Oriental Fruit Moth Life Cycles Per Annum Present Climate

The codling moth, Cyclia pomonella is a native of Eurasia. The larva familiarly known as `apple worm` is one of the most serious pests of apples, with injury especially severe in processing orchards (relative to fruit destined for fresh use). The larvae usually tunnels to the core of the apple, pushing out a mass of chewed material called frass, thereby greatly lowering the market value and storage quality of the fruit, as well as making it unfit for people to eat (OSU Factsheet, 2005). The oriental fruit moth infests all stone fruit and is found in various stages of its life cycle during the entire growing season, this Oriental fruit moth (OFM) larvae pupate in late winter to early spring, with up to five or more generations per season. Infested shoots and terminal leaves wilt and bend over, with this injury known as flagging, and leaves eventually dry up. Flagging stimulates lateral growth below the point of injury, providing wound sites for pathogens (Polk et al., undated). More critical even than flagging is fruit injury, occurring either early in the season or later after pit hardening to final swell, with gum and frass often exuding from the wound area. Computation of life cycles per annum of codling moth and oriental fruit moth were determined by computing degree days (base 10 degree Celsius), utilising 50 years of daily values of maximum and minimum temperatures generated by techniques described in Schulze and Maharaj (2004) at each of 430 000 one arc minute (1` x 1` latitude by longitude) grid points covering South Africa. The degree days accumulated over one year were then divided by the days required for one life cycle to be completed by codling moths (603 days) and oriental fruit moths (535 days), respectively.