What are the latest measures for pest and disease control in pear trees?
Pests and diseases in pear orchards are also one of the very important aspects. Besides keeping records of the types of pests and diseases and the damage they cause, as well as archives of the types, doses, frequencies and techniques of pesticide use, how to achieve rational use of pesticides plays a major role in pest and disease control.
First, use the right pesticide for the problem. Choose the most suitable pesticide variety to control each pest and disease. Different pathogens and insects respond differently to the toxicity of the same pesticide. In other words, every pesticide has a certain scope and target of control. For example, triadimefon can effectively control pear rust and powdery mildew, but its control effect on other diseases such as pear scab is very poor. Imidacloprid (Yibianjing) has a significant effect on controlling piercing-sucking mouthpart pests such as aphids and planthoppers, but is ineffective against mites. Deltamethrin (Decis) is effective against pear fruit moth, aphids, pear psylla, and various caterpillars and slug moths, but is ineffective against mites.
In addition, the sensitivity to pesticides differs at different stages of the disease infection process. When fungal spores are germinating and invading the pear tree, they are relatively sensitive to pesticides, and the control effect is better; once the pathogen has invaded the fruit tree and established a parasitic relationship, and the fungus has developed into mycelium, its tolerance to pesticides increases and the control effect becomes poorer; after fruiting bodies have formed, control becomes even more difficult, as with pear rust. Therefore, disease control should be carried out before the disease occurs or in its early stages.
Second, apply pesticides accurately. The correct pesticide concentration refers to the most dilute concentration that can effectively control pests and diseases without causing pesticide damage to the pear tree. Blindly increasing the pesticide concentration causes waste of the pesticide, easily leads to pest and disease resistance, and may also cause pesticide damage to pear trees, poisoning of humans and livestock, and contamination of fruit and the environment; too dilute a concentration fails to achieve the control purpose. There are many methods of pesticide application. When applying pesticides, the correct method should be selected according to the damage characteristics of the target pest, the pesticide variety and the characteristics of its formulation. For example, emulsifiable concentrates, wettable powders, suspension concentrates, aqueous solutions and soluble powders can be diluted with water for spraying; dusts and granules cannot be diluted with water for spraying. Spraying should proceed from the inside outward and from top to bottom, with no missed spots and no excessive spraying, so that the leaves are fully moistened without forming running droplets. The application rate is the amount of active ingredient of the pesticide per unit area. When controlling pear tree pests and diseases, attention should be paid not only to spraying branches, trunks, leaves and fruit evenly and thoroughly, but also to avoiding excess, especially when temperatures are high, since the liquid remaining on the leaves can quickly evaporate its water, causing the concentration to rise and possibly causing pesticide damage to the pear tree.
Third, use pesticides safely. The safe use of pesticides mainly includes safety for humans, livestock, fruit trees, fruit and natural enemies. When controlling pests and diseases in pear orchards, priority should be given to high-efficiency, low-toxicity, low-residue pesticides and biological pesticides, and the amount of pesticide used should be strictly controlled. Highly toxic and high-residue pesticides are strictly prohibited from being sprayed on fruit trees that have already set fruit. At the same time, the pesticides used must have the “three certificates” (pesticide registration certificate, production license, production approval certificate, standard number). Before operating, applicators should understand the properties of the pesticide and the precautions for safe use, and take the necessary safety measures.
Finally, protect natural enemies. Strengthening biological control of pests and diseases is necessary for producing green, pollution-free fruit. In nature, there are many natural enemies of fruit tree pests and diseases, including parasitic ones such as Trichogramma and pteromalid wasps, predatory ones such as ladybugs and green lacewings, and microbial natural enemies such as Bacillus thuringiensis and Beauveria bassiana that cause disease in pests. These natural enemies have a strong natural control effect on fruit tree pests and diseases, and we should try to protect them when carrying out chemical pesticide control.
1. Choose an appropriate application time. The best control period is when pests have reached the control threshold or the critical control period, while natural enemies have not yet become established. If there are many natural enemies in the orchard, pesticides should not be used or should be used selectively, so as to facilitate natural enemy control of pests. For example, in the early stage of aphid damage, natural enemies are few, so chemical control should be used; in the later stage, when the types and numbers of natural enemies increase, pesticides should be used as little as possible to protect natural enemies, as long as no economic damage is caused.
2. Use more systemic or highly selective pesticides and less broad-spectrum or highly toxic pesticides. For example, in the early stage of mites, specific, long-lasting acaricides should be applied to protect natural enemies. Broad-spectrum pesticides kill natural enemies while controlling pests. Natural enemies have weaker reproductive capacity than pests, so pest outbreaks are easily triggered. Choose an appropriate application time. The best control period is when pests have reached the control threshold or the critical control period, while natural enemies have not yet become established. If there are many natural enemies in the orchard, pesticides should not be used or should be used selectively, so as to facilitate natural enemy control of pests. For example, in the early stage of aphid damage, natural enemies are few, so chemical control should be used; in the later stage, when the types and numbers of natural enemies increase, pesticides should be used as little as possible to protect natural enemies, as long as no economic damage is caused.
3. Choose an appropriate application method. For example, seize the opportunity when pests occur locally and carry out selective control to reduce widespread large-area pesticide use. For example, Decis is frequently used in production because it can kill a wide variety of pests, but Decis severely harms natural enemies in pear orchards, and repeated comprehensive use can easily lead to mite outbreaks.
4. Choose an appropriate pesticide formulation. For the same pesticide, granules and micro-granules have less impact on natural enemies, while emulsifiable concentrates and dusts are more harmful to natural enemies. Choose an appropriate application method. For example, seize the opportunity when pests occur locally and carry out selective control to reduce widespread large-area pesticide use. For example, Decis is frequently used in production because it can kill a wide variety of pests, but Decis severely harms natural enemies in pear orchards, and repeated comprehensive use can easily lead to mite outbreaks.
Precautions, rational mixing. Because during a certain growth period of pear trees, multiple pests and diseases often cause damage at the same time, pear growers often mix two or more pesticides in a certain proportion and spray them together. However, pesticide mixing has strict requirements.
1. Pesticides of the same type have the same mode of action and control effect, and cannot achieve synergism or expand the control target, so they are not suitable for mixing.
2. Each mixed pesticide must not undergo changes in active ingredients after mixing, and after mixing the efficacy must not decrease or cause pesticide damage to pear trees. For example, mixing lime sulfur with Bordeaux mixture easily causes pesticide damage, and the control effect also decreases markedly.
3. The main target and occurrence stage of the current spraying must be clearly identified, and the effective pesticide or complementary pesticide for each control target must be determined.
4. If the toxicity of the mixed liquid becomes highly toxic, it is not suitable for mixing.