Predictive Year-end California Red Scale (Homoptera: Diaspididae) Orange Fruit Infestations Based on Catches of Males in the San Joaquin Valley

Abstract

Aonidiella aurantii (Maskell) infestations on ‘Navel’ and ‘Valencia’ orange fruit at the end of the calendar year were successfully predicted in the San Joaquin Valley based on data developed from catches of male scales in traps, female scales on twigs, and fruit infestations. Fruit infestations at harvest were regressed on the number of males trapped in the first, second, or fourth male scale flights or on the number of adult females on twigs. The equation that best explained the percentage of infested fruit as a function of male catches was a polynomial of the second degree. If the number of trapped males is known for the first, second, or fourth flights, the percentage of fruit infestation (≥1 scale per fruit) at the end of the season can be predicted. By regressing the percentage of fruit with ≥1 scale on that with ≥11 scales per fruit, a direct relationship to the flights was established. The citriculturist can select an acceptable action threshold by either recording total fruits with ≥:1 scale or patchy fruits with ≥:11 scales. Thus, the red scale pheromone trap can be incorporated as a valuable tool in the management of red scale populations.