Hopefully, the wet weather we have been experiencing will abate soon and allow vegetable growers to work their soil and move transplants to fields. Early-season insect problems on vegetables are very different than those later in the summer. Early season pests often impact the health and vigor of the plant rather than feeding on the portion of the plant we intend to market. We describe these as ‘indirect pests’ because they attack parts of plants we do not market. Direct pests attack the parts we plan on selling. This article describes common early season pests of our primary vegetable crops.
Tomato, Eggplant, Peppers–Several species of flea beetle are common, but serious injury to plants varies by plant type. Eggplant is the most susceptible to injury, followed by tomato and pepper. Tobacco, potato, and pale striped flea beetles can be common on the fruit vegetables. Flea beetles chew roundish holes in leaves (Figure 1) and, fortunately, do not transmit diseases to these vegetables. Eggs are laid around the base of plants in soil and the 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 for eggplant. As transplants become established in the field and grow rapidly, they are more tolerant of flea beetle damage.
Cucumber, Melons, Pumpkin, Watermelon–Depending on the type of cucurbit, cucumber beetles and squash bugs are 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 (Figure 2) transmits a different bacterium that can cause yellow vine decline of pumpkin, watermelon, and squashes. With organic growers, we recommend using row covers over plants that are sealed on the edges from the day of transplanting until 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.
Cutworms and stink bugs can be common problems on young seedlings. Generally, we would like to keep cutting damage by cutworms to less than 3% of the plants. When cutting occurs above the growing point, plants may recover without impacting yield. Stink bugs (Figure 3) feed with piercing-sucking mouthparts and inject enzymes into seedlings that cause a variety of symptoms. Feeding by stink bugs in seedling corn is recognized by the rows of dissolved holes in 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 applying sprays based on symptoms may have little effect. Producers should scout for stink bug feeding on seedlings at the soil line.
Effect of Winter on Pest Activity
I am commonly asked if the winter has eliminated our pest problems this year. I wish it were that easy. Many of our insect pests are well adapted to survive the winter. They either find protected locations to pass the winter or they are tolerant of the cold temperatures. So despite the bitter cold this winter, producers need to weekly monitor their crops for insect and mite pests.
By Ric Bessin, Extension Entomologist