Disease management of green beans What diseases do green beans have?

When we plant green beans, we sometimes find many diseases. So how can we better prevent and control them at this time?

Bean Pod Borer

Morphological characteristics: The adult body is 10-12 mm long, with a wingspan of 20-24 mm, and the body is gray-brown or dark yellow-brown. The forewings are narrow and long, with a white longitudinal band along the front edge, and a wide golden horizontal band near the 1/3 of the wing base. The hind wings are yellow-white, with brown along the outer edge. The eggs are oval, about 0.5 mm long, with inconspicuous reticulation on the surface. They are milky white when first laid, gradually turn red, and light chrysanthemum yellow before hatching. There are 5 larvae in total, and the mature larvae are 14-18 mm long. The newly hatched larvae are light yellow. Later, they are gray-green and purple-red. There is a "human"-shaped black spot in the center of the pronotum near the front edge of the 4th to 5th instar larvae, with 1 black spot on each side, and 2 small black spots in the center of the rear edge. The pupa is 9-10 mm long, yellow-brown, with 6 anal spines, and the pupa is covered with an oval cocoon made of white silk.

Damage symptoms: The larvae bore into the pods. After hatching, the larvae form a thin white silk cocoon on the pods, and bore into the pods from under the cocoon to eat the beans, causing the pods to be shrunken and empty. They can also damage petioles, flower buds and tender stems.

Prevention and treatment methods:

1. Make reasonable layout to avoid continuous or adjacent planting of leguminous crops and leguminous green manures, and implement water-land rotation where conditions permit to reduce insect sources.

2. Plough the land or remove weeds and loosen the soil in time. Where conditions permit, irrigate in winter and spring to eliminate overwintering insects.

3. Leguminous green manure should be plowed or fermented before pod formation. After soybean harvest, the plants should be pulled out in time and transported out of the field to reduce the number of overwintering larvae in the field.

4. Choose early-maturing and high-yielding varieties with a short pod-setting period and little or no hair.

5. Before the mature larvae enter the soil, apply 1.5 kg of Beauveria bassiana powder and 4.5 kg of fine soil per mu under high humidity conditions.

6. During the peak period of moth infestation and egg hatching, for soybeans in the early flowering stage, cowpeas and green beans in the bud and flowering stages, you can choose to use 90% crystal dichlorvos, or 50% cypermethrin emulsifiable concentrate, or 50% malathion emulsifiable concentrate, all at 1000 times dilution, or 2.5% cypermethrin emulsifiable concentrate at 3000 times dilution for spraying.

Borer

Green bean borer has one generation per year, and the mature larvae overwinter in the soil as cocoons. They float to the surface soil and pupate in late July of the following year. They begin to emerge as adults in late July and early August, with the peak emergence period in mid-August. After mating, the adults lay eggs on young pods, which hatch into larvae after 6 to 7 days. The larvae crawl on the pods for a few hours and then enter the pods to cause damage. The larval stage is 20 to 30 days, and they begin to shed their pods and enter the soil in September.

Prevention and treatment methods:

1. Prevention and control during the peak period of adult occurrence

To grasp the peak period of adult moths, we must first make a good forecast. From the beginning of August, we should investigate the number of adult moths every afternoon before sunset. When the number of moths in the field suddenly increases and the phenomenon of grouping appears, it is the peak period of adult moths (most years are from August 12 to 18). Prevention and control methods: One is fumigation with dichlorvos sticks. Use 100-150 ml of 80% dichlorvos emulsifiable concentrate per mu, cut the corn cobs or sunflower stalks into about 5 cm long sections, soak them in dichlorvos solution, and clamp the sticks on the green bean branches at a density of 1 stick every 4 ridges and 5 meters. This fumigation method is suitable for green bean fields with lush growth and dense shade between ridges, and the prevention effect can reach more than 90%. The second method is spraying. Use 25% quick kill emulsifiable concentrate or other pyrethroids, 25-30 ml per mu of water, use a backpack sprayer with the nozzle facing upwards and spray from the root of the bean upwards, so that the lower branches and leaves and the back of the top leaves are covered with medicine. This method of controlling adult insects is effective regardless of the growth condition of soybeans.

2. Prevention and control before larvae enter pods

After the larvae of green bean borer hatch, they usually crawl on the bean pods for no more than 8 hours. This time is difficult to grasp. Therefore, field surveys must be conducted to control the larvae. When eggs are seen on the green bean pods, pesticides can be applied. To control the larvae, pyrethroids are generally used to spray water. The spray should be even, especially on the pods. This method can achieve an effect of about 80% in controlling the larvae.

3. Prevention and control of green beans after harvest

Green beans are usually harvested in September, when some borers have not yet shed their pods. If they are not threshed in time, the borers can continue to cause damage in the pods and gradually shed their pods and go into the soil.