Identification
Larva:

• Cream colored
• Newly hatched larvae 1 to 2mm long - mature larvae up to 3 cm long
• Body with raised spots that are often dark colored

	Image courtesy of J. Kalisch, University of Nebraska: Lincoln

Eggs:

• Freshly deposited eggs cream colored, as near hatching black head capsule of larvae becomes visible
• Eggs laid in masses of 15 to 35 eggs on underside of leaves
• Eggs laid in overlapping pattern (fish scale pattern)

ECB can produce a single (univoltine), double (bivoltine) or multiple (multivoltine) generation type. The number of generations that occurs depends on both the genetic makeup of the individual and the environment. In the southern United States, multiple generations occur.

Additionally, two types or strains of ECB can exist in a population. The male of each type responds to a unique blend of female pheromone. The two types are called Z and E.

ECB overwinters as larvae in plant debris on the soil and in other plants on which they were feeding in the fall. Pupation occurs in late spring and lasts for 7 to 10 days. Adults emerge and females begin ovipositing on corn or other preferred crops and weeds. Oviposition will continue in corn preferentially until the silks begin to turn brown and the plants start to senesce. In cotton, as in corn, eggs are typically laid on the underside of leaves in clusters of up to 60 eggs with most egg masses being between 15 and 35 eggs. When temperatures are warm eggs can hatch in as little as five days. Under cooler temperatures it may take 14 days for eggs to hatch. On cotton, young larvae will feed on leaf tissue for about one day and then bore into plant parts. This is different behavior than what is observed in corn where tunneling does not occur until the larvae are third instar. Larvae usually feed for about 35 days. The larvae may then pupate or enter diapause depending on the number of generations that develop. Diapause (the state insects enter to overwinter) is partly triggered by daylength. If the larvae receive at least 14.75 hours of daylight before they reach the fifth instar, they will pupate. If they receive fewer hours of light, they will enter diapause. Other factors that influence pupation are temperature and food quality.

	Images courtesy of Dr. Ron Smith: Auburn University and University of Georgia IPM image website (http://www.ipmimages.org)

ECB are only a problem in areas where corn and cotton are both grown. Larvae feed on the underside of leaves for about one day, after which they will bore into plant parts. The boring by the larvae leaves very characteristic frass. Additionally, wilted plant parts, similar in appearance to drought stress, appear above where the larvae have tunneled. However, plants near the wilted plant will not appear stressed allowing for the distinction between symptoms. Stems that are tunneled may collapse, break off and result in lodging.

Larvae will also bore into bolls causing significant damage even though they do not feed as extensively in the boll as other lepidoptera. ECB typically enter bolls very near the base. This is different from other boll feeders, which tend to bore into the boll higher up.

Control
ECB populations can be adversely affected by rainfall in early summer during egg lay. Rain slows oviposition and can wash small larvae from plants. Additionally, ECB have several natural enemies that can help reduce the population. Predatory insects, parasites, entomopathogens, and vertebrate predators all help control the population.

ECB is only a pest of cotton in areas where corn is grown. In cotton, egg masses are very difficult to detect even when the population is very high. If egg masses are detected there is generally only about a 24-hour window available for effective insecticide application. After this time, the larvae will most likely have bored into the plant making insecticides ineffective. Applications made for other pests may also impact some of the borer if they have not moved into the plant.

Several factors appear responsible for the increased damage attributed to ECB in cotton. The success of the boll weevil eradication program has eliminated many insecticide applications that were probably also controlling ECB. Additionally, corn acreage has increased dramatically in the southern United States over the past few years.

Bt cottons, such as WideStrike™ Insect Protection, offer an excellent solution for ECB control. With conventional control, timing of the application is critical. Insecticide applications must be timed to be applied within 24 hours of egg hatch. This is difficult and most likely impossible due to the need for aerial application in most fields at this time. With Bt cotton, the Bt protein is expressed in the plant tissue and control occurs when the larvae feed on the plant. This eliminates all application timing concerns.