Effect of continuous light on the biology of the greenhouse whitefly, Trialeurodes vaporariorum, on roses

Continuous light is a promising method to reduce the problems with rose powdery mildew in greenhouse rose production. The effects of such a light regime on the performance of insect pests on roses have so far not been investigated. In the present study, survival, developmental time, and reproduction during one generation of the greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), were characterized on roses, Rosaxhybrida cv. Passion, grown in climate chambers with long-day conditions (L20:D4) or continuous light (L24:D0) at 21 degrees C and fluctuating relative humidity (mean 74%, range 47-96%). Whiteflies reared under continuous light had lower immature survival and fecundity and shorter female longevity than whiteflies reared under long-day conditions, but immature developmental time was only slightly affected. Life-table analysis showed that the net reproductive rate (R-o) and intrinsic rate of natural increase (r(m)) were reduced by 85 and 76%, respectively, and the time for the population to double its size (D) was 4.2 times longer under continuous light. This mean that the whitefly population growth under continuous light was strongly reduced compared with the traditional light regime used in rose production.