Spot disease
It is thought that the damage to the leaves is the main disease. Generally, the disease starts from the lower leaves (and a few starts from the middle leaves), and gradually spreads to the upper leaves.
At the initial stage of the disease, water-stained bluish-gray spots appeared on the leaves, and then gradually expanded along the leaf veins to both ends, forming large prismatic spots with yellow-brown central and brown edges. In the later stage, the diseased spots often appear longitudinal cracks. After most of the diseased spots are connected, the leaves turn yellow and die. The disease is first seen before and after the corn tasseling. Once it encounters rainy weather with a temperature below 22 degrees from the silking to the filling period, the disease will spread rapidly.
Chemical control can choose 70% thiophanate methyl or 50% carbendazim or 70% mancozeb wettable powder, 50-100 grams per mu, spray with 30 kg of water, prevent once every 7-10 days for total prevention 2-3 times.
Downy mildew
There are many types of symptoms, and the main symptoms are different in different years, different regions, and different fields, but no matter which symptoms, they are all manifested in the morphology of tassels, ears and plants.
Infected by pathogens, the above-mentioned parts of the tissues have hyperplasia, deformity and abnormal growth. 95% of the injured plants cannot bear fruit.
Corn downy mildew is difficult to find before tasseling, and it becomes symptomatic after tasseling. The occurrence of the disease is characterized by "large dispersion, small concentration", and there is no effective prevention and treatment method for the disease at present. After years of testing, we have used 25% metalaxyl, 90% panaxyl, 50% metalaxyl mancozeb, 90% methylaxyl copper wettable powder 600 times solution or 64% antitoxin alum wettable powder 400 times solution soaking 24 After hours, let it dry and sow, the control effect is more than 70%.
Corn borer
Adult: light yellow, 13-15 mm in body length, female moths are large and light in color, male moths are small and dark in color.
Larva: The body length is about 1.5 mm when it hatches, the shell is black, the body is milky white, and it is translucent. The mature larva is 20-30 mm long, the head shell is dark brown or light reddish brown, and there are 3 vertical lines, the dorsal line is more obvious.
Two generations a year occur in this area. The first generation of larvae mainly eats corn stalks, causing the corn stalks to collapse and fall down, and the second generation eats ears and makes the grain thin.
To control corn borer, we must seize the critical period, that is, the corn bell-mouth period. At this time, 25% Kungfu (1:10), 1.5% phoxim (1:15), or biological agent Beauveria bassiana 50 per acre can be used. Gram, 15 grams of Bt emulsion per mu, the above pesticides are made into arsenopyrite or granules, and 1-2 grams of each plant is sprayed into the big bell mouth.
The most thorough way to control corn borer is to completely remove the accumulated corn stalks of the previous year before the end of April each year to eliminate the source of overwintering insects.
Mythimna separata
Adult: 17 mm long, pale yellow-brown wings, with shiny silver-gray scales. There are two nearly circular yellow-white spots in the center of the forewing slightly near the front edge, a small white spot in the center, and a small black spot on its side. There are seven small black spots along the outer edge of the forewing, the hind wings are grayish white and the ends are grayish brown.
Larva: The mature larva is 38 mm long, has a reddish-brown head and a net pattern on the head. The back is often black when it occurs, the ventral surface is lightly stained, and the dorsal midline is white. The body color of the larva often changes due to different food and environment, so it is called the five-color insect.
The armyworm mainly damages corn in this city. After the wheat is harvested, the armyworm is transferred to the corn. If the control is not timely at this time, the armyworm will eat all the corn leaves. For this reason, the armyworm is controlled at the end of June and early July before the wheat harvest get on.
1. Spray with 100 grams of 90% crystal trichlorfon per mu and 30 kilograms of water.
2. 20% Dima EC (mixture) 100ml mixed with 30kg water spray.
3. 20 ml of 2.5% Kung Fu EC is sprayed with 30 kg of water.
4. 20 ml of 20% Sumobuting EC is sprayed with 30 kg of water.
Corn Red Spider
Corn spider mite is also called corn spider mite.
adult mites: oval in shape, red or rusty red in body color.
Eggs: spherical, smooth surface, the first laid eggs are colorless and transparent, then gradually turn orange-red, and red eye spots appear before hatching.
Larva: The newly hatched larva is round, transparent or light yellow, and turns light green after feeding.
Nymphs: The larvae become nymphs after peeling off their skins. They are oval in shape and change from orange to red in body color, with obvious spots on both sides of the back.
Occurs more than 10 generations throughout the year, alternate generations, due to the small size of the insects and feed on the back of the leaves, it is not easy to be found in the field. The damaged leaves changed from yellow to white and died, which affected the grain filling process of corn, resulting in a decrease in thousand-grain weight and a reduction in yield. For the prevention and control agent, use 50 ml of 40% dimethoate EC per acre and add 50 ml of 20% dicofol EC for mixed spray. In addition, 30-50 ml of 73% Gemite EC can be used per mu to control at least two to three times during the growth of corn. The interval of 10-15 days, each time you must spray enough liquid, 30-60 kg. When applying pesticides, the walking speed should not be too fast, and the nozzle should be upward to kill the spider mites that are mostly on the back of the leaves.
Corn aphids
Winged parthenogenetic viviparous aphid: body length 1.6-1.8 mm, black head and chest, shiny black, yellow-green or dark green abdomen, reddish brown compound eyes, transparent wings, three-pointed midrib.
Wingless parthenogenetic viviparous aphid: body length 1.8-2.2 mm, light green or dark green, compound eyes reddish brown.
The worm can harm the corn from the big bell mouth period until the harvest. Aphids alternate generations. Four generations gather in the heart leaves, leaf sheaths, and leaf tubes. The tassels and wrappers suck plant sweat, causing the affected parts to chlorosis, the heart leaves are twisted, and the tassels are severely unable to draw out, and the grains are thin. Production declines. The mucus excreted by the worm causes coal pollution in the upper functional leaves and other parts, which affects the light and function. To prevent and control corn aphids, use omethoate, dimethoate or 50% anti-aphicarb wettable powder, spray 15 grams per mu with 30 kilograms of water.
Underground pests
There are mainly grubs, mole crickets, golden needle worms and small cutworms. It mostly occurs before the 6-leaf stage of corn, and serious fields occur, which often results in lack of seedlings and ridges, which reduces the number of seedlings and seriously affects yield.
A good way to prevent and control underground pests is to dress seeds with medicament. If you use 19# furfur coated seeds, you don’t need to dress them.
1. Phoxim seed dressing: Mix 2-3 kg of water with 50% phoxim EC 50ml, and mix 50 kg of wheat seeds. (Or use 50% methyl 1605 emulsifiable concentrate with 50ml of water and 2.5 kg of water, mix with 50 kg of wheat seeds). After dressing, use it after mixing for 3-4 hours. Use it on the day of dressing. Phoxim should avoid sunlight when dressing seeds. Invalidate.
2. Use 1.5-2 kilograms of 3% phoxim granules per mu, add 20-25 kilograms of fine dry soil, and pour into the soil in combination with arable land.
Weeds
In recent years, through experiments and demonstrations, we have screened the special agent for preventing and controlling weeds between rows of maize-Ke Wuxian, also called paraquat. As the name suggests, it is a kind of biocidal herbicide, which has strong damage to all the green tissues on the weeds. Effect, in a short time after application, it will kill the green tissues. But because it has no conduction effect, it can only damage the part where the medicine is applied, and is ineffective on roots and underground tissues. For this reason, weeds will regenerate after application, but it will not affect the weeding effect on corn. The control time should be carried out after the wheat is harvested and when the corn resumes growth. Use 100ml of 20% gram of traceless water solution (produced by Benemen Chemical Industry Co., Ltd., USA) per acre, and spray 30 kg of water on the wheat strip weeds. Do not spray the solution on the leaves of corn. The sprayer must be carefully cleaned with hot alkaline water before it can be used for other crops.
