Bionomics, behaviour and control of the codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in pome fruit orchards in South Africa

[摘要] ENGLISH ABSTRACT:The codling moth, Cydia pomonella (L.) has been a major pest of pome fruits since before the turnof the last century. However, despite its high economic profile little is known about the bionomics and .behaviour of this pest in apple orchards in South Africa, information required for the development ofa sustainable integrated management programme.In field trials there was contingency between the time of year and the upper and lower half of the tree.First generation moths laid significantly more eggs in the bottom half of the tree while second and thirdgeneration moths laid significantly more eggs in the top half of the tree. The preferred oviposition siteson Granny Smith (GS) and Golden Delicious (GD) cultivars, in order of preference, were leaves, fruitand wood. More eggs were laid on the fruit ofGS spurs (35.6 %) than on those ofGD spurs (10.7%). On fruit spurs there was a significant increase in the number of eggs on GD leaves and GS fruitover the season, whereas the number of eggs on GS leaves and GD fruit remained constant. Onbranches there was an increase in the number of eggs on GD and GS leaves, but not on the fruit orwood. The preferred oviposition site on the fruit was the fovea of the stalk insertion and the roundedcheek area surrounding the fovea. The distribution within different fruit bearing classes (1 - 4 fruit perspur) was random only for one fruit per spur, while on the other spur classes clustering occurred.In laboratory studies of the embryonic and immature stages there was a linear relationship between rateof development and constant temperatures of 15, 17,20,25 and 30·C ± l·C. The lower thresholdtemperatures for embryonic, larval and pupal development were 11.1, 7.9, 9.9°C respectively. Thedegree-days required to complete embryonic, larval and pupal development were 80.5, 345, and 279respectively. The response of the different stages to constant temperatures was similar to that underfluctuating temperatures.At temperatures below 16°C or abouve 27°C moths did not mate and few eggs were laid. Mothlongevity decreased with increasing temperature. There was seasonal variation in longevity andoviposition at constant and fluctuating temperatures. Summer adults produced significantly more eggsthan spring adults at constant temperatures.At a constant temperature of2S·C and fluctuating temperatures there were five distinct larval instars.The similarity between the mean head capsule width and ranges for each instar reared on fruit of different stages of development at fluctuating temperatures indicates that fruit development andtemperature have little influence on mean head capsule width.From sleeve-cage studies in the orchard there was no significant difference in the fecundity of springand summer moths. In the beginning of October spring moths produced significantly fewer eggs thanin November. Egg mortality increased from 8.2 %in spring to 21.2 %in summer. Failure of 1st instarlarvae to penetrate the fruit ranged from 4.9 % to 19.5 %, while mortality oflarvae from egg hatchto emergence from the fruit ranged from 29.7 % to 42.9 %. Mortality of 5th instar larvae afteremerging from the apples ranged from 0 % to 8.7 % and pupal mortality from 0 % to 3.5 %.On large 27-year old trees more overwintering larvaewere found on Golden Delicious (13.9) than onGranny Smith trees (5.7), with over 70 % oflarvae being found in pruning wounds on both cultivars.On small 7-year old Golden Delicious and Granny Smith trees the mean number oflarvae was 0.5 and2.0 per tree.A combined mating disruption and insecticide control programme reduced codling moth resistantpopulations to levels requiring a minimum to no insecticide intervention for several seasons. Theefficacy of a pheromone based strategy, number of pheromone treatments, number of dispenserslhaand level of insecticide intervention required are strongly influenced by prevailing weather conditions.Fruit infestation in orchards under a mating disruption programme and under an insecticide programmewere greater along the borders compared to the interior.The presence of horticultural mineral oil on the leaves and branches did not have a detrimental effecton oviposition nor was there any significant ovicidal effect. A significant ovicidal effect was obtainedwhen applied after oviposition. In field trials, insecticides with lower levels of efficacy than the primaryinsecticide, azinphos-methyl, provided acceptable control when successfully incorporated into a sprayprogramme which followed a policy of alternation of insecticides across generations.The least variation in the number of degree-days between biofix and first egg hatch of the spring flightwas when the second trap catch (Biofix 2) was used as the biofix. A biofix based on the first eveningwhen the temperature reached or exceeded 1TC at 18:00 after first trap catch also showed lessvariation than when the biofix was based on first trap catch. The mean number of degree-daysaccumulated between Biofix 2 and first egg hatch was found to be 139.1 ° D. The number of degreedaysbetween the first and second flight biofixes varied between 531.2 and 488.87°D with a mean of508.1°D.

[发布机构] Stellenbosch University