Effects of heat stresses on fitness of three commercial predatory mites

To explore the performances of predatory mites under high temperature, we selected three predatory mites Amblyseius orientalis, Neoseiulus californicus and Neoseiulus barkeri to investigate the survival rate, development duration and fecundity after their eggs and female adults were treated with high temperatures. The results showed that both eggs and adults of N. barkeri were most tolerant to heat stress than N. californicus and A. orientalis. After heat treatment of 39°C on egg, three predatory mites all presented shorter developmental period and longevity as well as lower fecundity. The oviposition period of N. californicus was shortened by nearly 50% and the total egg production of A. orientalis decreased by about 40%. However, the N. barkeri was the least affected by high temperature with its fecundity reduced by only 30%. The short-term high temperature treatment at adult stage also had negative effect on the oviposition period and longevity. The oviposition period of A. orientalis was reduced from 18.26 days to 3.82 days at 39℃, and 100% mortality occurred at 40°C. The longevity of N. californicus and N. barkeri suffered at 40℃ was shortened by about 50%. Our study confirmed that N. barkeri is tolerant to high temperatures at some extent, while A. orientalis is more heat sensitive in either two life stage. In sum, the understanding of the heat resistance of commercial predatory mites can improve the better application of biocontrol agents when selecting mite species for pest mite control in the field.