INSECT PESTS

Northern Plains

Flea beetle (Phyllotreta crucifera) is an early season pest of canola, especially during hot and dry weather. Adult beetles overwinter in shelterbelts, fly into the emerging canola crop, and feed on cotyledons. The crop becomes tolerant to injury after the appearance of true leaves. Beetles mate, lay eggs and die. The larvae feed on canola roots. The new generation of adults emerges in summer. The beetles feed on remaining green foliage and pods, but the injury is usually negligible. In late summer, they move to the shelterbelts to overwinter. The management options for flea beetles are early planting, insecticides applied at planting, and foliar application of insecticides. Lack of moisture may limit uptake of the soil-incorporated insecticide into the plants, which may cause insecticide failures. Insecticides currently available are carbofuran (Furadan CR-10, temporary tolerance expires in the fall of 1997) and Imidacloprid (Gaucho). Gaucho is applied as a seed treatment at 10 oz per 100 lbs of seed and carbofuran is applied as a corn cob grit granular at 0.25 lb AI per acre. Based on a survey of producers in the Northern Plains, about 60 - 70% of the acreage is treated with either carbofuran or imidacloprid.

Bertha armyworm (Mamestra configurata) is a mid- to late season pest of canola. It overwinters as pupae, the adults emerge, and lay eggs in the late spring. The larvae feed on foliage. While the larvae are small and the crop has abundant foliage, the damage is low. During the ripening stage startng in late July, mature larvae feed on pods and cause significant damage. For monitoring of adult flight, pheromone traps are available. Management decisions are based on counts of larvae. As a cultural control, early swathing may be an option in infested fields. The recommended threshold for insecticide applications is 18 - 22 larvae per square yard. North Dakota has had section 18 labels for bifenthrin (Capture) and lambda cyhalothrin (Warrior) in 1995 and 1996, respectively.

Diamondback moth (Plutella xylostella) is a late season pest of canola. Areas in the North Central region are infested every spring with adult moths migrating from the south part of the region. Once established, a new generation occurs approximately every three weeks. The generations overlap and any of the life stages can be found in the field. Young larvae feed in mines in leaf mesophyll whereas older larvae feed on leaf surface. Damage may occur during flowering and ripening when larvae feed on buds, flowers, and especially on the surface of ripening pods. The recommended threshold is 25 - 30 larvae per square foot. Methyl parathion and endosulfan are the only registered products for this pest.

Southeast

Aphids (Complex consisting of turnip aphid, Lipaphis erysimi, green peach aphid, Myzus persicae, and cabbage aphid, Brevicoryne brassicae). Turnip and green peach aphids migrate into fields in the fall and feed through flowering in the spring. Cabbage aphid mostly occurs during flowering in the spring. Aphids disperse after flowering. Feeding injury mostly by the turnip aphid during seedling and rosette stages retards plant growth and makes plant more susceptible to cold temperature injury. Feeding injury during flowering reduces stem growth, causes flower abortion and inhibits pod and seed formation. Aphid resistant varieties are not available. Aphids caused about a 10 to 30% loss in canola yield if not controlled with an insecticide. Aphids populations can be naturally controlled by the weather and by natural enemies including a parasitic wasp and ladybird beetle larvae and adults. Fields are scouted for aphids. When populations exceed a threshold of 1-2 aphids per leaf, infestations are controlled using a foliar application of methyl parathion 4EC at the rate of 0.5 lb ai per acre. Gaucho seed treatment at the same rate recommended for flea beetle control also provides good control of aphid populations for 4 to 8 weeks after planting. A 12 month planting restriction currently prevents crops from being planted after canola unless Gaucho is registered for use on that crop which in the Southeast these crops are limited to cotton and grain sorghum. Soybeans can not be growth within 12 months after canola treated with imadcloprid. Endosulfan also is registered for aphid control but is not used because it is less effective especially against green peach aphid and is much more expensive than methyl parathion.

Cabbage seedpod weevil (Ceutorhynchus assimilis) does not occur in the coastal plain region of the southeastern U.S., where all commercial production currently is grown. The insect does occur in northern Georgia, Alabama, and South Carolina and would require preventive control if canola were ever grown in these areas of the Southeast.

Other Insects

Canola also harbors populations of thrips, (Frankliniella spp.), tarnished plant bug, (Lygus lineolaris), stink bugs, and false chinch bugs, (Nysius raphanus), during the spring. These insects typically do not damage the canola but build up on the canola and move the summer crops especially cotton in the same or adjacent field where they may cause significant damage.

Pacific Northwest

Cabbage Seed Pod Weevil, (Ceutorhynchus assimilis) Cabbage seedpod weevils overwinter as adults near canola fields in protected area such as under bark of trees, sheds, wood piles, and litter. Adults start flying in the spring when the temperature reaches 60 degrees F, the time when wild mustard, winter rapeseed, and canola plants start to bud. Adults feed on the flowers, buds, stem, and pod of the canola. When they fly into the canola field they have mated and are ready to lay eggs. The first eggs are laid when the pods are about 1-1/8 inches long. Eggs are laid within the pod, larvae feed on seeds within the pod, consuming 4 to 6 pods each. More than one larva can occur in a pod. Yield reductions to 30 percent are possible from larval feeding. Larvae eventually exit the pod, drop to the soil to pupate, and emerge as new adults. The newly emerged adults feed on canola and brassica weeds and move to overwintering sites. There is one generation per year. Late spring plantings may escape weevil attack, but are then more subject to flea beetle, aphid, and diamondback moth attack, and hotter weather. Control is limited to methyl parathion and endosulfan.

Aphids The same three species as in the southeast region attack spring-planted canola in the northwest. Late plantings are severely affected by aphid feeding, which can stop terminal growth leading to a reduction in plant size and seed yield. Control has been limited to methyl parathion and a Section 18 label for bifenthrin.

Flea beetle (Phyllotreta cruciferae) attacks fall-planted seedlings, late spring-planted seedlings, and sometimes pods and leaves of spring-planted canola. See northern plains section for biology. Furadan CR-10 was registered in Washington and Idaho in 1997. Foliar treatments has been limited to methyl parathion, but it is not as effective as imidacloprid or carbofuran.

Diamondback moth (Plutella xylostella) damage occurs leaves, buds, flowers, and pods of plants. Damage may be more severe on later plantings. Damage (numbers of insects) is more variable from year to year then the other canola pests in the region. Migration of the moth may be from local populations or populations that have developed in more southern latitudes. See northern plains section for biology. Control has been limited to methyl parathion and Bacillus thuringiensis (BT) products.

This site was last updated on April 19, 2000 at 04:39 PM -0500