Early Season Pests of Vegetable Crops

Early-season insect problems on field-grown vegetables are often very different than those later in the summer.  Early season pests often impact the health of the plant rather than feeding on the portion of the plant we intend to market. These pests that attack parts of the plant we don’t market are termed ‘indirect pests,’ and, in some instances, can be as important, or even more important, than direct pests. This article describes common early season pests of Kentucky’s primary vegetable crops.

Fruiting Vegetables

Crops include tomato, eggplant, and peppers.  Several species of flea beetles are common, but serious injury to plants varies by plant type. Eggplant is the most susceptible to injury, followed by tomato and pepper.  The tobacco, potato, and pale striped flea beetles can be common on the fruit vegetables. Flea beetles chew roundish holes in leaves, but they fortunately do not transmit diseases to these vegetables. Eggs are laid around the base of plants in soil and larvae feed on plant roots.  Systemic insecticide treatments at planting may provide 2 to 4 weeks of control, but supplemental control may be needed in some instances, particularly with eggplant.

Figure 1. Pale striped flea beetle with characteristic feeding damage on tomato plant. (Bessin, UK)

Figure 1. Pale striped flea beetle with characteristic feeding damage on tomato plant. (Bessin, UK)

Cucurbits

Crops include cucumber, melons, pumpkin, and watermelon.  Depending on the type of cucurbit, cucumber beetles and squash bugs can be critical early-season pests that must be managed.  Both of these pest groups can transmit bacterial plant diseases to young plants that can wreck havoc on plant production. Cucumber beetles (striped and spotted) transmit a bacterium that causes bacterial wilt of cucurbits. Melons, cucumbers, and some squash types are very susceptible. Squash bug transmits a different bacterium that can cause yellow vine decline of pumpkin, watermelon, and squashes. With organic growers, row covers that are sealed on the edges are recommended from the day of transplanting until the plants begin to open female flowers. Conventional growers often use systemic insecticide treatments at transplanting, followed by scouting and rescue foliar sprays beginning 3 to 4 weeks after transplanting.

Figure 2. Early season squash bug management is critical as older nymphs can be very difficult to control. (Bessin, UK)

Figure 2. Early season squash bug management is critical as older nymphs can be very difficult to control. (Bessin, UK)

Sweet Corn

Cutworms and stink bugs can be common problems on young seedlings. Generally the goal is keep cutting damage below 3% of the plants within a field. When cutting occurs above the growing point, plants may recover without impacting yield.  Stink bugs feed with piercing-sucking mouthparts and inject enzymes into the seedlings that cause a variety of symptoms.  Feeding by stink bugs in seedling corn is recognized by the rows of dissolved holes in the leaves. Seedlings may begin to tiller if the growing point is injured and plant leaves may form a buggy whip-like appearance.  Injury from stink bugs appears a week or more after feeding, so sprays based on symptoms may have little effect.  Producers should scout for stink bugs that are feeding on seedlings at the soil line.

Figure 3. A brown stink bug feeding at the base of corn plant. (Bessin, UK)

Figure 3. A brown stink bug feeding at the base of corn plant. (Bessin, UK)

Figure 4. Stink bugs often leave four characteristic holes in emerging leaves. (Bessin, UK)

Figure 4. Stink bugs often leave four characteristic holes in emerging leaves. (Bessin, UK)

By Ric Bessin, Extension Entomologist

Posted in Vegetables