Study On Bionomics And Behavior Of Paratrioza Sinica Yang & Li. And Its Natural Enemies

Paratrioza sinics Yang & L is one of the most important insects of wolf-berry in Northwest Area of China where wolf-berry (Lycitan spp.) is grown extensively and commercially. P. sinica Yang & Li. is a hemimetabolous insect and has 3 developmental stages: egg, nymph and adult. It has 4-5 generations per year and overwinters in the adult stage in the litter and in the uper layer of the soil. Nymphs feed on leaves, flower bud and younger berry. Overwintering adults emerge and begin laying eggs of first generation in early May. Eggs hatch in mid-May and nymphs have 5 instars. adults of the first generational apear in mid-June. All three developmental stages could be found from the end-May to the end of October. The threshold temperature-for egg development is 8.62 ± 1.5℃ , and egg hatch occurs after 116.97± 15.12 degree-days . The threshold temperature for nymph development is 10.07 ±2.55℃ and requires 267.79±64.81 degree-days to complete development.The process of host searching behavior of P. sinica includes the orientation, recognition and acceptance or rejection of plant. The olfaction stimulus plays an important role in the orientation, while vision has a subsidiary role in the behavior of adult. The volatile chemicals of host plant may be the main cue and the green color of host plant may be the secondary cue in host orientation. The acceptance or rejection of a potential host is determinded based on olfaction, tactile and by phagostimulation. The both of host volatile chemical and physical characteristic influence the host selection behavior of P. sinica..Different wolf-berry cultivars have different susceptibilitis to P. sinica Yang & Li. attach and subsquent damage.The physical characteristics of plants were investigated by dissecting leaves of three cultivars of wolf-berry. The thickness of leaves of three cultivars were different, and the density of P. sinica was higher on leaves with thicker spongy tissuse.Nymphs seldom change thier feeding sites unless the host plant withered. Nymphs can not move far and can only search for new feeding sites on the host in a random fashion. Tactile stimulus may play the major role in the feeding sites selection by nymphs.A life table study of P. sinica was conducted in the field in Huhhot, Inner Mongolia, for 3 years. The results showed out both the biotic and abiotic factors play an important role in P. sinica population dynamics. The two key factors causing the highest mortalitity were a parasitic wasp and heavy rain in early May. The predotary bug, Deraeocoris punctidatus Fallen, has a less important role influencing host dynamics.D. punctulatus Fallen, is a dominant predator, based on density per 100 cm branch of wolf-berry and as indicated by prey selection feeding tests on Aphis gossypii Glover and P. sinica. D. punctulatusFallen has 3-4 generations per year in Huhhot and overwintes in adult stage in the litter layer or under soft soil surface. In the laboratory feeding experiment, during its entile life D. punctulatus Fallen can consume 1138 nymphs of P. sinica, In spite of this relative high rate of prey consumption, it is only the third most important natural control agent after the parasitic wasp and precipitation.The parasitiod wasp, Tetrastichus sp., is a dominant and most important natural enemy of P. sinica and on average can cause 65-82% parasitism July and Auguest in the field.The parasitiod wasp, T. sp., is multivoltine extoparasitiod(the larvae feed outsid the host) that has 5-6generations per year.. The wasp is holometabolous abd has 4 developmental stages:egg, larva, pupa and adult. The duration of egg stage averages 18hr (range s from 12-20hr). Larval development takes about 4 days on average (range 3-5d). The pre-pupa stage lasts an average of 4.5d(range 4-6d). The pupa stage lasts 7d on average (range 6-8d). At the temperature of 23-27℃ one generation develops in 14-20d. the wasp prefers to lay its eggs on 3rd and 4th nymphal stages.The host searching behavior of Tetrastichus sp. was studied in laboratory using a sp...