Beet webworm, Hawaiian beet webworm
Spoladea recurvalis; previously known as Hymenia recurvalis.
Worldwide. Asia, Africa, North, South and Central America, the Caribbean, Europe (restricted), Oceania. It is recorded from Australia, Cook Islands, Fiji1, New Caledonia, New Zealand, Samoa, Solomon Islands, Tonga, Tuvalu, Tonga, Wallis and Futuna.
Mainly plants in the following families: Amaranthaceae (amaranthus), Fabaceae (beans, peanut, mung bean, soybean), Chenopodiaceae (beet, spinach), and Solanaceae (eggplant), and some weeds - amaranthus (pigweed) and chenopodium (lamb's quarters), and ornamentals (e.g., cockscomb).
The larvae do the damage, and when numerous can defoliate crops rapidly. They also attack, flowers and pods. At first, it feeds only on the lower surface, leaving the uppersurface as clear 'windows'; later, it eats inside a tube formed by rolling leaves or drawing adjacent leaves together with the aid of silken threads.
Egg are laid singly or in groups near the midrib on the undersides of leaves, and hatch to produce a creamy-white larva with numerous hairs (Photo 1). Mature larvae are up to 25 mm long, greyish-green, with a dark line down the middle of the back; they become reddish-pink before pupating in the soil inside a cocoon covered with soil particles. The adult is 10 mm long with a wingspan of 22-24 mm and characteristic white bands across the abdomen and wings (Photos 2&3). The life cycle is about 30 days.
Spread is by flight on the wing; the moth is famous for long distance migrations. Spread may also occur associated with the international trade in plants.
The larva is especially important on Indian spinach (amaranthus) in Fiji, and in beet plantations in Australia. The damage can be serious in leguminous crops if it coinsides with the time of pod filling. Economic damage is recorded on the ornamental cockscomb as the flowers can be easily damaged by just a few larvae.
Look for the larvae rolled in silken cocoons in the folds of leaves: they have a distinctive dark line along the back. Look for the adults that shelter beneath leaves and take flight when disturbed; they are brown with white markings. The adults are attracted to light.
There are many larval parasitoids, but there does not appear to have been programs to multiply and release them.
If pesticides are necessary, use botanical (plant-derived pesticides) sprays first, as these may cause less harm to natural enemies, and cost less than synthetic commercial products.
AUTHOR Grahame Jackson
1Information from Swaine G (1971) Agricultural Zoology in Fiji. Her Majesty's Stationery Office. London; and CABI (2017) Spoladea recurvalis (Hawaiian beet webworm) Crop Protection Compendium. (www.cabi.org/cpc); and from Rice weevil. Department of Agriculture and Fisheries, Queensland Government. (https://www.daf.qld.gov.au/plants/field-crops-and-pastures/broadacre-field-crops/integrated-pest-management/a-z-insect-pest-list/stored-grain-insect-pests/rice-weevil). Photo 1 Alton N. Sparks, Jr., University of Georgia, Bugwood.org. Photo 2 Mark Dreiling, Bugwood.org. Photo 3 McCormack, Gerald (2007) Cook Islands Biodiversity Database, Version 2007.2. Cook Islands Natural Heritage Trust, Rarotonga. Online at: (http://cookislands.bishopmuseum.org).
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
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