Influência de temperaturas flutuantes sobre Aphis gossypii Glover, 1877 (Hemiptera: Aphididae) e seus predadores Ceraeochrysa cubana (Hagen, 1861) e Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae)

Abstract

The fluctuations of daytime and night-time temperatures affect biological aspects of insect pests and their natural enemies thus it is necessary to investigate these effects to design strategies of biological control. The aim of this study was to evaluate the influence of different thermoperiods on the aphid Aphis gossypii Glover 1877 and the predators Ceraeochrysa cubana (Hagen, 1861) and Chrysoperla externa (Hagen, 1861). The insects of each species were kept in climatic chambers at four different combinations of day and night temperatures simulating the averages in the four seasons of the year: 11/21, 18/24, 21/27 and 26/30±1°C, characterizing winter, autumn, spring and summer, respectively, and photoperiod of 12 hours. The four treatments were evaluated in 60 replicates using a randomized design. The durations of instars, the nymphal stage, longevity and life cycle of A. gossypii on Caipira cultivar of cucumber, decreased with increasing temperatures. Increased temperatures reduced the reproductive and post-reproductive periods of A. gossypii. The temperatures did kept in climatic chambers at four different combinations of day and night temperatures simulating the averages in the four seasons of the year: 11/21, 18/24, 21/27 and 26/30±1°C, characterizing winter, autumn, spring and summer, respectively, and photoperiod of 12 hours. The four treatments were evaluated in 60 replicates using a randomized design. The durations of instars, the nymphal stage, longevity and life cycle of A. gossypii on Caipira cultivar of cucumber, decreased with increasing temperatures. Increased temperatures reduced the reproductive and post-reproductive periods of A. gossypii. The temperatures didnot affect the viability of instars and the nymphal stage of this aphid. The fluctuating temperatures significantly affected the development of C. cubana and C. externa observing reductions in the duration of the instars, the larval pre-pupal and pupal stages and the periods of prepupae to pupae and from larvae to adult emergence with increasing temperature combinations. The 11/21°C mortality was 67% of specimens from larvae to adult emergence of C. cubana, being the higher mortality observed in the prepupal stage. For C. externa the temperatures of 26/30°C caused 35% mortality in the period from larvae to adult emergence, and the largest percentage of deaths occurred in the first instar.