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Field Rate (field + rate)
Selected AbstractsEffects of the herbicide hexazinone on nutrient cycling in a low-pH blueberry soilENVIRONMENTAL TOXICOLOGY, Issue 2 2004D. M. Vienneau Abstract The herbicide hexazinone was applied as the commercial formulation Velpar® L at field-rate (FR) concentrations of FR (14.77 ,g ai g,1), FR×5 (73.85 ,g ai g,1), FR×10 (147.70 ,g ai g,1), FR×50 (738.50 ,g ai g,1), and FR×100 (1477.00 ,g ai g,1) to acidic soil, pH 4.12, taken from a lowbush blueberry field. Hexazinone was tested for inhibitory effects on various transformations of the nitrogen cycle and soil respiration. Nitrogen fixation was unaffected by hexazinone levels up to FR×100 following a 4-week incubation period. Ammonification was initially inhibited by all levels of hexazinone, but after 4 weeks, ammonification in all treatment systems was equal to or greater than the control. Nitrification was more sensitive to hexazinone; however, application at a field-rate level caused no inhibition. Inhibitory effects were noted above FR after a 2-month endpoint analysis and above FR×5 after a 6-month endpoint analysis. Hexazinone concentrations up to and including FR×100 stimulated denitrification. Soil respiration was also stimulated over a 3-week period when applied at a level up to 100 times the recommended field rate. In general, it was found that when applied at the recommended field application rate, hexazinone does not adversely affect the nitrogen cycle or soil respiration in acidic lowbush blueberry soils. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 115,122, 2004 [source] Orientational disruption of codling moth, Cydia pomonella (L.) (Lep., Tortricidae), by concentrated formulations of microencapsulated pheromone in flight tunnel assaysJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2005L. L. Stelinski Abstract:, The effects of two formulations of microencapsulated pheromone (CheckMate CM-F), containing 14.3% (E,E)-8,10-dodecadien-1-ol (codlemone), on the behaviour of the male codling moth, Cydia pomonella (L.), were evaluated in a flight tunnel after several periods of formulation ageing. The two treatments of CheckMate CM-F evaluated consisted of the label-recommended field rate of 50 g active ingredient (a.i.)/ha diluted in: (1) a standard 1000 l of water (low concentration 0.05 g/l), and (2) a low volume of 100 l of water (high concentration 0.5 g/l). The low-concentration treatment was formulated by diluting 0.071 ml of CheckMate CM-F in 500 ml of water and the high-concentration treatment contained 0.71 ml of CheckMate CM-F in 500 ml of water. Wax-paper strips (2.1 × 20 cm) were treated at 0.06 ml of solution/cm2. The mean (±SE) number of CheckMate CM-F microcapsules adhering to treated wax-paper strips in the high-concentration treatment (398 ± 38) was sevenfold greater than that (57 ± 5) counted on wax-paper strips treated with the low concentration. Both low- and high-concentration treatments prevented anemotactic orientation of male codling to an adjacent 0.1 mg codlemone lure for up to 24 h after application. These moths flew out of the release cages, but exhibited erratic and short flights not restricted to any plume and ending at the tunnel walls or the floor. This occurred with approximately 60 and 400 microcapsules per wax-paper strip in the low- and high-concentration treatments, releasing codlemone at approximately 0.15 and 1.5 ,g/h respectively. After 2 days of ageing, the low-concentration treatment no longer interfered with the ability of males to find the codlemone lure. However, the number of males contacting the lure was significantly reduced for up to 6 days with the high-concentration treatment relative to the control and low-concentration treatments. The high-concentration treatment no longer impeded normal orientational flight after 2,6 days of ageing; but, it diverted males from the codlemone lure by causing them to land on the adjacent treated wax-paper strips. This occurred at a release rate of approximately 0.7 ,g codlemone/h from approximately 400 microcapsules per wax-paper strip distributed as clumps of approximately 30 microcapsules per 14 mm2. We suggest that an initial but short-lived disruption mechanism like camouflage is followed by a longer period of false-plume following to clumps of microcapsules. The low-volume, concentrated application method for disseminating pheromone microcapsules warrants further investigation for moth codling, as well as other pests because this approach may improve the efficacy without the need for increasing the field application rate. [source] Toxicity of insecticides to the sweetpotato whitefly (Hemiptera: Aleyrodidae) and its natural enemiesPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 7 2007Leandro Bacci Abstract Efficient chemical control is achieved when insecticides are active against insect pests and safe to natural enemies. In this study, the toxicity of 17 insecticides to the sweetpotato whitefly, Bemisia tabaci (Gennadius), and the selectivity of seven insecticides to natural enemies of this insect pest were evaluated. To determine the insecticide toxicity, B. tabaci adults were exposed to abamectin, acephate, acetamiprid, cartap, imidacloprid, malathion, methamidophos, bifenthrin, cypermethrin, deltamethrin, esfenvalerate, fenitrothion, fenpropathrin, fenthion, phenthoate, permethrin and trichlorphon at 50 and 100% of the field rate (FR), and to water (untreated control). To determine the insecticide selectivity, adults of Encarsia sp., Acanthinus sp., Discodon sp. and Lasiochilus sp. were exposed to abamectin, acephate, acetamiprid, cartap, imidacloprid, malathion and methamidophos at 50 and 100% FR, and to water. Groups of each insect species were exposed to kale leaves preimmersed in each treatment under laboratory conditions. Mortality of exposed individuals was recorded 24 h after treatment. Cartap and imidacloprid at 50 and 100% FR and abamectin and acetamiprid at 100% FR showed insecticidal activity to B. tabaci adults. Abamectin at 50 and 100% FR was the least insecticidal compound to the natural enemies Acanthinus sp., Discodon sp. and Lasiochilus sp. The present results suggest that abamectin at 100% FR may decrease B. tabaci field populations but can still be harmless to predators. Implications of these results within an integrated pest management context are discussed. Copyright © 2007 Society of Chemical Industry [source] Sublethal responses of wolf spiders (Lycosidae) to organophosphorous insecticidesENVIRONMENTAL TOXICOLOGY, Issue 5 2002S. Van Erp Abstract The activities of cholinesterase (ChE) and glutathione S -transferase (GST) enzymes were assessed in the wolf spider (Lycosa hilaris) as biomarkers of organophosphate contamination in agricultural ecosystems. Spiders were exposed to simulated field rates of two commercially available organophosphorous insecticides [Basudin (diazinon) and Lorsban (chlorpyrifos)] under laboratory conditions. In terms of survival, chlorpyrifos and diazinon were more toxic to male than to female wolf spiders, but gender-specific differences in ChE activities were not evident. Cholinesterase activity in male spiders was inhibited to 14% and 61% of control activity by Basudin and Lorsban, respectively. Gluthathione S -transferase activity was not affected by either pesticide. Mortality and biomarker responses in the wolf spider were further investigated following the application of Basudin to pasture. Wolf spiders were deployed into field mesocosms; after 24 h mortality was 40%, and surviving spiders displayed significant inhibition of ChE activity (87%) compared with controls. Cholinesterase activity in spiders exposed for subsequent 24- or 48-h time periods was monitored until it returned to control levels 8 days post-application. Inhibition of ChE activity after a single application of Basudin indicate the potential use of this enzyme in wolf spiders as a biomarker for evaluating organophosphate contamination. © 2002 Wiley Periodicals, Inc. Environ Toxicol 17: 449,456, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.10078 [source] BEHAVIORAL ADAPTATIONS INCREASE THE VALUE OF ENEMY-FREE SPACE FOR HELIOTHIS SUBFLEXA, A SPECIALIST HERBIVOREEVOLUTION, Issue 4 2002Sara J. Oppenheim Abstract We investigated the importance of specialized behaviors in the use of enemy-free space by comparing the host-use behavior of two closely related moths, Heliothis subflexa Guenee and H. virescens Fabricius. Heliothis subflexa is a specialist on plants in the genus Physalis, whereas H. virescens is an extreme generalist, feeding on plants in at least 14 families. Heliothis subflexa uses the inflated calyx surrounding Physalis fruits as enemy-free space, and field rates of parasitism for H. subflexa on Physalis are much lower than for H. virescens on tobacco and cotton, common hosts found in the same habitat as Physalis. If Physalis' architecture were solely responsible for H. subflexa's low rates of parasitism on Physalis, we predicted thatH. virescens larvae experimentally induced to feed on Physalis would experience parasitism rates similar to those ofH. subflexa. We found, however, that specialized host-use and host-acceptance behaviors are integral to the use of enemy-free space on Physalis and strongly augment the effects of the structural refuge. In laboratory assays, we found considerable differences between the larval behavior of the specialist, H. subflexa, and the generalist, H. virescens, and these contributed to H. subflexa's superior use of enemy-free space on Physalis. We tested the importance of these behavioral differences in the field by comparing parasitism of H. virescens on Physalis, H. virescens on tobacco, and H. subflexa on Physalis by Cardiochiles nigriceps Vierick, a specialist braconid parasitoid. For H. virescens, a threefold decrease in parasitism occurred when feeding on Physalis (mean parasitism ± SEM = 13 ± 4%) rather than tobacco (43 ± 4%), a difference we attribute to the structural refuge provided by Physalis. However, parasitism ofH. virescens on Physalis was more than ten times as great as that of H. subflexa on Physalis (1 ± 4%), supporting the hypothesis that specialized behaviors have a substantial impact on use of Physalis as enemy-free space. Behavioral adaptations may be central to the use of enemy-free space by phytophagous insects and may act as an important selective force in the evolution of dietary specialization. [source] | ||||||||||