Banana weevil borer

Banana weevil borer (Cosmopolites sordidus)

Credit: Biovision-Infonet

The banana weevil is the most important insect pest of banana. It is about 1-1.5 cm long. The larva (grub) is most destructive: It bores irregular tunnels in the rhizome/corm and pseudostems at ground level. A large proportion of the tissue is destroyed, this reduces the amount of water and nutrients the plants can take up as well as lessening their anchorage. Heavy infestation may kill young plants. Older plants are easily blown over by the wind.What to do:

• Chop up the rhizome/corm and pseudo-stem to hasten decomposition, trapping and collection of the adults.
• To prevent an infestation, use non-infested planting material, destroy the shelter and feeding places of the adult weevil and maintain a clean area around the plant mat.
• Some ants are important natural enemies of the banana weevil and are being used for its control.
• Applications of neem powder effectively controlled weevils and nematodes in on-farm trials and in farmers’ fields in Kenya. Application of 60 to 100 g of neem seed powder or neem cake at planting and then at 4 months intervals significantly diminished pest damage and increased yields. Application of over 100 g or neem oil was phytotoxic and uneconomical. Neem applications were economical in fertile soils with moderate pest infestation. Neem applications to banana plants grown in poor soil and under very high pest attack were uneconomical.A combination of good crop management such as application of cow dung and neem treatments resulted in yield increases of 50 to 75% (Musabyimana, 1999).Dipping suckers in a 20% neem seed solution at planting protects the young suckers from weevil attack by reducing egg laying through its repellent effect on adult weevils. Egg hatching rates may also be lowered in neem-treated plants (Gold and Messiaen, 2000). For more information on Neem click here
• Hot-water treatment of banana suckers helps against banana weevils.