Key factors and control measures for the occurrence of main heart borer in apple

Key factors and control measures for the occurrence of main heart borer in apple

Apple is the largest fruit in China, and its cultivated area and yield rank first in the world. In the 1990s, the state implemented pollution-free agricultural production. In order to control fruit diseases and insect pests, reduce pesticide residues and improve fruit appearance quality, apple industry vigorously promoted fruit bagging technology. At present, the bagging rate of apples in Shandong is as high as 75% [1], which basically solves the problem of fruit decay caused by heart-eating insects, and pesticide residues are generally reduced. However, with the increase of labor costs and the aging and lack of fruit managers, bagging has become an obstacle to Apple's large-scale, efficient and high-quality production, such as the high cost of ① production. The cost of bagging each fruit is 0.20 yuan, and the cost of bagging in 666.7m2 orchard is more than 2000 yuan. ② reduces the inherent quality of apples. After bagging, the light decreased, the sugar content and hardness of the pulp decreased significantly, and the pericarp was easy to lose water and shrink during the shelf life. The new diseases and insect pests of ③ are seriously harmful. Apple bagged for many years, the fruit is easy to lack calcium, resulting in Kang's powder scale, black spot disease and bitter pox disease aggravated year by year, and the rate of secondary fruit increased. Therefore, some apple experts advocate unbagged cultivation to alleviate the contradiction between high input and low income in apple production. After taking off the bag, the apple will face a new problem of plant protection, the most important problem is the harm and control of fruit heart borer. How to master the occurrence characteristics and scientific control techniques of heart borer on apple under modern cultivation conditions are expounded from the following three aspects.

Table 1 comparison of morphological characteristics between peach borer and pear borer

1 occurrence characteristics of main heart-eating insects in apple

At present, there are mainly two kinds of heart borer on apples in Shandong Province, namely, peach small heart borer (also known as peach fruit borer) and pear small fruit borer (also known as pear fruit borer), respectively. Both of them can damage the fruit, cause fruit decay and shedding, and seriously affect the yield and quality of apple. However, there are great differences in their morphology and occurrence characteristics, which can be distinguished by comparison between Table 1 and Table 2.

Table 2 comparison of occurrence characteristics between peach borer and pear borer

2 the key factors affecting the occurrence of heart-eating insects

2.1 Biological environment

With the rapid development of urban and rural environmental greening, the planting of ornamental fruit trees is very common, such as begonia, apricot, peach, pear, cherry, plum, etc., together with the blue peach, cherry blossom, plum blossom, purple leaf plum and so on. These are suitable hosts for peach and pear heart borer. Under normal circumstances, the pests of these trees are rarely controlled, and the heart-eating insects are basically not controlled, which leads to the smooth flow and spread of the heart-eating insects on these trees, and gradually transferred to the nearby apple orchards.

In addition, in order to improve the fruit setting rate of apples, some begonia trees planted in most new large-scale orchards pollinate apples, but the control of crabapple trees is neglected in the prevention and control of diseases and insect pests, resulting in crabapple trees becoming a breeding ground and shelter for two kinds of heart-eating insects. Continue to provide insect sources for apples.

2.2 temperature and humidity

Temperature and humidity are the key factors affecting the growth, development and reproduction of insects. With the global warming, the annual average temperature generally increases, and so will the ground temperature. According to Liu Xianzhao and others, during the 40 years from 1961 to 1999, the annual average temperature in Yantai area increased by 0.6 ℃, in which the winter mean temperature increased the most, from-1.5 ℃ in the 1960s to 0.3 ℃ in the 1990s. Song Jiaying and Guo Lei analyzed the temperature change in Muping from 1971 to 2010 and found that the climate tendency rate was 0.49 ℃ / 10 years [4]. According to the effect of temperature on two kinds of heart borer, the mortality of overwintering larvae may decrease with the increase of air temperature, the occurrence period of overwintering adults will be earlier, the annual generation will increase, and even stimulate their reproduction [Cyclocarya paliurus]. Shen Changpeng et al reported in 1993 that the occurrence peak of overwintering adults of peach heart borer in apple orchard in Fushan District of Yantai City was from late June to early July [8]. In 2016, the overwintering adults in Fushan District and Laizhou City of Yantai City began to appear in mid-May, and the peak of Eclosion occurred in mid-June, which was obviously earlier than that in 1990, indicating that it was related to climate warming.

Many literatures have reported that the appearance of overwintering adults of peach heart borer is affected by humidity sooner or later [Jishan Huayao]. With the development of water conservancy facilities and the improvement of irrigation conditions in our country, the existing apple orchards basically have irrigation conditions, and spring irrigation has become the norm. Watering the orchard in spring will not only benefit the pupation and emergence of the overwintering larvae of peach borer, but also lead to the occurrence of overwintering adults in advance.

2.3 Grass growing technology

Many experimental results show that growing grass in orchard can increase the content of soil organic matter, adjust soil pH value, promote the root growth of fruit trees, and provide rich food sources and good habitat for natural enemies [13-14]. However, the recommendation between artificial rows is not conducive to clearing the orchard and ploughing the soil in winter, and is beneficial to the overwintering of peach borer and pear borer under deciduous weeds and surface soil, which increases the source base of overwintering insects and leads to serious occurrence in the next year. it is necessary to grow grass reasonably and strengthen field management.

2.4 drip irrigation technology

In general, peach borer and pear borer are mostly concentrated in the 50cm soil near the tree trunk to overwinter. the implementation of drip irrigation technology in apple orchard provides a guarantee for timely irrigation and maintaining stable soil water content around the root system. The soil around the tree trunk of the orchard with drip irrigation facilities keeps suitable moisture in spring, which provides favorable conditions for pupation and adult Eclosion of the two kinds of borer.

3 comprehensive techniques for the control of heart-eating insects

Artificial prevention and control. The fallen fruit was picked up in time in the field and concentrated into the biogas digester to prevent the larvae of two kinds of heart-eating insects from climbing into the soil from the fruit. Before the occurrence of overwintering adults, plastic film is covered under the tree to prevent the adults from coming out to lay eggs on the tree. Apple young fruit bagging protection to prevent peach heart borer and pear heart borer contact with apples. In addition, for the pear heart borer, the old rough skin and warped skin on the branches were scraped in winter and spring to eliminate the overwintering larvae; the damaged new shoots were removed in time during the growth period and concentrated treatment; before the overwintering larvae shed fruit, the weeds on the main branches and trunk were used to trap the fruit-free larvae and burn them in late autumn or early spring.

Grass grows naturally. Under the condition of natural grass growing in the orchard, the whole orchard can turn over the soil in autumn and early spring, destroy the overwintering places of the two kinds of heart-eating insects, make them exposed to the soil surface to be sunburned or frozen to death, and reduce the number of insect sources in the following year. At the same time, weeds can be cleared at any time in spring, so it is convenient to apply entomopathogenic nematodes and pesticides to control larvae and pupae in the soil.

Biological control. From May to September, when the peach heart borer larva lives in the soil, the entomopathogenic nematode suspension can be used to spray the soil under the crown to parasitize the peach larva and control the pear heart borer, grub, golden needle worm and so on. According to the prediction of trapping moths, the parasitic eggs of Trichogramma were released in the field during the adult occurrence of peach borer and pear borer respectively. The bees are generally released once every 4 or 5 days and released for 3 or 4 times in a row.

Trapping moths to control. At the initial stage of adult occurrence of each generation, sex attractants or isotropic filaments of peach and pear heart borer were hung in the field to trap and kill male adults or make males unable to find females, resulting in the decrease of field population mating and reproduction rate, and gradually reduced the number of offspring of the two kinds of heart borer. According to the chemotaxis of pear heart borer, hanging sweet and sour liquid cans in the field can trap and kill female and male adults.

Chemical control. The key period of tree spraying control of peach borer and pear borer is egg stage, and it is difficult to play a role once the larvae eat into the fruit or new shoots. The prediction of insect situation must be done before spraying, and the occurrence period of adults must be predicted by using the method of trapping male moths. Since late April, the sex attractors of peach borer and pear borer were hung in apple orchards to monitor the occurrence time and number of overwintering adults. When the overwintering adults were attracted in the field for 3 consecutive days, spraying on the trees and spraying the second time after 10 days could effectively control the eggs and newly hatched larvae of the first generation. The control of the eggs of the second generation is generally sprayed on the second day of the peak period according to the peak period of trapping moths. For the first time, 35% chlorobenzamide water dispersible granules were sprayed 8000 times, plus 2.5% deltamethrin EC 2000 times, and for the second time, 2500 times 1% methotrexate EC and 2500 times 2.5% cyhalothrin EC.