Insect and Bug Guide: Imported Cabbageworm

IMPORTED CABBAGEWORM: attacks cabbage, collards, broccoli, and other brassicas.

Imported cabbageworm caterpillars are green with yellow markings, and their skin has a velvety texture. Mature larvae are slightly longer than 1 inch. The adult butterflies have a wingspan of about 2 inches. The wings are white on top with black tips and a few black spots, but the undersides are pale yellow.

These caterpillars eat the leaves and can also attack flower clusters of broccoli and cauliflower. Severe defoliation can kill young plants or interfere with proper head formation, and heavy infestations can destroy large plants.

This insect is most common during the cooler parts of the year, which is when most cole crops are grown. Not only will you notice their presence by the damage they make on the leaves of the plant but you will tell that they are there by the dark pellets of excrement they kindly leave behind causing contamination.

Biological Controls 

• Assassin bugs, damsel bugs attack really young caterpillars, green lacewings attack really youn caterpillars, hover flies attack eggs and very young caterpillars, parasitic wasps are great biological options to controlling the Imported Cabbageworm.

  
  

• An application of compost tea complete with good biology of bacteria, fungi, nematodes, and protozoa will help protect your plant from chewing insects as well as any diseases that may result of the bad guys being on your plant.

  
  

• Hb nematodes can be sprayed at time of seed planting or 1 week before planting transplants to attack lavae in the soil. These nematodes can also be sprayed over a crop as well covering at least 70%-100% of the plants leaves and head formation.

  
  

• Bacillus thuringiensis kurstaki (Btk) is a gram-positive, rod-shaped bacterium native to the soil in a wide range of regions globally. A subspecies of Bacillus thuringiensis, Btk controls Lepidoptera.  One thing about Btk is that it does not pose a threat to other animals or insects outside of the order Lepidoptera in the environment once it has been sprayed or ingested by the target pest. Birds and other predators can feed on the infected pests without ingesting toxic chemicals. As with most biological control measures, Btk applications will be most effective when made early in the pest's life cycle, particularly during the larvae's 1st and 2nd instars. Once ingested, the alkaline environment of the caterpillar's digestive system triggers the Btk bacterium to release a crystalline protein, a type of endotoxin, which paralyzes the caterpillar's digestive tract. The caterpillars will stop feeding and die shortly after this occurs.

  
  

• Sprinkling cabbage leaves with cornmeal or rye flower causes the cabbageworms to bloat and die once they ingest it.

Mechanical Controls

• Cover susceptible plants with floating row cover early in season. Since no pollination is needed, the row cover can stay in place until harvest.

  
  

• Hand picking warms and squishing bullet shapped eggs found on leaves is always fun!

Cultural Controls

• Make sure that you have healthy soil.

  
  

• Choose cabbage varieties that have tighter heads as they are less susceptible to damage.

  
  

• Plant flowers that attract beneficial insects

Cabbageworm (mature)