Banana rust thrips Chaetanaphothrips signipennis (Bagnall) (Thysanoptera: Thripidae) is a key pest of bananas in Australia. Larvae and adults feed on the pseudostem under leaf sheaths and on fruit between the fingers. Damage first appears as water-soaked markings then later develops into reddish-brown ‘rust’ areas, making fruit unmarketable. Control relies upon chemical applications targeting the bunch. The chemical products available for use against thrips in bananas are being limited by registration withdrawals and anecdotal reports of resistance. Identifying alternative cultural or biological control strategies could reduce reliance on chemicals.
Conventionally grown bananas have limited ground covers protecting the soil beneath plants. Ground covers could be used to increase mortality of the soil-dwelling pupal stages of C. signipennis. Ground covers may provide refugia for predators and change the soil conditions that favour other natural enemies. A field trial comparing ground cover and bare soil banana plots assessed C. signipennis populations and identified several possible predators. Emergence traps were used to assess C. signipennis survival at the soil surface, while thrips populations and damage assessments were also measured on the pseudostem and in bunches. Additionally, a study of soil invertebrates of the groundcover and bare soil plots identified naturally occurring thrips predators. While this research showed no significant difference in mortality of C. signipennis between the ground cover and bare soil plots, ground cover features such as density and establishment time may have resulted in lowered abundance and diversity of the natural enemies. The absence of a deep litter layer may also account for the lack of natural enemies exerting control over thrips pupae. The soil study identified seven species of predatory soil mites that may impact C. signipennis populations. Three species were near Gaeolaelaps aculeifer (Canestrini) (Mesostigmata: Laelapidae) known predator of soil-dwelling thrips pupae, used commercially in vegetable and flower crops.