Study on the occurrence regularity of Lithocolletis ringoniella in apple orchards in Xinjiang Aksu

Abstract: 【Objective】Lithocolletis ringoniella is a kind of leaf pest of fruit trees that mainly harms apple trees and seriously reduces fruit production. With the development of the characteristic fruit tree industry in Xinjiang, L. ringoniella has occurred in the Aksu area in recent years. The study aimed to find out the occurrence regularity of L. ringoniella in Apple orchards in southern Xinjiang, and to provide scientific basis for integrated management of the pest.【Methods】In this paper, the occurrence and damage rule of the L. ringoniella was studied by the methods of sexing attraction trapping and field investigation in apple orchards with different ages, varieties and intercropping patterns. In each treatment orchard, three sets of traps were placed respectively. They were hung with wire on the trunk of a ventilated area on the dark side of the fruit trees at a height of 1.5 meters or in the middle and lower part of the tree crown. Each set of traps was hung with one sex attractant and a sticky trap was installed. From March 12 to September 28, the number of L. ringoniella on the sticky trap was surveyed once a week, and the sticky trap was replaced. The sex attractant was replaced every three weeks. From May 20 to September 28, 5 trees were selected from each orchard for marking, and 1 branch was identified fromthe east, south, west, north, and middle of each tree. 20 leaves were investigated on each branch. 100 leaves were investigated for each tree, and the number of damaged leaves was classified and counted. 【Results】The results showed that the L. ringoniella occurred 6 generations in a year in southern Xinjiang. The overwintering adults began to emerge when the average temperature of 7 consecutive days in spring was over 7.1 ℃. There was no obvious discontinuity between the generations of L. ringoniella adults in each treatment, and the number of the first and second generations was small and the duration was long. The number of L. ringoniella adults in the third and fourth generations increased significantly, and the duration was shorter. L.The ringoniella Adults of the fifth generation lasted longer and their numbers declined sharply after mid-September. The highest number occurred in July to August and the damage degree and occurrence amount in different types of orchards varied with different types of orchards with 20-year-old orchard > 5-year-old orchard, the conventional tillage management orchards > 1-year-old grass covering orchards > Medicagonie sativa orchards, and Red love orchard >Fuji orchard. The occurrence trend of L. ringoniella adults in different intercropping types of orchards was basically the same, with 6 peak periods, but the number of peak periods in each generation was different. The L. ringoniella adult peak of the overwintering generation was April 6, and the trapping capacity of conventional tillage management orchards, 1- year- old grass- covering orchards, and Medicagonie sativa orchards were 308, 158.25, and 142.75 heads on each sticky trap, respectively. The occurrence period of the overwintering generation of the Fuji apple (treatment A) lasted for a long time (mid-March to late April), and the average trapping amount of the L. ringoniella adult was 293 heads for each sticky trap during the peak period (March 30). The occurrence period of the overwintering generation of the Red love apple (treatment D) was concentrated (early April to late April), and the peak period (April 6) was about one week later than the occurrence period of the treatment A. The peak trapping capacity was 315 heads on each sticky trap. The pest indices and leaf damage rates of the two cultivars were 0.42, 0.17, 1.67%, and 0.67%, respectively, in the conventional tillage management orchard of Red love and Fuji. The pest situation index and leaf damage rate increased rapidly after July. By August 10, the pest situation index and leaf damage rate of Red love and Fuji conventional tillage management orchards were 18.67, 6.42, 41.33%, and 15%, respectively. In the middle and late September, the pest situation index and leaf damage rate reached the maximum, 26.91, 16.75, 77.67% and 32.67%, respectively. In the conventional tillage management orchards of Fuji, the overwintering generation of L. ringoniella occurred earlier in the 5- year- old apple orchards, and reached its peak on March 30 with 293 heads on each sticky trap, and reached its peak on April 6 with 57.25 heads on each sticky trap in the 20-year old apple orchards.【Conclusion】L. ringoniella lived through the winter with its pupae in the damaged leaf spots, and occurred six generations a year in the Aksu area. The most serious period of the damage to apple was from July to August, and more frequent damage of it was found in elderly orchards and clean cultivation orchards. There were also differences in the preferences of it for different varieties in apple.