Temperature and plant nutrient effects on the development, survival and reproduction of Cinara sp. nov., an invasive pest of cypress trees in Africa

Abstract

Abstract Cinara sp. nov., previously identified as Cinara cupressi (Buckton) (Homoptera: Aphididae), is an important alien aphid pest of cypresses and junipers, and invaded Africa in the late 1980s. The work reported here was carried out as part of a larger programme aimed at the classical biological control of the aphid in Africa. Basic life history attributes including life table statistics of the aphid were quantified in order to facilitate the development of efficient aphid culturing methods and essential baseline information necessary for the culturing of potential parasitoid biological agents prior to selection for introduction to Africa. Developmental rates and fecundity were studied under four constant temperatures (10 °C, 15 °C, 20 °C, and 25 °C). The effects of several plant nutrients (nitrogen, potassium and phosphorus) supplied at different dose levels on life history attributes of Cinara sp. nov. were also studied.Unlike most other aphids, the apterous morph of Cinara sp. nov. developed through only three instars, and the alate four instars. The aphid is highly aggregative and exploits a wide range of feeding sites from young green branches to woody stems. The developmental period of Cinara sp. nov. ranged from 9.3 days at 25 °C to 22.3 days at 10 °C and the developmental threshold was 0.61 °C. Reproduction was delayed, because of the longer duration of development, and nymph production decreased with decreasing temperature. The intrinsic rate of increase ranged between 0.117 at 25 °C and 0.060 at 10 °C. Aphid size increased significantly as temperature was lowered. Wing formation was not induced when apterae were reared for up to three generations at each constant temperature but continuous crowding in the supply cultures held at 21 °C resulted in a high number of alates being formed. No appreciable effects of the different plant nutrients, supplied either singly or in combination, on the duration of instars or overall survival could be detected.