Early Season Vegetable Insect Management

Early in the season it is important to get seedlings and vegetable transplants off to a good start. There are a few early season insects that need to be managed to ensure healthy stands.

Cole crops (Cabbage, Broccoli, Cauliflower)
Striped flea beetles, imported cabbageworm and diamondback moth larvae are the pests that attack this spring crop. With flea beetles on seedling plants, less than 4 to 5 true leaves, use a threshold of an average of two beetles per plant when deciding whether or not to spray. A threshold of 15 percent infested plants can be used with worms until either head-fill or crown formation, then the threshold drops to 5 percent infested plants. While the type of mixture of worms is not important when deciding when to spray, the types of worms will determine which insecticides are used.

Sweet Corn
Corn flea beetles and cutworms are the two primary pests that will attack seedling corn. Use 3 percent cut plants with cutworms actively feeding as the guideline for treating cutworms. Flea beetles can transmit the bacterium that causes Stewart’s Wilt, so wilt resistant cultivars may be needed in years following mild winters. If corn flea beetle is common, use 50 percent of the plants with leaf scars and some leaves turning white as the threshold for spray decisions.

Tomatoes and Peppers
Tobacco and potato flea beetles will attack both tomato and pepper plants. Usually, the plants will quickly outgrow moderate damage. Occasionally, serious damage can occur to plants less than six inches. Use 4 or more beetles per plant on plants less than 6 inches as the guideline for treatment. Colorado potato beetle can also do serious damage to tomato plants less than 8 inches. Use 10 beetles per 20 plants as the guideline for treatment when the plants are less than 8 inches.

Eggplant and Potato
As with tomato, flea beetles and Colorado potato beetle are serious early season pests of potato and eggplant. Use the same threshold for tomatoes above. Insecticide resistance continues to be a serious problem for Colorado potato beetle. Because of this, producers should not use insecticides with the same mode of action for consecutive generations of this insect. Often local populations of this insect may be resistant to one group of insecticides, and in other areas they may be resistant to others. For this reason, what works well in one area may not work at all in another.

Squashes, Cucumbers and Melons
Striped and spotted cucumber beetles can attack cucurbit crops anytime after seedling or transplanting. Cucumber beetles also transmit the bacterium that causes bacterial wilt. For this reason, cucurbit crops must be treated for cucumber beetles as soon as they are planted. With bacterial wilt susceptible crops, cucumber beetles need to be effectively controlled through the start of flowering. Keep in mind that cucurbits are insect pollinated, so measures need to be taken to control the beetles and avoid hurting pollinators. One method to avoid injuring pollinators during bloom is to spray in the early evening after pollinators have quit. The flowers that are open will be closed the next day and new blooms free of insecticide on the inner surface will be open the following day. Squash bug is known to persistently transmit the agent that causes yellow vine decline. Therefore, we need to preventively treat for squash bug as we do for cucumber beetles.

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