Occurrence And Control Of Soil Pests On Peanut In Shandy Soil Region

In shandy soil region of Dali County, Shaanxi Province, soil pests are dominant in peanut fields, while grub is one of the key pests which result in output reduction of peanut.Through 666.6m2 multiple spots sampling census at different growing stages in large scope, fixed-point observation, laboratory rearing, testing the product losses of peanuts at various densities of beetle larvae, and controlling with kinds of pesticides and spraying methods, this research uncovered the occurrence and control of the underground pests, showing the results as follows:1. There are many kinds of soil pests of peanuts in Shayuan region of Dali county, totally 17 species have been identified among 5818 pests collected from 2327 sample spots. Maladera varticalis Fairmaire, Malolontha incanus Motschulsky, Anomala exoleta Faldermann and Holotrichia parallels. Motschulsky are the predominant species, amounting to 95.7%. The remains arrayed according to quantity are the larvae of Anomala corpulena Motschulsky, Agrotis ypsilon Rott, Pleonomis canaliculatus Faldemann, Gryllotalpa orientalis Burmeister, Serica orientalis Motschulsky, Holotrichia diomphalia Bates, Melanotus caudex Lewis and Agriotes fuscicollis Miwa, etc. while other species are very few.2. Maladera varticalis Fairmaire occurs one generation per year, and overwinters by adults or larvae, the adults take place from the middle ten days of April to the first ten days of September, and reach culmination between the middle ten days of July and the last ten days of August. Malolontha incanus Motschulsky occurs one generation per 2 years, and overwinters by second star larvae, the adults appear from the beginning of June to that of July, and reach culmination in the last 20 days of June; H. parallela Motschulsky is univoltine, and overwinters by mature larvae, the adults act from the last 10 days of May to that of August, culminating between the middle 10 days of June and that of July; Anomala exoleta Faldermann is univoltine as well, and overwinters by mature larvae, the adults take place from the middle ten days of June to the first ten days of September, culminating between the last ten days of June and that of July.3. The occurrence of grub is close-related with the soil quality and the previous stubble, generally the damage caused by Malolontha incanus Motschulsky is heavy in the fields of Hemerocallis fulva L., peanuts straw and irrigating sandstorm soil, however in the non-irrigating sandstorm soil Maladera varticalis Fairmaire is predominant.4. Raveling the life history of Malolontha incanus Motschulsky, which is thepredominant species damaging at peanuts. It overwinters by larvae, one generation per 2 years. The adults emerge and excavate in the first ten days of June, culminating in the middle ten days of the same month, and ebbing in the last ten days of June, and this stage lasts for 20 ~ 26 days, average 24d. The adults are inverted hanging during copulation, the laying of female is 23 in general, often at the depth of 20~26cm, the egg stage lasts for 18~22d, average 20d, which can be easily affected by the soil humidity, while 20% hydrous quantity, then the rate of hatching reaches 95.46%, is proper. The larvae stage endures 648~663d, average 655d, the upright distribution is minor correlated with the change of soil temperature at the 10cm depth, except between the middle ten days of July and the last ten days of August, during which the larvae turn away the high temperature and aridity, the regression equation as Y=49.8-19.5x; the pupa stage go through 15~24d, average 2Id. After the second winter, the mature larvae, which will damage the peanut infancy no longer, molt and pupate after 4-6d in the 25-30cm depth soil.5. The seedling can come up out of land in gear even at different pest densities, however the mortality and the month rate of fruit will boost with the increment of pest density; the rate of product loss is plus correlated with the pest density, as the regression equation Y=25.26x —1.20, rxy=0.985. Via converting the correspond loss rate according to the fee on the control with 40% isofenphos-methyl in the peanut fields, then 231/666.6m2 of Malolontha incanns Motschulsky larvae in the peanut fields in which the product reach 330kg/ will arrive at the control index.6. Mixing the seeds and 40% isofenphos-methyl with the weight ratio of 0.3%-0.6% to control the grub in peanut fields, on the base of which it will achieve the best effect to ditch and pour medicine at the roots of peanuts with 1200mI/666.6m2 in the first ten days of June during which is the damage pinnacle (seedling stage of peanut sowed in summer), then the seedling mortality is only 8.35%, while the emendation mortality of pest is 89.5%.