In hot and rainy weather, the cotton bollworm that harms tomatoes enters the peak period. How to prevent it?

"Boss, take some pesticides to cure the tomato caterpillar. It's almost eaten up, leaving only straw."

"Liu, get me some medicine quickly. It's killing me. The persimmon will be eaten by the smoke bug!" !

"Mr Edition, is there any good medicine to cure the tomato caterpillar? I fell all over the floor, but I was so angry

"Liu, what is this bug? How so powerful! Normal years are rare. "

Ordinary tomato picture

Today is a big party in our town. People come in and out of our shop. Most of them come to buy agricultural materials. Many people come to buy pesticides, and they are clamoring that tomatoes have been eaten by insects. What's going on here?

In recent days, there has been frequent rainfall in Anqiu area of Weifang City, but the time is short. It's sunny after the rain, the temperature rises rapidly, and it's hot and humid. Such weather conditions are very conducive to the occurrence of pests. In recent days, many vegetable farmers have asked how to control these pests. Now unified reply, please pay more attention to tomato growers.

First of all, briefly introduce this pest.

1, morphology and harmful crops

This pest, which has recently shown explosive harm, is neither called tobacco budworm nor beet armyworm, but its real name is cotton bollworm. At first glance, people may think that the name "cotton bollworm" only harms cotton, but it is not. Helicoverpa armigera is an omnivorous pest, which is widely distributed and can harm more than 200 crops. For example, tomatoes are called tomato moths, corn borers and corn ear worms. Helicoverpa armigera can harm tomatoes, eggplants, potatoes, beans, pumpkins, cabbages, cabbages, broad beans, carrots and other vegetables, among which tomatoes suffer the most.

Helicoverpa armigera has many colors, and its body color varies greatly, including black, green, light green, red and yellow. Green and red cotton bollworms are common in tomatoes.

2. Harm of Helicoverpa armigera to tomato

Helicoverpa armigera mainly eats buds, flowers and fruits of tomato with larvae, and often eats tender stems, leaves and buds. After the bud is bitten, the bracts open and turn yellow-green, and then fall off in a few days. Young fruits are often eaten up or rotted. Although the fruit is only eaten by a part of the pulp, it is drilled out of the peel, which leads to the hollowness of the fruit. In this rainy weather, it is easy to get caught in rain or germs, which will cause rot and fruit drop. Harm of Helicoverpa armigera to young tomato fruit

Helicoverpa armigera began to damage tomato fruit after 3 years old, and by 4? At the age of 5, the food intake is greatly increased and the harm is aggravated. Can a cotton bollworm drill three? Five fruits can give birth to seven at most? Eight fruits, when ripe, like to eat ripe tomato fruits and tender leaves. How serious is the harm? The production reduction caused is very serious.

Why did the cotton bollworm appear in large numbers this year?

This is also a question asked by many vegetable farmers. Let's analyze it below.

Second, the special weather conditions this year are conducive to the occurrence of cotton bollworm.

1, local temperature situation

The weather in Weifang in May this year is like this. From May/KLOC-0 to May 5, the temperature soared to about 35℃. From the 6th, a heavy rain made the temperature drop to about 20℃ instantly, just like riding a roller coaster. It has been raining intermittently since mid-May, with abundant rainfall and high air humidity, but the rainfall time is short, the sunny day is fast, and the temperature rises rapidly, and the temperature is basically at 20? In the range of 32℃.

Does this weather have anything to do with the occurrence of cotton bollworm?

Let's take a look at the living habits of cotton bollworm.

2. Occurrence regularity of cotton bollworm.

Helicoverpa armigera overwinters in the soil as pupae, and begins to emerge in mid-May, reaching the peak of emergence in late May, and laying the first generation of eggs in late May, reaching the peak of the first generation of larvae. July is the harmful period of the second generation larvae, and the first half of August is the peak period. The damage period of the third generation larvae is from early August to early September. The fourth generation larvae mature in the first half of June in 5438+1October, and then they are buried and pupated for the winter. Harm of Helicoverpa armigera to Tomato Stem

Helicoverpa armigera lays a large amount of eggs, at 20? 2 after 30℃? Hatching in 9 days, usually at the age of 3, it begins to damage the fruit. Helicoverpa armigera is a pest that likes temperature and humidity, and high temperature and rainy weather are very beneficial to its occurrence. The optimum temperature for adults to lay eggs is above 23℃, and the optimum temperature for larval development is 25? 28℃ and 70% relative humidity? 90%。

How's it going? The weather in May this year is just suitable for the occurrence of cotton bollworm, so there is a danger of explosion. Then why isn't the usual year so heavy? Because we rarely have such weather here in previous years, it is usually drought, and the soil hardening caused by drought is not conducive to the burial and pupation of larvae, which inhibits the occurrence of cotton bollworm. Frequent watering during drought makes it difficult for buried larvae to pupate, which also inhibits their occurrence. Therefore, it happened less and less seriously in previous years, but this year is just right.

How to control cotton bollworm? You can take the following four measures to solve it.

Three or four measures to eliminate cotton bollworm and ensure tomato safety

Let's solve the current problem first.

1, mainly physical prevention

Now is the peak period of the first generation of cotton bollworm, and it is also the peak period of adult oviposition. Adults of Helicoverpa armigera have a taste tendency. You can cut some poplar branches and willow branches with leaves and put them in the sun until they wither. At this time, the branches and leaves will give off a fresh fragrance. Tie a bunch every 10, and then plant it in the tomato field, which is slightly higher than the tomato plant, and plant it per mu 10. Change it every 10 day. Every morning, if you put a plastic bag around the branches and pat them, you can catch the hidden adults and kill them.

The adults of Helicoverpa armigera also have phototaxis, and can also be killed by insect traps. Trapping effect of trapping agent on cotton bollworm. Vents in the greenhouse are equipped with insect nets, etc. Collect damaged fruits, such as fallen fruits and fruits with holes, and take them out of the site for centralized burial or add quicklime for burial. Fruit diagram of tomato damaged by cotton bollworm

2. Chemical control

The suitable application period for controlling cotton bollworm is from the peak of egg hatching to the peak of 2nd instar larvae. At this time, the larvae have just hatched and have not yet entered the fruit, so the control effect of pesticide application is high. It is usually sprayed when the first ear of tomato is big. You can also check the situation of eggs in the field. When half of the eggs have turned gray-black, it means that the cotton bollworm is about to hatch. At this time, spraying control is an appropriate time.

For the choice of drugs, it is suggested to choose cypermethrin, avermectin, Bacillus thuringiensis, Helicoverpa armigera nuclear polyhedrosis virus, B-t biological agents and other low-toxicity and low-residue pesticides. Pay attention to the spraying time, especially in the morning, mainly spraying the middle and upper parts of tomato plants, because cotton bollworm is also afraid of heat, and will climb to the middle and upper parts of the plants at night, and hide in the lower parts of the plants after the temperature is high. Therefore, it is necessary to grasp the time of medication. Some people spray it many times, but it is not obvious, just the wrong time to use it.

3. Agricultural control

Winter irrigation kills overwintering pupae. In the process of daily pruning, forking and topping, the egg branches are removed and the stem borers are concentrated. Planting corn belts in tomato fields to lure adults to lay eggs. Plastic film mulching can prevent mature larvae from entering the soil to pupate, and at the same time prevent eclosion moths from coming out from under the film.

4. Biological control

If conditions permit, Trichogramma can be released during the oviposition period of cotton bollworm adults to inhibit the occurrence of pests. Harm map of cotton bollworm

To sum up, the occurrence of cotton bollworm has a great relationship with climatic conditions. The special climatic conditions this year are extremely favorable for the occurrence of pests and diseases. According to the relevant information, if the occurrence of aphids, thrips, whiteflies, caterpillars, cotton bollworms, prodenia litura and other pests on tomatoes this year is moderate and heavy, please pay close attention to it and prevent it early to ensure crop safety and reduce losses.