What are the latest control methods for corn thrips?
Thrips is the collective name for the order Thysanoptera in the class Insecta. The thrips that harm corn in China mainly include Anaphothrips obscurus, Haplothrips tritici, and rice tube thrips, all three of which belong to Thysanoptera; the first two belong to the family Thripidae, while rice tube thrips belongs to the family Phlaeothripidae. They occur in 2 generations on corn and reproduce by parthenogenesis. Damage is mainly caused by adults feeding on corn. Let us take a look below at the control methods for corn thrips!
Damage characteristics
Thrips mainly cause damage inside the corn whorl and also release a sticky substance, preventing the whorl leaves from unfurling. As the corn grows, the corn whorl forms a “whip-like” shape. If measures are not taken in time, this will cause reduced yield or even total crop failure. Adults move slowly and mostly cause damage on the underside of leaves, creating discontinuous silvery-white feeding streaks accompanied by specks of insect feces, while the corresponding parts on the upper leaf surface show yellow streaks. Adults lay eggs in the mesophyll at feeding sites, and tiny white specks the size of needle tips can be seen when held against the light. Damage is mostly concentrated on the second to fourth or second to sixth leaves from bottom to top, and even after new leaves grow out, the pests rarely move to the new whorl to cause damage.
Occurrence pattern
In spring, yellow thrips first reproduce and cause damage on crops such as wheat, and afterward some gradually move to spring corn. Because the wheat area is relatively large, the insect source for spring corn and middle-season corn mainly comes from wheat. Generally, from late May to early June, there is a nymph peak on wheat and spring corn; in mid-June, there is another adult peak on wheat, spring corn, and middle-season corn; in late June, there is still another nymph peak; and in early July, another adult peak appears on spring corn, middle-season corn, and summer corn. Therefore, for the appearance of these several peaks, measures should be taken in time according to the pest situation during control.
Occurrence characteristics
Thrips prefer relatively dry conditions. They occur more in low-lying, poorly ventilated, and arid corn fields, and interplanted corn in fields with short and sparse wheat plants often suffers more severe damage. Rainfall from May to July in a year has a relatively large impact on the degree of thrips occurrence; drought and little rain are favorable for occurrence. Generally speaking, the occurrence quantity on corn is, in order, spring corn > middle-season corn > summer corn. Although the number of insects per plant on middle-season interplanted corn is lower than on spring corn, the damage is more severe, and under conditions of water and fertilizer deficiency, the damage is even more severe.
Control methods
1. When thinning and fixing seedlings of corn, pay attention to pulling out insect-infested seedlings and carrying them out of the field for composting, which can reduce the spread and damage of Haplothrips tritici. Manually remove the hardened parts at the leaf tips so that new leaves can resume growth. Irrigate and fertilize at the appropriate time and strengthen management to promote early and rapid growth of corn seedlings, which can effectively reduce thrips damage.
2. In the early stage of corn thrips occurrence, spray 10% imidacloprid wettable powder at 1500 times dilution, or 20% imidacloprid soluble liquid at 3000-4000 times dilution, or 26% lambda-cyhalothrin · acetamiprid water-dispersible granules at 5000 times dilution, or 3% acetamiprid at 1500 times dilution, or 10% cypermethrin emulsifiable concentrate at 2500 times dilution, or 2.5% Baode emulsifiable concentrate at 2000-3000 times dilution, or 20% imidacloprid soluble concentrate at 3000-4000 times dilution.