Research Of Sitobion Avenae As An Alternative Host For Aphelinus Asychis In In A Banker Plant System

The green peach aphid, Myzus persicae(Sulzer)(Hemiptera: Aphididae), is oneof the primary insect pests of vegetable crops belonging to the families Solanaceaeand Brassicaceae, including chili pepper and cabbage. In the last fewer decades, chemical insecticide was oneof theimportantmeasures. Theindiscriminate useofpesticidenot only increased the pest resistance but alsoleaded to pesticide residues. The augmentative release measureof biological control was mostly used to control this pest, but there were some disadvantages, such as the higher price of biological control agents, the shorter effective duration, repeat releasing and so on, which limited the application rang of traditional biological control. The banker plant system, combining the advantages of protective and augmentative biological control, was a new concept of biological control, which could release the nature enemy and maintain the population in a long period. Therefore, establishing the suitable banker plant system and studying the influence of environmental factors on efficiency of banker plant system was good for controlling the agricultural pest.Aphelinus asychis Walker(Hymenoptera:Aphelinidae) is native to Old World(e.g., Europe, Asia and Africa) and a solitay endoparasitoid of aphid. A. asychisfemale parasitizes and hostfeeds on more than 40 aphidspecies, including green peach aphid, Myzus persicae Sulzer and Sitobion avenae Fabricius. In the previous reports, A. asychis is a potential biological controlagent against M. persicae.The specific objectives were toevaluate(1) the host specificity of an alternative non-pestinsect host, Sitobion avenae;(2)The functional responses of A. asychistoM. persicae feeding on cabbage and chili pepper;(3) the host fitness of Aphelinus asychisparasitizing M. persicaeon chili pepper and cabbage;(4) the influence of starvation on the host fitness of A. asychis;(5) the influence of heat shock on the host fitness of A. asychis;(6) the influence of back cross on the host fitness of A. asychis;(7) the influence of four constant temperatures on the host fitness of A. asychis;(8) the influence of cold storage on the host fitness of A. asychis;(9) the dispersal ability and control efficiency of A. asychisin the green house. The main research results were as follows:1. In the no-choice test, the number of S. avenaeadults on wheat plant increased significantly with time, the number of S. avenaeadults on chili pepper and cabbage plants showed the opposite trend. In the two-choice test, the number of S. avenaeadults on wheat, chili pepper and cabbage plants showed the similar trends to the no-choice test. In the multiple choice test, the number of S. avenaeadults and nymphs on the three plants showed the similar trends to the no-choice test. In conclusion, S. avenae has a strong specificity to wheatplantfor feeding and oviposition2. The functional responses of A. asychistoM. persicae feeding on cabbage and chili pepper fitted well with Holling II and Holling III models. Both feeding and parasitizing searching rateof A. asychis on M. persicae infesting cabbage and pepper decreased as aphid density increased. The searching rate of A. asychisparasitizingM. persicae on pepper were greater than on cabbage at all densities. In feeding functional response, the instantaneous attacking rateand dealing timeof A. asychis preying on M. persicae on cabbage(a′= 0.3289, Th = 0.2597) was greater than on pepper(a′= 0.2335, Th = 0.1954). And in parasitizing function response, the instantaneous attacking rate of A. asychis feeding on M. persicae on cabbage(a′= 0.8213) was less than on pepper(a′= 0.8956), but the dealing time showed the contrary result(cabbage: Th = 0.0275, pepper: Th = 0.0255). In addition, the maximum number of feeding and parasitizing of A. asychis to M. persicaeonpepper(Namax=3.9573, Namax=36.3636) were greater than on cabbage(feeding: Namax=5.1177, parasitism: Namax=39.2157). The results indicated that A. asychis could partlycontrol M. persicae at all host densities, and the control efficiency on M. persicae damaging pepper was greater than cabbage.3. The parasitoids reared from S. avenae could successfully parasitize and host-feed M. persicae on chili pepper and cabbage. The parasitoids had a shorter developmental duration, higher proportion of female progeny, longer longevity, higher fecundity and feeding rate when parasitizing the aphids on chili pepper than on cabbage. Based on the life table parameters, the including intrinsic rate of increase(r), net reproductive rate(R0) and net aphid killing rate(Z0), A. asychis reared from S. avenae performed better as a biological control agent of M. persicae on chili pepper than on cabbage.4. The survival rate of starved A. asychis female adults decreased sharply. The longevity of thestarved parasitoids decreased significantly as extending the starvation time. The number of aphids killed by the starved parasitoids were similar to those in the control. However, the number of aphids on chili pepper killed by the treated A. asychis females in their lifespan was significantly less than the control group. Our results indicated that a short time starvation might be beneficial to control low density of M. persicae at early release, but the influence of long time starvation on A. asychis females in the whole lifespan was negative.5. Our results showed several major consequences on the parasitoid adults after brief heat stress. First, the survival and longevity ofthe brief heat stress-treated A. asychisfemale and male adults decreased significantly. Second, the number of M. persicae nymphs infesting chili pepper killed through host-feeding by the treatedA. asychisfemales decreased significantly. Third, the cumulative number of parasitism or mummified aphids and female progeny produced by the treated A. asychis also significantly decreased. Our results suggested that high temperatures should be avoided to ensure the success of biological control of M.persicaeand other aphid species using this parasitoid species.6. The eggs of F1 generation in backcross treatment could hatch and pupate successfully. The developmental time and longevity of both A. asychis female and male in backcross treatment was significantly longer than those in controls. The intrinsic rate of increase(r) of A. asychis in control was significantly greater than that in backcross treatment. The net reproductive rate(R0) and net killing rate(Z0) in backcross treatment was greater than that in control.The finite killing rate(θ) of A. asychisin control was similar to that in backcross treatment.In conclusion, the negative influence of backcross on the control efficiency of A. asychis was negligible.7. The increasing temperature significantly decreased both the development time and longevity of A. asychis females and males, respectively. Both the net reproductive rate(R0) and net killing rate(Z0) also decreased significantly as the temperature increased. The intrinsic rate of increase(r) increased firstly and then decreased significantly with the increasing temperature. The finite killing rate(θ) at 24oC-32 oC was significantly greater than those at 20 oC, and the values were 0.3140, 0.4503, 0.5414 and 0.4312, respectively. In conclusion, A. asychis could complete its life cycle in the range of 20°C-32°C and the control efficiency of A. asychis onM. persicae at 24oC-32 oC was greater than those at 20 oC.8. The emergence rate of tested mummies, the longevity, the number of next generation mummies and female progenies decreased significantly as the storage time increased in both alternate and constant temperature treatments. Both the emergence rate of tested mummies and the longevity of A. asychis female adult in 21-30 days alternate temperature treatment was significantly greater than those in the same time constant temperature treatment. The number of next generation mummies in 18-30 days alternate temperature treatment was significantly greater than those in the same time constant temperature treatment. A. asychis female adults stored for 3 and 24-30 days with alternate temperature produced significant more female progenies than that with constant temperature. After 24-30 days cold storage, A. asychis killed significant more aphids for host feeding at alternate temperature than that at constant temperature. In conclusion, the cold storage treatment negatively decreased the quality of A. asychis partly, and alternate temperature was more suitable to store A. asychis mummies longer than 18 days in the mass production.9. The data of dispersal test of A. asychis proved that A. asychis adults could migrate from wheat banker plant to chili pepper plant at a speed of 2.5 m per hour. The banker plant system decreased significantly the number of M. persicae infesting chili pepper in greenhouse experiment. Economically speaking, the yield of chili pepper in banker plant system treatment was significantly greater than that in control. The results showed that the banker plant system significantly benefits the greenhouse chili pepper production.In conclusion, wheat and S. avenaewas suitable to establish the non-crop and non-pest banker plant system. The influence of high temperature and starvation on the population fitness of A. asychiswasnegative. The alternate temperature cold storage was more suitable to keep the quality ofA. asychis pupa in the mass production.Thenegative effect of backcross on the control efficiency of A. asychis was negligible. The suitable temperature range of A. asychisto control M. persicaewas 24oC-32 oC. The ‘wheat- S. avenae- A. asychis’ banker plant system could effectively control M. persicaeinfesting chili pepper plant in greenhouses.