Corn borer, also known as corn borer, is a worldwide corn pest. Corn borer is a polyphagous pest with up to 200 host plants, but the main crops are corn, sorghum, and millet.
1. Symptom identification: Corn borer larvae are borers, and the typical symptom is that after the heart leaves are pierced, the unfolded corn leaves appear neat rows of small holes. After the tassels are withdrawn, the corn borer larvae injure male flowers, often causing the male flower base to break. After the emergence of this ear, the larvae transfer the female ear to take the filaments and tender tenderloin leaves, and enter the cob or eat the young seeds. Another part of the larvae from the stem and leaf sheath into the stem, feeding pith, so that the stem easily blown by the wind. The grains of the affected plants are not full, with premature aging of blue-green, and some spikes even without grains, resulting in serious reduction of yield.
The life of corn borer is also divided into four stages: adult (moth), egg, larvae, and pupa. The adult corn borer is smaller than the ground tiger. Female adult cephalothorax is light brown on the back, ventral and foot white, yellowish-brown forebrain, with 3 dark wavy lines; abdomen and hind wings yellow-white, with dark curved lines in the middle and proximal part of the hind wings. The head of the male head is milky white, with reddish-brown or dark yellow-brown wings; the hind wings are light brown with 2 bands. On the surface of eggs, there are polygonal reticular patterns of different sizes, which are milky at the time of first production, and turn pale yellow or light green afterwards. They are dark brown before hatching, and they produce irregularly shaped egg masses, each of which has 15-60 eggs. Scale arrangement of fish. The larvae have a white cloud with a pink, grayish-brown or gray-brown back, brown head, and dark spots. Brownish brown, with a slight ridge on the back of the cell, and phlegm in the host stem, with a thin beak.
2, living habits: corn quail because of different climatic conditions, 1 year can occur 1-6 generations. As winter larvae in the corn stalks and corn cobs, some of the larvae overwinter in the weed stems. Due to the large differences in temperature and humidity in various overwintering sites, the overwintering larvae are affected by eclosion and eclosion, resulting in an extremely irregular occurrence period. At the same time, because of the damage of corn borers on different hosts, the nutritional value of these hosts also affected the irregularities in their growth and development, resulting in the overlapping of modern generations.
Adults usually emerge at night, and they lay eggs on the second day after emergence. Oviposition of corn borers has the highest number of nests on the height and site of the West plant. Plants over 50 cm in length must produce the most eggs. Most of the spawning sites are midribs in front of the corn leaves.
After hatching, the larvae still gather in their original place and eat egg shells. Scattered and dispersed after one hour, part of the drooping drooping, wind drifted to neighboring plants. The larvae hatched from one egg mass are scattered to many plants in this way, resulting in a more concentrated phenomenon of the affected plants.
3, the occurrence of pests factors:
(1) Base population: The number of base populations of the previous generation is an important factor affecting the severity of corn borers. The population of insects is large, and in severe environmental conditions, they often cause serious damage.
(2) Temperature and Humidity: Corn borer is suitable for growth and development under high temperature and high humidity conditions. The optimum temperature for each insect growth and development is 16 -30°C and a relative humidity of 60% or more. Corn borer occurs mainly from June to September, and the temperature is suitable. Therefore, the amount of corn borer changes depends on humidity and rain.
(3) Maize varieties: Different varieties of corn, the damage is very different. There is an anti-mite material in the corn tissue. Adult eggs are produced on corn varieties with high Dbu content and the mortality of hatched larvae is high. In addition, due to the different tissue morphology of the corn, it is possible to avoid adult spawning and reduce the damage. For example, if the hair on the stem is long and dense, then the damage is very light. Therefore, different corn varieties, corn borer population and corn damage are not the same.
(4) Natural Enemies: There are many types of natural enemies of corn borer, but Trichogramma is the most effective inhibitor of corn borer. Trichogramma parasitizes in the eggs of corn mash, making the eggs unable to hatch normally, or hatching larvae can not grow normally, which can play a decisive role in driving down the aphids.
4, prevention and control methods:
(1) Prevention and control during wintering period: The vast majority of corn borer larvae live in corn stalks and cobs during the winter, and Huanchun is one of them. Before the end of April, the corn stalks and cobs should be burned as fuel, or be used for feed processing and crushing. And should clear the wintering hosts such as xanthium and weeds, which is the basic measure to eliminate the corn borer.
(2) Prevention and treatment at the heart and leaf stage: In the late stage of the heart leaf, the mosaic rate of corn foraging should reach 10%, or the leaf silk period of summer and autumn corn should be controlled when the ear rate reaches 5%. Control methods can be granules and liquid perfusion. Use 50% 1605 emulsion or 50% methamidophos emulsion 0.5 kg to mix 40 kg of fine sand (or cinder); also use 3% carbofuran granules every 26.7 kg of 666.7 square meters to 5 times fine sand, made into poison sand, sprinkle with Heart of corn leaves. The liquid perfusion method can be used 80% dichlorvos milk, diluted into 2500-3000 times, 10-15 ml per corn irrigation, the control effect of up to 85%, while the effectiveness of the treatment of corn thrips up to 96.8%.
(3) Prevention at the ear stage: Use 50% of dichlorvos emulsion 0.5 kg, add 500-600 liters of water, make a small mouth in the top of the female ear, inject a small amount of liquid, and 1 litre of liquid can generally irrigate 360 ​​female ears.
(4) Biological control: Trichogramma has a significant effect in eliminating corn borer, and its cost is low. At the beginning of the oviposition period and the end of the boom period, the bees were placed with bees, and 10,000-30,000 bees were laid every 666.7 square meters, and 2-4 bees were placed. Use a corn leaf to roll up the egg card. It is advisable to keep the egg card 1 meter away from the ground.
In addition available microbial pesticides Bacillus, 7216, Beauveria bassiana. There are two ways to use it: one is the filling of the leaves, and the filling of the leaves is done by using 1 kg of water, 1000 kg of water, and 1 000 g of water per gram of spores. The other way is to formulate the bacteria or granules. The bacteria soil usually uses 1 kilogram of acaricidal bacteria or ash 100-3000 grams. The granules are generally formulated to be approximately 20 times (1 kg white fungus powder and 20 kg slag granules are mixed and prepared), and 2 g per plant is applied.
(5) Selection of insect-resistant varieties: such as Sidan 8 and Danyu 13