When the corn two - spot armyworm attacks in a cornfield, the damage it causes can quickly become severe. This pest, belonging to the Noctuidae family of Lepidoptera and commonly found in cornfields, specifically targets the basal part of corn seedling stems. The basal part of the stem is as crucial to a corn seedling as a cornerstone is to a high - rise building. Once bitten, corn seedlings are highly likely to topple over, and soon, gaps and ridges with missing seedlings will appear in the field. As a result, the yield drops significantly. In severe cases, the entire field may even experience a complete crop failure, causing substantial losses to farmers. Especially after the wheat harvest, cornfields covered with a large amount of wheat straw are like a "paradise" for the corn two - spot armyworm. Compared with other plots, the pest density here is high. They voraciously chew on corn seedlings, causing far more damage than in other areas, and it's extremely difficult to defend against.
Early detection of pest infestations can effectively prevent and control the harm.
Monitoring is typically carried out from mid - June to early July. This period is when the corn two - spot armyworm is most prevalent. Particular attention should be paid from after the wheat harvest until the corn seedling stage. The key areas for monitoring are cornfields, especially those with a thick layer of wheat straw and chaff and high humidity. These are ideal habitats and breeding grounds for the corn two - spot armyworm.
There are several monitoring methods. For adult pests, insect - killing lamps can be used. For instance, frequency - vibration insect - killing lamps with a black - light wavelength of around 365nm work well. Install one lamp for every 30 - 50 mu, with the lamp placed about 1.5 meters above the ground. By counting the number of trapped adults and the male - to - female ratio, the peak emergence period and the expected number of adults can be predicted.
For larval monitoring, the five - point sampling method or the checkerboard sampling method can be used. At each sampling point, check the number of larvae around the base of corn seedlings within a 1 - square - meter area. Gently push aside the wheat straw to look carefully. Sugar - vinegar traps can also be used. Prepare the sugar - vinegar solution with a ratio of sugar:vinegar:wine:water = 3:4:1:2 and add a small amount of trichlorfon. Regularly check the trapping results. For egg - mass monitoring, look for egg masses that are shaped like small buns and covered with fine hairs on the underside of corn leaves, in the leaf sheaths, and at the base of the stems. Conduct inspections every 3 - 5 days.
The Corn two - spot armyworm monitor is an intelligent pest - monitoring device that significantly improves the efficiency and accuracy of monitoring. This system can collect and analyze pest - related data in real - time. For example, it uses sensors to automatically gather environmental data such as field temperature, humidity, and light conditions. Combining with image - recognition technology, it can automatically identify and count the number of adults, larvae, and egg masses of the corn two - spot armyworm, enabling continuous 24 - hour monitoring. The data is then transmitted promptly to the terminal devices of farmers or agricultural departments, allowing relevant personnel to stay informed about pest trends at any time.
Based on the monitoring results, a series of control measures can be implemented. Once a sharp increase in the number of adults is detected, or when the larval density reaches the control threshold of 3 - 5 per square meter, an immediate warning should be issued. During the peak emergence period of adults, in addition to using insect - killing lamps, 3 - 5 sex - pheromone traps can be set up per mu to disrupt adult mating and reduce the pest population.
When the egg - hatching rate reaches approximately 80% or during the peak period of young larvae, pesticides such as emamectin benzoate and lambda - cyhalothrin - chlorantraniliprole can be selected for spraying. Focus on spraying the base of corn seedlings and the surrounding soil. Root - drenching with pesticides like chlorpyrifos can also be carried out.
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