Cabbage

Great Southern White

Ascia monuste

Insect

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In a Nutshell

  • Feeding damage on leaves.
  • Irregular holes along the leaf edges.

Can also be found in

2 Crops
Cabbage
Cauliflower

Cabbage

Symptoms

A clear sign of an infestation is when plant leaves are damaged by feeding. The caterpillars of the Great Southern White butterfly are the one doing the damage. Usually they eat the edges of the leaves, starting from the outer parts and moving inward. This kind of feeding often creates uneven holes along the edges of the leaves. The caterpillars are capable of eating the entire plant parts above the ground. They are voracious eaters of cruciferous vegetables (cabbage, cauliflower, broccoli). Keep an eye out for clusters of eggs on the top side of the leaves and caterpillars feeding together in groups. You may also spot adult moths in the field.

Recommendations

Organic Control

Consider using Bacillus thuringiensis (Bt) spray, a natural insecticide that targets and kills cabbage worm larvae while being safe for humans and beneficial insects. Apply neem oil spray, derived from the neem tree, as a natural repellent and insecticide.

Chemical Control

Always consider an integrated approach with preventive measures together with biological/environment friendly treatments. According to literature most of the following insecticides efficiently controlled Ascia monuste, but not all of them are safe for natural enemies: Chlorantraniliprole, cyantraniliprole, indoxacarb, spinosad, chlorfenapyr. Additionally, the use of pesticides can lead to cases of resistance, where pests become less affected by the insecticides over time.

What caused it?

The damage is caused by the caterpillars of the insect Ascia monuste. It is a very harmful pest that causes significant losses in cruciferous crops. Female adults lay groups of yellow, spindle-shaped eggs on the top side of leaves. This happens between November and May, which is the warm and rainy season in tropical areas. The caterpillars are yellow with gray stripes. The stripes run along their bodies and they have small black spots. The adult butterflies are white (males) and dirty white to gray (females). The adults live for about 19 days. They will travel long distances to find food, mates, and good conditions for those in juveniles stages to grow. Studies have shown that these pests do best in wet and warm conditions with temperatures ranging from 16 to 35 °C. Yet cold weather and heavy rainfall make it difficult for them to survive.

Preventive Measures

  • Using resistant cultivars or varieties, if available.
  • Plant purple or red cabbage varieties, as they are less appealing to cabbage worms and moths.
  • Monitor plants regularly for signs of infestation, such as feeding damage and groups of eggs.
  • Remove eggs manually when found. Preserve biodiversity by protecting habitats for natural enemies of the moth, such as predatory insects and birds.
  • Use floating row covers, preventing these pests from reaching your plants.
  • Use polyculture and companion planting by interplanting with herbs like thyme, sage, and rosemary, as well as marigolds and nasturtium.
  • Hang decoy moth traps to capture male moths and disrupt their reproduction.

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