A PRELIMINARY STUDY ON THE SMALL BROWN PLANT HOPPER, DELPHACODES STRIATELLA FALLN IN SOUTH KIANGSU

The Delphacodes striatella F., is widely distributed in Soochow, Wusih, Changchowof the Taihu Lake rice region in Kiangsu. It is one of the worst pests of our rice crop.The crops from the double cropping early rice and single cropping middle rice are injuredeven more severely. By our observations, the host plant of this small brown planthopper is changedseasonally. The most common hosts are rice in summer or autumn and wheat, Alope-curus aequalis Sobol. in spring or winter. Supplementary hosts include barley, Leersiajaponica Makino, Zoysia japonica Steud., etc. According to the degree of embryonic development the growth of the egg is dis-tinguished in six stages, such as: Blastoderm, Germ band, Yellow spot, Blastokinesis,Eye spot, Accessory-podite and Hatching. The development of nymph goes through about five instars, it becomes adult afterthe fifth moult. The period of each stage is limited by temperature. At 25--26℃, theegg stage is about eight days, the nymph stage is about sixteen days, the adult is aboutfourteen days, the adult is about seven days. The sexual muturation period of the Brachypterous type is 1--2 days earlier than theLongipennate. The female copulates with the male immediately. The eggs are depositedinto the leaf sheath or beside the leaf mid-rib. The egg streak consists of double rowof eggs. Delphacodes striatella F. produces six generations per year. The first generation isfrom late April to early July. The second generation is from early June to early July.The third generation is from early July to August. The fourth generation is from earlyAugust to middle September. The fifth generation is from early September to middleOctober. The nymph of the sixth generation hatches in early October. During the3rd and 4th instars it hibernates on wheat, alfalfa or weeds. The activity of hymenpterous parasites, nematodes and spider in June and July sup-presses the multiplication of the small brown planthopper. The difference of the popula-tion in some regions or in the field is closely related to the nutrition of the host and themicroclimate. The results of laboratory and field tests indicated that: spraying 6% γ wettableB.H.C. (1:200), 46.6 Folidol (1:3000) and 15% wettable Malathion (1:1500) at100 kg of the solutions per mou, gave very successful control.