Stage and Age Influence on the Susceptibility of Coccinella Septempunctata (Coleoptera: Coccinellidae) after Direct Exposure to Neemix, a Neem Insecticide

Abstract

The effects of Neemix 4.5 EC on predatory Coccinella septempunctata L. larvae were determined after direct spray exposure. First instars were treated by direct application with 0, 40, 100, 200, 400, 600, and 1,000 ppm and 4th instars were treated with 400, 600, 800, and 1,000 ppm azadirachtin, the active ingredient in Neemix. Survivorship and development of the larvae were affected in a dose-dependent manner. Symptoms of exposure included delay or prevention of pupation, blackening of the pupal case, formation of pupal-adult intermediates, and deformation of wings and elytra in adults. To account for the slow action of the pesticide, probit analysis of survivorship data was performed after all surviving larvae from each replicate had emerged as adults: day 16 for 1st instars and day 13 for 4th instars. The LCso values and 95% FL for 1st and 4th instars were estimated to be 1,120 (719-3,677) ppm and 520 (405-600) ppm azadirachtin, respectively. These values were much higher than the recommended rates for control of aphids (3 weekly applications of 20 ppm), suggesting that Neemix might be used in integrated pest management programs because application of rates that control aphids should not result in appreciable mortality of predators. The slopes and intercepts of the probit regression lines were significantly different, indicating that the 2 instars responded to the pesticide differently. Fourth-instar C. septempunctata were innately more sensitive to the growth disrupting effects of acute exposure to Neemix than 1st instars. Disruption of morphogenetic hormone levels is more critical immediately before metamorphosis than during early instars, thus accounting for the differential susceptibility observed. It may be possible for early instars to sustain the effects of Neemix as long as the pesticide is detoxified before the onset of pupation. Our results suggest that it is extremely important to examine> 1 life stage of a species to estimate the total effect of pesticides.

Indirect Effects of Pesticides on Natural Enemies

“…Likewise, as also demonstrated by [124], development time of Coccinella septempunctata larvae was indirectly affected in a dose-dependent manner with fourth instar larvae more sensitive to azadirachtin than first instar larvae, which suggests that any indirect effects may be stage and age specific. As such, azadirachtin may be more indirectly harmful to nymphs and larval instars than adults under laboratory conditions whereas under semi-field or field conditions any indirect effects associated with these life stages are nullified [115].…”

Bio-rational control of red flour beetle Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in stored wheat with Calneem® oil derived from neem seeds

“…Generally, IGR effects are more consistent between species than antifeedancy effects (Nicol and Schmutterer 1991;Mordue and Blackwell 1993;Mordue 1998). Azadirachtin, the major component in neem, inhibits the release of prothoracicotropic hormones and allatotropins, thereby affecting metamorphosis in insects (Banken and Stark 1997). In our studies, the growth regulator effect was demonstrated by low mortality of late larvae and pupae exposed to 0.5% Calneem Ò compared to egg and early larvae.…”

Control of green apple aphid (Aphis pomi De Geer) in organic apple production

“…However, azadirachtin causes various toxic and/or harmful sublethal effects on Coccinellidae species (Banken andStark, 1997, 1998;Bernardo and Viggiani, 2002). In view of a risk of harming predator populations, bioinsecticide use needs to be restricted to a necessary minimum.…”