Cabbage worms on Plants

Symptoms

The most visible sign is damage to the leaves. The larvae chew large, irregular holes in them, and the holes look ragged. On young plants, they also chew the seedlings.

Check the heads of your cole crops next. The larvae bore into the heads of cole crops such as cabbage. Broccoli, cauliflower and Brussels sprouts are also named as hosts of this pest.

Harvested produce can carry greenish-brown fecal pellets from the larvae. The larvae can also contaminate heads and leaves with their bodies and frass.

Chewing is the main damage to look for, and it can appear on seedlings, on leaves and in heads. Each of these signs comes from the same larvae. Two larvae are named as the cause, the imported cabbageworm and the cabbage looper.

Seedlings, leaves and heads of cole crops can all show damage. Damage to the leaves appears as holes, while damage to the heads comes from larvae boring into them. Contamination of the harvested produce is a further problem beyond the holes.

Causes

Two kinds of larvae are named as the cause of this problem. The larvae of the imported cabbageworm, Pieris rapae, are one cause. The larvae of the cabbage looper, Trichoplusia ni, are the other.

Nearby cruciferous weeds are also listed as a cause. Weeds such as mustards can host the pest. Controlling those weeds is one treatment listed for this problem.

Three causes are on file for this problem, two larvae and one group of weeds. Larvae chewing seedlings, making large, irregular holes in leaves and boring into heads are all the work of these pests.

Natural enemies provide biological control of the pest. Broad-spectrum insecticides can disrupt that biological control. Hedgerows of insectary plants can attract and support those natural enemies.

Cabbage, broccoli, cauliflower and Brussels sprouts are the crops these pests are recorded on. Greenish-brown fecal pellets on harvested produce are left by the feeding larvae. Eggs and small larvae are both mentioned for the timing of treatment.

Diagnosis

This page names no look-alike problems, so the diagnosis rests on the signs and causes it records. Holes that are large, irregular and ragged match the chewing damage the larvae cause. Seedlings that have been chewed fit the same pattern.

Cole crops such as cabbage, broccoli, cauliflower and Brussels sprouts are the hosts named for this pest. Open a head of cabbage or a similar crop and check for larvae that have bored in.

Examine the produce for greenish-brown fecal pellets. Also look for larval bodies and frass on heads and leaves.

Hand-picking the caterpillars from plants is a listed treatment. Go over the leaves and heads for the caterpillars themselves. Nearby cruciferous weeds such as mustards are a listed cause. Check the area around the bed for them.

Two larvae are named, the imported cabbageworm and the cabbage looper. Chewing damage on leaves, seedlings and heads, together with pellets or frass, is the pattern to confirm.

Treatments

Treatment for this problem falls into cultural, organic and chemical methods. Cultural methods come first. Control cruciferous weeds such as mustards, since they can host the pest.

Use row covers to help manage the pest. Hand-pick the caterpillars from plants. Avoid broad-spectrum insecticides that disrupt biological control of the pest by its natural enemies. Maintain hedgerows of insectary plants to attract and support natural enemies of the pest.

Two organic options are listed. Bacillus thuringiensis is applied as a foliar spray, along with biological and cultural control, in certified organic production. Spinosad, in the Entrust SC formulation, is applied as a foliar spray in certified organic production when eggs are present or larvae are small.

Six chemical options are listed. Chlorantraniliprole is applied as a foliar spray with an effective adjuvant for best performance. Spinetoram is applied as a foliar spray, and it is toxic to some natural enemies, including predatory beetles, syrphid fly larvae and predatory thrips.

Methoxyfenozide is applied as a foliar spray for early-season applications to young crops. Emamectin benzoate is applied as a foliar spray, observing the label's preharvest interval for the crop. Indoxacarb is applied as a foliar spray with a wetting agent to improve coverage. Cryolite is applied when early larval instars are present, since the insect must ingest it to be affected.

The product label is the legal instruction, so follow it for the crop and site you are treating. This page gives no doses, rates, dilutions or spray intervals.

Prevention

Prevention here is about the conditions around your crop. Keep cruciferous weeds, such as mustards, under control near your cabbage, broccoli, cauliflower and Brussels sprouts, since they can host the pest. Row covers can help with these pests.

Hedgerows of insectary plants attract and support natural enemies of the pest. Broad-spectrum insecticides can disrupt biological control of the pest by those natural enemies, so avoid them.

Hand-picking the caterpillars from plants is another cultural method on the list. Watch seedlings, leaves and heads for chewing, since the larvae feed on all three.

Cabbage, broccoli, cauliflower and Brussels sprouts are the hosts named for this pest. Weeds, covers, hedgerows and careful choice of insecticide are the conditions this page lists.

Plants most often affected

The crops named as hosts are cabbage, broccoli, cauliflower and Brussels sprouts. The larvae bore into the heads of cabbage and other cole crops. Seedlings and leaves of these crops can be chewed too. Cruciferous weeds such as mustards can host the pest as well. These are the crops to check first for the damage described above.

No plant page in this build records this problem yet.