Studies On The Danger Of Aceria Litchii (Keifer)to Leaves Of Litchi(Litchi Chinensis Sonn.)

Aceria litchii (Keifer), also called Litchi gall mite or Mao zhizhu, is one of the major pests of litchi (Litchi chinensis Sonn.) and longan. In this paper, the insect damage degree was studied in leaves of litchi. We expect playing a guiding significance in the prevention and control of Aceria litchii (Keifer).The main contents and results are listed as follows:1. The preliminary standard classification of the periods of A. litchii invasion was established in litchi. The invasion of litchi by A litchii was divided into five periods: plague period; villus period; erineum initial period; erineum interim period; erineum later period. At the same time, the relationship between damage degree and pest population was investigated in different periods. Finally, we found that the thirdly period is the peak occurrence of insect life-stages.2. In this experiment, the internal structure of A. litchii gall was detected with microscope by paraffin section and cryo-sectioning at different periods of A. litchii invasion. The results indicated that the co-parasites of symbiotic A. litchii and Cephaleuros virescens Kunze can lead to thinner of the epidermis cell layer, larger of the cell gap until break off in the leaves of litchi. At same time, the mesophyll cells had gradually dehydrated and disappear, the erineum grew more dense and finally come off from the leaf surface. Moreover, the method of Cryo-sectioning can be better maintain the integrity of leaf structure and can be visually observed the change of chlorophyll content by comparing the method of paraffin section.3.The secondary metabolites of litchi leaves during the growth of normal(CG) and Aceria litchii (Keifer) invasion(TG), was extracted by Soxhlet(SE) and Ultrasonic(UE) methods, respectively. Then, its constituents were separated and indentified with GC-MS. The results showed on changes in chemical composition and content of litchi leaves by Aceria litchii (Keifer) invasion. Mainly reflects in the elevated levels of phytosterol, such as the γ-clionasterol(SE:CG4.285%â†'TG5.894%;UE:CG2.307%â†'TG4.025%), and the reduced levels of phytol(SE:CG7.823%â†'TG2.992%;UE:CG2.033%â†'TG0.64%), which was involved in plant defense and photosynthesis respectively. In addition, there were more kinds of secondary metabolites extracted by the ultrasonic extraction method compare with soxhlet extraction method.4. In this study, the impact of photosynthesis was detected at different periods of A. litchii invasion in the leaves of litchi. The results shows that the degrees of light compensation, light saturation point and maximum photosynthetic were decrease in the leaves of litchi by A.litchii invasion in contrast to the health ones. The content of chlorophyll decreased in the mass during the whole period of A.litchii invasion, and the SPAD values showed more decline in the late period. We are confident that photosynthetic capacity of litchi can be seriously affected by the parasitize of A. litchii.