Why do peach aphids often occur on peach trees and how to prevent them?

Myzus persicae is one of the main pests that harm peach leaves, and it occurs in most main peach producing areas in China. When the insect occurs in large quantities, it will intensively suck juice on the terminal buds of tender leaves, leaves, tender stems and buds, making the leaves of peach trees curly, pale and deformed, and in severe cases, it will fall off in large quantities. According to the severity of the disease, combined with the production practice, the symptoms, occurrence regularity, causes and control methods of the disease were introduced in order to guide the production of fruit farmers.

I. Symptoms of Myzus persicae

Aphids belong to Homoptera Aphidae. Through field investigation, it is found that there are three main kinds of aphids that harm peach trees: peach aphid, peach aphid and peach aphid. The symptoms of different aphids are different, as follows:

1. Harmful symptoms of Myzus persicae

Myzus persicae mainly lives in the buds, leaves and shoots of peach trees in the form of adults and nymphs. The back of the damaged leaves will curl irregularly and fall off naturally after a long time. Myzus persicae not only causes direct harm to plants, but also causes a large number of peach tree coal diseases through its excrement, and is also the transmission medium of most virus diseases.

2. Harmful symptoms of Myzus persicae

Myzus persicae also lives in groups as adults and nymphs, but it mainly infects by absorbing nutrients from leaves. The damaged leaves will be yellowed to varying degrees, accompanied by leaf back curl and ash stratification.

3. Harmful symptoms of Myzus persicae

The infection mode of Myzus persicae is similar to that of Myzus persicae, but the difference is that its harm will make the leaf edge curl backward into a tube, and in severe cases, it will curl into a rope, and then dry up and fall off.

Second, the occurrence law of Myzus persicae

1. Climate and environment

The optimum temperature for the growth and reproduction of Myzus persicae is 14℃-26℃. Compared with other pests, Myzus persicae has strong low temperature tolerance and low development threshold temperature, so this pest will last longer. The optimum humidity for the growth and reproduction of Myzus persicae is 50%-85%. In this humid environment, aphids will multiply in large numbers, aggravating the degree of infection. For humidity and temperature, they play a complementary role, in other words, when the temperature is suitable, humidity becomes the decisive factor affecting the occurrence of aphids; On the contrary, when the humidity is suitable, the temperature becomes the decisive factor of the occurrence degree of aphids.

2. onset period.

Peachtree aphids can produce 20-30 generations every year in the north, and generally reproduce by parthenogenesis in March-April every year, and initially start to infect and harm; It will reach the peak of breeding in May, when the damage will be further aggravated and last until September of that year; After June 65438+ 10, aphids began to move back to prepare for winter.

3. Hosts and natural enemies

Peachtree aphids are mainly rape, Chinese cabbage, cabbage and so on. In Cruciferae, peach, plum, apricot, etc. Vicia faba of Rosaceae, pea of Leguminosae, pepper, potato, eggplant, etc. In a word, plants that can be used as food for aphids are their potential hosts, which reminds us what we should pay attention to around Taoyuan. In terms of natural enemies, it is mainly divided into predatory and parasitic natural enemies, among which predatory natural enemies mainly include ladybug, Chrysopa grandiflora, stinkbug parviflora, syrphidae with black belt and so on. Parasitic natural enemies mainly include Myzus persicae, Aphidae and Aphidae.

3. Causes of Myzus persicae

1. The temperature rises early and fluctuates greatly.

The temperature in peach tree cultivation area rises rapidly in early spring, which on the one hand will lead to early germination and flowering of trees, on the other hand, it will also lead to early hatching of aphid eggs, increasing the number of breeding generations, which is more harmful. However, the large temperature difference between day and night and the wide temperature fluctuation range in the cultivation area will cause the plant to grow slowly, the flowering period will be relatively prolonged, and the leaves will grow slowly, which creates very favorable external conditions for the incubation, reproduction and diffusion of aphids.

2. Orchard air drying

Through the analysis of the relative humidity required for aphid occurrence, it is found that this humidity is lower than that of other pests. Therefore, in some cultivation areas in spring, when the rainfall is low and the air volume is high, the air inside the orchard will be relatively dry, and aphids like a dry, warm and sunny environment, which creates an indispensable favorable condition for aphid occurrence.

3. Farming management is not in place

Affected by traditional fertilization methods, some fruit farmers still pay too much attention to the application of nitrogen fertilizer in fertilizer selection, which leads to the futile growth of trees, the decline of overall tree vigor and the decline of pest resistance. In addition, due to the influence of climate and environment, the hatching and reproduction of aphids in some areas will be advanced. At this time, if fruit farmers still carry out prevention and control according to previous prevention and control experience, it is easy to spray pesticides when aphids mature, and the efficacy is not as good as before. Finally, in recent years, in order to save time and effort, most fruit tree planting areas will use a large number of broad-spectrum insecticides for pest control, which will easily lead to a significant reduction in the number of natural enemies of Myzus persicae, thus reducing the effect of biological control.

Four, peach aphid control measures

For the control of Myzus persicae, fruit farmers should combine agricultural control with chemical control, but the role of biological control can not be ignored. The specific operation is as follows:

1. Agricultural control

First of all, combined with the pruning of peach trees in winter, the dead branches and injured branches on the plants are cut off, at the same time, the old warped skin is scraped off, and the dead leaves in the yard are removed, and then the orchard is pulled out for centralized treatment, so as to achieve the purpose of eliminating overwintering eggs. Secondly, in March of the first year, the whole garden was sprayed with 5 Baume of stone sulfur mixture to continue to strengthen the elimination of eggs. Thirdly, because the occurrence of Myzus persicae is related to the nutritional status of trees, formula fertilization should be combined with the characteristics of peach phenology in the process of fertilization, so as to minimize the application of nitrogen fertilizer, cultivate strong or moderate tree vigor and enhance the disease resistance of trees. Finally, when aphids occur, you can choose to hang sweet and sour liquid, yellow board and black light in the garden to trap and kill aphids.

2. Biological control

The natural enemies of aphids include predatory natural enemies, such as ladybug, Chrysopa grandiflora, stinkbug parviflora, Syrphidae, etc., and parasitic natural enemies, such as Myzus persicae, Aphididae, etc. In view of these natural enemies, fruit farmers in aphid-prone areas should pay attention to protecting these natural enemies. Specifically, we can try to avoid excessive use of broad-spectrum pesticides by reducing the frequency and dosage of spraying. Even if pesticides need to be used for control, biological pesticides such as pyrethrins and rotenone can be selected for control. This control method is very beneficial to the adoption of green and pollution-free producing areas.

3. Chemical control

The key period of peach aphid control is within 10 days after peach blossom. At this time, 2000-3000 times of 10% imidacloprid wettable powder and 2500 times of acetamiprid or pyrethroid pesticides can be sprayed for control. In addition to spraying pesticides, you can also choose to smear 10% imidacloprid 2- 10 times on the trunk or the base of the trunk to form a drug ring with a width of 6cm, and then wrap it with plastic film for prevention and control.