The USDA NRCS EQIP high tunnel cost-share program has been very successful in Kentucky and there are many new high tunnels across the state. High-tunnels extend the growing season for high value crops with tomatoes as one of the most commonly grown crops. However, late in the season, one of the key pests of tomatoes is tomato fruitworm. This pest goes by many names: corn earworm, soybean podworm, and cotton bollworm. As with the other crops, this is a direct pest that attacks fruit.
Fruitworm and Their Damage
Late in the season, tomato fruitworm is attracted to tomatoes and lays eggs singly near flowers. This corresponds with the time relatively large populations of corn earworm moths are leaving field corn. Young larvae preferentially feed on green fruit, but will feed on other parts if immature fruit are not available. The larva chews a hole (Figure 1), often near the stem end of the fruit, which results in a water-filled void in the fruit. One larva may chew multiple holes or feed in multiple fruit.
The light colored eggs are laid singly and have deep ridges. Tomato fruitworm larvae (Figure 2) can be variable in color, ranging from yellow to green to red to brownish black. They generally have a light colored head capsule and have a sandpaper-like feel to their body due to numerous microscopic spines covering their body. When fully mature, a larva can reach 1½ in size.
The moth (Figure 3) has a wing span of about 1½ inches. The front wings of males are usually tan; those of females are a bit darker. Each front wing has a dark spot in the center.
Generally, most tomato fields and high tunnels will not have tomato fruitworm problems in most years. Although infrequent, this is a relatively high-value crop, so producers should be regularly monitoring for tomato fruitworm and be prepared to control them, if necessary. Research at Virginia Tech has shown that the action threshold for tomato fruitworm is reached when 10 percent of the plants have one or more fruitworm eggs. When scouting for eggs, attention should be given to leaves and buds around the upper flower clusters. After the first spray is made, the need for additional sprays is based on the percentage of fruitworm damaged fruit. If more than 3 percent fruit damage is noted, then the crop should be retreated.
In terms of insecticide choices, it makes a big difference whether tomatoes are grown in the field or a high tunnel/greenhouse. A high tunnel is considered a greenhouse, so any pesticides that are prohibited for use in a greenhouse are also prohibited in a high tunnel. A list of recommended insecticides for fruitworm control on field tomatoes can be found on page 94 of ID-36, Vegetable Production guide for Commercial Growers, 2014-2015. Any of those can be used in the high tunnel with the exception of Avaunt, Belt, Coragen, and Radiant.
Ric Bessin, Extension Entomologist