<h1>1 apple small heartworm</h1>
Apple small heartworm, insectae Lepidoptera ( Lepidoptera ) small curl moth family ( Olethreut-idae). Also known as the apple moth. The hosts are mainly apples, pears, sand fruits, begonias, hawthorns and mountain butchers. Sometimes the harm to pears is heavier than the harm to apples. It is found in Northeast China, North China, Northwest China and Northern Jiangsu. It is more serious in the apple-producing areas of southern Liaoning and Shandong Peninsula. It is also found in Japan and North Korea. Poor adaptability to high temperatures limits its distribution to the south.
<h1>2 Morphological characteristics of apple small heartworms</h1>
Adults: 4.5 to 5.0 mm in length and 10 to 11 mm in wingspan. The morphological differences between male and female moths are minimal. The whole is dark brown with a purple luster, the head scales are gray, the back of the antennae is dark brown, the end of each segment is white, and the lips are gray and slightly upturned. The forewing margin has 7 to 9 groups of white hook-like stripes of varying sizes, and there are many white scales on the wing surface forming white spots, and the white spots near the outer edge are neatly arranged. The outer edge is significantly oblique, and the outer edge is formed by the two forewings when stationary, and the outer edge is about 90 degrees or less than 90 degrees. The striations on the anus are inconspicuous, with four black spots, a large dark spot at the apex, and gray-brown margins. The hindwings are lighter in color than the forewings and have a light greyish brown belly and feet.
Eggs: flattened oval, central bulge, flattened periphery, with occasionally noticeable and irregular fine wrinkles on the surface. The initial milk is white, later pale yellow, translucent, shiny, and pale yellowish brown near hatching.
Larvae: 6.5 to 9.0 mm long, yellowish or reddish in the entire non-ossified area. The head is pale yellowish brown, the forebreast shield is yellowish brown, the front thorax is hairy in the group of 3 hairs, and there are two peach-red stripes on the back of each body segment, one thick in front and one small in the back. The buttocks are pale brown, with irregular dark markings, the buttocks are dark brown with 4 to 6 teeth, the ventral toe hooks vary from 15 to 34, most of them are about 25, and the gluteal toe hooks are 10 to 29, most of which are 15 to 20.
Pupae: 4.5 to 5.6 mm in length, yellowish brown or yellow, no spines on the back of the first abdominal segment, a row of small spines on the dorsal anterior and posterior margins of the 2nd to 7th abdominal segments, a small spine on the anterior margin of the 3rd to 7th abdominal segment, and only one larger spine in the 8th to 10th abdominal segment. The ventral end has 8 hook-like spiny hairs. The cocoon is oblong-oval and off-white.
<h1>3 Habits of life</h1>
Apple small heartworms occur in 2 generations a year on apple trees in Liaoning, Shandong, Hebei and Shaanxi, and mostly 1 generation on pear trees. Old mature larvae overwinter in cracks in bark, tree poles, hanging branches grass flies, fruit baskets and other gaps, and the number of late-maturing varieties of trees is the largest. In Southern Liaoning and Hebei Province in mid-to-late May of the following year began to pupate, early June appeared overwintering adults and the first generation of eggs, the egg period of 5-7 days, hatched larval borer fruit pest, larval stage of about 20 days, generally in the late July to early August larvae mature after the old ripening of the pupa, pupal period of 10-15 days, after feathering into the first generation of adults, the peak in early August, mid-August, laying 2 generations of eggs on the fruit, hatching of 2 generations of larvae in the fruit development, about 20 days or so in late August mature and successively defruiting, overwintering. Adults lurk during the day, are active in the evening, and mate at night, and the eggs are mostly produced in the carcass of the fruit. Low temperatures of 14 °C and 34 °C kill eggs. Below 50% humidity, the eggs cannot hatch. The optimal temperature for spawning is 25 to 29 °C and the relative humidity is 95%.
4 Occurrence and hazard characteristics
The larvae feed on the fruit, but do not go deep into the heart, generally only moth in the shallow subcutaneous area, and the red around the first borer hole is commonly known as the red eye circle. Later, the damaged part gradually expanded and withered and depression appeared brown to black brown, commonly known as dry scars, with several small worm holes on the scars, and a small amount of insect feces. Young fruit victimization often causes deformity. The larvae do not survive after the fruit is destroyed, and the peel around the borer hole becomes green, called a blue boil. When small fruits are harmed, such as hawthorn, the larvae can moth into the heart of the fruit. Adults lurk under the leaves during the day and have certain chemotaxis on molasses, fennel oil and sassafras oil, but the phototropism is very weak. Adults like to lay eggs on the carcass of the fruit, and there are very few eggs in the stems and calyxes, so when spraying egg killing drugs, the fruit surface should be sprayed thoughtfully. After ovulation, the larvae burrow into the fruit after a short crawl time. The larvae defoliate in the fruit after about 20 days. The second generation of apples is small and harmful to the apples of the late maturing varieties, so the prevention and control work in the later stage cannot be relaxed.
<h1>5 Prevention and control methods</h1>
(1) Selection of fruit forests. The establishment of fruit forests should take full account of differences in geographical environment. When the fruit forest is selected on the slope, it should have a sunny slope with good soil conditions and perfect water conservancy facilities; if it is flat, the planting method of high ridge and deep ditch should be selected. Rational layout of different types of fruit trees to avoid the occurrence of mixed species and avoid the transfer of heartworms. If there are 2 or more fruit trees in the orchard, a barrier should be established.
(2) Cover to kill insects or trap overwintering larvae. Mulching is available for areas where heartworms broke out in the previous year, with the option of mid-to-late May, covering a 1m area centered on the trunk. At the end of April, the soil is cultivated under the tree, and the soil thickness is controlled to about 9 cm, but the soil needs to be removed in early June, and the tile method can also be used. Several of the above methods can prevent the emergence, pupalization and feathering of overwintering larvae. Overwintering larvae can be trapped, and in early September, grass or sacks are tied around tree trunks and large branches to induce the larvae to lurk. Grass handles or sacks are collected and burned in the early spring of the following year, but this method has the disadvantage of accidentally injuring the natural enemies of insects. Applying lime to the trunk is also a good method, which can effectively kill the larvae hidden in the trunk.
(3) Bagging, scraping and shearing. Bagging should be carried out after fruiting, at which time the physiological fruit fall is over, and the time is about 35 days after the flower fall. The time to remove the bag should vary depending on the variety, mostly 20 days before picking, which is conducive to apple coloring and avoiding pests. The prevention and control of heartworms in double-layered bags has the best effect and should be vigorously promoted. Scraping can effectively reduce the base of the pest's mouth. Before winter, for older apple trees, the coarse bark is stripped and the peel is collected and burned; in early spring, the epidermis at the base of the tree (about 15 cm deep) is cleaned and the overwintering cocoon is scraped off. After the larvae are found to be mothed into the new shoots, they are pruned and burned before transfer. In winter and spring, in the process of pruning, remove dead branches, insect branches and galls in time.
(4) Picking insect fruits and clearing the garden. The picking of the insect fruit should run from July to the end of the harvest, followed by the clearance of the garden. The frequency of picking is maintained at 10 d/time, which can be carried out in combination with fruit thinning and removal before the larvae are out of the fruit. The apple pile is covered with sand and compacted to pile the fruit, luring the larvae into the sand and collecting the sand to kill. Remove weeds and dead leaves from the orchard and bring them out of the orchard to burn. It is also possible to perform a deep turn to destroy the shaded place of the pupae.
(5) Forecasting. In general, in the apple-producing areas of northern Hebei and southern Liaoning, eggs are checked every 3 days from the beginning of June. Each plot of land is randomly sampled with 3% to 5% of the plants, each tree randomly selects 100 fruits from the middle of the canopy, calculates the egg fruit rate, and if the egg fruit rate reaches 0.5% to 1%, spraying should begin.
(6) Physical prevention and control. In the control of apple heartworms, the following three methods are often used, namely sweet and sour booby trap, sex inducer booby trap and black light booby trap. The sweet and sour method of booby-trap is to use a basin or other container containing sweet and sour liquid combined with dish soap or washing powder to place in an orchard on a sunny day, with a hanging height of about 1.8m, hanging before sunset, and retrieved in the morning. This method is simple and practical, and the effect is better. Sexual inducer booby-trap is a new technology that can effectively predict insect infestation, and can trap male adults and interfere with their normal mating, which is a green technology with strong pertinence. The black light booby trap method is to use the strong tendency of adult heart-eating insects to black light to kill adult insects, and their working hours are mainly at night. From late April, high-voltage grid insecticide lights and black light lamps were set up in the orchards, and large-mouth containers filled with water were placed under the lights to remove dead insects on the second day.
(7) Biological control. The biological control of apple heartworms mainly includes the control of natural enemies, the control of biological pesticides and the control of interference mating. Under the condition of medium and high level of apple heartworm egg density, the use of pine caterpillars and red-eyed bees for prevention and control is better. It can also be used as natural enemies of heartworms, spiders, grasshoppers, Chinese tooth-legged wasps, pear small heart-eating white cocoon bees and beetle-bellied cocoon bees. The biopesticides of heartworms include Thuringiensis, White Zombie, Green Paulowe Emulsion, etc., which have little pollution and are a good choice for organic fruit production. Interference mating refers to the use of sexual pheromones, interfering with the mating of male and female moths, and the often used mithromed silk and sexual pheromone microcapsules.
(8) Chemical control. Spraying on trees to control borers. Spray 50% borer pine emulsion 1000 times liquid during the overwintering adult and first generation adult occurrence stages. The first and second generations of eggs are sprayed once each during the peak period.
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