic variability existing in the crop. Close

• 75. [Article] Estimating Wholesale Demand for Live Reef Food Fish in Hong Kong

  Wholesale demand systems for live reef food fish in Hong Kong are analysed using the Linear Approximate Almost Ideal Demand System (LA/AIDS). Results suggest that price elasticities of demand are inelastic, ...

  Citation × Citation Citation Abstract Copy Title: Estimating Wholesale Demand for Live Reef Food Fish in Hong Kong Author: Petersen, Elizabeth Wholesale demand systems for live reef food fish in Hong Kong are analysed using the Linear Approximate Almost Ideal Demand System (LA/AIDS). Results suggest that price elasticities of demand are inelastic, with relatively high-valued species exhibiting greater elasticity than relatively low-valued species. Cross price elasticities are negative suggesting that different live reef fish species are complements. Live reef fish are found to be normal goods, with relatively high-valued species being less expenditure-elastic than relatively low-valued species. SARS is found to shift expenditure away from high-valued species to low-valued species. There is no evidence that Chinese New Year has a significant impact on demand. Title: Estimating Wholesale Demand for Live Reef Food Fish in Hong Kong Author: Petersen, Elizabeth Wholesale demand systems for live reef food fish in Hong Kong are analysed using the Linear Approximate Almost Ideal Demand System (LA/AIDS). Results suggest that price elasticities of demand are inelastic, with relatively high-valued species exhibiting greater elasticity than relatively low-valued species. Cross price elasticities are negative suggesting that different live reef fish species are complements. Live reef fish are found to be normal goods, with relatively high-valued species being less expenditure-elastic than relatively low-valued species. SARS is found to shift expenditure away from high-valued species to low-valued species. There is no evidence that Chinese New Year has a significant impact on demand. Close

• 76. [Article] Crop and tree response to planting patterns in alley cropping systems

  Growing trees as a green manure crop together with an annual food crop is a new technology for farmers in Oregon. To promote farmer participation and to acquire a broad knowledge of the processes involved ...

  Citation × Citation Citation Abstract Copy Title: Crop and tree response to planting patterns in alley cropping systems Author: Seiter, Stefan Growing trees as a green manure crop together with an annual food crop is a new technology for farmers in Oregon. To promote farmer participation and to acquire a broad knowledge of the processes involved in species interactions, three feasible alley cropping and two sweet corn monocrop planting patterns were studied in a replicated factorial experiment. Each alley cropping pattern was planted twice, with either red alder (Alnus rubra Bong) or black locust (Robinia pseudoacacia L.). The annual crop component used was sweet corn (Zea mays L.). Sweet com population was the same in all plant arrangements, except one alley cropping pattern. The monocrop control, planted at 63.5 cm row spacing, yielded highest while the lowest com yield was produced in the alley cropping system that involved alternate com and black locust rows. The highest com yield produced among alley cropping patterns surpassed the control planted at 89 cm row spacing. Com yield in planting patterns was dependent on the relative space occupied by each species. A high ratio of tree occupation was negatively correlated with com yield. Greatest pruning biomass was produced in alley cropping systems with highest tree population and greatest percentage of tree space occupation. Compared to black locust, biomass produced by red alder trees was minimal. Within alley cropping patterns of the same tree species, lower crop yield coincided with highest pruning biomass implicating trade-offs between potential soil improving effects and crop yield. Tree biomass was more strongly affected by changes in relative space occupation than com yield. Yield of individual com rows within treatments varied considerably. In alley cropping systems where several com rows were separated by double rows of trees, com rows adjacent to trees yielded significantly more than those neighboring com rows on either side. Com row position had no significant effect in monocrop or patterns where tree and com alternated. Mean yield of individual com plants decreased when both neighboring com rows and neighboring tree row were in close proximity. The approach of using a few planting patterns as experimental treatments did not permit to precisely model the relationships between single proximity factors and yield components. However, the approach permitted identification of factors contributing the most to changes in tree and crop yield and demonstrated basic trends. Title: Crop and tree response to planting patterns in alley cropping systems Author: Seiter, Stefan Growing trees as a green manure crop together with an annual food crop is a new technology for farmers in Oregon. To promote farmer participation and to acquire a broad knowledge of the processes involved in species interactions, three feasible alley cropping and two sweet corn monocrop planting patterns were studied in a replicated factorial experiment. Each alley cropping pattern was planted twice, with either red alder (Alnus rubra Bong) or black locust (Robinia pseudoacacia L.). The annual crop component used was sweet corn (Zea mays L.). Sweet com population was the same in all plant arrangements, except one alley cropping pattern. The monocrop control, planted at 63.5 cm row spacing, yielded highest while the lowest com yield was produced in the alley cropping system that involved alternate com and black locust rows. The highest com yield produced among alley cropping patterns surpassed the control planted at 89 cm row spacing. Com yield in planting patterns was dependent on the relative space occupied by each species. A high ratio of tree occupation was negatively correlated with com yield. Greatest pruning biomass was produced in alley cropping systems with highest tree population and greatest percentage of tree space occupation. Compared to black locust, biomass produced by red alder trees was minimal. Within alley cropping patterns of the same tree species, lower crop yield coincided with highest pruning biomass implicating trade-offs between potential soil improving effects and crop yield. Tree biomass was more strongly affected by changes in relative space occupation than com yield. Yield of individual com rows within treatments varied considerably. In alley cropping systems where several com rows were separated by double rows of trees, com rows adjacent to trees yielded significantly more than those neighboring com rows on either side. Com row position had no significant effect in monocrop or patterns where tree and com alternated. Mean yield of individual com plants decreased when both neighboring com rows and neighboring tree row were in close proximity. The approach of using a few planting patterns as experimental treatments did not permit to precisely model the relationships between single proximity factors and yield components. However, the approach permitted identification of factors contributing the most to changes in tree and crop yield and demonstrated basic trends. Close

• 77. [Article] Evaluation of popcorn cultivars as resistant rotation crops to Columbia root-knot nematode : a systems approach

  This study examined the management situation for the Columbiaroot-knot nematode (Meloidogyne chitwoodi) in potato, using an approach with systems thinking and interactive meetings. The focus of current ...

  Citation × Citation Citation Abstract Copy Title: Evaluation of popcorn cultivars as resistant rotation crops to Columbia root-knot nematode : a systems approach Author: Cardwell, Derek This study examined the management situation for the Columbiaroot-knot nematode (Meloidogyne chitwoodi) in potato, using an approach with systems thinking and interactive meetings. The focus of current research for control of this nematode was evaluated. Control practices include crop rotation, and this study also evaluated popcorn cultivars for their potential as resistant rotation crops. Popcorn cultivars were grown in M. chitwoodi race 1 infested soil at the Hermiston Agricultural Research and Extension Center (HAREC), Hermiston, OR. Soil samples were taken soon after planting (initial) and before harvest (final), and the number of M. chitwoodi juveniles / 250 g dry soil was calculated for each sample. A reproduction index was calculated for the nematode reproduction on each cultivar: R value = initial / final population. Cultivars were categorized as good, poor- and nonhosts depending on their R values. Popcorn cultivars were also tested for their host status in the greenhouse. Plants were inoculated with approximately 5000 M. chitwoodi eggs (initial), and after 55 days, eggs were extracted from the roots (final). In the field and greenhouse tests, field corn (FC) cv Pioneer 3578 was tested as a good host check. Among cultivars tested in both the field and greenhouse, the seven with the lowest R values as % of FC 3578 were: WOC 9508 (4%), W206 (16%), WOX 9512 (23%), Robust 33-77 (30%), Robust 20-70 (38%), and WOC 9504 (42%). Cultivars more susceptible than field corn were (R values as % of FC 3578 - mean of field, greenhouse tests): W 104 (119%) and Robust 90477 (102%). Popcorn cultivars WOC 9531, WOC 9556, WOX 9528, and WOX 9511 were more resistant than field corn but still need to be also tested in the field. Cultivars with R values < 1.0 in field tests can be functional in decreasing or stabilizing nematode populations, thus increasing the effectiveness of prepotato nematicides or winter cover crops. This nematode pest situation was analyzed with use of diagrams showing interacting components of the system. This system includes people, nematodes, and potatoes. Issues and questions emerged as the situation was viewed in a systems manner. Some of these issues and questions were the foci of a Farmer-Scientist Focus Session conducted on June 28th, 1995 in Hermiston, OR. Participants included growers, researchers, and extension educators. The meeting was interactive and facilitated the expression of ideas, perspectives, and concerns of the crop rotation possibilities for controlling M. chitwoodi. The opportunities and challenges using non-host crops in potato rotations were discussed. Growers expressed desire for more agronomic information about currently available poor- and non-host cultivars. They did not emphasize a need for a more diverse selection of resistant cultivars. From the grower's perspective, the main opportunity of resistant crop rotation is the integration of suppressive winter cover crops. The main challenge is the small market size for most non-host crops. Additional interactive meetings are needed to stimulate the creation of new ideas and to refine the vision and direction of research in a cooperative manner. Title: Evaluation of popcorn cultivars as resistant rotation crops to Columbia root-knot nematode : a systems approach Author: Cardwell, Derek This study examined the management situation for the Columbiaroot-knot nematode (Meloidogyne chitwoodi) in potato, using an approach with systems thinking and interactive meetings. The focus of current research for control of this nematode was evaluated. Control practices include crop rotation, and this study also evaluated popcorn cultivars for their potential as resistant rotation crops. Popcorn cultivars were grown in M. chitwoodi race 1 infested soil at the Hermiston Agricultural Research and Extension Center (HAREC), Hermiston, OR. Soil samples were taken soon after planting (initial) and before harvest (final), and the number of M. chitwoodi juveniles / 250 g dry soil was calculated for each sample. A reproduction index was calculated for the nematode reproduction on each cultivar: R value = initial / final population. Cultivars were categorized as good, poor- and nonhosts depending on their R values. Popcorn cultivars were also tested for their host status in the greenhouse. Plants were inoculated with approximately 5000 M. chitwoodi eggs (initial), and after 55 days, eggs were extracted from the roots (final). In the field and greenhouse tests, field corn (FC) cv Pioneer 3578 was tested as a good host check. Among cultivars tested in both the field and greenhouse, the seven with the lowest R values as % of FC 3578 were: WOC 9508 (4%), W206 (16%), WOX 9512 (23%), Robust 33-77 (30%), Robust 20-70 (38%), and WOC 9504 (42%). Cultivars more susceptible than field corn were (R values as % of FC 3578 - mean of field, greenhouse tests): W 104 (119%) and Robust 90477 (102%). Popcorn cultivars WOC 9531, WOC 9556, WOX 9528, and WOX 9511 were more resistant than field corn but still need to be also tested in the field. Cultivars with R values < 1.0 in field tests can be functional in decreasing or stabilizing nematode populations, thus increasing the effectiveness of prepotato nematicides or winter cover crops. This nematode pest situation was analyzed with use of diagrams showing interacting components of the system. This system includes people, nematodes, and potatoes. Issues and questions emerged as the situation was viewed in a systems manner. Some of these issues and questions were the foci of a Farmer-Scientist Focus Session conducted on June 28th, 1995 in Hermiston, OR. Participants included growers, researchers, and extension educators. The meeting was interactive and facilitated the expression of ideas, perspectives, and concerns of the crop rotation possibilities for controlling M. chitwoodi. The opportunities and challenges using non-host crops in potato rotations were discussed. Growers expressed desire for more agronomic information about currently available poor- and non-host cultivars. They did not emphasize a need for a more diverse selection of resistant cultivars. From the grower's perspective, the main opportunity of resistant crop rotation is the integration of suppressive winter cover crops. The main challenge is the small market size for most non-host crops. Additional interactive meetings are needed to stimulate the creation of new ideas and to refine the vision and direction of research in a cooperative manner. Close

• 78. [Article] Estimates of genetic variance and heterosis in F₁ winter x spring barley crosses (Hordeum vulgare, L.)

  Four winter and four spring barley cultivars along with their F₁ hybrids were grown on the Hyslop Agronomy Farm near Corvallis, Oregon, a high rainfall site (over 1000 mm annually) located in the Willamette Valley. ...

  Citation × Citation Citation Abstract Copy Title: Estimates of genetic variance and heterosis in F₁ winter x spring barley crosses (Hordeum vulgare, L.) Author: Harrabi, Moncef Mohamed Four winter and four spring barley cultivars along with their F₁ hybrids were grown on the Hyslop Agronomy Farm near Corvallis, Oregon, a high rainfall site (over 1000 mm annually) located in the Willamette Valley. The experiment consisted of four replications. Ten seeds of each F₁ and parents were seeded in a three meter row. Plants were spaced 30 cm between and within the rows. Investigations were made to evaluate the presence of hybrid vigor when hybridizing winter and spring barley. Gene action estimates contributing to yield and its components were obtained. Additional information concerning the inheritance and the association of 12 agronomic traits and yield were also evaluated. The data were analyzed by using the factorial technique, analysis of variance, correlations, path-coefficient, parent-progeny regressions, and by polynomial and multiple regressions. The traits measured were: (1) total yield per plant, (2) kernel weight, (3) tiller number per plant, (4) kernel number per spike, (5) heading date, (6) plant height, (7) flag leaf area, (8) flag leaf width, (9) flag leaf length, (10) culm diameter, (11) head length, and (12) head extrusion. Heterobeltiosis was observed in all of the hybrids except in the cross between Adair and Short Wocus. The absence of hybrid vigor in this cross may be attributed to the fact that these two parents are closely related. Combining ability analysis as well as narrow sense heritability estimates indicated that additive gene action is more predominant in the expression of heading date, plant height, tiller number, head length, culm diameter, flag leaf width and kernel weight. Heterobeltiosis and high SCA estimates were observed in most of the hybrids for yield per plant and kernel number per spike. This implies that most of the genetic variation associated with these two traits resulted from non-additive gene action. The high SCA estimate observed for head extrusion indicates that this trait appeared to be controlled by non-additive gene action. Both additive and nonadditive gene action are important for the expression of flag leaf area and flag leaf length. When the 12 traits were correlated and the r values partitioned into direct and indirect effects it was observed that tiller number, kernel weight and kernel number per spike exerted the highest direct effect on yield. Plant height had a small positive direct effect, but an indirect effect on yield through kernel weight. It was further observed that a negative association exists between tiller number and kernel weight. This indicates that, in this barley population, it would be difficult to select for a plant containing large grain type and short stature, but it may be easy to select short plants with a relatively large number of tillers and high kernel number per spike. Path coefficient analysis indicated further that flag leaf area has a negative direct effect on yield and the remaining six traits have a negligible or no direct effect on yield, indicating that these traits can not be used as selection criteria. More genetic variability for tiller number and kernel number per spike was noted in the winter barley while more genetic variability for kernel weight was found in the spring barley. The results of this study suggest that increases in yield could be achieved by selecting plants with relatively high tiller number and high kernel weight. Selection for a high kernel number per spike can be accomplished by selecting for large culms and longer peduncle. By this procedure the breeder can take advantage of the additive genetic variance associated with tiller number and kernel weight and by the positive correlation that exists between culm size and peduncle length with kernel number per spike. Title: Estimates of genetic variance and heterosis in F₁ winter x spring barley crosses (Hordeum vulgare, L.) Author: Harrabi, Moncef Mohamed Four winter and four spring barley cultivars along with their F₁ hybrids were grown on the Hyslop Agronomy Farm near Corvallis, Oregon, a high rainfall site (over 1000 mm annually) located in the Willamette Valley. The experiment consisted of four replications. Ten seeds of each F₁ and parents were seeded in a three meter row. Plants were spaced 30 cm between and within the rows. Investigations were made to evaluate the presence of hybrid vigor when hybridizing winter and spring barley. Gene action estimates contributing to yield and its components were obtained. Additional information concerning the inheritance and the association of 12 agronomic traits and yield were also evaluated. The data were analyzed by using the factorial technique, analysis of variance, correlations, path-coefficient, parent-progeny regressions, and by polynomial and multiple regressions. The traits measured were: (1) total yield per plant, (2) kernel weight, (3) tiller number per plant, (4) kernel number per spike, (5) heading date, (6) plant height, (7) flag leaf area, (8) flag leaf width, (9) flag leaf length, (10) culm diameter, (11) head length, and (12) head extrusion. Heterobeltiosis was observed in all of the hybrids except in the cross between Adair and Short Wocus. The absence of hybrid vigor in this cross may be attributed to the fact that these two parents are closely related. Combining ability analysis as well as narrow sense heritability estimates indicated that additive gene action is more predominant in the expression of heading date, plant height, tiller number, head length, culm diameter, flag leaf width and kernel weight. Heterobeltiosis and high SCA estimates were observed in most of the hybrids for yield per plant and kernel number per spike. This implies that most of the genetic variation associated with these two traits resulted from non-additive gene action. The high SCA estimate observed for head extrusion indicates that this trait appeared to be controlled by non-additive gene action. Both additive and nonadditive gene action are important for the expression of flag leaf area and flag leaf length. When the 12 traits were correlated and the r values partitioned into direct and indirect effects it was observed that tiller number, kernel weight and kernel number per spike exerted the highest direct effect on yield. Plant height had a small positive direct effect, but an indirect effect on yield through kernel weight. It was further observed that a negative association exists between tiller number and kernel weight. This indicates that, in this barley population, it would be difficult to select for a plant containing large grain type and short stature, but it may be easy to select short plants with a relatively large number of tillers and high kernel number per spike. Path coefficient analysis indicated further that flag leaf area has a negative direct effect on yield and the remaining six traits have a negligible or no direct effect on yield, indicating that these traits can not be used as selection criteria. More genetic variability for tiller number and kernel number per spike was noted in the winter barley while more genetic variability for kernel weight was found in the spring barley. The results of this study suggest that increases in yield could be achieved by selecting plants with relatively high tiller number and high kernel weight. Selection for a high kernel number per spike can be accomplished by selecting for large culms and longer peduncle. By this procedure the breeder can take advantage of the additive genetic variance associated with tiller number and kernel weight and by the positive correlation that exists between culm size and peduncle length with kernel number per spike. Close

• 79. [Article] How to reduce bee poisoning from pesticides

  Published December 2006. A more recent revision exists. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http:/...

  Citation × Citation Citation Abstract Copy Title: How to reduce bee poisoning from pesticides Author: Washington State University. Extension, Barbour, Jim, Pacific Northwest Cooperative Extension, Johansen, Erik, Brewer, Linda J., University of Idaho. Extension, Riedl, Helmut., Oregon State University. Extension Service Published December 2006. A more recent revision exists. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog Title: How to reduce bee poisoning from pesticides Author: Washington State University. Extension, Barbour, Jim, Pacific Northwest Cooperative Extension, Johansen, Erik, Brewer, Linda J., University of Idaho. Extension, Riedl, Helmut., Oregon State University. Extension Service Published December 2006. A more recent revision exists. Facts and recommendations in this publication may no longer be valid. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog Close

• 80. [Article] Phenology and monitoring of the cabbage maggot, Delia radicum (L.), in brassica root crops

  In Oregon’s northern Willamette Valley, cabbage maggot (CM), Delia radicum (L.) (Diptera: Anthomyiidae) often renders Brassica root crops unmarketable. Scheduled insecticides are the only current control. ...

  Citation × Citation Citation Abstract Copy Title: Phenology and monitoring of the cabbage maggot, Delia radicum (L.), in brassica root crops Author: Dreves, Amy J. In Oregon’s northern Willamette Valley, cabbage maggot (CM), Delia radicum (L.) (Diptera: Anthomyiidae) often renders Brassica root crops unmarketable. Scheduled insecticides are the only current control. Studies were conducted to: 1) describe and characterize spring emergence of CM flies and their seasonal flight activity relative to degree-day (DD) accumulations; 2) measure impact of CM by assessing crop damage; 3) define influence of seasonal planting and harvest dates relative to root damage; 4) identify the occurrence of ovipositional activity in relation to time of season, age of crop, distribution in field; and 5) study relationships among flight activity, oviposition, and crop damage. Commercial rutabaga and turnip fields were studied from 2001 through 2005. Spring emergence from overwintering puparia was monitored using emergence cages. A bimodal spring emergence pattern for CM was observed: approximately 70% of the overwintering population peaked in late March. A second smaller peak was observed at the end of May. The mean DD accumulations at 10, 50, and 95% of spring emergence using a lower and upper developmental threshold of 4.3°C and 30°C beginning January 1 had corresponding DD values of 200 ± 50.2 (8 March), 330 ± 22.2 (4 April) and 762 ± 60.1 (28 May), respectively. Spring flight patterns, monitored with yellow water traps, mirrored the bimodal emergence pattern but with an apparent lag. Rutabaga crops sustained 1.7x higher damage levels than did turnip crops. Damage caused by CM was significantly greater (37-52%) in spring crops planted prior to an accumulated 900 DD, than in summer crops planted after 900 degree-days or in fields planted in the fall after 1500 DD. Maggot damage is abated by planting after the spring flight (> 900 DD) and harvesting before the relative peak of fall flight (< 2600 DD). Fields documented with less than an average of 100 flies collected in a water trap over a crop’s duration in the field, had the lowest sum of percent weekly egg assessments (38.6 ± 6.1; based on 7 weekly egg level assessments), and the least amount of root infestation by CM (< 20% per 60 root samples). Fields with greater than 100 flies per trap over crop duration in the field had the greatest sum frequency of plants with eggs (95.6 ± 6.7), and the most CM root infestation (> 20%). Oviposition significantly increased in fields at 30.9 (± 1.1) days after seeding. Large plants with > 5 leaves, root diameter of > 6 mm, and increased crop canopy were more heavily infested with CM eggs than smaller plants. A strong relationship was seen between the frequency of older plants with eggs (> 9 leaves, >19 mm root size and partially-closed canopy) and crop damage at harvest (r2 = 0.83). Egg incidence was significantly higher (46%) on plants located on the outside periphery of fields than on plants located in the field centers. Spring monitoring of emergence and flight arrival, and density of D. radicum allows useful predictions of oviposition and crop damage. Appropriate oviposition assessment, combined with timely planting and harvesting schedules, and use of egg thresholds to time treatments could greatly reduce maggot populations. Title: Phenology and monitoring of the cabbage maggot, Delia radicum (L.), in brassica root crops Author: Dreves, Amy J. In Oregon’s northern Willamette Valley, cabbage maggot (CM), Delia radicum (L.) (Diptera: Anthomyiidae) often renders Brassica root crops unmarketable. Scheduled insecticides are the only current control. Studies were conducted to: 1) describe and characterize spring emergence of CM flies and their seasonal flight activity relative to degree-day (DD) accumulations; 2) measure impact of CM by assessing crop damage; 3) define influence of seasonal planting and harvest dates relative to root damage; 4) identify the occurrence of ovipositional activity in relation to time of season, age of crop, distribution in field; and 5) study relationships among flight activity, oviposition, and crop damage. Commercial rutabaga and turnip fields were studied from 2001 through 2005. Spring emergence from overwintering puparia was monitored using emergence cages. A bimodal spring emergence pattern for CM was observed: approximately 70% of the overwintering population peaked in late March. A second smaller peak was observed at the end of May. The mean DD accumulations at 10, 50, and 95% of spring emergence using a lower and upper developmental threshold of 4.3°C and 30°C beginning January 1 had corresponding DD values of 200 ± 50.2 (8 March), 330 ± 22.2 (4 April) and 762 ± 60.1 (28 May), respectively. Spring flight patterns, monitored with yellow water traps, mirrored the bimodal emergence pattern but with an apparent lag. Rutabaga crops sustained 1.7x higher damage levels than did turnip crops. Damage caused by CM was significantly greater (37-52%) in spring crops planted prior to an accumulated 900 DD, than in summer crops planted after 900 degree-days or in fields planted in the fall after 1500 DD. Maggot damage is abated by planting after the spring flight (> 900 DD) and harvesting before the relative peak of fall flight (< 2600 DD). Fields documented with less than an average of 100 flies collected in a water trap over a crop’s duration in the field, had the lowest sum of percent weekly egg assessments (38.6 ± 6.1; based on 7 weekly egg level assessments), and the least amount of root infestation by CM (< 20% per 60 root samples). Fields with greater than 100 flies per trap over crop duration in the field had the greatest sum frequency of plants with eggs (95.6 ± 6.7), and the most CM root infestation (> 20%). Oviposition significantly increased in fields at 30.9 (± 1.1) days after seeding. Large plants with > 5 leaves, root diameter of > 6 mm, and increased crop canopy were more heavily infested with CM eggs than smaller plants. A strong relationship was seen between the frequency of older plants with eggs (> 9 leaves, >19 mm root size and partially-closed canopy) and crop damage at harvest (r2 = 0.83). Egg incidence was significantly higher (46%) on plants located on the outside periphery of fields than on plants located in the field centers. Spring monitoring of emergence and flight arrival, and density of D. radicum allows useful predictions of oviposition and crop damage. Appropriate oviposition assessment, combined with timely planting and harvesting schedules, and use of egg thresholds to time treatments could greatly reduce maggot populations. Close