Effects Of Mixed Prey System On Bioefficacy Of Neoseiulus Barkeri (Acari:Phytoseiidae)

In recent years,the application of predatory and parasitic natural enemies in pest control has received extensive attention.Neoseiulus barkeri is one of the excellent predatory mites which has been commercialized in China,and has a high prevention and control effect against small sucking pests such as Tetranychus urticae,Thrips palmi,and Bemisia tabaci.However,most of the research focus on single predator-single prey systems,while the control efficiency of natural enemies is often affected by complex ecosystems and variety of insect pests in the field,resulting in unstable control and prevention effects.For example,B.tabaci occur together with T.urticae in the Vigna unguiculata,and T.palmi occur together with B.tabaci in the Solanum melongena.The objective of the present study was to evaluate the control efficiency of N.barkeri against a variety of pests that occur simultaneously on vegetables.Experiment with three kinds of commonly harmful organisms?T.urticae,T.palmi and B.tabaci?–N.barkeri as the research system,the main research is to investigate prey preference,prey patch selection and oviposition site selection,as well as the effect of the prey type?single or mixed?on development and reproduction of N.barkeri.The main results are as follows:1 Prey preference of N.barkeri feeding on different preysThe prey preference of N.barkeri when offered different stages of prey or different prey species was studied by using small cages.The results showed that:in the different stages of T.urticae,N.barkeri showed a slight tendency to feed on larvae of T.urticae compared with eggs and protonymphs,and in the different stages of B.tabaci,N.barkeri significantly preferred B.tabaci eggs to B.tabaci 1^st instar nymphs.In feeding on larvae of T.urticae and eggs of B.tabaci,the predatory mite preferred the larvae of T.urticae??=0.72?.When feeding on eggs of B.tabaci and1^st instar nymphs of T.palmi,the predatory mite preferred the eggs of B.tabaci??=0.59?.In feeding on larvae of T.urticae and 1^st instar nymphs of T.palmi,the predatory mite preferred the larvae of T.urticae??=0.73?.The prey preference of N.barkeri to three prey species was ranked in descending order:larvae of T.urticae?eggs of B.tabaci?1^st instar nymphs of T.palmi.2 The preference of feeding sites and oviposition sites between different prey systemsThrough the experiment of wax bridge,we studied the selection of feeding behavior and the selection of oviposition behavior in the mixed prey of N.barkeri.The results showed that:when one side was blank,other side was T.urticae or B.tabaci or T.palmi,N.barkeri preferred the leaf disc which had T.urticae?prey patch choice rate:87%?or B.tabaci?66%?,but didi not have significant tendency to the leaf disc which had T.palmi?55%?.When the prey patch was B.tabaci,B.tabaci and T.urticae?76%?or T.palmi,T.palmi and B.tabaci?65%?or T.palmi,T.palmi and T.urticae?81%?,respectively,N.barkeri preferred the leaf disc which had mixed prey.When the prey patch was T.urticae,T.urticae and B.tabaci?47%?or T.urticae,T.urticae and T.palmi?46%?or B.tabaci,B.tabaci and T.palmi?46%?,respectively,N.barkeri did not have significant difference between single prey and mixed prey.When one side was blank,other side was T.urticae or B.tabaci or T.palmi,N.barkeri preferred to oviposit in the leaf disc which had T.urticae,but did not have significant difference to the leaf disc which had B.tabaci or T.palmi.When the prey patch was B.tabaci,B.tabaci and T.urticae or T.palmi,T.palmi and T.urticae,respectively,N.barkeri preferred to oviposit on the leaf disc which had mixed prey.When the prey patch was T.urticae,T.urticae and T.palmi or B.tabaci,B.tabaci and T.palmi or T.palmi,T.palmi and B.tabaci,respectively,N.barkeri did not have significant difference to the leaf disc between single prey and mixed prey.3 The effect of the prey type?single or mixed?on development and reproduction of N.barkeriN.barkeri was able to complete its life cycle on all the six treatments.Its developmental duration was longest?7.8 day?when fed with 1^st instar nymphs of T.palmi,and its developmental duration was shortest?5.7 day?when reared on larvae of T.urticae.The developmental duration of N.barkeri feeding the mixed prey ranged from the developmental period of feeding the corresponding single prey.The amount of predation in the immature period of N.barkeri was significantly affected by prey type.Feeding mixed prey,compared with a single prey,N.barkeri feeding more mixed prey to develop into an adult mite.The oviposition of predator feeding on different prey type varied significantly with diets.And except for feeding 1^st instar nymphs of T.palmi and eggs of B.tabaci,compared with only feeding 1^st instar nymphs of T.palmi,the N.barkeri didn't have significant difference on the amount of oviposition,the number of eggs oviposited by N.barkeri which consumed mixed prey was significantly higher than those consumed single prey.It shows that the mixed prey can increase its population density by increasing the reproductive rate of the N.barkeri.