Photo 2. Larvae of ladybird beetles, possibly, Epilachna signatipennis, stripping the leaf surface of yard long bean.
Photo 3. Grazing and small holes in eggplant leaves caused by the 28-spotted ladybird beetle, Epilachna species.
Photo 4. Holes on leaves of eggplant made by adult eggplant or 28-spotted ladybird beetle, Epilachna species.
Photo 5. Larvae of eggplant or 28-spotted ladybird beetles, Epilachna species, grazing on eggplant, whereas the adults chew through, making large holes.
28-spotted ladybird beetles
Epilachna (Henosepilachna) species. Note, 28-spotted ladybird beetles are a complex of species. Note, too, the number of spots is variable, and cannot be used to identify ladybird beetles. Waterhouse lists five species that are recorded from Oceania: Epilachna vigintioctopunctata pardalis; Epilachna vigintisexpunctata; Epilachna vigintisexpunctata doryca; Epilachna cucurbitae; and Epilachna guttatopustulata.
Widespread. Asia, South America (Brazil), Oceania. The five species of ladybird beetles are recorded as follows:
Epilachna vigintioctopunctata pardalis is recorded from Australia, Fiji, French Polynesia, New Caledonia, Niue, Samoa, Solomon Islands, Tonga, and Vanuatu. Epilachna vigintisexpunctata is recorded from Australia; Epilachna vigintisexpunctata doryca is recorded from Australia, Papua New Guinea, and Solomon Islands; Epilachna cucurbitae is recorded from American Samoa, Australia, Papua New Guinea, New Caledonia, Samoa, Solomon Islands, and Tonga; and Epilachna guttatopustulata Australia, Papua New Guinea, Solomon Islands, and Vanuatu.
Epilachna vigintioctopunctata pardalis feeds on Solonaceae; Epilachna vigintisexpunctata on Solanaceae; Epilachna vigintisexpunctata doryca on Solanaceae; Epilachna cucurbitae on Curcurbitaceae; and Epilachna guttatopustulata is destructive on potato.
Another species, Epilachna signatipennis, has been identified from yard long beans, and most likely can be found on other legumes. All have similar life cycles.
The adults and larvae eat the surface of the leaves (Photo 1); the larvae graze the under surface, leaving the upper surface intact (Photo 2), whereas the adults feed on both sides of the leaf, often making holes as they chew (Photos 3-7). Attacks cause death of seedlings.
The adults are like typical ladybird beetles with wing cases of dull orange and black spots; however, close inspection shows that the upper surface is covered in short downy hairs. This distinguishes plant-feeding ladybird beetles from their beneficial bug-feeding relatives.
The oval yellow eggs (1 mm x 0.4 mm) are laid upright in batches of 10-20 on the underside of a leaf. They hatch in about 4 days. The pale yellow-whitish larvae have long, dark-tipped branched spines on their backs; they grow to 6 mm through three moults in the next 18 days, before attaching themselves to the undersides of the leaves and developing into pupae. This stage lasts another 4 days.
The adults fall to the ground when disturbed, pretending to be dead. They also produce a yellow fluid that wards off predators.
Seedlings may be killed by the attack, and growth and yield of more mature plants reduced. Epilachna species are serious pests of potato in Fiji, and cucurbits are attacked as well. They are major pests in French Polynesia, New Caledonia, and Samoa, too, with Epilachna vigintioctopunctata pardalis and Epilachna cucurbitae the most likely cause.
Many Pacific island countries have rate 28-spotted ladybirds as among their worst pests, of great importance locally.
Look for the distinctive grazing on one side of the leaf, often leaving the surface of the other side intact. Look for the larvae, mostly on the underside, and the adults on the top of leaves, but always check that the beetles are leaf eating, i.e., they are feeding on the leaf, and are not beneficial species feeding, for instance, on aphids (green flies). Look at the upper surface to see the short downy hairs, which distinguishes leaf-eating from beneficial ladybird beetles.
Note, the taxonomy of these beetles has been confused in the past, and specimens should be examined by experts to obtain correct identification. Note, too that Epilachna guttatopustulata on potato has different colours from the others: few spots - orange-red on top, and yellow o the sides - on a dark background. The others have many black spots on a dull yellow background.
The parasitic wasp (Pediobius foceolatus) was introduced into Fiji from India in 1971, but it is not known whether it establsihed. Documented success was achieved with this wasp when introduced into Guam to control Epilachna vigintisexpunctata philippinensis. However, as there are different species of the beetles, identification needs to be done carefully. Also, care should be taken to ensure that any Pediobius introduced are specific to the pest species, and not likely to attack beneficial members of the ladybird beetle family.
None known, although comparative resistance of varieties of eggplant is known in India.
If chemical control is needed, do the following:
AUTHORS Helen Tsatsia & Grahame Jackson
Informatiion from Waterhouse DF, Norris KR (1987) Biological Control Pacific Prospects. Inkata Press. Assistance; and from Wilco Liebregts, Eco-Consult Pacific, Fiji. Photo 1 Gerald McCormack, Cook Islands Biodiversity & Natural Heritage. (http://cookislands.bishopmuseum.org/). Photos 2&4 Graham Teakle, Canberra.
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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