Control insects in the bin
For decades, farmers have aerated their grain bins to maintain the quality of stored grain by keeping it cool while at the same time managing pesky insects.
Few studies performed recently, however, have looked at whether the direction of airflow is better from above or below as a way of using temperatures 60˚F. or lower to control insects in the bin.
To determine this, USDA entomologist Frank Arthur and agricultural engineer Mark Casada experimented with bins cooled with one of two types of aeration: suction and pressure.
Suction Vs. Pressure
The difference between the two systems is how the air is pushed or pulled through the bin. Suction aeration reverses fans to pull air from the top downward. Pressure aeration uses fans to push ambient air from the bottom of the bin upward.
Conducting two eight-month-long trials, the researchers, who work at the ARS Center for Grain and Animal Health Research in Manhattan, Kansas, used six metal bins with perforated floors and storage capacities of 1,250 bushels of wheat. Stored insects examined included the rice weevil, the lesser grain borer, as well as the five pictured above (from left to right): the red flour beetle, the rusty grain beetle, the hairy fungus beetle, the saw-toothed grain beetle, and the foreign grain beetle.
The study revealed that during the summer, suction aeration cooled the upper portion of wheat, also referred to as the surface zone, more quickly than pressure aeration.
That difference also correlated to fewer insect pests. For example, in suction aeration-treated bins, 662 rusty grain beetles and 772 red flour beetles were found in surface-zone traps compared to 3,290 and 8,210 beetles, respectively, in pressure aeration-cooled bins.
According to Arthur, because the surface zone is where insects initially infest grain after flying in from outside, suction aeration’s rapid cooling of the grain’s surface zone is definitely advantageous.
Both researchers say larger-scale studies are needed and note that one potential benefit of suction aeration could be reduced use of phosphine to control insects. Phosphine-producing materials have become the predominant fumigants used for treatment of bulk-stored grain throughout the world.