Cut Worm on Banana
The infestation occurs mainly during early growth stages of the trees. White patches, consisting of eggs clusters covered by hairs, are visible on the leaves. Larvae feeding on the leaves can be found in high amounts. Initial symptoms appear as scrapping damage on the underside of leaves done by young larvae. Over time, the older larvae start to bore holes starting from the axils through the young leaves. This way of feeding results in the formation of a pattern of irregular holes parallel to the veins that become visible when leaves have unfolded. The voracious feeding leads to the drying of large patches on the leaves, which is followed by defoliation.
Moths are nocturnal, and have a 15 mm long body with a wing span of about 30 mm. They have a gray-brown, stout body with long distorted antennae. The forewings are variegated reddish-brown with fine white oblique lines. The hindwings are translucent white with brown edges. The female moth lays up to 2000 eggs in groups on the leaves and covers them with hairs and scales. Larvae are pale greenish or brown, with dark markings and a black ring around both ends of the body hatch. The larvae can grow to up to 45 mm within about 2-3 weeks. The nocturnal larvae hide in the leaf axis during day time and feed at night. Once they have reached maturity, they move into the spoil and pupate in a nest there. After an additional 7 days, the new generation of adult moths hatch.
A variety of predatory spiders feed on S. litura eggs, larvae and pupae. Parasitic insect species such as the paasitoid wasps Telenomus spodopterae and Telenomus remus can be used to control the pest. Bioinsecticides based on pathogenic microorganisms such as Aspergillus flavus, Beauveria bassiana, Bacillus thurengiensis and Nomuraea rileyi can be applied as soil and foliar sprays. Some viruses and some nematode species have also been studied for the reduction of populations of Spodoptera litura but so far field experiments are scarce.
Always consider an integrated approach with preventive measures together with biological treatments. If insecticides are needed, products containing carbaryl, quinalphos, azinphos-ethyl or chlorpyrifos can be used as foliar spray applications, in particular on the leaf axis. The listed chemicals are toxic or very toxic to human health as well as to animals such as mammals, bees, fish and birds.