Study On The Evolutionary Law Of Cotton Bollwormin The Cotton District Of Shaanxi Province

Cotton bollworm (Helicoverpa armigera Hubner) is one of the three major pests in the cotton. Its occurrence and disaster restrict production and scale of Shaanxi cotton district seriously. Exploring that the law of development and causes disaster of cotton bollworm, putting forward the effective control tactics, having very important theory meaning and practice meaning to the sustainable and stable development of cotton district of cotton production of Shaanxi province.In this paper, the law of development of cotton bollworm in the area of planting cotton of Shaanxi province was studied through collecting and putting the cotton district relevant materials about cotton bollworm during 1992-2004 years in order, and from worm source base figure, climate factor, planting structural adjustment, plant mode change, the result shows:The law of development of cotton bollworm in the area of planting cotton of Shaanxi province was that the period of breaking out and cause disaster was in the earlier stage 1990s, the period of interim endangering was in the mid-end stage 1990s, the period of slight endangering was in the earlier stage 21st century. In the earlier stage 1990s, the main cause of the formation of developing is that the adjustment of planting structure was accelerated on the earlier stage 1990s. The rapid growth of area of crops relying on fruits and vegetables, area of grain reduce, the area of eating host's of cotton bollworm enlargement constantly, the base number of the population increase; The adjustment of planting structure makes the planting mode of cotton in the area of Shaanxi cotton district to take place heavy change. The single cotton field reduced greatly, the substitute is the interplantings field of the intercropping, such as a cotton-padded covering of wheat, cotton-padded covering of melon, etc. Interplanting cotton broadcast directly cotton generally getting late about one month, which offered a good condition of feeding for the three-four generitions of cotton bollworm. In the mid-end stage 1990s, the main cause was try to planting cotton of resistant to cotton bollworm. The main variety were 33 B, Chinese 41 cotton, Chinese 45 cotton, SGK321,etc. The result of planting cotton of resistant to cotton bollworm were very outstanding, show as the larva amount in field was extremely low and harming degree for cotton was lighter. Regretfully, the area of cotton of resistant to cotton bollworm was too small. Up till 1999 the extension of cotton of resistant to cotton bollworm began large-scaled. So far, the planting area of resistant to cottonbollworm in Shaanxi province accounted for more than 95% of the cotton plan planting area, which was the main reason that bollworm damage slightly in the earlier 21st century.In this paper the forecast of bollworm including mainly blacklight, poplar twig bunch traps, using different methods of sex attractant examining attracted effect to adult of contton bollworm was studied at the same time. The result shows: The amount of moth using sex attractant was far greater than the blacklight and poplar twig bunch traps. Its advantage is to lure moth's strength strongly, the sensitivity is more high, and it is simple to install, the effect is steady, with lower costs, the validity is longer. By setting up bollworm's data base which strengthen forecast work of cotton bollworm.