No description available.

No description available.

No description available.

Historically, most twospotted spider mite, Tetranychus urticae Koch, infestations occurred during the late season near maturity, but since 2005, infestations of cotton have become more common throughout the entire season. Several factors may have contributed to the increasing frequency of mites in seedling cotton, one of which is a shift in production practices from furrow applied aldicarb to neonicotinoid seed treatments for thrips control. Another factor that may impact T. urticae densities in seedling cotton is a shift from pre-plant tillage to conservation tillage or no-till cropping systems. Although the literature confirms that T. urticae can cause extensive cotton yield losses, there is a need to further refine potential late-season yield loss. From 2007 to 2009 a series of experiments were conducted to address these issues. In a series of 12 field experiments, neonicotinoid seed treatments resulted in twospotted spider mite densities greater than those in the untreated check, aldicarb, and acephate treatments. Untreated check and aldicarb treatments had the lowest mite densities. Only aldicarb controlled mites compared to the untreated check. A twospotted spider mite host survey determined that henbit, Lamium amplexicaule L., was the most consistent and preferred host. Carolina geranium, Geranium carolinianum L., cutleaf geranium, Geranium dissectum L., vetch, Vicia spp., volunteer soybean, Glycine max L., purple deadnettle, Lamium purpureum L., and spiny sowthistle, Sonchus asper (L.) Hill, were other frequently infested dicotyledonous species. Herbicide burndown timing in reduced tillage cotton production was not critical, given all weeds were killed before cotton was planted. The herbicide glufosinate was efficacious against T. urticae, providing control equal to low- to mid-rates of labeled acaricides. Including glufosinate in a herbicide burndown program was only beneficial for mite control if living weeds were present at planting. Artificial infestation experiments were adversely affected by unseasonably wet and cool weather. Infestations established at the third true leaf resulted in an average yield loss of 44.7%. It is difficult to make any conclusions about infestations made from first bloom and later because of the difficulty in establishing mite populations later in the season.

No description available.

The two principal objectives of this study were: (i) to estimate and compare net revenue associated with alternative pest management strategies for Virginia soybean producers, and (ii) to compare attractiveness of different pest management options when net revenue risk is considered in conjunction with the corresponding level of expected net revenue. The method used to complete the first objective was to modify 1983 Virginia Cooperative Extension Service soybean budgets to correspond with alternative pest management strategies and then compare the average net revenue of the alternatives. The method used for completing the second objective was to develop a simulation model of net revenue for a representative Virginia soybean farm using alternative pest management strategies. Probability distributions of net revenue were generated and then compared using stochastic dominance analysis. Results from the net revenue comparisons of both expected net revenue and net revenue risk suggest that producers would prefer strategies which incorporate an integrated pest management (IPM) approach to pest control rather than an approach which relies completely on pesticides. Since pesticide usage is associated with negative environmental effects, the IPM alternatives, which in general decrease pesticide usage, would be preferred from the social as well as the private viewpoint. / M.S.

The studies described herein focused on the use of intermittent halogenation to control biofouling of water intake systems by the zebra mussel, Dreissena polymorpha, the comparative response of zebra mussels and the Asian clam, Corbicula fluminea, to a surfactant -based chemical control agent, the nontarget impact associated with the control agent, and the use of the Asian clam as a biomonitor of the control agent. Effects of intermittent (2-4 hr/day) treatments with chlorine or bromine at levels of 0.5 and 1.0 mg/L (total residual oxidant) upon settling of zebra mussel veligers were examined in studies conducted in a field laboratory on western Lake Erie. Veliger densities in the water column at the field site peaked at 530/L, while mussel densities on settling monitors reached 147,083/m² over the course of the study period. Zebra mussel settling in test systems treated with the halogens was reduced by as much as 91 % in comparison with controls, although mussel densities of up to 6,044/m² still occurred. Treated mussels which remained settled had growth rates similar to controls, and reached 2-4 mm length over 30 days. The intermittent halogen treatments had no significant impact on either adult zebra mussels or Asian clams. The studies indicate that while the treatment regimes may reduce zebra mussel densities within intake systems, the threat of eventual fouling due to cumulative settling remains. / Ph. D.

Studies were conducted on the penetration and permanence of 1.0% chlorpyrifos [0,0-diethyl 0-(3,5,6-trichloro-2-pyridyl) phosphorothioate], formulated as Dursban® TC (Dow Chemical Co.), in pine (Pinus spp.), spruce (Picea spp.), and fir (Abies spp.). Results indicated the highest degree of penetration in southern yellow pine. Surface roughness and orientation had an effect upon chemical penetration. Longevity studies ranging over time periods from three to 52 months revealed rapid loss of chlorpyrifos from the surface of the wood but relatively stable below-surface concentrations. Similar studies with 0.5% permethrin [(3-phenoxypheny]) methyl] (+) - cis, trans-3-(2,2-dichloroethenyl)-2,2dimethylcyclopropane-carboxylate] applied to the same wood types revealed comparable penetration differentials between types of wood. Formulation differences had little significant effect on penetration. One-year longevity studies revealed surface losses less drastic than those reported for chlorpyrifos, as well as superior below-surface stability. Studies employing volumes five, 10, and 25 times less than that required to achieve a runoff application revealed significantly lower chlorpyrifos penetration with reduced volume. Some reduced volumes resulted in below-surface concentrations of chlorpyrifos higher than the LC₉₀ value for Hylotrupes bajulus (Coleoptera: Cerambycidae). Toxicity testing with chlorpyrifos on first-instar larvae of H. bajulus, the old house borer, revealed contact LC₅₀ and LC₉₀ values of 14 ppm and 78 ppm, respectively. Similar tests with permethrin indicated LC₅₀ and LC₉₀ values of 2 ppm and 8 ppm. Tests with first-instar larvae on wood treated with 1.0% chlorpyrifos and 0.5% permethrin resulted in 100% mortality on wood aged for nine months in the case of chlorpyrifos, and six months in the case of permethrin. Tests utilizing H. bajulus eggs placed on treated wood revealed ovicidal properties of permethrin and lack of ovicidal effect with chlorpyrifos. Accelerated ageing studies employing an environmental chamber (40°C, 70% RH) at a 1:6 ratio of accelerated to natural weathering indicated no significant difference in surface or below-surface concentrations of permethrin in wood aged artificially for one month and in wood aged naturally for six months. Similar results were obtained with chlorpyrifos-treated wood artificially aged for 10 months and aged naturally for 4-1/3 years. Mathematical models were developed to predict surface and one millimeter concentrations of chlorpyrifos and permethrin after five and 10 years. / Ph. D.

Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2005. / The South African table grape industry exports approximately 60% of the table grapes produced. A major threat to the export of these grapes is the phytosanitary risk that insect pests pose. This study was conducted in the Hex River Valley, South Africa’s main table grape producing area. The aim of this study was to reduce the number of phytosanitary rejections from insects on table grapes from the Hex River Valley. Thus the main objectives of the study were to identify the most important phytosanitary pests in the Hex River Valley; the determination of their presence in the vineyards with possible means to control them; and to assess the possibility of using postharvest quarantine treatments in the Western Cape. Further aims were to determine the effect of different colour harvesting crates on the phytosanitary pests and whether the phytosanitary pests infested the grapes via packhouses. The most important phytosanitary pests of table grapes of the Hex River Valley are in order of importance: Phlyctinus callosus (Schonherr) (Coleoptera: Curculionidae), Epichoristodes acerbella Walker (Lepidoptera: Tortricidae), Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), Gonocephalum simplex Fabricius (Coleoptera: Tenebrionidae) and Dysdercus fasciatus Signoret (Hemiptera: Pyrrhocoridae). 12.71% of rejections were from species that were not identified, while a further 33% of the rejections were possibly identified incorrectly. Phytosanitary control of P. callosus appeared to be far more effective using Plantex® than pesticides. Weather conditions appeared to affect the abundance of P. callosus, especially warm weather, while bunches harboured less P. callosus later in the day. Control of E. acerbella with DiPel® (Bacillus thuringiensis var. kurstaki) appeared to at least reduce the population within the vineyards, and so its use is recommended. P. ficus is a non-actionable species for the USA market and is not listed as a phytosanitary pest for the Israeli market and so should not be causing any phytosanitary rejections. C. capitata appeared to be successfully controlled by the fruit fly sterile release program and the cold sterilisation it currently undergoes. G. simplex caused few rejections. It is still unclear where this pest infests the grapes, as it was found in both the field and in the packhouses. D. fasciatus occurrence on grapes was probably accidental. It was shown that picking during the early and late parts of the day, when this species was less active, reduced its occurrence in bunches. Gryllus bimaculatus (De Geer) (Orthoptera: Gryllidae), although not reported as a reason for rejections in table grapes for the past two years, was an actionable species that was present in large numbers in the Hex River Valley. There was a strong correlation between increasing quantities of pesticides and higher abundances of G. bimaculatus. It appeared to be an indicator of the overuse of pesticides. Results of this study showed that infestation by the phytosanitary pests came from neighbouring vineyards. The creation of barriers to prevent the movement of these pests between vineyards is suggested. Methyl bromide is the most commonly used postharvest quarantine treatment. Owing to the ozone-depleting properties of methyl bromide, it is scheduled to be outlawed in many countries from 2005. Alternative postharvest treatments are irradiation, extreme temperatures, forced air, vapour-heat treatments and the use of controlled atmospheres. Irradiation treatments appeared to control the pests at doses that do not damage the grapes. Controlled atmosphere treatments also have a high probability of success, although more research is required on this treatment. Low temperature treatments are relatively cheap as most exported fruit already undergoes cold storage, and appears to control species in the families Pseudococcidae and Tephritidae, although further research is required for the other pest. Colour or location of the harvesting crates in the vineyards appeared not to influence the number of phytosanitary pests collected, as they were not attracted to these crates.

Mozambique has potential to boost its banana exports. To fully realise this, agronomic practices in production should be fully developed to combat physiological disorders associated with banana within the region. Currently, lower temperatures are being experienced in some production sites, consequently affecting yield and quality. The objective of this study was to evaluate use of bunch protection covers on banana cultivars Grand Nain and Williams banana cultivars, for performance under different fruit protection materials to determine best fruit protection bag suitable for Metocheria, Nampula. Plants were not selected near plantation borders, drainage canals, cable way and roads, as this would influence the growth pattern of plants and fruit development. Treatments consisted of control (no bag on bunches), white perforated polyethylene, white non-perforated polyethylene, blue perforated polyethylene, blue non perforated polyethylene, green perforated polyethylene, green polyethylene non perforated and cheese cloth bags arranged in a complete randomised block designed CRBD with 26 plants replicated eight times. During 2012/2013, bagging treatments did not considerably improve weight in hands, banana finger weight, total fruit weight, marketable weight and percentage marketable fruit weight and box stem ratio (BSR) of Grand Nain. However there was reduction of fruit defects in all bagging treatments compared to control (no bags). In Williams during the 2013 season bagging treatments improved weight but no significant differences were observed on weight of hands in 2012. Bagging of banana bunches reduce defects in both seasons. Both green and blue perforated bags improved box stem ratio. Bagging treatments increased Williams‟s cultivar yield (per ton) in both seasons / Agriculture and  Animal Health / M. Sc. (Agriculture)