Corn Earworm / Tomato Fruitworm
Helicoverpa (= Heliothis) zea
The corn earworm/tomato fruitworm can feed on many different plants; however, the most commonly damaged are corn and tomatoes. The species has been given many different common names, including cotton bollworm, soybean podworm, and so on. These pests are also known to consume tobacco, legumes, grain sorghum, and other vegetables and fruits.
Found throughout North America.
Adult moths are usually light yellowish olive to tannish brown, with a single dark spot near the center of each front wing. The wingspan is about 1 1/2 inches. The larvae come in a wide variety of colors, including shades of pink, yellow, green, brown, and black. The color is derived to some extent from the host plant. They usually have darker or lighter stripes running lengthwise on the body. Eggs are small, round, and almost transparent white.
Earworms overwinter as pupae in the top several inches of soil. First-generation adults begin to emerge from late March to May, dependent on geography and climate. The population may be augmented by migrating moths from other regions. After mating, eggs are laid on the buds or fruit of host plants. Eggs hatch in less than 5 days. Larvae feed for 2 to 4 weeks before dropping to the ground to burrow into the soil to pupate. They prefer buds or fruit but will also feed on the leaves of many different plants. There are one to four generations per year.
Damage and Detection
- Larvae burrow into ripe tomatoes and occasionally peppers, leaving a visible black hole at the base of the fruit stem. Tunneling is evident when the tomato is cut.
- Larvae also feed on buds and chew large holes in leaves.
- In corn, larvae feed on fresh silks, then move down the ear to the kernels, leaving trails of excrement. Early and late corn cultivars are the most affected.
- Larvae will also feed on a broad range of vegetable crops, fruits, and flowers.
Prevention and Control
- Monitoring early in the season is important to prevent damage.
- Inspect leaves above and below the highest flower cluster for eggs. When fruit is present, check for damage and the presence of larvae.
- Collect and dispose of infested fruit before the pest completes its life cycle.
- Minimize local food sources. Avoid planting tomatoes near corn or other hosts to minimize populations.
- Introduce parasitic wasps, which parasitize fruitworm eggs, and other natural enemies such as lacewings, big-eyed bugs, and damsel bugs which attack eggs and young larvae.
- Biological pesticides can kill larvae during the warmest months.
- Spray BTK or spinosad on the leaves and fruit of plants where fruitworms are feeding. In the event of severe infestation, spray with neem.
- Be fastidious about the collection and disposal of infested plants
- Introduce parasitic wasps and other natural predators, as with tomato fruitworm.
- Chemical pesticides can be effective with corn earworms, however, the timing of application is very important because once the larvae move down under the husk, pesticides are ineffective.
- Pheromone traps can be used to monitor moth build-up and determine when to release parasite eggs or apply pesticides.
- Plant resistant corn hybrids which have husks that are tight around the ear.
- Treat with mineral oil. To arrest the travels of a young caterpillar into the ear of the corn, place a drop of mineral oil on the silks of the young ears of corn.
USGS Bee Inventory, Judy Gallagher, Flickr, Jean Faucett, Marcos Cesar Campis, Shutterstock
While every effort has been made to describe these plants accurately, please keep in mind that height, bloom time, and color may differ in various climates. The description of these plants has been written based on numerous outside resources.