| Amblyseius orientalis (Ehara) is an important natural enemy for spider mite, and it has effectivecontrol for several kinds of mites. But application of A.orientalis has been restricted of mass productionfor a long time. A. orientalis always thought to be the special predator for spider mite, but we found thatit also can prey Bemisia tabaci (Gennadius) in our lab. So the control and application effect of A.orientalis on B. tabaci need the further research. In order to resolve these problems, this paper studieson the alternative prey and the functional response of A. orientalis on egg and1st-nymph of B. tabaci inthe laboratory, the development and fecundity of A.orientalis feed on B. tabaci, and the controleffeciency of A. orientalis on B. tabaci on sweet pepper plant in the greenhouse. All of these wouldprovide theoretical and practical basis for the large-scale, commercial production of A. orientalis, andbecoming the first good kind of native phytoseeiidae mite for controlling B. tabaci. The results are asfollows:1. The life table of the experimental population of A. orientalis feeding on Carpoglyphus lactis(Linnaeus) was established by studying its development and reproduction under controlled temperature(25℃) and humidity (80%) conditions. The results showed that the developmental duration of differentstages of A. orientalis were shorter,1.77,0.77,1.05and1.05d, respectively. The mean generation time(T), intrinsic increase rate (rm), finite increase rate (λ) and the time for double population were14.07d,0.18,1.2and3.87d, respectively. Daily fecundity and fecundity of single female were1.71and22.50.So we conclude that C. lactis is a good alternative prey for A. orientalis.2. The functional response of different stages of A. orientalis on egg of B. tabaci could bedescribed by HollingⅡtype, Na=0.742×Nt/(1+0.0386Nt), Na=0.464×Nt/(1+0.0501Nt) andNa=0.565×Nt/(1+0.0429Nt), the attacking rates were0.742,0.464and0.565, the handling time were0.052d,0.108d and0.076d, the daily maximum predations were19.23,9.25,13.16, respectively. Atthe low density (3,5), there was no significant difference among the predacious number of differentstates of A. orientalis on B. tabaci egg, conversely at the high density (7,9,11,13). In case of the samedensity of B. tabaci egg, there was no significant difference between female adult and juvenile at lowdensity (3,5), conversely at the high density (7,9,11,13). But they always had significant differencewith male adult. The results showed that female adult of A. orientalis consumed much more eggs of B.tabaci than juvenile, and the male adult is the weakest.3. The functional response of different stages of A. orientalis on lst-nymph of B. tabaci could bedescribed by HollingⅡtype, Na=0.398×Nt/(1+0.0279Nt), Na=0.199×Nt/(1+0.0310Nt), Na=0.529×Nt/(1+0.0259Nt), the attacking rates were0.398,0.199and0.529, the handling time were0.07d,0.156dand0.049d, the daily maximum predations were14.29,6.41,20.41, respectively. At the low density (3,7), there was no significant difference among the predacious numbers of different states of A. orientalison B. tabaci lst-instars nymph, conversely at the high density (11,15,19). In case of same density of B.tabaci lst-instars nymph, there was no significant difference between female adult and juvenile at low density (3,7,11), conversely with the male adult. At the high density of (15,19), the juvenile hadsignificant difference with the female and male adult. The results showed that the juvenile of A.orientalis could prey much more lst-instars nymph of B. tabaci than female adult, and the male adult isthe weakest.4. The life table of the experimental population of A. orientalis feeding on egg and lst-instarsnymph of B. tabaci was established by studying its development and reproduction under controlledtemperature (25℃) and humidity (80%) conditions. The results showed that A. orientalis could finishthe normal growth and development, but the female mite had low fecundity or almost don’t lay eggs.The developmental duration of different stages of A. orientalis were extend,2.00,0.80,3.75and4.70d,respectively. The total duration was11.25d. The mean generation time (T), intrinsic increase rate (rm),finite increase rate (λ) and the time for double population were25.33d,-0.048,0.95and-14.58d,respectively. Daily fecundity and fecundity of single female were0.34and1.40. So we conclude thatfeeding on the mixed prey eggs and lst-instars nymphs of B. tabaci is not beneficial to populationgrowth of A. orientalis.5. Releasing A. orientalis on the sweet pepper plant in the greenhouse to study actual controlefficiency of A. orientalis on B. tabaci. This experiment compared three treatments, every treatmentdesigned with three replications. Treatments consisted of two releasing rates (B. tabaci: A. orientaliswas3:1or6:1) and the check. The results showed that the control efficiency of A. orientalis on egg of B.tabaci, the3:1treatment plot was68.10%, and the6:1treatment plot was up to70.51%. For thepopulation of B. tabaci, the highest control efficiency of3:1and6:1treatment plot were48.00%and40.58%, respectively. For the upper position of plant, the highest control efficiency of6:1treatment plotwere21.35%. For the middle position of plant, the highest control efficiency of3:1treatment plot were51.75%. For the lower position of plant, the highest control efficiency of6:1treatment plot were72.09%, and the3:1treatment plot was up to59.53%. So we conclude that A. orientalis could suspressthe growth of egg and the population of B. tabaci effectively, but it did not have obvious control effecton the nymph of B. tabaci and the effect on adult whitefly had lagged. At the initial stage of releasing, A.orientalis has certain control effect on B. tabaci, but with the passage of time, the control effectdecreased gradually. The6:1treatment plot has higher control efficiency on the upper and lowerposition of the plant than the3:1treatment plot, conversely at the middle position. The results showedthat A. orientalis has control efficiency on the B. tabaci on sweet pepper plant. Under the conditions ofthis experiment, the higher releasing rate has better suppression than the lower releasing rate. |
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