Phytotoxic effect of GF-120 NF fruit fly bait on fruit of mandarin (Citrus reticulata Blanco cv. Nadorcott): Influence of bait characteristics and fruit maturity stage

Abstract

The phytotoxicity of the fruit fly bait GF-120 NF (containing 0.24 g/L spinosad and fruit fly attractants including a protein hydrolysate, ammonium acetate and a number of additives including sugar, polyethylene glycol, polysorbate and soybean oil) on fruit of mandarin (Citrus reticulata Blanco cv. Nadorcott) was investigated in an orchard in Mpumalanga, South Africa. Trials were conducted on ‘Nadorcott’ mandarin fruit at different stages of maturity. Droplets of GF-120 were applied on marked areas at the stylar ends of fruit in the orchard. The effects of GF-120 concentration, droplet size, droplet coverage and bait wetness on incidence of phytotoxicity were determined.Phytotoxicity of GF-120 was recorded on ‘Nadorcott’ mandarin fruit which were at the green and colour-break stages. Incidence of burn increased with increasing concentration of GF-120. Phytotoxicity of GF-120 was accentuated with increasing droplet size, droplet coverage and prolonged wetness of bait droplets. No phytotoxicity was observed when GF-120 was applied on Nadorcott mandarin at full rind colour development.Alternative methods of GF-120 application other than ground-based canopy sprays would therefore have to be sought for ‘Nadorcott’ mandarin orchards, especially if baiting is to start early before full colour development. Use of other fruit fly management techniques such as bait stations would also help avoid the risk of phytotoxicity on fruit of ‘Nadorcott’ mandarin at the green and colour break stages.