Studies On Occurrence Of Two Eriophyid Mites And Physiology Of Gall Disease In Pears

In this paper, two eriophyid mite species collected from pears in Gansu are identified. They are Eriophyespyri Pagenstecher(EPP) collected from Pyrus u.ssuriensis Maxim.(PUM) and Epitrimeru.spyri(Nalepa)(EPN) collected from Pyrus bretschneideri Rehd.(PBR). Light green galls appear on the back of PUM leaves injured by pear blister mite, Eriophyespyri Pagenstecher. EPP mainly overwinters as adults beneath bud scales. The galls do not appear on leaves injured by pear rust mite, Epitrimerus pyri (Nalepa). The diseased tissues become spongelike. The injured parts turn into rust red color and dent towards the back of PBR leaves. The leaves distort and wrinkle. EPN overwinters as adults, settling behind bud scales, in the crack or any other protected area. Physiological and biochemical processes in pear leaves injured by Eriophyes pyri Pagenstecher and Epitrimerus pyri (Nalepa) are changed in several aspects. The chlorophyll decreases by 3 1.85% and 50.05%. The soluble sugar decreases by 24.6 1% and 19.86%. The soluble protein increases by 34.14% and 29.17%. The free amino acid increases by 29.95% and 21.59%. The free proline increases by 84.08% and 104.20%. The activity of hydrogen peroxidase increases by 29.82% and 22.62%. The membrane permeability increases by 86.74% and 150.43%. Morphological change to pear leaves by pear-leaf blister mite, Eriophyes pyri Pagenstecher, is examined by tissue sectioning. Small light green spots appear on leaves primarily injured by the gall mite. When the number and size of spongy tissue cells increase, galls gradually appear and become larger and larger. At this time, palisade tissue is not influenced. The tissue of injured parts protrude towards the back of PUM leaves. At last, spongy tissue is broken and cells begin to be separate. At the same time, palisade tissue is also influenced. The injured parts gradually blacken. In a word, there is an interaction relationship between eriophyid mites and pear leaves. In order to grow, develop and reproduce better, eriophyid mites induce the tissue structure, physiological and biochemical processes in injured leaves to change. On the other hand, leaves produce some resistant substances to reduce the damage.