With the late corn planting, growers need to be watching their corn for fall armyworm feeding. With this insect it is important to catch infestations early as later stages of the insect are more difficult to control. While many fields have been planted to corn hybrids expressing Bt genes that provide partial to high levels of fall armyworm control, non-Bt corn planted in refuge fields should be monitored regularly.
Corn is most attractive to fall armyworm while it is in the vegetative stages. Late planted fields that remain vegetative later into the season will be most likely to experience some level of fall armyworm infestation. As the larvae increase in size while feeding they begin to form a frass ‘plug’ in the whorl and feed underneath its protection. The plug can limit the penetration of insecticides into the whorl. For this reason, it is always much easier to control younger fall armyworm larvae rather than older larvae.
Begin checking corn at the mid whorl stage for fall armyworm activity. Survey 20 consecutive plants (selecting the first randomly) from at least 5 locations in the field. Small larvae cause “window pane” damage to leaves similar to European corn borer. A few days before tasseling, look for large larvae in the whorls which will be pushed out when the tassels emerge. These larvae may attack young ears. Continue to check for this insect until silks begin to dry. Control needs to be considered when egg masses are present on 5% of the plants or when 25% of the plants show damage symptoms and live larvae are still present. Controlling larger larvae, typically after they are hidden under the frass plug, will be much more difficult.
The first reported case of blue mold in the U.S. was found in Chester County, Penn., on June 23. The outbreak occurred on burley seedlings in float beds, and all plants were destroyed; no blue mold has been found to date on field-grown tobacco in the area. For Kentucky producers, the PA source does not pose a serious risk at this time. The North American Plant Disease Forecast Center is projecting that spores from areas with blue mold will move up the eastern coast of the U.S. Even though the threat is low from blue mold at this time, our weather has been favorable for disease development so growers should scout fields regularly and be prepared to act if the disease is found.
For recommendations on the control of tobacco diseases, please consult past issues of the Kentucky Pest News, or the Kentucky-Tennessee Tobacco Production Guide (ID-160), available at http://www.ca.uky.edu/agc/pubs/id/id160/id160.pdf. For up-to-date reports on the status of blue mold and other tobacco disease information, check the KY Blue Mold Warning System online at www.uky.edu/Agriculture/kpn/kyblue/kyblue.htm