Hello everyone, I am a farmer. I believe that the farmers who grow walnuts must have encountered the abnormal blackening of the peel of green-skinned walnuts, and most of these black-skinned walnuts will fall fruit early, and the peach kernels of unpopular walnuts will also become black, dry, and lose their economic value. However, the cause of walnut black skin is not more than one, sometimes easy to confuse, resulting in us to the wrong direction of prevention and control, today I will summarize all the reasons for "black walnut" and the distinction, prevention and control methods.
<h1 class= "pgc-h-arrow-right" > causes of disease</h1>
1. Walnut black spot disease
Symptom category:
Relatively speaking, black spot disease is relatively easy to identify, as the name suggests, the walnut skin infected with this disease does not directly turn black in a large area, but first produces small black-brown spots; when wet, the center of the small black spot will produce white mold spots. As the disease worsens, the black spots gradually expand and join into one piece, resulting in black-skinned walnuts, but the spots are dry and do not decay.
Prevention and control methods:
If there is a record of black spot disease in previous years, it is best to spray the drug in advance for prevention. In early to mid-March, carefully spray the 3-5 degree stone sulfur compound before germination; after walnut leaf spreading, before flowering, spray 3,000 times the liquid with streptomycin (1 million units), and spray it again after the flower falls; spray Bordeaux liquid about 15 days apart after the walnut sits on the fruit.
Walnut black spot disease is a bacterial disease, and most of the drugs on the market today are aimed at fungal diseases, which are not effective in the treatment of black spot disease. If black spot disease has already occurred, treatment with antibiotics and copper preparations is more effective.
2. Walnut anthrax
Anthrax is transmitted very quickly and the degree of destruction of walnuts is extremely high, so it is the most important thing for us to pay attention to and prevent and control in time. Some farmers have difficulty distinguishing between walnut black spot disease and anthrax, but in fact, it is easy to distinguish between a little bit of memory. Above we said that the black spot fruit spots are dry and not rotten, and in the early stage of the disease, the black spots are only manifested on the peel, basically do not affect the inside of the fruit, after cutting the walnut can be found that there is no serious rot in the fruit. The spots on the green-skinned walnuts infected with anthrax will not only rot and be accompanied by a sour taste, but also rot inside the fruit.
Anthrax is high in humid and hot climates, so before the summer rainy season arrives, we need to start strengthening our precautions. After entering the rainy season, Bordeaux liquid can be sprayed in walnut gardens every half a month or so for sterilization and control; it is also possible to spray 300 times of copper acetate before walnut germination, and spray 2% niacin 500 times liquid or 10% phenylethoconazole 3000 times liquid before flowering, and the control effect is better.
Once the symptoms of infection are found, the diseased fruit should be removed in time, and 20% pentrazole 2000 times liquid and 80% daisen manganese zinc 800 times liquid should be sprayed 2-3 times. For severely ill walnut orchards, 2% nitropycin 500 times liquid and 10% phenoxymethanazole 3000 times liquid can be sprayed alternately.
<h1 class= "pgc-h-arrow-right" > second, the cause of insect pests</h1>
1. Walnut lifting moth
The walnut lifting moth will moth into the walnut fruit during the larval stage, and as the larvae grow, they will cross the fruit to eat the pest. The main characteristic of the green-skinned walnut that is harmed by the lifting moth is that the peel will have a significant dry shrinkage depression. And the walnut kernel is stunted, showing dry shrinkage and blackness.
2. Walnut fruit weevil
Weevil larvae generally occur before the hard core of the fruit, and the peel becomes black due to the lack of nutrients in the fruit due to the lack of nutrients caused by the nuts being eaten. Walnut fruit weevils are relatively easy to identify due to their large insect type, and walnut surfaces that are harmed by walnut weevils often have obvious wormholes. We can also cut open the affected fruit to see if there are elephant beetles or worm droppings inside the fruit.
3. Pest control methods
Spraying begins in early May with an interval of 10-12 days and a total of 3-4 sprays. The following agents are used alternately: 6000 times solution of insecticide, 1500 times liquid of 2.5% kung fu emulsion, 2.5% of enemy killing 1500 times liquid, 25% of cypermethrin 2500 times liquid, 45% oxidized Leguo 1500 times liquid. When spraying, it should be done without leakage and re-spraying, and the medicine should be sprayed to the back of the leaves as much as possible.
Orchards with serious insect pests must pay attention to the winter clearance. Before winter, the tree tray is planed to turn the soil under the canopy deeply to eliminate the overwintering larvae; the fallen fruit is picked up in time, and the damaged fruit on the tree is removed and taken out of the orchard for incineration; and the soil can be disinfected by sprinkling grass and wood ash. The use of permethrin insecticides for root irrigation may also be recommended to kill larvae.