Swede Midge

This pest is not currently known to occur in British Columbia. It is, however, present in eastern cole crop growing regions of N. America. Symptoms include galling on seedlings and transplants, swollen or twisted stalks and stems, crinkled leaves, scarring, blind heads and multi-headed plants. Damage can create entry points for disease. Symptoms can be confused with nutrient deficiency, herbicide damage, seed variability, bolting caused by heat stress or buttoning caused by frost damage. Broccoli, gai lan and brussels sprouts sustain the worst damage, but Swede midge can infest any brassicae plants including rutabagas, canola, ornamentals and weeds. Check suspect damage for presence of maggots within the plant tissue. Surveillance of BC cole crops is currently underway. Please report any suspect damage to your local BCAGRI office. Swede midge can be prevented from entering BC by:

• ensuring transplants are pest-free; and
• employing good field sanitation practices.

Root Maggots

The adult is a gray fly, half the size of a housefly, which lays white eggs at the base of plants. Legless white maggots hatch and tunnel roots causing rotting of the roots and wilting of the plant. This pest is especially destructive in seed-beds and to young plants after setting in field.

Broccoli, Brussels Sprouts, Cabbage, Cauliflower Greenhouse Transplant Drench

Apply Entrust SC (Registration # 30382) using the rate of 25 mL in 2 L of water per 1000 plants as a drench before transplanting.  Immediately after applying, apply 2 L of water per 1000 plants to rinse the product off the plants and into the soil.  Do not rinse the product out of the transplant medium.  Make one application per year.  Do not re-enter treated area for 24 hours after applying.

Or:

Apply Success (Registration # 26835) using the rate of 12.5 mL in 2 L of water per 1000 plants as a drench before transplanting.  Immediately after applying, apply 2 L of water per 1000 plants to rinse the product off the plants and into the soil.  Do not rinse the product out of the transplant medium.  Make one application per year.  Do not re-enter treated area for 24 hours after applying.

Control

Note: Root maggot resistance to chlorpyrifos (Lorsban /Pyrinex/Nufos) has been reported in the Lower Mainland and Vancouver Island. Use these products with caution. Check to see if emergency use products are registered.

Seed-bed

If no granular chlorpyrifos reatment was used, apply Lorsban 4E, Lorsban NT, Nufos 4E or Pyrinex 480 EC at 210 mL per 1000 m of row.  Apply in one drench spray in 1000 L/ha (400 L/acre) spray solution, 10 cm on each side of the plant, 7 to 10 days after seeding.

Field

Growers have the option of applying a granular insecticide or a post-planting liquid drench. Use of granules is the normal practice for direct-seeded crops while for transplants the drench is preferred.

Granules:

Using a granular applicator, apply the insecticide in a band in front of the seed coulter so that the seeding operation incorporates the chemical. Application directly in the furrow puts a high concentration of chemical in direct contact with the seed and may reduce the stand or stunt seedlings.

Lorsban 15 G at 0.6 to 1.0 kg/1000 m of row. The following lists rates of Lorsban 15G at various row spacings:

To protect wildlife, every effort should be made to completely incorporate granules. Granule deposits from spills and accumulation at row ends should be covered with soil.

Postplanting Drench:

“Drench” means to spray the insecticide in at least 1000 L/ha (400 L/acre) water, 10 cm on each side of the plants in the row. Drench within 3 days of transplanting (after plant recovery) or 7 to 10 days after seeding (if granular treatment was not applied) with:

Lorsban 4E, Lorsban NT, Nufos 4E or Pyrinex 480 EC at 1.68 L in 1000 L of finished spray.  Apply 12.5 L of this solution to 100 m of row on the soil.

Note: The second application should not be made to transplanted broccoli as the crop may mature before the required days to harvest waiting period.  A repeat drench may be applied 21 days after the transplant drench or 28 days after seeding if a granular treatment was not applied.  However, where establishment and early growth are good, a repeat drench should not be necessary.

Lorsban 4E, Lorsban NT, Nufos 4E or Pyrinex 480EC must not be applied within 32 days of harvest.  If no granular chlorpyrifos application was made, do not apply more 2 times per season on broccoli, cabbage or cauliflower.  If no granular chlorpyrifos application was made, do not apply more than three times per season on Brussels sprouts.  

If a granular chlorpyrifos treatment was made, do not make a follow-up application of Lorsban 4E, Lorsban NT, Nufos 4E or Pyrinex 480EC more than 1 time per season on broccoli, cabbage or cauliflower; and do not follow up with more than 2 applications per season on Brussels sprouts.

Do not re-enter treated area for 24 hours.  For cauliflower, do not re-enter treated area for 10 days.

Cabbage Aphids

These small, soft, gray, winged or wingless sucking insects are found clustered on the new leaves and growing point. If present in high numbers they will cause yellowing, distortion and stunting of the crop. They are a serious contaminant and if not controlled will cause the crop to be unmarketable.

Control

See Table 2, Cole Crops Insect Control.

Loopers, Climbing Cutworms, and other Caterpillars

The most common and damaging species are the imported cabbageworm, diamondback moth, cabbage and alfalfa looper. These pests chew holes in leaves and contaminate heads. Even if damage is light, low levels of caterpillars or loopers in the harvested crop can result in rejection by buyers.

Control

Aphids and caterpillars should be controlled within an overall management and spray program. See IPM section for information on cultural controls and monitoring.

Adequate spray coverage (high pressure and volume) is necessary to obtain good control. Cole crop leaves are very waxy so use a spreader recommended on the pesticide label to improve coverage. Use drop pendant nozzles (see Spray Equipment section of this guide) for effective control on Brussels sprouts when plants are over 50 cm high.

To deter insects from developing resistance, do not rely on a single insecticide but alternate between the chemical groups listed in Table 2 (Cole Crops Insect Control). Note that some materials will control only aphids, some only caterpillars and some will control both. Choose products according to which pests are present in the field. Tank-mixes may be necessary. Follow product label guidelines or local experience.

When planning a spray program, pay particular attention to the days to harvest restrictions. Products such as Lorsban must only be used well in advance of harvest. If pests need to be controlled close to harvest, products such as Decis or Dibrom should be used.

Note: Days to harvest restrictions are the waiting period necessary between application and harvest to ensure that pesticide residues on the marketed produce are below legal tolerance. These numbers are not equivalent to the length of time a product will provide pest control.

Flea Beetles

These small, active, black or bronze, jumping beetles eat holes in leaves causing shot-holes. They are especially damaging to young plants.

Control

Sprays applied for root maggot, aphid and looper control will usually keep flea beetles in check.

Lygus Bugs

See Pest Management section of this guide.

Red Turnip Beetles

These red and black beetles are a pest in the Interior and Peace River areas. The dark-brown immature larvae eat foliage.

Control

This pest will be controlled if a regular root maggot control program is followed.

Slugs

Slow-moving, soft-bodied, slimy creatures found in various sizes up to 10 cm. They can be a serious problem on Brussels sprouts as the heavy canopy provides them with a cool, moist environment. They feed directly on the forming sprouts causing them to be unmarketable. Damage most often occurs on the field edges. They are most severe in fields which were previously in grass, clover or weeds.

Control

Growers should monitor fields by applying bait stations early in the season prior to plowing. If high numbers of slugs are found, treatments should be applied before plowing or when plants are small and first damage occurs. If slugs are not controlled before early August, they will escape treatment with bait or sprays and serious crop damage will occur.

Apply metaldehyde (Deadline) or apply ferric phosphate (Sluggo, Ferramol or Slug & Snail Bait) to soil surface at label rates. Treatments should be made in the evening to the soil between the rows and the headlands. Avoid direct application to plants.

Lannate TOSS-N-GO is registered to control slugs on Brussels sprouts. Apply at 775g/ha (310g/acre) Apply when plants are small and slugs are first detected. Spray must directly contact slugs so application should be made at night when slugs are up on plants. Apply only once per season at this rate. Do not apply within 30 days of harvest. Do not enter the treated area for 12 hours. (Lannate is registered at a lower rate for use on loopers and caterpillars. At the lower rate, days to harvest restriction is 7 with a maximum of 3 applications per season).

Thrips

Thrips are very small (1 mm), slender, yellowish to brown insects which may be either winged or wingless. They rasp and puncture plant tissue and may cause scattered blister-like growths on leaves and heads of cabbage. Thrips often move into cabbage fields after hay is cut. They are worse in hot, dry summers.

Control

Good weed control will minimize thrips populations. Cabbage varieties vary in their tolerance to thrips. Over-mature cabbage is prone to thrips damage - harvesting at the proper maturity will help reduce injury.

Apply Mako (formerly Ripcord 400 EC) or Up-Cyde 2.5 EC at label rates for control of thrips. Do not apply within 3 days of harvest. Do not use on muck soils. Maximum of 3 applications per season.

Begin spraying when cabbage leaves cup prior to heading or when thrips appear. Synthetic pyrethroid insecticides (See Table 2 Cole Crops Insect Control) applied for caterpillar control will also control thrips.