Cereal crops - insect threshold levels

Pest Control thresholds Sampling recommendation Additional notes
Aphids:

Corn aphids

Oat aphids

Barley yellow dwarf virus can be spread by low aphid numbers, especially by winged aphids flying into crops. Low numbers are difficult to detect Corn aphids are usually found in the furled leaves of tillers. Oat aphids are usually found on the outside of tillers NA
Beetle: Cockchafers (Heteronyx obsesus) 3-5 grubs per shovel full of soil can cause crop damage especially if seedlings do not have extensive root systems Many native cockchafers are present in soil, under the roots of crops. Only Heteronyx obsesus is known to cause extensive crop damage NA
Beetle: Desiantha weevil If adult desiantha weevils were present in the previous years crop or present in the paddock prior to seeding it is likely there will be larvae present in the soil Under the soil, Sometimes are difficult to find NA
Caterpillars: Webworm 25% of seedlings are damaged at or just after emergence Feed at night and found in web lined tunnels in the ground usually with plant part protuding NA
Caterpillars: Cutworm 2-3/m2 cutworm caterpillars Feed at night and hide in soil during the day NA
European earwig Cause shredding damage to tillers, rarely cause plant death but can slow down plants Look for them under debris and clogs of soil Reducing stubble residues in paddocks known to harbour earwigs will help to keep their numbers lower
Lucerne flea Consider control measures if holes are increasingly being found on leaves On weeds on seedlings NA
Mites: Balaustium mite Look for white bleaching on extensive areas of leaves and stress caused plants Estimate the number of mites/100cm2 (10x10cm) around the base of plants. Repeat at 5-10 sites. Avoid sampling in bright light, sample on cloudy days early morning or late afternoon NA

Mites:

Redlegged earth mite (RLEM)

Blue oat mites (BOM)

Wheat and barley: 50 mites/100cm2 (5000 mites/m2) Estimate the number of mites/100cm2 (10x10cm) around the base of plants. Repeat at 5-10 sites. Avoid sampling in bright light, sample on cloudy days early morning or late afternoon RLEM and BOM can occur in mixed populations. There is evidence that the two species have different susceptibilities to chemical sprays. Determine the species composition of the population before making spray decisions
Slugs: Black keeled slug Black keeled slugs: 1-2/m2 Detect incidence early in the season using shelter traps, for example, moist hessian bags laid on the soil Invade from crop edges
Slugs: Reticulated slug Reticulated slugs: 5/m2 Detect incidence early in the season using shelter traps, for example,moist hessian bags laid on the soil Invade from crop edges
Snails 40 or more snails per m2 A management plan for the year starting soon after harvest is needed to avoid damage and contamination Found on leaves, stems or onother nearby objects
Snails: White Italian snail 20 or more snails per m2 for white Italian A management plan for the year starting soon after harvest is needed to avoid damage and contamination Found on leaves, stems or onother nearby objects

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Page last updated: Wednesday, 21 February 2018 - 12:54pm