Control Efficacy Of Neoseiulus Californicus And Euseius Nicholsion On Three Spider Mites Of Rubber Trees And Their Adaptability To These Preys

Spider mites is one of the important pests groups on rubber trees Eotetranvchus sexmaculatus(Riley),Eutetranychus orientalis(klein)and Oligonychus biharen(Hirst)are three key phytophagous species damaging rubber trees.Euseius nicholsi(Ehara et Lee)and Neoseiulus californicus(McGregor)are two important predacious mites,of which E.nicholsi is the predominant predator of phytophagous mites found on rubber trees in China,and N.californicus can be reared and used commercially at home and abroad for the control of spider mites and thrips,etc.To clarify the application prospects of these two predators for the control of the spider mites in rubber trees in this study,E.nicholsi and N.californicus were evaluated for their control potential on these three spider mites of rubber trees and their population characteristics fed with these three preys.The main results are as follows:(1)The selectivity of N.californicu and E.nicholsi to the spider mites of rubber treesThere are some differences in the selectivity of N.californicu and E.nichlsi to different spider mites.When the same stages of the three species of spider mites existed simultaneously,it was found that N.californicu did not show preference to different species,while the E.nicholsi preferred to feed on E.sexmaculatus and did not eat the eggs of O.biharen.When different stages of the same species existed at the same time,both N.californicu and E.nicholsi showed preference to the larva.(2)The control efficiency of N.californicu and E.nicholsi on three species of spider mites of rubber treesThe functional responses of N.californicu and E.nicholsi on three species of spider mites were compared at different temperatures.The results showed that the prey consumption numbers of the predators increased with the rise of prey densities.At the temperatures of 21 ℃、24℃、27℃、30 ℃、33℃ and 36℃,the predation numbers increased with the temperature rise,reaching the maximum at the temperature of 30℃ or 33℃,The functional responses of N.californicus and E.nicholsi to E.sexmaculatus,E.orientalis and O.biharen at different temperatures fitted to the Holling-Ⅱ equation.But there were some differences in the temperatures at which these two predatory mites showed highest predation efficiency on the target spider mites.The predation capability of N.californicus on various stages of O.biharen,E.sexmaculatus and the nymphs and larva of E.orientalis peaked at 30℃.But to the female adult and egg of E.orientalis,the peak of predation capability appeared at 33℃.The predation capability of E.nicholsi on E.orientalis and O.biharen peaked at 33℃,however,the peak of predation capability of E.nicholsi on E.sexmaculatus appeared at 30℃.The self-density interference effects of N.californicus and E.nicholsi on three species of spider mites were consistent with the Hassell-verley interference model.The predation ration of californicus and E.nicholsi would gradually decrease with the rise of itself density,which proved that obvious competition and self-interference indeed existed among N.californicus and E.nicholsi.(3)Influences of different spider mites on the development and reproduction of N.californium and development of E.nicholisThe life table of N.californicus fed with E.sexmaculatus,E.orientalis(klein)and O biharen were established.The results showed that the developmental durations of N.californicus feeding on E.orientalis,O.biharen and E.sexmaculatus were 5.88d,8.08d and 13.16d in average,respectively,with significant differences among them.Fed with E.orientalis,the net reproductive rate and intrinsic increasing rate of N.californicus were the highest,which were 28.700 and 0.273,respectively,followed by 19.661 and 0.231,respectively when fed with O.biharen The intrinsic increasing rate of N.californicus was-0.013 when using E.sexmaculatus as food.The results showed that E.orientalis is the most beneficial prey for the population growth of N.californicus,followed by O.biharen.It is difficult to maintain the population of N.californicus when it exposed to E.sexmaculatus solely.The developmental duration of E.nicholsi from egg to adult fed with E.sexmaculatus was significantly different from that fed with E.orientalis and O.biharen The developmental duration feeding on E.sexmaculatus was the shortest,which was 3.86d,followed by E.orientalis and O.biharen.E.sexmaculatus is the most suitable prey for the development of E.nicholsi compared with the other two preys,but the reproduction of E.nicholsi feeding on three species of spider mites is to be studied.