Codling 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). Codling moth larvae also attack pears, walnuts, quince and other fruit (OSU Factsheet, 2005). 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).

Life cycles per annum 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.