Department of Entomology

Title: Integrated Pest Management of Aphis spiraecola (Hemiptera: Aphididae) in clementines: enhancing its biological control

Abstract: Aphis spiraecola Patch. (Hemiptera: Aphididae) is a key pest of clementines in the Mediterranean basin. This aphid colonizes tender clementine shoots in spring and causes important economic losses. Integrated management of this aphid in clementines is currently based in chemical control because its Biological control is still poorly known and previous unsuccessfully efforts were based on the use and conservation of parasitoids. On the other hand, the predator complex of A. spiraecola is well known but its impact on populations of this aphid has not been documented. The three main objectives of this dissertation were : i) to disentangle the reasons behind the low parasitism of A. spiraecola; ii) to determine when and how predators can control A. spiraecola populations; and, finally, iii) to evaluate whether a ground cover of Poaceae plants can enhance the biological control of this aphid in clementines. In the first objective we determine the parasitoid complex and parasitism (and hyper-) rates. In addition, we developed a DNA-based approach to untangle the structure of the aphid-parasitoid food web in citrus. For the second objective we determine the effect of aphid predators on A. spiraecola colonies and damage over a three-year period. To promote the early presence of predators in clementine orchards, in the third objective, we evaluated ground cover management, as strategy of conservation biological control. This ground cover management may provide alternative preys to natural enemies. The sown cover was effective in terms of biological control of A. spiraecola in the citrus canopy. It promoted the early presence of predators in citrus which attacked aphid colonies in the canopies before their exponential increase. These attacks resulted in satisfactory aphid control since citrus orchards with ground cover never exceeded the aphid economic threshold.