Current Status And Regularity On The Harm Of Forest And Grassland Insect And Rodent Pests In Ningxia Yellow River Irrigating Region

Irrigated faming depends on yellow river and forests mainly are artificially protective forests in Yinchuan plain. Based on consulting a great deal of historic data from pests and rodent pests of forest and grassland in this region, we established 26 pieces of sample plots in villages and towns by means of setting up samples equably in 12 counties(cities) of Ningxia Huang-river irrigating region through investigating from 2001to 2003.According to their own characteristics of three aspects from forest trunk borers,leaf-ate pests and rodent(hare) pests of cropland and grassland, we dealt with and analyst the data introducing different measures and index systems. The results showed that: (1)Trunk borers mainly are A.nobilis Ganglbauer and Anoplophora glabripennis (Motschulsky) in this region.They mostly hazarded Populus spp.,Salix spp.,Ulmus spp etc. In the end, they have great effects on the protective forests. The evil characteristics include four kinds: The first type: lower density of population, middling rate of harmed trunk to the total and middling crowded degree, higher rate of trees against pests, pests present diffused trend. Harmed degree of this type is light, therefore there will get twice the result with half the effort if we strengthen checking and controlling and cure pests in time. The second type: higher density of population, higher rate of harmed trunks to the total, less crowded degree, lower rate of trees against pests, pests distribute on the most trees. Pests mainly distribute on the easily sensed trees such as small-leaved poplar, Beijing-poplar, I-214 and Jia-poplar. To this type, we should control timely not to generate severe disaster. The third type: lower density of population, lower rate of harmed trunks to the total, middling crowded degree, lower rate of trees against pests, pests present diffused trend. Because the age of trees is lower, the time of pests imperiling is shorter. So we should reinforce checking highly sensed trees and control timely. The fourth type: lower density of population, lower rate of harmed trunks to the total, higher crowded degree, pests exhibit mass distributing, the component of population is relatively stable, the lower rate of trees against pests is above the half. We should inspect timely to prevent its expanding. At the same time, we take 7 items of integrated control measures against the pest, including over 20 kinds of concrete methods and pieces of advice. (2)Apocheima cinerarius (Erschoff) and (orgyia ericae germar) are the main leaf-ate pests in the half-aired desertification fields lying in the middle and east of Ningxia Huang-River irrigating region. The number of population is small, but they distribute largely during hiding in winter. The degree of harm gives priority to the middle and light. They behave spreading trend. (3)Density of rodent (hare) pests on the ground and rodent (hare) pests under the ground investigating Microtus forestis distribute mostly in Huang-River irrigating region and dried sand. The zones, harmed severely, are qingtong-xia city,pingluo and yongning counties. The mice and hares on the ground both imperil these zones. Field mice distribute mainly in lakes,canals and the brushwood of low-lied and damply terra. There are few field mice in wheat fields because it is very dry here. On the contrary, field mice imperil the paddy fields drastically, for it is wet and there are abundant foods here. There exist violent harm in maize fields and woodlands near the water-receded canals. The harm is gently in forest nets of yellow river irrigating region, however, the harm is intense in beaches and washes. According to the investigation in autumn, 2001 and in spring, 2002, the forest area is 677×104 acres when the rate of harmed trees to the total is below 10%, 164.5×104 acres of the rate from 11% to 20% and 8.9×104 acres of the rate above 20%. The amount of Microtus forestis rises rapidly in the recent years, whereas it is one of the predominant bandicoots of fierce harm. The trees harmed by Microtus forestis are main the Fraxinus spp.,S.matsudana Koidz,P.alba var.pyramidalis,E angustifolium(Linn.)Scop.,R.pseudoacacia Linn.,M.pumila Mill.,L.chinense Mill etc. According to the degree of harm, yellow sand is greater than the sand near the river, the sand near the river greater than the alkali soil or the black alkali soil. The rate of sex usually maintains within the range of 1:1. If the rate of the female is greater than that of the male, it will indicate the trend of disaster, otherwise it will represent the downtrend. It is properly because abusing mortal pesticide and disturbing artificially result that the amount of natural enemy reduces extremely.