A questionnaire was distributed as part of a presentation on Area Wide IPM at Grain Elevators at 1998 Minnesota Pesticide Applicators Recertification Workshop and 50 of 127 participants filled out the questionnaire. The questionnaire characterized the type of grain storage facilities represented by participants and their pest management practices (insect monitoring, use of thermocouples, aeration, sanitation and fumigation) including reasons for moving grain and fumigation. Twenty-two participants ranked the importance of all reasons for moving grain and 28 identified some reasons as more important than others. The rank for each reason for moving grain varied extensively among participants but price was most often number 1, thermocouples show grain heating number 2, high moisture content number 3, fumigation number 4, make room for new crop number 5, grain stored too long numbers 6 and 7, cleaning grain number 8, grain had been stored on farm number 9 and pick up fertilizer number 10. Blending was the exception and was spread over ranks 2 to 7. One participant concluded that all reasons for moving grain are equally important at different times. Another participant added government loan due or farmer sells grain and transportation available. For participants not ranking all 10 reasons for moving grain, 20 selected price as important, 20 selected make room new crop, 18 selected blending, 18 selected thermocouples show grain heating, 17 selected cleaning grain, 16 selected high moisture content, 14 selected grain stored too long, 13 selected fumigation, 6 selected grain had been stored on farm and only 1 selected pickup fertilizer.
The rank for each reason for fumigation varied extensively among 10 participants but in response to insects in grain sample was most often number 1, in response to rising thermocouple readings or prior to shipping number 2, 3 or 4, when turning number 3 and when dictated by buyer number 5. For participants not ranking all 5 reasons for fumigation, 33 selected in response to insects in grain samples as important, 13 when turning, 11 in response to rising thermocouple readings, 6 when dictated by buyer and only 1 prior to shipping. Participants added prior to loading into bin and at harvest as cheap insurance. One participant said that fumigation was last resort, another had not fumigated in 3 years and a third used housekeeping, aeration and grain cleaning by aspiration instead of fumigation because bins were not sealed well enough to fumigate.
Twenty-five of 50 participants had policy for removing grain residues from empty bins. Six said yes but did not elaborate. One said yearly, another before harvest and another as soon as possible. Thirteen sweep and/or vacuum before reusing bin and 6 of these applied a residual insecticide too (Tempo or malathion mentioned). One removed aeration ducts as part of cleaning empty bin and another swept the side walls. Fifteen estimated number of hours per month spent sweeping to be between 10 and 60 hours, another 600 hours and two others 4 and 5 hours per day. Others said alot (2), too many hours (1), daily (2) and continuously (2). Participants disposed of sweepings in dust or screenings bin (10), by hauling away (2) or in dumpster (10). Fifteen cleaned grain using aspiration. Two participants mentioned selling sweepings or grain and dust removed by aspiration as animal feed. One participant mentioned that aspiration was less effective at removing live insects.
One participant commented on insect monitoring by saying “adequate sampling necessarily”. Although 20 participants took only one sample per truck load to detect insects, some took 3 or 4 grain samples per truck during unloading or every 2 to 15 minutes, or larger grain samples (2 or 5 quarts, 1, 2 or 2.5 gallons, 2, 3, 4 or 5 pounds, 1000, 2000 or 2,500 grams). Only 17 had thermocouples in all bins to detect grain heating due to insects and/or molds. Thermocouples were checked every other day, twice per week, weekly, every other week and monthly and time to check them varied from 2 to 45 minutes or 1 to 5 hours. If grain temperature increases by 5 to 60oF, grain is turned (36 out 50), fumigated (15 out 50) or sold (12 out 50). Twelve out of 50 use traps and 17 out of 50 had heard about automation of insect monitoring acoustic sensors.
For 29 elevators, 20 to 100% of the storage had aeration, 43 used thermocouples to monitor aeration and 7 used aeration controllers. Aeration fans were run most frequently when outside temperatures were between 40 and 50oF for 3-8 days or 3-8 weeks but the best answer to “How long are aeration fans run?” was that the fans ran until cooling front had moved through the grain. Grain from dryer was cooled by aeration. Twenty-one of 34 participants ran fans continuously.
The total storage capacity of 35 elevators ranged from 0.025 to 8.5 million bushels including 88.7% concrete, 7.4% metal, 3.7% flat and 0.1% wood. The number of legs ranged from 2 to 9. Only eight were associated with mills. From 1 to 7 types of grain were stored at 24 elevators and grains were fairly evenly divided between Fall (177.8 million bushels corn, soybeans, canola and sunflower seeds) and Summer (157.5 million bushels wheat, oats and barley) harvests.
Taking more grain samples (Hagstrum and Flinn 1992) and depending less on grain heating which requires large numbers of insects for detection of insects could improve pest management. This could also help reduce the spread of insects to larger amounts of grain when blending. Sanitation could be improved by disposing of the sweepings and the material removed by aspiration, and removing grain from empty bins sooner, so that these were not sources of insect infestation. Aeration could be improved by using aeration controllers to cool grain sooner and monitoring the movement of cooling front through grain (Flinn et al. 1997, Reed and Harner 1998a,b).
References
Flinn, P. W., Hagstrum, D. W., and Muir, W. E. 1997. Effects of time of aeration, bin size, and latitude on insect populations in stored wheat: A simulation study. J. Econ. Entomol. 90: 646-651.
Hagstrum, D. W. and P. W. Flinn. 1992. Integrated pest management of stored‑grain insects. In Storage of Cereal Grains and Their Products. Ed. D. B. Sauer. Amer. Assoc. Cereal Chem., St, Paul, Minn. p. 535-562.
Reed, C., and Harner, J. 1998a. Cooling of stored wheat in multiple or single cycles using automatic aeration controllers. Appl. Eng. Agric. 14: 497-500.
Reed, C., and Harner, J. 1998b. Thermostatically controlled aeration for insect control in stored hard red winter wheat. Appl. Eng. Agric. 14: 501-505.
storedproductinsects 