Active Substances Of Mulberry To Larvae Of Plutella Xylostella And Spodoptera Exigua Growth Inhibition

Plutella xylostella and spodoptera exigua are major worldwild pests. At present, the main pests prevention in our country is chemical control, the long-term use of chemical pesticides cause serious consequences. In order to reduce and delay the resistance producing of plutella xylostella and spodoptera exigua, people began to use botanical pesticide. Mulberry contains DNJ and quercetin and so on many kinds of biological active substance, can effectively restrain glycosidase activity, can greatly reduce lepidoptera families to the harm of crop pests. This test selects main active substances DNJ and quercetin from mulberry, mixed made into different concentration of solution, water treatment as controls. Research the inhibition of the two kinds active substances to biological activity and enzyme activity of plutella xylostella and spodoptera exigua larvae, the main results are as follows:1. DNJ and quercetin all have apparent effect to selective food refusal and non-selective food refusal of the plutella xylostella larvae, food refusal rate increases with active substances concentration increase. Two kinds active substances all have obvious growth inhibition rate to the plutella xylostella larvae, the effect of quercetin is slightly less than DNJ. DNJ and quercetin have the same effect of contact toxicity and stomach toxicity to experiment insect, and the mortality of stomach toxicity is higher than contact toxicity. Pupate rate of experiment insect decrease with active substances concentration increase, even there is no insect pupate in high concentrations.2. Because the spodoptera exigua larvae has a larger body, so there has more significant results of the two active substances on its food refusal rate and the growth inhibition rate, the decline range of experiment insect eating area and weight is more. Through the calculating the mortality rate and Adjusted mortality rate we know that two active substances have a obvious function of contact toxicity and stomach toxicity on spodoptera exigua larvae, and the mortality of stomach toxicity is higher than contact toxicity in general. The spodoptera exigua larvae have a stronger ability than plutella xylostella larvae in resistance to the pupate inhibition of active material act on experiment insect.3. Under the action of two kinds active substances, the protective enzyme SOD, POD and CAT activity of two kinds experiment insect increase, and the internal protein content decrease. But the sustainability of quercetin effect is poorer, the effecting time of inhibition is longer. DNJ have a obvious inhibition in PO relative activity of two kinds experiment insect, quercetin have a obvious inhibition in PO relative activity only in spodoptera exigua larvae who have a larger body.4. Coarse extract NAGase from spodoptera exigua larvae, DNJ have a obvious inhibition in NAGase activity, confirm DNJ is a-glycosidase enzymes inhibitors. Compared with DNJ, the inhibition effect in NAGase activity of quercetin is limited.