Pacific Pests, Pathogens & Weeds - Mini Fact Sheet Edition

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Shallot Spodoptera army worm (178)

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Photo 1. Caterpillar damage on onion leaves caused by Spodoptera sp. Often the caterpillars are found inside the tubular leaves.

Photo 2. Egg mass of Spodoptera exugia. Note the hairs over the eggs taken from the abdomen of the female.

Photo 3. Late stage caterpillar, Spodoptera exugia. Note the lines along the side of the body and the one along the back.

Photo 4. Adult moth, Spodoptera exugia.

Summary

• Worldwide distribution. Not recorded in Oceania. On onion and relatives, food legumes, and potato and cabbage families. Usually, a minor pest in Pacific islands.
• Young caterpillars scrape the surface of outside leaves; larger ones make holes and eat all the leaves.
• Eggs hatch and larvae stay together at first then fan out until there is only one per plant. They pupate in the soil, producing a moth that is a strong flyer.
• Cultural control: handpick; grow under nets; mass trapping using lights; weed; 1-2-year crop rotations.
• Chemical control: PDPs: chillies, neem, pyrethrum, or derris; or, if grown for sale, Bt (Bacillus thuringiensis) on young caterpillars.

Common Name

Common cutworm, beet armyworm. Note that the species on onion has not been identified in Pacific islands where damage to shallots has been seen. In this fact sheet, it is assumed to be Spodoptera exigua. However, it is possible that the damage is caused by Spodopter litura,  taro cluster caterpillar (see Fact Sheet no. 31).

Scientific Name

Spodoptera spp. The common species on onion in other parts of the world is Spodoptera exigua (common or beet armyworm); however, this has not been identified in Pacific island countries, and the species attacking onion is likely to be Spodoptera litura.

This mini fact sheet is a part of the app Pacific Pests, Pathogens & Weeds

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