Studies On Species And Biological Characteristics Of Watermelon Diseases And Insect Pests

The watermelon's diseases and insect pests occur gravely in Soochow, while few studies probe into this area. This thesis involves the investigation of the species of the watermelon's diseases and insect pests in Soochow. And the biological characteristics of the diseases and insect pests are analyzed . The results are as follows:1 Isolate the pathogeny from the plant with watermelon wilt disease, and identify the pathogeny as Fusarium oxysporum f . sp. niveum. The indoor studies show that the pathogeny would grow in an environment of 28～30℃and pH6.08～8.2, and we also find that light has a tiny influence on the pathogeny, but 12 hours'illumination and 12 hours'darkness is good for the growth of pathogeny, while 24 hours'illumination would restrain the growth of pathogeny. The culture medium with 1%,2% cane sugar accelerates growth of the pathogeny. 75% Chlorothalonil is the best bactericide. The restraining rate of Richards medium to watermelon seed radicel is up to 95.6%, except PD medium, the others restrain the seed radicel more and more terribly along with augmenting toxin's concentration. And the time is longer, with larger concentration toxin's Richards medium can control young watermelon plants more and more well.2 While surveying the watermelon wilt disease, we discover a new watermelon disease in Soochow-- watermelon leaf blight. So far there are a bit few researches on the disease at home and overseas, this thesis for the first time investigates the biological characteristics of watermelon leaf blight pathogeny in Soochow. By isolating the watermelon leaf blight'pathogeny, and mensurating the growth characteristics, I get the results that the pathogeny grows fastest under the condition of 27.84℃, pH6.57. 70% of Mancozeb W.P and 53.8% of Kocide 2000 can restrain the pathogeny quite well.3 Through observation in the watermelon filed, I know the main pests for instans Diaphania indica Saunders, Trialeurodes vaporarionm Westwood, Aphis gossypii Glover, Liriomyza bryoniae (Kaltenbach)'damage characteristics and Diaphania indica Saunders larva gnaw into the watermelon leaves, and living behaviour. And discover that the insects affect watermelon plant dominating during June and September.