CANOLA INSECT SCOUTING GUIDE Millimeters Inches SCOUTING METHODS SCOUTING SCHEDULE BY PLANT GROWTH STAGE Scout fields weekly, checking both high and low in the canopy and Pre-seed/Seedling Seedling Rosette Budding Flowering Ripening inspecting all plant parts, including roots. When insect pest numbers approach action threshold levels, sample more frequently. Occasional insect Bertha armyworm pests may be present in crops but are typically found in low quantities with less frequency (seldom requiring control measures). Common insect pests Cabbage root maggot are encountered more frequently, can be in high quantities and may require Cabbage seedpod weevil control measures. The recommended method for each of the common canola insect pests is shown in the chart on the left. Cutworms Plant counts – The number of insects per canola plant Diamondback moth Area insect count – The number of insects/metre2 Flea beetles Flea beetles Sweep net count – Using a 38 cm diameter net, sweep a full Grasshopper 180o arc 10 times/100 acres Lygus bug Root zone inspection – Look for insects near roots or on plants Percentage defoliation – Percentage of area eaten away COMMON INSECT PESTS BERTHA ARMYWORM (LARVA) CABBAGE ROOT MAGGOT (LARVA AND ADULT) • Pale brown to velvety black (colour variations are common) with yellow/orange stripe along each side • Long, whitish larvae feed on root and create tunnels into roots • Move to pods as leaves are consumed and larvae grow which can lead to disease-causing infection • Action threshold is 6-34/m2, depending on seed and spray costs • Adults resemble house flies but smaller and covered in black (control typically required around 20/m2) bristles; don’t cause damage 40mm 8mm (Larva) CABBAGE SEEDPOD WEEVIL CUTWORMS (LARVA) (LARVA AND ADULT) • Redbacked (pictured), pale western, darksided and dingy cutworms • White, grub-like larvae with brown heads feed in pods on 5-6 all cause damage; feed on cotyledons, leaves or stems at or under soil developing seeds; exit holes in <25% pods (when leaving to pupate) surfaces, or may climb plants (vary by species) indicate populations below damaging levels • Scout top 5 cm of soil around cut-off plants/margins of damaged • Adults have a grey body with prominent, curved snout and feed area (at seedling to rosette stage) on buds causing bud-blasting and lay eggs on developing pods 30mm • Action threshold is ~25-30% stand reduction, but damage may be patchy 3mm (Larva and Adult) DIAMONDBACK MOTH (LARVA AND ADULT) FLEA BEETLES (ADULTS) • Larvae are smooth, pale, yellowish-green worms that are narrow at • Oval bluish black bodies (crucifer flea beetle) or black with two both ends and fatter in the middle and wriggle violently on a silk yellow stripes (striped flea beetle) thread or drop off when disturbed • Feeding causes shot-hole appearance on cotyledons and leaves • Tunnel into leaves and feed on leaf surface, leaving only veins or • Action threshold is >25% cotyledon defoliation if still feeding “window panes”; feed on pod and stem, causing striping on newly developing plants. Canola can recover from 50% loss • Action threshold is 100-150 larvae/m2 in immature to flowering of cotyledon with no yield loss 8mm (Larva) plants or 200-300 in flowering/podding plants (in dense stands) • Adults are small, thin moths that feed on nectar 3mm LYGUS BUG (NYMPH AND ADULT) GRASSHOPPER (ADULT) • Nymphs are pale green, often with black dots. Adults are green to • Some nymphs are pale green, while others have variable markings. reddish brown/black, with a “V” in the upper center of their backs Adults have darker/more distinct colouration but both feed on • Suck sap from buds, flowers and pods, causing flower blasting and leaves, stems and pods shriveled seeds. Heavy feeding, with sap covered plants should be • Most significant damage is done when feeding on pods monitored closely 38mm • Action threshold is likely >12 grasshoppers/m2; better • Only count older nymphs with black spots or developing wing to control younger instars 6mm (Adult) ”shoulder” pads (not younger nymphs without spots) OCCASIONAL INSECT PESTS BENEFICIAL INSECTS * ALFALFA LOOPER (LARVA) APHID (NYMPH PARASITIC WASP (ADULT) AND ADULT) • Light green/olive worm with a paler • Numerous species of Braconid and head and light stripes down each side • Small, often green, soft-bodied, pear- Ichneumonid wasps, with slender and two along the back shaped winged or wingless insects waists and long antennae • Feeds on leaf margins and clips flowers • Often seen in a dense layer at tips • Parasitize plant bugs, bertha 25mm and pods in patchy infestations 2mm of canola; feeding may lead to 15mm armyworm, diamondback moth • Generally don’t cause economic compressed growth and other caterpillars damage but heavy defoliation could warrant control CARABID BEETLES (ADULTS) BEET WEBWORM (LARVA) BLISTER BEETLE (ADULT) • Large, somewhat flattened beetles (often black or brown) that have better • Change from dark green to black as • Large, narrow, often shiny beetles survival in minimum tillage fields they mature; have two white stripes • Feeds on leaves and flowers – 30mm • General predators of cutworms, along the center of the back with two generally in clusters/patches diamondback moth, bertha armyworm rows of paired circular figures outside in a field of the stripes larvae, lygus nymphs and many 25mm 25mm • They may move to canola when other insects • Feed on leaves, then stems and pods nearby alfalfa is cut causing early desiccation; spin silk “webs” at plant tops • Action thresholds may be similar HONEY BEE (ADULT) to bertha armyworm • Clear-winged adults have a black and yellow body and pollinate canola CLOVER CUTWORM IMPORTED 15mm (LARVA) CABBAGEWORM (LARVA AND ADULT) • Dark grey or green body with yellowish GREEN LACEWING pink stripes and light brown head; curls • Larvae are green worms with a (LARVA AND ADULT) up when disturbed velvety texture and faint yellow stripe down the back; feed on leaves 30mm • Progresses from feeding on leaf • Larvae have tiny alligator-shaped, undersides to all parts as they mature • Adult feeds on nectar and doesn’t yellowish to mottled grey bodies with red, brown or black markings and short • Similar in appearance to bertha 30mm (Larva) damage canola (the adult stage is armyworm but appear earlier in not a pest) bristle clumps. They mainly feed on soft-bodied insects like aphids, thrips, the season and damage tends to 10mm (Larva) be in patches lygus nymphs and small caterpillars as well as insect eggs • Adults are pale green with a slender, delicate body and clear wings. They feed on nectar of flowering plants PAINTED LADY (LARVA) RED TURNIP BEETLE * • Black worms with spikes along the back (ADULT AND NYMPH) and yellow stripes along the side HOVER FLY (ADULT, • Beetle with red and black patches • Feed on leaves on the head and three black stripes PICTURED, AND LARVA) down the back • Larvae are flattened yellowish maggots 40mm 7mm • Larvae are black and 10-12 mm long with pale stripes and eat aphids • Primarily feeds on leaves but can • Adults are small brightly coloured consume entire young plants 10mm hairless flies that resemble bees and • Often found just inside of field edges pollinate canola SWEDE MIDGE (LARVA AND ADULT) LADY BEETLE (LARVA AND ADULT) • Larvae are pale, semi-transparent worms when younger and turn yellow THRIPS (ADULT* • Larva looks like a tiny alligator, with as they mature. Older larvae can flip or AND NYMPH) orange and black patches on the back fling themselves when disturbed and three sets of legs • Larvae attack growing points, • Appear as black specks in a sweep • Mainly feed on soft-bodied insects, causing flowers to remain unopened, net (very tiny). Up close, have a 4mm (Larva) 10mm (Larva) including aphids and lygus nymphs, undeveloped or to turn brown and narrow, brown/black body and can and insect eggs dry up. Brown, corky scarring visible be winged (and fringed with fine under magnification hairs) or wingless • Control options are very difficult 1mm • Best identified by the twisted ROVE BEETLE (ADULT) to time because of multiple, pods resulting from feeding overlapping generations (see damage, also pictured) • Usually slender, elongated, • Adults are tiny, delicate-looking flies cylindrical flattened bodies with *Pictured with long legs (don’t damage canola, several abdominal segments visible except for egg deposition) from above due to shortened wing 20mm covers (elytra) • Adults and larvae prey on cabbage root maggot eggs and larvae, aphids, mites and other insects CCC 6164 (2015) CCC For more information on appropriate thresholds and managing canola insects, contact your local Canola Council of Canada agronomy specialist, sign up for our Canola Watch e-newsletter at canolacouncil.org, or call toll-free at (866) 834-4378. 400-167 Lombard Avenue, Winnipeg, Manitoba R3B 0T6 Phone: 204-982-2100 Toll-Free: (866) 834-4378 Photo credits: John Gavloski, MAFRD, Tyler Wist AAFC Saskatoon, Vincent Hervet University of Lethbridge.