On-Farm Stored Grain Management: Stored-Grain Insects

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On-Farm Stored Grain Management: Stored-Grain Insects

Author:	OMAFRA Staff
Creation Date:	13 May 2009
Last Reviewed:	13 May 2009

Pub 811: Agronomy Guide >On-Farm Stored Grain Management > Stored-Grain Insects

Excerpt from Agronomy Guide for Field Crops
Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Scouting Technique for Stored-Grain Insects

In the grain pile, place four plastic probe traps (see Plate 34) halfway between the centre and edge of the bin, in an X pattern, with the centre of the bin as the centre point of the X. Place the traps vertically into the grain so that the top of the probe traps are about 25 cm (10 in.) below the grain surface. Retrieve and examine them at least once a week. Under high infestation levels, insects may be trapped in a day or two. These probe traps are very sensitive and will show an infestation well before it is economically threatening. If insects are present in probes, follow the management strategies listed in Table 11-2, Insect Management Strategies for Farm-Stored Grain. Insecticide and fumigant recommendations can be found in Publication 812, Field Crop Protection Guide.

Plate 34. Insect probe for stored grain is inserted into grain to trap insects.

Photo showing insect probe.

Table 11-2. Insect Management Strategies for Farm-Stored Grain

Description	Life History	Damage	Management Strategies
Rusty Grain Beetle (see plate 35)
flat, reddish-brown beetle approx. 2 mm (1/16 in.) long antennae are as long or longer than its head and thorax combined flies when temperatures are above 25°C larvae are white, approx. 3 mm (1/8 in.) long, have two brown projections at the rear moves easily through the whole grain pile because of its small size	cold-tolerant overwinters as an adult lays up to 500 eggs on surface of kernels larvae hatch in 35 days larvae penetrate seed and pupate inside adults emerge, leaving distinctive exit hole	adult and larvae feed on germ and bran feeds on cracked or sound grain feeds throughout pile of grain high infestations generate heat, causing grain to mould and spoil	proper sanitation and monitoring practices treatment with diatomaceous earth to protect from re-infestation See OMAFRA Publication 812, Field Crop Protection Guide, for insecticide and fumigant information.
Indian Meal Moth (see plate 36)
adult approx. 12 mm (1/2 in.) long "A-shaped" when wings are at rest wings are grey, bottom half are bronzy active in the evening larvae grow to approx. 8 mm (3/8 in.) long larvae range from pinkish-cream to pale yellow to pale green/yellow with black heads larvae have three pairs of legs on thorax, five pairs of abdominal prolegs mature larvae wander, looking for places to pupate	can go through its entire life cycle in approximately 21-30 days under warm conditions not cold-tolerant temperature limits number of generations per year females lay eggs on kernels of grain on pile surface young larvae found in grain clumps (3-10 kernels) held together by silk	adults do not feed or cause damage larvae feed on germ and bran, leaving kernels with these missing all stages of larvae spin webbing (increases as preparing to pupate) typically stays on top of pile, no more than 50 cm (20 in.) deep high populations result in a mat of grain with silks up to 50 cm (20 in.) deep	moth is resistant to malathion remove webbed layer of grain before fumigation See OMAFRA Publication 812, Field Crop Protection Guide, for insecticide and fumigant information.
Granary Weevil (see plate 37)
adult is a dark-brown snout beetle approx. 4 mm (3/16 in.) long larvae are white, wrinkled and wingless, 4 mm (3/16 in.) long larvae always found inside grain, only leave kernel as adults only attacks cereal grains, not legumes cannot fly can be confused with rice weevil: on surface of thorax, the small pits are round rather than oval cannot survive cold	female lays eggs into holes in the grain created with her snout cements holes shut larvae develop inside grain adults live up to 8 months	adult and larvae feed on sound grain larvae spend entire life in one kernel, feeding on endosperm several larvae can be inside one kernel leaves round exit holes when exits kernel as adult	See OMAFRA Publication 812, Field Crop Protection Guide, for insecticide and fumigant information
Pea/Bean Weevils
two species that attack peas or beans damage and larvae resemble that of granary weevil adults are short and squat(34 mm or 1/8-3/16 in.) heads are tapered at front usually tan coloured with faint longitudinal striping larvae are creamy, yellow, legless and have a brass-coloured head capsule		pea weevils attack peas, bean weevils attack beans adults lay eggs in maturing beans in field with no apparent visible damage damage noticed when new adults emerge from seeds, leaving round holes	monitor beans for damage in storage react with a fumigation sort beans visually to remove "picks" heavily infested peas or beans can be fed to livestock See OMAFRA Publication 812, Field Crop Protection Guide, for insecticide and fumigant information.
Lesser Grain Borer (see plate 38)
adult is a brown-to-black beetle approximately 2 mm (1/16 in.) long cylindrical in shape small numerous pits on surface of wings adult identified by location of head head is turned downward and covered by large hood (prothorax) larvae are creamy-white, C-shaped, with a dark head tucked into the thorax musty odour associated with this pest	female borer lays eggs in cluster on surface of kernels larvae hatch and bore into the kernel completes development inside kernel	pest may move into Ontario due to climate warming adult and larvae cause damage to sound grain bore irregularly shaped holes into the grain leave only shell and powdery dust adult and larvae enter and exit several grain kernels several individuals may attack same kernel also feed off grain dust	advise provincial field crop entomologist if found See OMAFRA Publication 812, Field Crop Protection Guide, for insecticide and fumigant information
Grain Lice
also known as psocids or book lice adults are soft bodied approximately 1-2 mm (1/32-1/16 in.) long have large heads with long antennae range from brown to white and often are opaque can be winged or wingless resemble aphids young are smaller and slightly paler than adults	incomplete metamorphosis (young nymphs resemble adults) several generations can multiply quickly under warm conditions	not a direct pest of grain secondary pest that feeds on grain dust and damaged kernels can be seen running over pile when numerous; visually inspect grain surface for tiny, fast-moving insects generally restricted to the top of the grain pile	turning and cleaning the grain reduces populations lice are found in damp conditions lowering humidity lowers populations See OMAFRA Publication 812, Field Crop Protection Guide, for insecticide and fumigant information.
Mites
adults barely visible to the naked eye approximately 0.5 mm (1/64 in.) long rounded eight-legged yellowish-brown larvae look like adults but have six legs two nymphal stages look similar to adult with four pairs of legs		incidental insect on grain going out of condition prefers damp grain feeds on grain dusts and moulds	keep grain dry and in good condition See OMAFRA Publication 812, Field Crop Protection Guide, for insecticide and fumigant information.

Plate 35. Rusty grain beetle adults have antennae as long as or longer than their head and thorax combined.

Photo showing that rusty grain beetle adults have antennae as long as or longer than their head and thorax combined.

Plate 36. Indian meal moths leave webbing on top of the grain pile.

Photo showing how indian meal moths leave webbing on top of the grain pile.

Plate 37. Granary weevil is a snout beetle that has oval pits on the surface of the thorax.

Photo showing a granary weevil is a snout beetle that has oval pits on the surface of the thorax.

Plate 38. Lesser grain borer's head is turned downward and covered by a large hood (prothorax). A musty odour is often associated with this pest.

Phot showing how a lesser grain borer's head is turned downward and covered by a large hood (prothorax).

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