Causes and countermeasures of occurrence of black spots on pear fruit
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According to the survey, it has been found that there are more black spots in the young fruit of Huangguan pear, and there are fewer occurrences of pear and snow pear. Most of the pears that had black spots occurred after spraying on May 12-14. No black spots were found at other times.
I. Causes of Black Spots Produced by Pear
1. Different pear varieties, different developmental stages and different growth potentials have different sensitivities. In the early growth period of pear trees, young leaves and young fruit are more sensitive to pesticides, chemical fertilizers, and hormones. In particular, Huangguan pear, Dangshan pear, Laiyang pear, and other fruit surfaces are delicate and are likely to cause fruit surface damage. In addition, triazole pesticides such as Tebuzole, Diniconazole, and Myclobutanil may cause leaf curling and fruit stagnation in the early stage, but they are equivalent in the later growth stage (after the formation of leaves, fruits, and wax layers). Stability and security.
2. There are differences in the sensitivity of different pharmaceutical ingredients. Many formulated pesticides, such as compound thiophanate-methyl, compound carbendazim, etc., themselves contain sulphur powder or copper preparations, and sulphur or copper-containing mixtures can also cause harm to fruit surfaces at slightly higher temperatures.
3 drug technology, medication time, dosage and drug mix.
1 When the spray gun is over-stressed, it may cause damage to the fruit surface. Excessive pressure on the spray gun or spraying too close to the fruit and staying too long will cause some damage to the fruit surface. It is suggested that the spray gun pressure should be moderate when spraying, and keep a certain distance from the fruit, so the atomization effect is also good, which is conducive to the development of liquid medicine.
2 The concentration of pesticide sprays is arbitrarily increased. This is a common problem in agricultural production. Many farmers are arbitrarily increasing the dosage and increasing the concentration of the drug because of concerns about the bad effect of spraying. This not only causes the waste of pesticides, increases the input of pesticides, aggravates the environmental pollution, but also increases the damage to the fruit to a certain extent. probability.
3 The names of pesticides on the market are relatively chaotic, and some pesticides are not clearly identified. When pesticides are mixed with several pesticides, it is prone to duplication of ingredients and inadvertently increase the amount and concentration of pesticides.
4 When pesticides are mixed, some fertilizers and wettable powders are used as pesticides. They do not need to be diluted and dissolved in advance. Fertilizers or pesticides are used when they are not completely dissolved, and they are prone to phytotoxicity.
4. The impact of environmental factors. In general, temperature is proportional to the occurrence of injury. When the temperature is high, not only the chemical activity of the pharmaceutical agent is strong, but also the metabolism of the plant is strong, which facilitates the rapid infiltration of the pesticide into the tissue and is prone to phytotoxicity. Many pharmaceuticals have stable performance at low temperatures and are prone to problems when used at high temperatures. High humidity also facilitates dissolution or infiltration of the drug. Therefore, it is prone to phytotoxicity when spraying in the more exposed and rainy weather.
In summary, in mid-May, the causes of black spots after spraying in some pear-producing areas of our province were many and may be related to the climate conditions of the past few days, such as the temperature, humidity, and the microclimate of the orchards. In the morning, although the temperature is low, but the humidity is high, it is also prone to phytotoxicity. This is also the same barrel of medicine that appears in some orchards. The black spots are sprayed in the morning and the dark spots gradually decrease.
Second, after the emergence of black spots management measures First, when the fruit thinning, sparse black fruit, preserved young fruit smooth surface; Second, to strengthen the management of fertilizer and water, spraying some cytokinin pesticides such as love more income, To a certain extent, the black spots on the fruit surface can be reduced. In addition, some other leaf fertilizers were sprayed to increase the yield and improve the quality of Huangguan pear.