Consumption Of Bemisia Tabaci By Amblyseius Tsugawai And The Impact Of Prey On Its Reproduction

The whitefly,Bemisia tabaci,is an important agricultural pest worldwide that often causes severe injury to plants and is difficult to control.Using natural enemies to control whiteflies is a promising research direction,due to its specialist and environmental safety features.Many predatory mites among Phytoseiidae are effective biological control agents,among which some also have potential in whitefly control.Amblyseius tsugawai is a dominant phytoseiid species in China.Preliminary experiments showed this species comsume B.tabaci eggs.In the present study,functional response,prey preference,and life table parameters of A.tsugawai were estimated to evaluate its potential in whitefly control.Our results showed that A.tsugawai produce much fewer eggs and have lower emergence rate when fed with B.tabaci than when fed with T.urticae.We further estimated the impact of parental nutritional status and male age on reproduction of this species.Major results and conclusions of this study were listed as follows:Functional response of A.tsugawai females and males on the eggs and 1~stt instars of B.tabaci were estimated at 25±1℃.Except for males that hardly consume 1~stt instars B.tabaci,Holling’s type II functions were achieved in all other three treatments Na=1.151*Nt/(1+0.0587*Nt),Na=0.741*Nt/(1+0.2112*Nt),Na=0.973*Nt/(1+0.0910*Nt).The theoretical maximum daily consumption rate were 19.6,3.6,10.7 for females on eggs,males on eggs,and females on 1~stt instars,respectively.Overall,A.tsugawai showed higher concumption rates to the eggs of B.tabaci.Amblyseius tsugawai preferred eggs among B.tabaci stages,and preferred larvae among T.urticae stages.The prey preference(α)of A.tsugawai to B.tabaci eggs and T.urticae larvae were 0.75±0.06,and 0.89±0.05,respectively,when they coexisted.This result suggesting a random selection pattern between the two kinds of prey.Amblyseius tsugawai is able to complete its life cycle on either B.tabaci or on T.urticae,with its developmental durations being 7.05d and 6.75d,immature survival rates being 82.5%and 63.9%,respectively.Using T.urticae as prey,the total fecundity of A.tsugawai is 31.54,among which 57%are females,and the intrinsic rate of increase is 0.145.In contrast,using B.tabaci as prey,the total fecundity(4.55),proportion of female offspring(0.42),and intrinsic rate of increase(0.013)are all significantly lower.Although it is able to maintain the population on B.tabaci,the lower fecundity and emergence rate suggested B.tabaci is not an optimal prey for A.tsugawai.Two experiments were further conducted to investigate the impact of parental nutritional status and male age on reproduction.In the first experiment,individuals fed with either T.urticae or B.tabaci were allowed to mate with individuals either using the same or the different prey.When both the parents fed with T.urticae,the total fecundity is 30.33,proportion of female offspring is 0.61,and offspring immature survival is 80.80%.When only the male fed with B.tabaci,the total fecundity,proportion of female offspring,and offspring immature survival were 15.67,0.40,and 72.79%.In contrast,when only the female fed with B.tabaci,the three parameters were 4.07,0.32,38.89%,respectively.The lowest parameters(3.40,0.20,22.90)were achieved when both parents fed with B.tabaci.These results suggested both the nutritional condition of the male and female have significant impact on its reproduction capability,but greater negative impact was expected when the female is under poor nutritional condition.Its reproduction capability was further reduced when both the parents were under poor nutritional conditions.In the second experiments,newly emerged female adults were allowed to mate with males 0,5,10,20 d after emergence to investigate the male age on reproduction.Results showed significantly reduced reproduction capability in aged males,with total fecundity reduced from 30.33 to 18.47,and proportion of female offspring reduced from 0.61 to 0.56.In conclusion,Amblyseius tsugawai showed a higher concumption rate to the eggs of B.tabaci and is able to maintain the population on B.tabaci.It is a good predatory mite species for B.tabaci in China.In field application,A.tsugawai can be released with Encarsia formosa to have good effect in controlling B.tabaci.In addition,A.tsugawai can be reproduced with Carpoglyphus lactis as food.The feeding process is simple and the price is low.As a generalist predator,A.tsugawai can not only choose whitefly as prey,but also two-spotted spider mite or pollen.Therefore,we speculate that A.tsugawai can maintain a long-term control effect against B.tabaci in field.