Lloyd T. Wilson - Academia.edu (original) (raw)

Papers by Lloyd T. Wilson

American Entomologist, 1992

…, 1989

... French prune trees: Refuge for grape leafhopper parasite by L. Ted Wilson, Charles H. Pickett... more ... French prune trees: Refuge for grape leafhopper parasite by L. Ted Wilson, Charles H. Pickett, Donald L. Flaherty, Teresa A. Bates pp7-8, doi#10.3733/ca.v043n02p7 Abstract Prune trees planted next to vineyards allow early-season buildup of Anagrus epos, an important ...

Improving rice models for more reliable prediction of responses of rice yield to CO2 and temperat... more Improving rice models for more reliable prediction of responses of rice yield to CO2 and temperature elevation . International Crop Modelling Symposium

California Agriculture, 1984

Not available – first paragraph follows: Six species of spider mites are associated with almond t... more Not available – first paragraph follows: Six species of spider mites are associated with almond trees in California's Central Valley. The lack of economical and reliable sampling techniques has hampered not only research on these mites but also the grower's ability to estimate control status or population density in a minimum amount of time. Three of the six spider mite (tetrany-chid) species — the European red mite, brown almond mite, and citrus red mite — are occasionally abundant enough to require chemical treatment. European red mite and brown almond mite are most often found in the northern and central Valley, and the citrus red mite, in citrus-producing areas of the southeastern Valley.

Environmental Entomology, 1990

Laboratory studies were conducted to determine if there were biological or behavioral differences... more Laboratory studies were conducted to determine if there were biological or behavioral differences among populations of Trissolcus basalis (Wollaston) (Scelionidae: Hymenoptera) collected from France, Italy, and Spain. Observations of isolated and mated females indicated little difference in fecundity, adult longevity, male and female progeny produced, length of oviposition period, and percentage of parasitism of Nezara uiridula (L.) (Heteroptera: Pentatomidae) eggs. Females from all locations showed greater fecundity and rates of parasitism during the first week after emergence. The French population showed a significantly higher emergence rate from N. uiridula eggs than those from Italy or Spain. When male T. basalis were continuously present with females, fecundity, number of male progeny, and percentage of parasitism were significantly higher than when females were isolated. Over the lifetime of T. basalis females, the sex ratio of adult progeny favored female; however, there was a progressive shift from predominantly female to male progeny as the female aged. Adult males lived longer than females. No significant differences in adult male or female longevity were detected across geographic populations. However, the Italian population took significantly more time to complete immature development than the French or Spanish population. N. vtridula egg mortality was significantly higher when female T. basalis were continuously present than when absent, indicating that parasites may cause some mortality in addition to that resulting from parasitism. There were no significant differences in mating, egg selection, or oviposition times among the geographic populations. Females from Italy spent significantly less time in marking N. utridula eggs than those from Spain or France. The results of these studies suggest that the three populations compose a single T. basalis biotype.

Environmental Entomology, 1983

Oviposition pattems of Heliothis m i. Mandi4c.u spp., Spodopterci exigiia, and Trichoplusiu ni we... more Oviposition pattems of Heliothis m i. Mandi4c.u spp., Spodopterci exigiia, and Trichoplusiu ni were studied in processing-tomato fields of northem Califomia. The initiation of egg laying appears to be related to flower formation, with peak egg deposition occurring in relation to the peak number of open flowers per plant for H. zea. S. e.rigctu, and T. ni. Oviposition by Munditca spp. increases as the season progresses. All species deposit most of their eggs on leaves of the terminal halt of the branch. The majority of eggs are located on the ventral leaf surface, within one leaf of the inflorescence. From these data, it is possible to estimate the number of plants that would have to be sampled to find an egg of one species at a given egg density.

Environmental Entomology, 1982

This paper reports the within-lant distribution of cabbage looper on cotton through results in a ... more This paper reports the within-lant distribution of cabbage looper on cotton through results in a greater proportion of eggs being oviposited on mainstem leaves, and closer to the mainstem terminal. As the plants age and increase in size, the eggs are found higher on the plant. The larvae appear to prefer leaves 5 to 10 nodes from the terminal.

Environmental Entomology, 1991

This study addresses the potential impact of natural enemies on the abundance of spider mites, Te... more This study addresses the potential impact of natural enemies on the abundance of spider mites, Tetranychus spy., on cotton in the San Joaquin Valley of California. These natural enemies are omnivorous predators, and include the big-eyed bug, Geocoris pallens StAl and G. punctipes (Say), the minute pirate bug, Orius trfsticolor (White), and the western flower thrips, Frankliniella occidentalis (Pergande). Simple linear regression suggested that omnivorous predators were potentially effective in delaying the buildup of spider mites, with the highest rz (0.65) recorded for adult F. occidentalis. Geocoris showed the potential to suppress the rate of spider mite population increase (rl = 0.73). All three tested predator species exhibited the capacity to suppress early season spider mite abundance, with the highest r2 (0.62) recorded for Ceocoris and Orius. Predators were also potentially able to suppress mid-to late-season spider mite populations. Multiple regression analysis indicated a significant negative correlation between mid-to late-season spider mite abundance and early season predators. Results from a second year were less conclusive, suggesting that the reduced range of spider mite abundance limited our ability to discern potentially significant interactions during that year.

Journal of Economic Entomology, 1984

Lygus hesperus (Knight) on cotton in the field were, on the average, distributed on the fifth thr... more Lygus hesperus (Knight) on cotton in the field were, on the average, distributed on the fifth through seventh nodes from the terminal. Most nymphs were located on squares, while the majority of adults were found on bolls In comparison, adults 011 glasshouse plants were located predominantly in the upper four mainstem nodes; most were found on leaves. In the glasshouse, L. hesperus that were on fruit structures were almost entirely on squares. The difference in distribution between L. hesperus populations in the field and glasshouse appeared to be largely due to different plant growth patterns. Glasshouse plants were spindly, with a simple canopy characterized by short branches, few fruits, and relatively little vegetation. Plants in the field developed a full canop) , larger and more branches, and more fruit per branch, thus providing more habitat turther down the plant for L. hesperus to feed. These results suggest that glasshouse experiments provide biased information on L. hesperus distribution and, possibly, feeding behavior. Lygus hesperus (Knight) is a pest of cotton in California's San Joaquin Valley. Feeding is reported to occur primarily in fruiting structures in the upper terminal area of the plant (Jubb and Carruth 1971, Tugwell et al. 1976, Gutierrez et al. 1977, Mauney and Henneberry 1979); young squares (flower buds) are preferred (Mauney and Henneberry 1979, Pack and Tugwell 1976). Tugwell et al. (1976) estimated for two cultivars that about 10 and 1% of the potential yield in their field trials was lost due to Lygus spp. damage to bolls. The actual amount of feeding on bolls was possibly less and that on squares greater since, when older squares are damaged by Lygus bugs, development of the fruit often continues but results in a damaged boll (Pack and Tugwell 1976). The amount of damage to bolls is also likely to depend on the relative phenologies of the crop and the Lygus spp. Large early season populations probably cause more damage to squares, while populations developing later probably damage more bolls. Since bolls are located further from the plant terminal than are squares, the distribution of Lygus bugs on the plant may affect the relative availability of squares and bolls as feeding sites. Lygus adults are flighty; for this reason, most detailed studies of feeding behavior and damage have concentrated on nymphs (Tugwell et al. 1976) or on caged nymphs or adults (

Entomologia Experimentalis et Applicata, 1989

ABSTRACT

Ecological Modelling, 1998

Three algorithms for solving a simplified 3-D advection-diffusion equation were compared as to th... more Three algorithms for solving a simplified 3-D advection-diffusion equation were compared as to their accuracy and speed in the context of insect and spore dispersal. The algorithms tested were the explicit central difference (ECD) method, the implicit Crank-Nicholson (ICN) method, and the implicit Chapeau function (ICF) method. The three algorithms were used only to simulate the diffusion process. A hold-release wind shifting method was developed to simulate the wind advection process, which shifts the concentration an integer number of grids and accumulates the remaining wind travel distance (which is less than the grid spacing) to the next time step. The test problem was the dispersal of a cloud of particles (originally in only one grid cell) in a 3-D space. The major criterion for testing the accuracy was R 2 , which represents the proportion of the total variation in particle distribution in all grid cells that is accounted for by the particle distribution through numerical solutions. Other criteria included total remaining mass, peak positive density, and largest negative density. High R 2 values were obtained for the ECD method with (DtK z)/(Dz) 2 50.5 (Dt=time step; K z =vertical eddy diffusion coefficient; Dz= vertical grid spacing), and for the two implicit methods with DtK z /(Dz) 2 55. The ICN method gave higher R 2 values than the ICF method when the concentration gradients were high, but its accuracy decreased more rapidly with the progress of time than the ICF method with a combination of a large grid spacing and a large time step. With very steep concentration gradients, the ICF method generated huge negative values, the ICN method generated negative values to a lesser extent, and the ECD method generated only small negative values. It was also found that good mass and/or peak preservation did not necessarily correspond to a higher R 2 value. Based on the R 2 value and the requirement for concentration positivity, for simulations with steep concentration gradients, the ECD method would be most appropriate, followed by the ICN method, and the ICF method would be least appropriate due to large negative values. For simulations with low concentration gradients, the ECD or ICF or ICN method could be used, but the ICN method would not be appropriate for use in a combination of a large time step and a large grid spacing. The results from this study

Bulletin of Entomological Research, 1991

Biological Control, 2011

A 2-year field cage experiment was conducted in Beaumont, Texas to estimate parasitism of sugarca... more A 2-year field cage experiment was conducted in Beaumont, Texas to estimate parasitism of sugarcane borer, Diatraea saccharalis (F.), by Cotesia flavipes (Cameron) on rice. A lab experiment showed that the number of hosts parasitized per female per day reached a maximum (0.961) at 28°C. Parasitized larvae recovered from the field experiment produced an average of 27.9 ± 19.1 (x ± s.d.) parasitoids, with a 2.57:1 (female/male) sex ratio. A cohort-based age-structured model was developed to simulate the population dynamics and economic impact of sugarcane borer and C. flavipes in rice, as affected by overwintering larval density, timing and rate of parasitoid aerial release, and year-to-year climate (temperature and rainfall). The results suggest the cumulative seasonal damaging larval density (3rd or later instars) is negatively correlated with winter temperature, while maximum parasitoid density and maximum proportion parasitized are positively correlated with the cumulative seasonal damaging larval density. C. flavipes was most effective when released 40 or 50 days after rice planting, with simulated yield loss reduced by up to 50.9% when the release rate was 10 females and 4 males m À2. The maximum simulated economic benefit ($59.48 ha À1) is ca. 6.7% of that provided by insecticide-based control, which occurred when the release rate was 1 female and 0.4 males m À2. The inability of C. flavipes to provide economic control in temperate-subtropical areas is due to its high rearing cost, a low effective search rate, a low maximum number of hosts parasitized per female, and failure of the spring emerging parasitoids to find hosts.

Environmental Entomology, 1997

Analysis of larval and pupal age-structured data indicates that the soil core sampler-soil separa... more Analysis of larval and pupal age-structured data indicates that the soil core sampler-soil separation method underestimates the abundance of early instar rice water weevil, Lissorhoptrtls ortjzophilus Kuschel. The estimates for bias were used to derive seasonal larval age-structured population estimates for 4 yr of field data from 2 experiments representing untreated and carbofuran treated plots. These estimates were used as input to a physiologically based rice population model to simulate the response of rice to rice water weevil injury. An iterative halving-grid size optimization approach enabled least squares estimation of the larval feeding rate as a function of larval mass, the effect of larval crowding on root mass consumption by larvae, and the effect oflarval feeding on root nitrogen uptake efficiency. A statistically based parameterization-verification-validation procedure was used to quantify the robustness of the model at simulating rice straw mass, grain yield, and total above ground mass. The model accurately Simulated each of these variables for the range of rice water weevil seasonal age-structured population patterns, and explained 95% of the yield variability in the observed data. In contrast, a multiple linear regression of grain yield as a function of cumulative larvaldensity degree-days and the timing of peak density explained only 58% of the variability. An analysis of the benefits and costs accrued from the carbofuran treatments suggests that the current rice water weevil action threshold may be too high when infestations begin during early stages of crop growth. Results from sensitivity analyses indicate that the stage of crop growth during which rice water weevil injury occurs greatly affects crop tolerance for root injury, suggesting that optimal timing of rice water weevil controls should take into account both larval density and stage of crop growth.

GCB Bioenergy, 2018

Current knowledge of yield potential and best agronomic management practices for perennial bioene... more Current knowledge of yield potential and best agronomic management practices for perennial bioenergy grasses is primarily derived from small-scale and short-term studies, yet these studies inform policy at the national scale. In an effort to learn more about how bioenergy grasses perform across multiple locations and years, the U.S. Department of Energy (US DOE)/Sun Grant Initiative Regional Feedstock Partnership was initiated in 2008. The objectives of the Feedstock Partnership were to (1) provide a wide range of information for feedstock selection (species choice) and management practice options for a variety of regions and (2) develop national maps of potential feedstock yield for each of the herbaceous species evaluated. The Feedstock Partnership expands our previous understanding of the bioenergy potential of switchgrass, Miscanthus, sorghum, energycane, and prairie mixtures on Conservation Reserve Program land by conducting long-term, replicated trials of each species at diverse environments in the U.S. Trials were initiated between 2008 and 2010 and completed between 2012 and 2015 depending on species. Field-scale plots were utilized for switchgrass and Conservation Reserve Program trials to use traditional agricultural machinery. This is important as we know that the smaller scale studies often overestimated yield potential of some of these species. Insufficient vegetative propagules of energycane and Miscanthus prohibited farm-scale trials of these species. The Feedstock Partnership studies also confirmed that environmental differences across years and across sites had a large impact on biomass production. Nitrogen application had variable effects across feedstocks, but some nitrogen fertilizer generally had a positive effect. National yield potential maps were developed using PRISM-ELM for each species in the Feedstock Partnership. This manuscript, with the accompanying supplemental data, will be useful in making decisions about feedstock selection as well as agronomic practices across a wide region of the country.