It is often seen in pear orchards that the branches of pear trees with relatively extensive management show a phenomenon of drying up or even dying, resulting in the defoliation of the tree body, and the fruit also appears in a circle of red spots, which directly leads to a decline in the value of fruit commodities. Then, in view of such a situation, it is necessary to understand the causes and control methods to protect the pear tree from harm.
In fact, this is a phenomenon caused by pest damage, it is a common pear roundworm in the orchard, and it is also known as pear pill shell worm, pear branch round shield worm, and rotifer shell worm. Is the same order, insects of the family Ophidae, it not only harms pear trees, but also occurs in china's major fruit-producing areas, common apples, walnuts, dates, cherries, plums, persimmons and other fruit trees can be seen, its harm is wide range, food habits are more mixed.
Pear roundworm is one of the international quarantine objects, and is still mainly distributed in the northern fruit producing areas. Pear roundworm can parasitize all the aerial parts of fruit trees, especially the branches, after the pear roundworm sucks the branches, causing the decay of cortex wood plugs and phloems, catheter tissue, cortical bursting, inhibiting growth, causing leaf fall, and even branches drying up and the whole plant dies. When parasitizing on the fruit, it is mostly concentrated in calyxes and stems, forming purple-red spots around the shell.
The female of the pear roundworm is covered with a nearly rounded mesohull with a diameter of 1.8 mm, grayish-white or gray-brown, with concentric chakra, and the yellow or yellow-brown umbilical part protruding from the center of the mesemb is called the bright spot. The female is an orange-yellow flat oval worm with a body length of 0.91 to 1.48 mm and a width of 0.75 to 1.23 mm, with filamentous mouthparts, located in the center of the ventral surface, and the eyes and feet are degenerated.
The male insect shell is oblong oval, smaller than the female shell, and the shell point is located at one end of the shell; the male insect body is orange-yellow, the body length is 0.6 mm, the eyes are dark purple-red, the mouth organ is degenerated, and the 11 antennae are rosary-shaped, with 1 pair of wings, and the tailparts are sword-like. The nymphs are 0.2 mm long, oval orange-yellow, with 3 pairs of well-developed feet and 2 long hairs at the end of the tail.
The number of generations that occur in 1 year varies from region to region and host. 4 to 5 generations occur in the south and 2 to 3 generations in the north; 2 generations occur in Liaoning and Hebei in 1 year, and 4 generations occur in Zhejiang, all of which overwinter with 2-year nymphs attached to the branches, and the next year the bud germination begins to continue to be harmful.
The feathering period of adults in the overwintering generation of Changli, Hebei Province, is concentrated in early to mid-May, the males die after feathering and mating, and the females give birth from early to late June. The first generation of adults feathered from mid-July to early August and the littering period was from mid-August to mid-September.
Pear roundworms reproduce in both sexes and give birth to oviparities. The hatching nymphs crawl out of the female shell, move quickly, migrate to the young branches, leaves, and fruits, find a suitable part, insert the mouthparts into the host tissue, fix and no longer move, and begin to secrete wax and gradually form a shell.
The first nymphs shed their first skin after 10 to 12 days, and the female nymphs molt twice after becoming female adults; the male nymphs pupate after 3 years of age, from pupa feathers to adults. Overwintering female insects are mostly fixed in the branches and branches, mainly on the sunny side of the branches, the male insects are mostly fixed on both sides of the main veins of the leaves, and the nymphs that occur in summer and autumn migrate to the leaves. In general, there are few harmful fruits before July, and after August, the harmful fruits gradually increase.
<h1>Prevention and control methods</h1>
1. Artificial prevention and control. Pear roundworms often occur in spots and pieces on pear trees, and even on one tree, only one or two branches are serious, and other branches can not even find insects. Therefore, the pear tree can be artificially erased with the control method of overwintering nymphs, or the branches of the mesozoite host can be cut off and taken out of the park for centralized burning treatment.
2. Pharmaceutical prevention and treatment. Pear roundworm that occurs on pear trees, overwintering insect feathering and female littering period concentration, is a favorable time for growth period control, can be sprayed 0.3 baumedo stone sulfur binder, 25% thiazide hydrability powder 1500 times liquid, 24% spirant ethyl ester suspension 4000 ~ 5000 times liquid spray, 20% imidacloprid concentrated solvent 3000 times liquid, 20% permethrin or 2.5% cypermethrin emulsion 3000 ~ 4000 times liquid.
3. Protect predators. During the growing season, pear orchards or other orchards try to avoid the use of broad-spectrum insecticides with long residual effects to facilitate the occurrence of natural enemies.
4. Strengthen plant quarantine. Strict inspections of seedlings and scions transferred to other places should be carried out to prevent pear roundworms from being carried along with the seedlings.
For the introduction and control methods of pear tree pest pear roundworm is roughly the above content, if there is a more reliable and practical control technology, welcome to leave a message in the comment area. Fruit tree disease and pest control is the top priority, fruit farmers should pay enough attention to take relevant preventive measures in advance, can achieve a multiplier effect of prevention and control, and fully protect pear trees and fruits from being affected.