Latest Occurrence of Corn Aphids and Control Measures
The corn aphid is widely distributed in corn-producing areas and can damage corn, wheat, sorghum, rice and various gramineous weeds. During the seedling stage, adult and nymph aphids gather in the whorl to cause damage; after tasseling, they damage the ear, sucking sap, hindering growth, and can also transmit various gramineous cereal viruses. It belongs to the order Homoptera, family Aphididae. Common names: wheat aphid, greasy bug, ant bug. Distributed throughout the country.
[Damage characteristics] Adult and nymph aphids pierce and suck plant tissue sap, causing leaves to turn yellow or red, affecting growth and development, and in severe cases causing the plant to die. Corn aphids mostly gather in the whorl; when damaging leaves they secrete honeydew, producing black mold-like substances. This differs from the sorghum aphid. On compact corn varieties, they mainly damage the tassel and the upper 1—5 leaves, while lower leaves are less affected; they pierce and suck the sap of corn, causing leaves to turn yellow and die, often making the leaf surface moldy and black, affecting photosynthesis, reducing grain weight, and spreading viral diseases that cause yield loss. Hosts: corn, sorghum, wheat, foxtail grass, etc.
[Feature description] Winged viviparous female aphid body length 1.5~2.5 mm, head and thorax black, abdomen grayish green, each segment before the cornicles with dark lateral spots. Antennae 6-segmented; antennae, rostrum, legs, intersegmental areas of the abdomen, cornicles and cauda black. Wingless parthenogenetic aphid body long-oval, live insect dark green, covered with a thin white powder, appendages black, compound eyes reddish brown. Head and thorax black and shiny, abdomen yellow-red to dark green. Antennae 6-segmented, shorter than the body. Other features similar to the wingless type. Egg oval.
[Occurrence pattern] From north to south, 10~20 or more generations occur per year; it generally overwinters as wingless viviparous female aphids in the whorls of wheat seedlings and gramineous weeds. In late April and early May it migrates to spring corn and sorghum. Before corn tasseling, it continuously gathers in the whorl to reproduce and cause damage; after tasseling it spreads to the tassel and ear to reproduce and cause damage. The flowering stage is the most favorable period for corn aphid reproduction and damage, so the appropriate control period should be before corn tasseling. Suitable temperature and high humidity, that is, a ten-day average temperature of about 23°C and relative humidity above 85%, when corn is at the tasseling and flowering stage, is most suitable for corn aphid proliferation and damage, while storms have a relatively large controlling effect on corn aphids. In fields with heavier weed occurrence, corn aphids also occur more heavily.
[Control methods]
1. Timely clear weeds in the field and at field edges to eliminate the breeding grounds of corn aphids.
2. When the rate of aphid-infested plants reaches 50% during the corn whorl stage and the number of aphids per 100 plants reaches more than 2000, spray evenly with 50% pirimicarb 3000-fold solution, or 40% omethoate 1500-fold solution, or 50% dichlorvos 1000-fold solution, or 2.5% deltamethrin 3000-fold solution; the above solutions can also be used to pour into the whorl, or 40% omethoate 50~100-fold solution can be used to coat the stem.