Insects diamondback moth Plutella

Insects have evolved resistance to Bt toxins in the laboratory, yet only one crop pest, the diamondback moth (Plutella xylostella), has evolved resistance to Bt toxins under open field conditions (Tabashnik et al. 2003). But this resistance was not caused by Bt crops, rather it occurred in response to repeated foliar sprays of Bt toxins to control this pest on conventional (non-GE) vegetable crops (Tabashnik 1994). Based partly on the experience with diamondback moth and because Bt crops cause season-long exposure of target insects to Bt toxins, some scientists predicted that pest resistance to Bt crops would occur in a few years. 

Using 3rd instar larvae of the diamondback moth Plutella xylostella), the antifeedant and insecticidal activities of sixteen quassinoids were compared with those of known insect antifeedant chlorodimeform (= galecron), as shown in Table 16. The insecticidal activity of quassin (78) was higher than that of chlorodimeform, although its antifeedant activity was nearly identical to that of the reference compound [39]. 

For the diamondback moth, Plutella xylostella (syn. A. maculipennis) (another crucifer-feeding insect), (2/ )-hy-droxy-3-butenylglucosinolate (progoitrin) (21) was more effective than other glucosinolates in inducing feeding on artificial diets. 

Pyridalyl controls a wide variety of lepidopterous pest strains such as the diamondback moth (Plutella xylostella) which is resistant to various existing insecticides (8). This insecticide is also effective against thysanopterous pests. Moreover, it does not exert an adverse effect on various beneficial arthropods such as natural predator insects (e.g., Oristar-A ) and honeybees. Therefore, this novel insecticide is expected to be a usefiil material for controlling lepidopterous and thysanopterous pests in IPM and insecticide resistant management programs. 

An example of a larval parasitoid that responds to the host sex pheromone is seen with Cotesiaplutellae (Braconidae), also a parasitoid of the diamondback moth. These insects were attracted equally to the pheromone blend (31,32,33, see above), the acetate 32, or aldehyde 31 components [80]. This larval parasitoid, however, was also strongly attracted to host frass volatiles, in particular, dipropyl disulfide 34, dimethyl disulfide 35, allyl isothiocyanate 36, and dimethyl trisulfide 37. In contrast, the egg parasitoid Trichogramma chilonis was only weakly attracted to 36. In both, T. chilonis and C. plutellae, plant volatiles, in particular (3Z)-hex-3-en-l-yl acetate 38, significantly enhanced attraction by the pheromone [80]. 

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. 

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