Overview
- What pests affect cabbage?
- Cross-striped cabbageworm
- Imported cabbage worm
- Diamondback moth
- Cabbage looper
- Beet armyworm
- Harlequin bugs
- Flea beetles
- Cabbage webworm
- How do I manage cabbage pests?
- Summary
Cabbage is an important agricultural crop. Approximately one million metric tons of cabbage are produced annually in the United States, while in Canada, around 12,600 acres of cabbage are harvested each year. Damage caused by cabbage pests can reduce yield and marketability, causing significant harm to the industry. This article focuses on cabbage pests, how to identify them, and the damage they cause. It finishes with a discussion of approaches for combating these threats, including the use of biological methods.
What pests affect cabbage?
Cole crops, including cabbage, broccoli, cauliflower, and kale, are impacted by a huge variety of pests. Many species of moth, including imported cabbage worms, attack cabbage plants during their larval phase, while other species, like harlequin bugs and flea beetles, damage cabbage leaves in their adult forms. Cabbage pests cause yield loss and complete crop failure in severe cases.
Cross-striped cabbageworm (Evergestis rimosalis)
This pest is a species of moth that feeds on cabbage plants in its larval stage. Adult moths are grey or yellowish-brown and have a wingspan of 25 mm. Larvae are blue-grey with many lateral black stripes on their backs. A large black and yellow stripe runs the length of their bodies on each side of the striped area. They feed on all tender parts of cabbage plants but prefer to feed on terminal buds.
Imported cabbage worm (Pieris rapae)
This pest is a species of butterfly. Adults are white with black spots on the forewing, have a 4.5 cm wingspan, and lay eggs on all parts of the plant. Larvae are green with a light yellow stripe down their back and grow to 32 mm in length. They feed on all parts of the plant, but are most commonly found feeding near the centre of the plant. Damage appears as holes in cabbage leaves.
Diamondback moth (Plutella xylostella)
This moth species causes damage to cabbage plants in its larval stage. Adult moths have a grey-brown body, and males have a characteristic three-diamond pattern on their backs. Females lay eggs on the underside of leaves. Diamondback moth larvae are pale green/yellowish and grow to about 8 mm in length. They feed on all areas of the plant, but mainly on the undersides of leaves. Damage appears as holes in the undersides of leaves.
Cabbage looper (Trichoplusia ni)
This pest is a species of moth that damages cabbage plants during its larval stage. Cabbage looper moths are grey-brown with a wingspan of 2.5 to 3.8 cm. Larvae are green, 2.5 to 3.8 cm long, and emerge from eggs that are usually laid on the underside of leaves. They typically feed between the veins of leaves and work their way towards the centre of the plant. Damage will appear as holes in leaves, and frass (excrement) may be present.
Beet armyworm (Spodoptera exigua)
This pest is a moth species that attacks plants in its larval stage. Adults are grey-brown with a 32 mm wingspan. Females lay hundreds of eggs in about one week under white cottony scales. Larvae appear in many colours from pale green to black and can grow up to 32 mm in length. Larvae feed on cabbage leaves and may leave webbing where they feed. Extensive cabbage leaf loss can occur with severe infestations.
Harlequin bugs (Murgantia histrionica)
This pest is a species of stink bug, also known as the cabbage harlequin bug. They have a characteristic black, red, and orange pattern on their backs. Their eggs are also distinct with a black and white striped “barrel-like” appearance. Adults feed on cabbage plants by piercing leaves with their mouthparts and sucking out plant fluids. Harlequin bug damage appears as lighter “fan-shaped” marks on leaves.
Striped flea beetle (Phyllotreta striolata)
Many species of flea beetles attack cabbage crops. These small bugs appear in various shades of brown to black. Adults cause “shot-hole” damage in leaves and are particularly damaging to younger plants. Larvae are white with brown heads and attack the roots of plants. Adults can live through the winter in plant debris. The striped flea beetle (Phyllotreta striolata) is a particularly damaging pest to cabbage crops, and damage appears as irregularly shaped holes in leaves. Adults grow to 2.5 mm in length and have a shiny black colour with a greenish tinge.
Cabbage webworm (Hellula rogatalis)
This pest is a species of moth that attacks cabbage plants in their larval phase. Adults are grey-brown with a wavy pattern and have an 18 mm wingspan. They lay eggs on the outer leaves of cabbage plants. Larvae are light in colour with dark heads and brown stripes running the length of their body. They reach about 13 mm in length. Damage appears as holes in leaves, discolouration, and skeletonisation as larvae feed on soft tissues between the leaf veins. Extensive damage causes leaves to break and collapse.
How do I manage cabbage pests?
There are several methods for managing pests that damage cabbage crops. A combination of approaches using integrated pest management practices and biological control methods often works well in many cases.
Monitoring
Watch carefully for the symptoms described above, which may indicate cabbage insect activity in your field or garden. Holes in cabbage leaves are the primary symptoms of damage from the pests we have discussed above. With large infestations, high numbers of larvae may be visible on the leaves. An increase in the number of adult moths in the growing area can also indicate an infestation. Look out for eggs on the undersides of leaves.
Cultural control
Cultural control involves using specific farming or gardening practices to lower the risk of pest infestations. This method of crop management depends on correctly identifying the pest. Clearing the growing area of plant debris and weeds is important for removing the opportunity for pests like flea beetles to live through the winter and for different moth species to form cocoons and complete their lifecycle. Floating row covers are lightweight fabric sheets sealed at the edges with soil or stakes, which prevent pests from attacking crops, including cabbage. They are considered a type of mechanical pest control.
Biological control
- Natural Substances: These are typically derived from plants and can be used in sprays to repel or kill pests. For example, azadirachtin, an extract from the neem plant, can be effective in managing the cabbage webworm.
- Semiochemicals: These are messaging compounds that can be used to disrupt pest behaviour. For example, beet armyworm pheromones can be used to lure these pests into traps.
- Microbials: These are microorganisms like bacteria, fungi, and viruses that harm pests but not crops. For example, Bacillus thuringiensis is a species of bacteria that can combat a huge variety of pests in their larval stage, including cabbage loopers.
- Macrobials: These are larger animals, like certain insects, that feed on or parasitise pests. For example, the insidious flower bug is a predatory insect that feeds on many insect pests, including diamondback moth caterpillars. The parasitic roundworm Steinernema carpocapsae is effective for managing many cabbage pests in their larval phase.
Chemical Pesticides
As a world leader in nature-based pest management knowledge implementation, CABI encourages Integrated Pest Management (IPM) as the preferred, ecologically-based approach to producing healthy crops, which allows for chemical pesticide use only as needed, and when adhering to measures that limit the exposure of people and the environment to them (see FAO, International Code of Conduct on Pesticide Management).
Before considering the use of chemical pesticides, farmers should explore all available non-chemical control solutions. These might include cultural practices like handpicking pests such as caterpillars, removing diseased plants, using resistant crop varieties, applying crop rotation and consulting the CABI BioProtection Portal for identifying and applying suitable biological control products (microbials, macrobials, natural substances and semiochemicals).
In case chemical pesticides are considered for use, farmers should look to select lower-risk chemical pesticides which, when used as part of an IPM strategy, help manage pest problems while minimizing harmful effects on human health and the environment. Agricultural advisory service providers can provide information on lower-risk chemical pesticides that are locally available and are compatible within an IPM strategy. These experts can also advise on the required personal protective equipment.
Summary
Cabbage and other cole crops face significant threats from a range of pests, including moths, beetles, and stink bugs, which can significantly reduce yields and crop quality. Identifying these pests early and understanding their impact is vital. Effective pest management combines cultural practices, monitoring, biological controls, and, as a last resort, chemical methods. Integrated pest management offers a sustainable approach to protecting cabbage crops and maintaining the health and productivity of agricultural systems.
For tailored pest management advice, visit the CABI BioProtection Portal, where you can enter your location and pest problem to explore customised solutions.
We have also prepared extensive guides on dealing with pests such as chilli black thrips and protecting specific crops, including coffee.
