The longer grain is in the bin, the greater the potential for problems with stored grain insects. Those most likely to cause the biggest problems this spring are commonly called fungus feeders.
Scott Hartley, insect control specialist with Saskatchewan Agriculture, said insects such as the rusty grain and red flour beetle feed directly on the grain. Others, such as the adult foreign grain beetle, psocids and grain mites, affect grain stored when still damp.
“Because of last fall’s poor harvest conditions, these fungus feeders may be a bigger concern this spring.”
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The best way to control fungus feeders is to reduce the moisture in the stored grain. Chemical control is not necessary.
Most stored grain insects cannot multiply at temperatures below
18 C, so cooling the grain through aeration or moving it several times should provide effective control. Moving the grain using grain vacuums can also effectively remove insects in stored grain.
“Maintaining core grain temperatures below 18 C will stop beetles from reproducing and laying eggs. Maintaining temperatures below
15 C limits movement and feeding activities,” Hartley said.
The only organic option to control stored grain insects is Protect-it, a diatomaceous earth product registered for control of rusty grain beetles in wheat. It reduces an insect’s ability to retain moisture, causing it to die from dehydration. But the insects must be active. The product is most effective when used in dry grain.
Malathion Grain Protectant Dust is registered for use in wheat, rye, barley and oats, and is only effective if the insects are active. It cannot be applied within seven days of the grain being sold. The Canadian Grain Commission allows only eight parts per million of malathion residues in stored grain.
Phostoxin and Gastoxin are fumigants available as pellets or tablets that can be applied to a wide variety of stored crops, but regulations require an appropriate pesticide applicator’s licence to use them. If the grain is less than 5 C, the tablets will not release the gas until the grain warms up. This may result in poor control and accidental exposure to Phostoxin or Gastoxin at a later date.
The most common stored grain beetle is the rusty grain beetle. It is flat, rectangular, reddish-brown and two millimetres long with long threadlike antennae. It feeds on the seed germ or embryo. Heavy infestations can cause grain to heat and spoil.
The red flour beetle is reddish-brown and four mm long. It cannot feed on undamaged, dry seed with less than 12 percent moisture; it prefers grain dust, broken grain and milled stocks. The saw-toothed grain beetle, which is brown and about three mm long, is more common in stored oats than in stored wheat and barley.
Fungus feeders include the adult foreign grain beetle, which is brown and about two mm long. It resembles the rusty grain beetle, but can be distinguished from it by club-shaped antennae. When placed in a glass jar, foreign grain beetles will climb up the side; rusty grain beetles cannot climb the sides.
Other fungus feeders are the soft-bodied psocids, which are about one mm long, with long antennae relative to the body size. Grain mites are whitish, soft-bodied, and so minute – about 0.2-0.5 mm long – they can be hard to see.
Damaged kernels or insect sightings indicate the presence of a stored grain problem, so regular monitoring of the grain is necessary, especially this spring.
