R. B. Dadson

Effect of Insecticide Spray Applications, Sowing Dates and Cultivar Resistance on Insect Pests of Cowpea in the Delmarva Region of the United States

ABSTRACT Field studies were conducted to determine the effect of insecticide spray applications, sowing dates and cultivar resistance in diverse cowpea genotypes in the Delmarva (Delaware, Maryland and Virginia) peninsula region of the United States. A mixture of cypermethrin and dimethoate was applied in the first experiment and the number of spray applications ranged from two to six. The second experiment had two sowing date treatments and received four spray applications of endosulfan. Also, ten genotypes of cowpea were planted and observations were taken on the incidence of major insect pests and pod damage. There was a 30% increase in cowpea seed yield as a result of spraying the mixture of cypermethrin + dimethoate insecticides. The damage to cowpea pods was also significantly reduced in the sprayed treatments. The first and second sowing dates of cowpea sprayed treatments gave 30% and 45% increase in the seed yield over the first and second unsprayed dates of sowing cowpea treatments, respectively. The first sowing date treatment gave significantly higher seed yield than the second sowing date treatments. There were significant differences in the number of some major insect pests and also on pod damage among the ten diverse cowpea genotypes grown under the Delmarva field conditions. This study provides information on the incidence of insect pests of cowpea in the Delmarva region, the potential of insect pests to cause significant yield losses, and variation in insect pest resistance among ten diverse cowpea genotypes.

The Potential of Bt Corn as a Trap Crop for the Control of Corn Earworm, Helicoverpa zea Boddie, in Soybean

ABSTRACT Corn and soybean are two important crops in the Delmarva (Delaware, Maryland and Virginia) peninsula region. Both crops are attacked by corn earworm (CEW), Helicoverpa zea (Boddie). The larvae cause significant ear damage to corn serving as a primary nursery for CEW populations which shift to soybean later in the season. In soybean, CEW larvae cause serious yield losses if not controlled by insecticides. Many farmers in the Delmarva region have been increasing the acreage they grow with genetically engineered corn hybrids that contain insecticidal proteins expressed by the genes of Bacillus thurngiensis sub sp. kurstaki (Bt) as an alternative to the application of chemical insecticides. A study was conducted to investigate the use of Bt corn as a trap crop for the management of CEW in soybean. Bt corn was planted as a trap crop in a ten percent of the area of soybean as a peripheral trap, trap in the middle and trap in the intermittent rows in soybean. CEW moths were attracted and observed on the newly formed silks of the ears of Bt corn in all types of traps including peripheral trap, trap in the middle and trap in the intermittents rows planted in soybean. CEW eggs were also observed on the silk of transgenic corn. The moths, eggs and larvae (CEW) were hardly observed in soybean grown as a main crop. Clearly, we were able to divert the CEW adults on Bt corn from soybean. The number of CEW eggs was significantly higher in the peripheral trap and trap in the intermittent rows compared with trap in the middle of the plots, suggesting that Bt corn planted as a peripheral trap crop could be more practicable and effective for the farmers in reducing the CEW damage in soybean.

Potential of Corn Genotypes for Phosphorus Removal in Poultry Manure-Enriched Soils

The repeated application of poultry manure to agricultural lands in poultry-producing regions of the world has resulted in excess farm-level phosphorus (P) with various undesirable effects. To reduce high P accumulation in soil and its undesirable environmental consequences, plant-based P-remediation strategies have been suggested. Our objective was to determine the difference in P uptake in various genotypes of corn (Zea mays L.) harvested at the milk stage of grain formation in poultry manure-enriched soils. Field experiments were conducted during three growing seasons at two sites: One site had a history of heavy poultry manure applications during the past 10 years, and the other site had not received poultry manure applications. Results showed that genotypes 57K14 and DKC 64-11 exhibited superior P uptake in both amended and unamended soils. The superior P extraction of genotypes 57K14 and DKC 64-11 relative to that of other genotypes indicates that there is potential to improve P uptake in corn genotypes and that it is possible to use this innovative approach for phytoremediation of soils to sustain the agroecosystems.

A modified nitrogen oxide-ozone photolytic cycle

Nitrogen Oxide-03 photolytic cycle is dependent upon the presence of NO in ambient air. From our air monitoring observations we have found that the NO concentration in the atmosphere is often zero (0 to 5 ppb). This suggests a need to modify/change the photolytic cycle. Linear regression analyses on the O3 and NO2 concentrations in ambient air, measured in real time were carried out. The predicted values of O3 and NO2 from these regression equations were close to the observed values. On the basis of these two observations a modified photolytic cycle, including some other components (such as HONO2) is discussed.

Linear regression analyses of ozone and sulphur dioxide in ambient air

Abstract Linear regression analyses were performed on ozone and sulphur dioxide concentrations measured in real time. The predicted values of O3 and SO2 from these regression equations were close to the observed values. The relationship between O3 and SO2 is explained on theoretical considerations: sulphur dioxide absorbs light and forms an excited electronic state of molecular oxygen which readily combines with O-atoms.

Antibiosis in Soybean Breeding Lines for the Management of Corn Earworm for Sustainable Soybean Production

ABSTRACT Corn earworm (Helicoverpa zea Boddie), is one of the major insect pests of soybean in many soybean growing areas. A study was conducted during three soybean growing seasons to evaluate the antibiosis type of resistance in soybean breeding lines which were grown in replicated field trials. A plant introduction, ‘PI 229358’, with a known antibiosis type of resistance against corn earworm was included as a resistant check and four commercial varieties including Hutcheson, Stalwart, Charleston and Croton also were included in the experiments for comparison. The results of antibiosis tests showed that some breeding lines such as ‘E3582019’ and ‘D6874003’ provided level of antibiosis to corn ear-worm comparable to that found in the commercial variety Stalwart. Also, ‘M3583009’ and ‘D358B3010’ provided antibiosis to corn earworm which was similar to a commercial variety, Stalwart. However, none of the breeding lines provided the resistance which was similar to ‘PI 229358’. The intermediate antibiosis found in some of the breeding lines could play an important role in the management of corn earworm and other insect pests coupled with other desirable agronomic traits such as higher seed yield.

Antibiosis to Corn Earworm, Helicoverpa zea Boddie, by Cowpea Genotypes

ABSTRACT Corn earworm (Helicovrpa zea Boddie) is a pest of cow-pea in many regions of the United States. The larvae chew round holes in cowpea pods to feed on the developing grains, and thus, affect the yield and seed quality. Studies were conducted to identify antibiosis to corn earworm (CEW) in diverse cowpea genotypes which had been identified to provide better yields in the Delmarva (Delaware, Maryland and Virginia) peninsula region. A series of bioassays were performed to evaluate the newly formed terminal trifoliolates of field grown cowpea for antibiosis to CEW. Results showed significant differences in larval weights in all bioassays. The genotypes which gave the lowest larval weights were Mississippi Silver and Quick pick Pinkeye, while the genotype, Champion, provided the largest weights of larvae in virtually all tests. Therefore, this genotype could probably be used as a susceptible check for future cowpea antibiosis studies to CEW. Results also indicate that some genotypes of cowpea that provided consistently lower weights of larvae, including Mississippi Silver and Quick pick Pinkeye, have higher levels of antibiosis to corn earworm larvae than genotypes Champion and Dixielee. These superior genotypes need to be evaluated for multiple pest resistance and other desirable agronomic traits. The antibiosis could be integrated with other methods of cowpea pest management to reduce the amount of insecticides for the management of CEW and other insect pests of cowpea.

Potential of Fodder Soybean Genotypes for Phosphorus Removal in Poultry Manure-Enriched Soils

Plant-based phosphorus (P) remediation strategies have been suggested to reduce high P accumulation in soil. Eleven fodder soybean genotypes were evaluated to explore their potential for the removal of P from poultry manure-enriched soils. Field experiments were conducted at a site that had a history of heavy poultry manure applications. Green house experiments were conducted using the soils selected for field trials to confirm the results. Harvesting of whole plants, excluding roots of the genotypes, was done at the pod formation stages and plant samples were oven dried at 70°C for three days. The dry samples were ground and analyzed for total P content. Genotype 091734, provided the maximum P removal from amended and unamended soils. Fodder soybean genotypes could play an important role in the extraction of P from poultry manure-enriched soils, which are important from the ecological point of view.

Cowpea as an Alternative Crop for Sustainable Crop Production in the Delmarva Region of the United States

ABSTRACT Field experiments were conducted to determine the possibility of growing cowpea as an alternative crop in the cropping system of the Delaware, Maryland and Virginia (Delmarva) region of the United States. Cowpea genotypes were grown for two seasons and the parameters evaluated mostly included grain yield, biological yield, flowering and maturity dates. Results showed significant differences in grain and biological yields of various genotypes. Genotypes Colossus, Mississippi Silver and California Blackeye 5 gave significantly higher seed yields. The highest biological yield was provided by genotypes Champion, White Acre and California Blackeye 5 making these genotypes good candidates to be used for green manuring or as cover crops in the region. Genotypes Quickpick Pinkeye and Elite were found to be early maturing and might escape the terminal drought. Soils in the Delmarva region are sandy, prone to drought but support corn and soybean which are the major crops in the region. The results indicate that introduction of cowpea in the Delmarva region could play an important role in replacing some of the areas currently being used for corn and soybean production, an important source of vegetable proteins to many ethnic groups in the area, play an important role as an alternative crop, improve soil fertility to sustain crop production, and also to serve as an insurance crop, especially during drought years in the Delmarva region.

Prediction of ozone concentration from sulphur and nitrogen dioxides in ambient air: part 1 (regression analyses)

Computer modeling and simulation, of ambient air pollutants, for predictive purposes are somewhat incomplete. Based on real time observations of O3, SO2 and NO2 concentrations in ambient air and subsequent linear analyses of these data, regression equations have been obtained that are suitable for predicting concentrations of these ambient air pollutants. Ozone concentration can best be predicted from the combined concentrations of SO2 and NO2.