Soybean leaf folder

Omiodes diemenalis (Guenée)

Lepidoptera: Pyralidae

The soybean leaf folder, Omiodes diemenalis, is commonly found in Africa, Asia, and Australia. This species is known under many synonyms and has been placed by different authors into the genera Nacoleia and Lamprosema. It is possible that O. diemenalis constitutes a complex of several sibling species.

Host plants and damage

The soybean leaf folder is a polyphagous insect on various leguminous plants. Larvae feed on leaves of Glycine max (soybeans), Phaseolus vulgaris (garden beans), Vigna radiata (mung beans), and other important leguminous crops. It is also reported from green-manure plants in Africa.

Early symptoms of infestation are young leaves spun together. Larger larvae roll-up leaves and feed inside. Last instar larvae may reduce the leaves to a skeleton.

Morphology & biology

Final larvae are about 20 mm long and grayish green in color with yellowish heads. They live in a shelter made from a rolled up leaf.

Adults have a wingspan of 20-22 mm. They are brown in color with yellow to light brown patches. The body is brown with white stripes.

Monitoring

Look in the field for defoliation and/or folded or webbed leaves. Larvae are found in those leaves webbed together. Leaf folding was in India the most common symptom on Vigna radiata (green gram) caused by soybean leaf folder larvae.

Pest management

Biological control

There are Trichogramma spp. egg parasitoids and the larval parasitoids Goniozus sp. and Trichomalopsis apanteloctena J.C. Crawford on soybean leaf folder recorded in India. The main pupal parasitoids were Sarcophaga sp., Orgilus sp., and Phanerotoma sp. In Malaysia the larval parasitoids Dolichogenidea inquisitor (Wilkonson) and Elasmus philippinensis Ashmead were recorded.

Cultural control

In India the infestation of soybean leaf folder on different V. radiata gram varieties were studied. There were big differences in their susceptibility to soybean leaf folder larvae. In China eight genotypes of Glycine max (soyabean) were resistant to bean pyralids such as the soybean leaf folder.

Intercropping V. radiate with less related crops such as Zea mays (maize) results in more reduced pest populations.

Chemical Control

Several contact insecticides are recommended against soybean leaf folder. Use sticker to ensure that feeding larvae get in contact with insecticides. In field trials in India several systemic insecticides were effective against soybean leaf folder.