Neonate larvae sensitivity

External excitatory and inhibitory stimuli for acceptance or rejection of food are modified by the internal condition of the insect (e.g., hunger). This modification can cause a given stimulus to produce different responses, depending upon the internal condition of the insect. After host acceptance, there are still obstacles that the insect must overcome in order to survive, grow, and reproduce. These hurdles include allelochemicals that block nutrient availability, defenses of susceptible plants, poor balance of essential nutrients, and less than optimal water content. Neonate larvae may be far more sensitive to some of these obstacles than older ones. 

The physical handling of insect larvae is a common practice in rearing programs. In Table 1, neonates that were picked up with a paint brush shortly after eclosion grew more slowly and weighed less than undisturbed larvae 10 days later. This sensitivity decreases with age but still can be demonstrated many hours following emergence. 

Reese (37) has studied nutrlent-allelochemical Interactions using diets supplemented by plant extracts. He has concluded that many of the deleterious effects may be due primarily to various Interactions between these allelochemical and essential nutrients. It Is Important to not only consider the presence of nutrients, but also the bloavallability of these nutrients to the phytophagous Insect. He cited findings where neonate larvae were found more sensitive to plant allelochemicals than older larvae, and Interpreted the greater resistance of the older larvae In terms of Increasing capability to utilize available nutrients, probably because of the Induction of enzymatic detoxification systems. 

Bt used in spray-on formulations is, perhaps, the most successful biopesticide. Reasons for Bt s success include ease of handling and a very high specific activity against sensitive insects. For example, a Bt insecticidal protein called CrylAc has a LCjq on Heliothis virescens neonate larvae as low as 0.07 ppm [10]. However, most individual Bt insecticidal proteins have a narrow activity spectrum. As mentioned, CrylAc is very active against H. virescens, while another Bt toxin called CrylCa is not. CrylCa is active against Spodoptera exigua, but CrylAc is not. This is perhaps... 

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