What to Do When Vegetables Have Aphids? Control Methods and Pesticide Recommendations

With the development of the vegetable planting industry, the damage caused by vegetable aphids has become increasingly prominent. So, what should you do when vegetables have aphids? What are the control methods for vegetable aphids? What pesticide is best to use? Today, the editor will guide everyone through an introduction:

Vegetable aphid damage

There are many kinds of vegetable aphids, including turnip aphid, cabbage aphid, tobacco aphid, green peach aphid, melon aphid, bean aphid, etc., among which turnip aphid, cabbage aphid, and tobacco aphid are the main ones harming vegetables. Vegetable aphids occur about 20 generations a year. They often gather in dense clusters on the undersides of vegetable leaves, mainly sucking the sap of vegetables, causing severe water loss and malnutrition in the plants, making them grow slowly and even stop growing when the damage is severe. After the leaves are damaged, they curl, turn yellow, and become deformed; after tender stems, flower stalks, etc. are damaged, they become deformed, affecting seed setting. In addition to directly harming vegetables, a large amount of honeydew excreted by the aphid bodies both affects yield and reduces vegetable quality. In addition, aphids are the main transmitters of various viral diseases. They can transmit viruses from infected vegetables to healthy plants in a short time, and the losses caused by the viral diseases they transmit are no less than the direct damage caused by the aphids themselves.

In winter, vegetable aphids continue to cause damage in protected areas and greenhouses; in open-field vegetable areas, they overwinter on (Chinese cabbage) as eggs or parthenogenetic aphids, and some also overwinter on overwintering spinach. In March to April of the following year, the eggs hatch. After the overwintering hosts reproduce for several generations, winged aphids are produced, then migrate to cruciferous vegetables, and gradually spread to solanaceous vegetables or other vegetables to cause damage, forming a spring peak of damage. In summer, because there is more rain, the temperature is high, and there are also many natural enemies, it is not favorable for vegetable aphids to occur, so the damage is relatively light; in late August, as the temperature gradually drops and rainfall decreases, conditions become suitable for vegetable aphid reproduction, forming an autumn peak of damage. Therefore, autumn is an important period for controlling vegetable aphids. In October, winged aphids are produced and migrate to overwintering hosts to cause damage and reproduce, and sexual aphids are produced to mate, lay eggs, and overwinter.

Reasons for severe outbreaks of vegetable aphids

1. Expanded host range and long damage period

In recent years, with the increase in vegetable cultivation varieties, the area of protected cultivation has expanded. Vegetable varieties have increased from more than ten to more than 30, providing aphids with sufficient food sources and overwintering sites. Previously, vegetable aphids had an overwintering stage of several months in winter, but with the development of protected cultivation, vegetable aphids no longer overwinter but continue to cause damage, and the base population for occurrence in the following year is large. When severe outbreaks occur in spring and autumn, no vegetable variety is spared; in addition, excessive application of nitrogen fertilizer and overly shaded vegetable fields also cause severe aphid occurrence.

2. Large food intake and fast reproduction rate

Both adult and nymph vegetable aphids use piercing-sucking mouthparts to suck the sap of host plants. According to measurements, the weight sucked by 1 adult aphid in 24h is 8 times its own body weight. Aphids have very strong reproductive capacity. Each female aphid can produce about 70 nymphs in her lifetime. When food is abundant in the field, the number of wingless aphids is relatively large, and they gather to cause damage; when food is scarce in the field or environmental conditions are unsuitable, a large number of winged aphids will appear and can spread outward to cause damage, resulting in relatively large losses.

3. Strong pesticide resistance, difficult to control, and high labor and investment costs

According to surveys, the labor, investment, and pesticide use for controlling vegetable aphids account for more than 50% of the entire vegetable disease and pest control effort. Because of the large amount of pesticide used and the high number of control applications, incidents of human and livestock poisoning also occur from time to time.

4. Poor natural enemy control

Aphids are greatly affected by natural enemies. For example, when the number of field natural enemies such as aphidid wasps, ladybugs, lacewings, and hoverflies is large, they have a certain inhibitory effect on aphids. However, because vegetable growers spray pesticides blindly and spray as soon as they see insects, this is highly lethal to the natural enemies of aphids, causing aphids to lose natural control.

5. Impact of temperature and humidity on occurrence

From observations in recent years, it can be seen that temperature and rainfall have a great impact on the occurrence of aphids. A temperature of 20-25°C is favorable for the occurrence and damage of aphids, while a temperature exceeding 30°C suppresses aphid occurrence. If the winter is dry and the temperature is relatively high, then the occurrence in the following spring will be severe. High-temperature and high-humidity weather in summer is unfavorable for aphid occurrence. If autumn is dry, then the damage in autumn will be severe.

Control methods for vegetable aphids

1. Agricultural control

In the cropping system, rotation should be implemented as much as possible, and continuous cropping should be avoided. After the previous crop of vegetables is harvested, the soil should be plowed and the ridges exposed in time, and field debris should be cleared to reduce aphid sources. Aphids like to feed on carbohydrates. During vegetable cultivation, more decomposed farmyard manure should be applied, chemical fertilizers should be used as little as possible, and especially too much fertilizer should not be applied at one time, so as to avoid vegetable leaves becoming too dark green and leggy. If carbohydrates in the plant body increase sharply, aphids will break out into disaster in a short time.

2. Using natural enemies to control aphids

There are many kinds of natural enemies of aphids, mainly the seven-spotted ladybug, harlequin ladybug, lacewing, hoverfly, and entomopathogenic fungi. Pay attention to protecting these beneficial natural enemies and making use of them, and then a large number of aphids can be eliminated, keeping the aphid population within a number insufficient to cause large-scale damage. When there are not many aphids in the field and there is a certain number of natural enemies, do not apply pesticides, so as not to harm the natural enemies and destroy the ecological balance. When aphid damage reaches the control threshold and pesticide use is needed, the pesticide should also be applied to the damaged parts of the plant, such as the growing points, tender leaves, young stems, and undersides of leaves, so as to target the treatment precisely and fully protect natural enemies.

3. Yellow boards to trap aphids

Winged adult aphids have a relatively strong tropism toward yellow and orange-yellow. In production, yellow cardboard boards 15 cm × 20 cm in size can be made, and a layer of No. 10 machine oil or pesticides commonly used for aphid control can be applied to the boards. The yellow cardboard boards can be inserted or hung between vegetable rows and kept level with the tops of the vegetables. Machine-oil yellow boards should be replaced in time after being covered with aphids, while pesticide yellow boards can kill aphids as soon as they touch the pesticide.

4. Silver-gray film to repel aphids

Aphids have a relatively strong avoidance response to silver-gray. Some silver-gray plastic strips can be hung in the field, or silver-gray plastic film can be used to cover vegetables.

5. Urea-detergent mixture to kill aphids

Make a urea-detergent mixture by combining urea, washing powder, and clean water in a ratio of 4:1:400, and spray it evenly and carefully on both the front and back sides of the leaves, using 60 kg of spray liquid per mu, for 2 to 3 consecutive sprays. Spraying the urea-detergent mixture not only has a good control effect on vegetable aphids, but also has the effect of foliar fertilization to promote growth. However, the urea-detergent mixture should be prepared and used immediately to prevent urea from volatilizing and losing effectiveness.

6. Plant-based aphid control

(1) Grind tobacco into fine powder, add a small amount of lime powder, and spread it; (2) Soak chili peppers or wild mugwort in water for a whole day and night, filter, and spray; (3) Crush castor leaves and spread them, or soak them in water at a ratio of 1:2, boil for 10 minutes, filter, and spray; (4) Soak peach leaves in water for a whole day and night, add a small amount of quicklime, filter, and spray.

7. Plants to repel aphids

For example, the volatile odor of Chinese chives has a repellent effect on aphids, so planting Chinese chives together with other vegetables can reduce aphid density and lessen the degree of aphid damage to vegetables.

8. Pig bile liquid to kill aphids

Add an appropriate amount of baking soda or washing powder to 10% pig bile liquid, and spray it directly on vegetable plants damaged by aphids and cabbage caterpillars to effectively kill the pests. The diluted liquid can remain effective for 10 to 12 days.

9. Lime powder to kill aphids

Sprinkle lime powder on vegetable leaves with aphids, and the aphids will soon be killed.