Walnut black aphid occurs in our region for more than 10 generations every year, overwintering in branches, leaf marks and bark slits, and the overwintering eggs begin to hatch in mid-April of the following year, and the hatched aphids look for expanded tree buds or leaf spines to suck and eat, and the adult aphids are more lively and can migrate to neighboring trees. In mid-September, a large number of sexual aphids are produced, and after mating, the females choose suitable parts to lay eggs and overwinter. There are two peaks of black spotted aphids in our region in 1 year, in mid-to-late June and mid-to-late August. Adult aphids and aphids are in the leaf back and young fruit on the stinging as a pest, because of the secretion of honeydew, can pollute the leaves and fruits, seriously affect photosynthesis, when serious, can cause walnut leaves to lose green scorching, resulting in walnut kernel shrinkage, kernel yield decreased by about 20%, causing a greater impact on walnut yield and quality.
First, the occurrence of monitoring
From June 24 to 26, the plant protection technicians of the prefecture and county (city) jointly monitored the occurrence of walnut black spot aphid in some townships (towns) of Aksu City and Wensu County. A total of 9 walnut orchards were investigated, covering an area of 650 acres, and a total of 262 leaves were checked, of which 62 leaves had 189 insects (including 4 winged aphids), the average leaf rate was 23.7%, and the number of louvers was 72.1, which was slightly higher than the previous survey data of the same period last year (in early June last year, the average leaf rate was 9.5%, and the number of louvers was 68). The ratio of winged aphids to wingless aphids is 1:47.3.
From the above survey data, it can be seen that it is the beginning of the occurrence of walnut black spotted aphid. Recently, the weather in the region is sunny and rainy, and there are relatively many windy weather processes, which is generally conducive to the breeding and migration of walnut black spotted aphids.
Second, the occurrence and prevention period prediction
According to field monitoring and the occurrence of black spotted aphid, combined with meteorological data prediction and analysis: it is predicted that the overall occurrence of walnut black spotted aphid in our region is medium (grade 3), and the local bias (grade 4) occurs, and the degree of occurrence is heavier than that of the previous year. The occurrence areas are Aksu City, Wensu County, Awati County, Xinhe County, Hongqipo Farm, Experimental Forest Farm and other places. At present, the walnut black spotted aphid has entered the peak period of harm, and the peak period of harm is expected to be in early to mid-July and mid-to-late August. It is hoped that all counties (cities) will earnestly strengthen monitoring and do a good job in prevention and control work in a timely manner.
Third, prevention and control methods
1. Yellow plate booby-trap: The use of winged adult aphids has a strong tendency to yellow, and the yellow plate booby trap is carried out. According to the age of the tree and the height of the tree, 3-5 trees are hung, and the hanging height is 1.5-2 meters.
2. Protect natural enemies and prevent and control them in a timely manner. The natural enemies of walnut black spotted aphid mainly include seven-star ladybird, heterochromatic ladybird, large grasshopper, etc., and attention should be paid to protection and utilization. When the number of natural enemies is large, the amount of aphids is small, and the role of natural enemies can be controlled. At the same time, before the peak period of the occurrence of aphid nigricanium, to strengthen field monitoring, when the amount of aphids per compound leaf reaches more than 50, plant insecticides 0.5% matrine aqueous agent 1500 times liquid, 50% anti-aphid wettable powder 5000 times liquid, or 20% acetamidine emulsion (Mbilang) 2500 times liquid, 10% imidacloprid emulsion 3000 times liquid for control.
Source: Aksu Regional Centre for Agricultural Technology Extension