Insect mortality

Insects % Mortality DDT DFDT Dosage Experimental Period, Hours Reference... 

It was realized also that the carbon tetrachloride in the aerosol might in itself be a factor in the insect mortality which resulted. Therefore parallel tests were run in several instances in which carbon tetrachloride was omitted, and it was concluded that in the mixtures DDT was the principal toxic ingredient, at least when dispersed as a thermal aerosol. 

One aspect of the deposited spectrum which is of particular practical significance is its relationship to the evaporated emitted spectrum. We have seen that the evaporated vmd is approximately 58 y a value considerably lower than is commonly used with ultra low volume applications. Yet, of 5000 droplets sized on fir needles 90A% were smaller than 60 y. Since this method of application has proven efficacious over millions of hectares of New Brunswick forest, one must conclude, yet again, that small drops are not merely effective but, in all likelihood, are responsible for the bulk of insect mortality. 

The positive p values of these correlations for reactions of substituted phenyl phosphates may indicate a common feature in these reactions where a nucleophilic attack on phosphorus is a critical step. The magnitudes of the p values of Equations 13 and 14 are very close to each other but significantly larger than that of Equation 12. Thus, the electronic effect of the substituents on the insect mortality can be related mostly to an effect on the enzyme inhibition and plays only a minor role in the... 

These compounds were tested against a series of Lepidoptera including Plutella xylostella Px, diamondback moth), Hdiothis virescens Hv, tobacco budworm), and Spodopterafrugiperda (Sf, fall armyworm). Insecticidal activity is reported in Tables I-111 as percent plant protection at various concentrations where reduction in plant damage generally resulted from insect mortality rather than cessation of feeding. 

Studies carried out on the protease content of the gut of different Coleoptera have shown the presence of cysteine proteases, which, in many cases, represent the major class of digestive proteases [33]. The cDNA of OC-I, a rice cysteine PI, has been constitutively expressed in different plant species. When expressed to a level of 1 percent of the soluble proteins in poplar, it causes an increase in insect mortality however, this lethal effect is observed mainly at the end of the larval stages [34]. A significant growth reduction in Colorado potato beetle larvae was observed when OC-I was expressed in potatoes [35]. However, OC-I expression in oilseed rape failed... 

The insecticidal effects of heartwood flavonoids have also been studied in recent years. Again, the isoflavonoids show significant toxic effects on several insect pests. It is interesting that those isoflavonoids that are especially fungitoxic are those that show the most dramatic effects on insect mortality in laboratory experiments (16, 34). 

A pioneer study of the distribution of this substance in the tissues of rats to which it had been fed was made by Laug (3). He evaporated ether extracts in Erlenmeyer flasks, so that a deposit was left over the bottom. Female houseflies were confined in the flasks, and the mortalities after 20 hours were compared to those obtained with known amounts of 7-hexachlorocyclohexane. Because most of the inner surface of the flask was untreated, the flies were out of contact with the toxicant during an unknown fraction of the exposure period. The exposure period was so long that the insects had to be fed dur-... 

The flaking off of very heavy deposits—e.g., of < -, / -, or 7-hexachlorocyclohexane or of p,p -DDT—sets a limit to the amounts to which insects can be exposed in the vials. In this respect the present procedure differs sharply from those in which the toxicant is applied to a piece of filter paper or other porous material. Under such conditions enormous amounts may be employed, but a large percentage is completely removed from contact with the test insects and dosages so determined for 50% or any other mortality have little meaning. 

Accessibility of the deposit to the insects by contact is the chief feature of the small vial method, but fumigant action cannot be eliminated entirely. In the case of DDT this has been found to be unimportant, for flies kept in the vials out of contact with the surface are not affected. But with 7-hexachlorocyclohexane or parathion there is a noticeable toxic effect. If the vials are stood upright, laid on the side, or hung upside down, there is a decrease in the mortality produced in the order given. The position on the side has been adopted because it avoids extremes and because practical use of an insecticide often involves limited but not accentuated ventilation. 

Roaches have also been used in studying the length of time for which deposits of dieldrin are active (7). Table IX gives some of the data obtained using the German roach as the test insect. In this case, the toxicants were applied at the rate of 1 mg. per 1000 sq. cm. of surface the table lists the mortalities obtained when the insects were left on surfaces of various ages for periods of 24 and 48 hours. DDT is not included in this tabulation, because it is inactive at the dosage rates tested. 

In yet another application of plant virus peptide presentation systems, Borovsky [52] used TMV to present a peptide, trypsin modulating oostatic factor (TMOF), that terminates trypsin biosynthesis in the mosquito gut and causes larval mortality. This unique study uses plant virus particles for the biological control of insect pests. 

Overgaard, N.A., L.R. Barber, D.F. Walsh, R.E. Mapor, G.D. Hestel, and J.E. Gates. 1983. Evaluation of Modified Powr-Till Seeder for Soil Incorporation of Carbofuran to Provide Insect Control and Minimize Bird Mortality in Pine Seed Orchards. U.S. Dep. Agric., Forest Serv., South. Reg., Tech. Publ. R8-TP3. 35 pp. 

After 63 days, 46-55% mortality in centrarchid populations, and 75% reduction in insect populations of caddisflies, mayflies, and midges (Macek et al. 1972)... 

Toxaphene is extremely toxic to freshwater and marine biota. In laboratory tests of 96-h duration, 50% mortality was recorded for the most sensitive species of freshwater and marine teleosts, marine crustaceans, and freshwater insects at nominal water concentrations of less than 10 pg/L of toxaphene, and, in several cases, less than 1 pg/L (Table 27.2). Bioassays of longer duration, based on exposure of aquatic organisms for the entire or most of the life cycle, produced significant adverse effects on growth, survival, and reproduction at toxaphene concentrations between 0.025 and 1.0 pg/L (Table 27.3). Toxaphene was most toxic to freshwater fishes in soft water at elevated temperatures (Saleh 1991). Based on its high toxicity and extensive use, it is not surprising that toxaphene was considered a major cause of nationwide fish kills in 1977 (USEPA 1980b). 

Sodium molybdate and other molybdenum compounds in toxic baits have potential for termite control (Brill et al. 1987). Baits containing 1000 mg Mo/kg were fatal to 99% of the termite Reticu-litermes flavipes in 48 days. After 8 to 10 days, termites became steel-gray in color, but appeared otherwise normal. Mortality began only after day 16. Termites did not avoid the poisoned bait, even at concentrations of 5000 mg Mo/kg. Yoshimura et al. (1987) reported similar results with another species of termite sodium molybdate killed 100% of the workers in a colony of Copotermes formo-sanus within 24 h after eating filter paper treated with a 5% solution. Some other species of insects — including fire ants (Solenopsis sp.) and various species of beetles and cockroaches — were not affected when exposed to baits containing 5000 mg Mo/kg for 48 days (Brill et al. 1987). 

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