Anastrepha ludens (Loew) (Diptera: Tephritidae) is an important pest of mango and citrus in Mexico. Here, we report the effect of the entomopathogenic fungus Metarhizium anisopliae (Metsch.) Sorokin strain MAAP1 on mortality and food consumption in A. ludens adults. Experiments were carried out under laboratory conditions at 26 ± 2 °C, 60 ± 5% RH and 12:12 photoperiod. To assess pathogenicity and sublethal effects, we sprayed flies with 1 × 109 conidia/ml and 1 × 106 conidia/ml solutions, respectively. Food consumption was measured by providing known amounts of food through capillary tubes to caged flies. We found that M. anisopliae was highly virulent to A. ludens, causing 92.3 ± 0.62% mortality at day 13 post-exposure. Interestingly, food consumption reduced by 17% in flies exposed to the fungus. These results support the implementation of M. anisopliae within current strategies used for the integrated pest management of A. ludens.

Soybean [Glycine max (L.) Merr. ‘Hark’] plants responded similarly to a sublethal application of metribuzin [2-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] or to low light intensities. Both treatments increased soluble amino acid, ATP, nitrate reductase, and nitrate levels (up to 67, 140, 190, and 10,000%, respectively) and decreased soluble reducing sugars (33%), malate levels (86%), and the chlorophyll a/b ratio (24%). The similar response of light-limited and of chemically photosynthesis-inhibited plants is thought to be induced by a carbohydrate stress or another parameter related to a decreased rate of photosynthetic electron flow. However, during the induction process in shaded plants, light quality might play an important role in some cases. The results obtained with metribuzin and soybean plants are compared to and discussed together with (a) the results obtained by other authors working with s-triazine herbicides and (b) results obtained with methabenzthiazuron [N-(benzothiazol-2-yl)-N,N′-dimethylurea] in earlier experiments.

The aphid species Sitobion avenae and Rhopalosiphum padi are the most important pests in wheat growing regions of many countries. In this study, we investigated the sublethal effects of imidacloprid on fecundity, longevity, and enzyme activity in both aphid species by comparing 3-h exposure for one or three generations. Our results indicated that 3-h exposure to sublethal doses of imidacloprid for one generation had no discernible effect on the survival, fecundity, longevity, or enzyme activity levels of aphids. However, when pulse exposures to imidacloprid were sustained over three generations, both fecundity and longevity were significantly decreased in both S. avenae and R. padi. Interestingly, the fecundity of R. padi had almost recovered by the F5 generation, but its longevity was still deleteriously affected. These results indicated that R. padi laid eggs in shorter time lags and has a more fast resilience. The change in reproduction behavior may be a phenomenon of R. padi to compensate its early death. If this is stable for the next generation, it means that the next generation is more competitive than unexposed populations, which could be the reason underlying population outbreaks that occur after longer-term exposure to an insecticide. This laboratory-based study highlights the sublethal effects of imidacloprid on the longevity and fecundity of descendants and provides an empirical basis from which to consider management decisions for chemical control in the field.

Lufenuron, N–[2, 5–dichloro–4–(1, 1, 2, 3, 3, 3– hexafluoropropoxy) –phenylaminocarbonyl]–2, 6–difluorobenzamide, a novel acylurea insect growth regulator, exerted significant sublethal effects in larvae, pupae and adults of the diamondback moth, Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae). Second, third and fourth instars were treated at their respective LCM using a standard 'leaf–disc dip' method of bioassay. Sizes and weights of pupae from the treated lots were significantly reduced but larval and pupal durations remained unaffected. All the pupae formed from larvae treated as fourth instars were deformed and produced no adults. Only 38 and 14% of adults emerged from the pupae formed following treatment at the second and third instar, respectively, as compared to 88–92% adult emergence in the controls. Apart from significant reduction in body length, some adults from the treatments had fringed and twisted wings which prevented normal flight. IGR treatment also resulted in pronounced reduction in fecundity (up to 10.2 eggs per female in comparison with 135.8 per female in the control) and oviposition periods (up to 3.2 days in comparison to 7.8 days in the control). Field trials to investigate the management of P. xylostella using lufenuron are recommended.

Mortality is the most extreme effect of ultraviolet-B radiation (UV-B; 280–315 nm) on living organisms, but sublethal effects of UV-B may also be important. Moreover, there may be population differences in response to UV-B, but this aspect has not been well explored for animal populations. Amphibians have been a model system for studying the detrimental effects of UV-B. However, previous research on the effects of UV-B on amphibians has mainly focused on embryos. Few studies have investigated how UV-B affects larvae. We examined potential sublethal effects of UV-B on the long-toed salamander Ambystoma macrodactylum from two different populations. Observational data from field transects indicated that larvae are potentially exposed to UV-B in their natural habitat. Choice tests indicated that larvae select shaded regions more often than those in the sun, but do not directly distinguish between regions with high and low UV-B. Laboratory experiments indicated a survivorship difference between individuals from low- and high-elevation sites. When exposed to relatively low levels of UV-B individuals from low-elevation sites experienced higher mortality than controls (no UV-B). There were no differences in mortality between UV-exposed and non-exposed larvae from the high-elevation population. Although mortality of UV-B exposed larvae was not significantly different from controls in the high-elevation population, sublethal effects on growth were observed. Individuals from the high-elevation site grew significantly less when exposed to UV-B than individuals shielded from UV-B. Our study demonstrates that larval A. macrodactylum are exposed to UV-B in nature, that UV-B exposure can cause mortality as well as having sublethal effects on growth and that there are potential population differences in sensitivity to UV-B radiation.

Gravid Lucilia treated topically with ivermectin (0.05μg/g, which represented approx. 4% of the 48 hr LD50) laid fewer viable egg batches (less than 50% of controls) and more sterile ones, when compared to untreated (P = 0.019) and acetone-treated flies (P = 0.028). This effect was also seen when mature third instar larvae were dosed with 7.6 μ g ivermectin/g (P = 0.0075 and 0.016 respectively); number of viable egg batches produced were only 25% of the number laid by the progeny of untreated larvae.

Dosage with fenthion stimulated an increase in the number of viable egg batches laid when incorporated in the original larval feeding medium at 0.2 μg/g liver; fewer viable egg batches were laid by the flies which developed from mature larvae treated with 7.6 μ g fenthion/g. Acetone solvent alone had a mild stimulatory effect on topically dosed flies.

Tanzanian strains of Tribolium castaneum (Herbst), Gnatocerus maxillosus (F.), Sitophilus oryzae (L.) and Sitophilus zeamais Motschulsky were confined to maize grain treated with a dilute dust of permethrin at the rates of 1.5, 3.0 and 6.0 ppm active ingredient. The adult mortality and resulting F1 generation were recorded. G. maxillosus was very susceptible to the insecticide and even the lowest dose brought complete control. T. castaneum adults survived all treatments but few F1 were produced. Adult survival of s. oryzae and S. zeamais was progressively reduced by increasing dosage, although S. zeamais was much less susceptible to the treatment than S. oryzae.

The repellency of grain, treated with 3.0 ppm permethrin, to S. oryzae, S. zeamais and T. castaneum was tested in a simple choice chamber. Neither male nor female T. castaneum were repelled but significantly fewer eggs were laid on treated grain. For both Sitophilus spp there was no significant difference between the numbers of females or eggs observed on treated or untreated grain, but males were repelled from permethrin.

The importance of these results is discussed in relation to a recent recommendation that the treatment of shelled grain with 3.0 ppm permethrin should be adopted in Tanzania in order to control Prostephanus truncatus (Horn), a new and serious storage pest.