Insecticides for Protection of On-Farm Stored Grains

Published: October 7, 2009

Successful protection of stored corn and wheat grains from insect pest infestations is best achieved by:

1. Sanitation

is an important component of a stored grain insect IPM program for prevention of stored grain insect infestations in fall harvested grain crops. Sanitation around storage facilities is most effective in prevention of stored grain insect infestation when applied 30-45 days prior to harvest, although following good sanitation procedures are encouraged throughout the year. Removal or elimination of any waste grain scattered in the area outside the storage facilities, in combine and grain handling augers, and under drying floors inside the storage facility will help prevent pest outbreaks.

2. Preventative Insecticides

are available for use on areas surrounding bins and in bin interiors. Insecticides labeled for use as structural sprays or bin preparation sprays in empty bins include Beta-cyfluthrin (Tempo SC Ultra, Tempo WP Ultra and Tempo Ultra WSP), Chlorpyrifos-methyl and deltamethrin (Storcide II), and Malathion available as several products. Two additional non-traditional products available for use in treating empty bins include Diatomaceous earth/Silicon dioxide (sold as several products) and Methoprene (Diacon II). Diatomaceous earth kills insects by either scratching the insect cuticle which allows for desiccation and death of the insect or by plugging the insects breathing structures causing insect death through suffocation.

3. Grain Mass Management

Methods and Insecticides Grain placed in on-farm storage this fall should be treated with an insecticide if it will remain in storage into the summer months of 2010. Grain stored for just winter months is best managed by cooling the entire grain mass to a temperature of 50 degrees Fahrenheit or less as soon as fall temperatures allow. Regardless of which management optionis selected, regular monthly inspections of the surface and body of the grain mass are recommended to prevent loss from stored grain insects.

Insect infestations may occur throughout the grain mass, on the upper surface of the grain mass, or in both areas depending on the species of insects infesting the bin. Indian meal moth is the most common insect problem found in the upper twelve inches of the grain mass where larval feeding results in areas of moist, sour smelling grain and thick webbing. If such an infestation occurs and larvae are still active, removal of the damaged grain and insect webbing followed by an insecticide application to the remaining grain surface may be one method of control. Pest strips hung above the grain mass inside the storage tructure may help prevent Indian meal moth infestations from developing and help with control of moths if present in the air space inside the bin and above the grain mass.

If an infestation of various flour beetles, grain weevils, or other stored grain beetles is found infesting the grain mass, then immediate use of the grain mass, moving and treatment of the grain mass with insecticide, or use of fumigants are some possible control options. If fumigation is selected, a professional fumigator should be used as a self-contained breathing apparatus is required plus the poisonous gases associated with fumigation are extremely dangerous if used improperly. The best option for management of stored grain insect infestations in summer is to immediately use the grain as livestock feed or some other use where the insects do not cause a problem in the end product.

Insecticides labeled for use on grain mass are best applied when bin or structure is being filled with grain. Insecticides label for control of stored grain insects found in the grain mass include Pirimiphos-methyl (Actellic 5E) labeled for use on corn and sorghum, but not labeled for use on empty bins or storage structures, Chlorpyrifos-methyl and deltamethrin (Storcide II)labeled for use on the grains of wheat, sorghum, barley, oats and rice, but in not labeled for corn. The non-traditional stored grain products of Diatomaceous Earth and Methoprene (Diacon II) are labeled for grain use, however diatomaceous earth can alter grain flow if applied to entire grain mass and methoprene is a growth regulator which will not prevent larval feeding, but will eventually prevent the development larvae from changing into the adult stage. Methoprene (Diacon II) is labeled for use on corn, wheat, grain sorghum, barley, oats, and rice.

4. Scouting Methods

differ by location in the bin. Indian meal moth infestations can generally be seen by observing the top of the grain mass from the roof access door. If no webbing or foul grain odors are found, then it is unlikely that Indian meal moths are present in high numbers. If the grain was properly leveled and treated with an appropriate insecticide after filling of the storage facility the previous fall, it is best not to break or disturb the protective cap of insecticide applied at that time. Some probing of the grain surface from the side access door may be necessary to determine level of insect infestations if found. Scouting for stored grain insects in the grain mass can be accomplished by using a grain probe to collect samples through the side access panel. Grain collected should be placed in a glass jar, plastic bag, or some other container through which insects can be seen if they are present in the grain. These containers of grain should be placed in a warm area to allow the grain to warm to at least 60 degrees F or higher in order to stimulate insect activity.

5. In Summary

several insecticides are labeled for use outside of grain bins, for inside surfaces in empty bins, for addition to the grain mass at the time of filling or possibly when insect infestations occur in the storage structures. All insecticides for stored grain insects have very specific labeled uses so pay special attention when selecting an insecticide for these specific uses. Some insecticides are only labeled for empty bin use while others are labeled for use on the grain mass. Some insecticides are labeled for wheat only or corn only, whereas others may be labeled for both. Using the wrong insecticide (not labeled for your use) can result in the grain being destroyed. Be sure to read and follow all insecticide label instructions, restrictions, and precautions when using insecticides for management of stored grain insect pests.

6. Additional Information

Moisture in the grain mass is one very important factor which attracts insect pests to these structures. Charles Ellis discussed the aeration and moisture zones in on-farm grain storage facilities in the January 15, 2009 issue of this newsletter (Volume 19, Number 1). Proper aeration of the grain mass to manage moisture and grain mass temperature is essential for good insect control. Note: it often requires a week or more of aeration to move a moisture layer through and out of a grain mass depending on several factors including the volume of air moved, the size of the storage structure, and the temperature of the air being moved into or out of the grain mass. Color images of common stored grain insects can be found on the Commercial AG Electronic Bulletin Board at http://www.agebb.missouri.edu/storage/pests/insect.htm.