Stored grain should be monitored regularly to determine grain moisture content and temperature and to detect insect infestations. Sample stored grain for insects at least monthly from November through April and at least twice monthly from May through October.
Measurements of grain temperature and moisture should be taken twice monthly all year-round. Pay particular attention to the grain surface and the central core of the grain mass, but also sample additional locations and depths.
Examine grain from any locations where temperature or moisture readings are substantially higher than average.
Deep-bin probes and sectioned grain triers are most commonly used for withdrawing samples from beneath the grain surface. Probe traps and sticky pheromone traps also are available for monitoring insects within the grain mass and flying moths, respectively.
Sampling equipment is available from most bin sales and service companies. When insects are found in stored grain, a logical question is: Are there enough insects present to warrant control?
The importance of an insect infestation is determined not only by insect numbers but also by type of grain, insect species, time of year, grain temperature and moisture, the planned duration of storage, market potential, and local elevator quality and dockage guidelines.
Revised (1988) Federal Grain Inspection Service (FGIS) standards for grain insect infestation are presented in Table 2, but local elevators may enforce more stringent standards. Insect-damaged kernels also may result in price discounts.
Options:
When insects are detected in stored grain, consider several possible management practices. Sometimes the most profitable action is to clean and sell the grain immediately without any chemical treatment. Immediate sale is appropriate if early stages of insect infestations are detected before insect numbers reach a buyer’s detection or discount level.
During cool weather, aerating to cool the grain below 50°F prevents insect activity and allows an extended period of safe storage. Sometimes insect problems are limited primarily to the surface or central core of stored grain. If Indian meal
moth is the only problem, light infestations can be controlled by using Bt, Actellic, Reldan, Storcide II, or diatomaceous earth as outlined in Table 1. Unincorporated applications of these insecticides will not control Indianmeal moth larvae already present a few inches below the grain surface. Where abundant webbing indicates a severe infestation, webbing should be raked from the surface before treating; fumigation may be necessary in these situations.
If secondary beetles are confined primarily to a central core of fine material, removing one or two loads of grain to extract that core may allow safe storage of the remaining grain. Infested grain that cannot be treated successfully in any other way should be fumigated. Safety concerns and protective equipment requirements for fumigants suggest that fumigating farm-stored grain is potentially dangerous and difficult.
Hiring a professional fumigator is strongly recommended, especially for the fumigation of bins with capacities greater than 5,000 bushels. Farmers who wish to fumigate their own grain must pass a specific Private Applicator Grain Fumigation Exam. Training materials for that exam cover the products and procedures used for farm bin fumigation.
For those who hire a professional fumigator, the fumigants that may be used in stored grain include methyl bromide, phosphine (from aluminum phosphide or magnesium phosphide pellets or tablets that release phosphine gas), and sulfuryl fluoride.
A combination of phosphine and sulfuryl fluoride (Profume) also may be used. Additionally, carbon dioxide, alone or in combination with nitrogen or with phosphine (ECO2Fume), can be used effectively in bins that are very well sealed. Sealing the seams of bolted farm bins is necessary to reduce CO2 leaks and make the process cost-effective.
Beneficial Insects:
One or more companies market programs that call for periodic releases of beneficial insects (predators and parasitoids of pest species) for pest management in stored grains. Although considerable research has been directed at this practice, questions remain unanswered concerning the ability of releases of beneficial insects to lower pest populations to levels required by current grading standards.
Published studies conducted in on-farm storage sites have not achieved adequate levels of control. Where management efforts must be limited to ”nonchemical” methods of control, sound cultural practices (sanitation, adequate drying, cleaning, aeration, and annual rotation of the commodity) outperform the release of beneficial insects.
Special Considerations for Stored Seeds:
Seed corn in bulk storage (in cribs, bins, and granaries) can be protected from insect damage by using the storage practices and protectant insecticides discussed previously. These practices include proper sanitation, drying, cleaning, and temperature management (aeration), and the use of protectant insecticides such as pirimiphos-methyl (Actellic or Nu-Gro Insecticide S.P.), Bt, and pyrethrins plus piperonyl butoxide.
Where fumigation of bulk-stored seed corn is necessary, aluminum phosphide fumigants or carbon dioxide can be used effectively without affecting seed germination. In bagged seed corn (usually not treated with any insecticide), several stored-grain insects may be a problem, but the Indianmeal moth is the most common.
Although bulk seed treatments with Actellic, Bt, or Nu-Gro provide residual control of Indian meal moth larvae, such treatments must be applied before or during bagging. Small quantities of valuable seed can be protected by cool storage or by adding diatomaceous earth to seed packets.
To limit infestations of insects in untreated, bagged seed corn, warehouses may be fogged periodically during the summer with pyrethrins plus piperonyl butoxide. Using proper warehouse sanitation methods, maintaining cool temperatures, and excluding pests (by using screens, tightfitting doors and windows, caulking, and so forth) also are important.
Bagged seed can be fumigated effectively with aluminum phosphide fumigants. Hiring a professional fumigator is advised.
Authors:
Rick Weinzierl : Department of Crop Sciences
Russell Higgins : Matteson Extension Center
