Economic thresholds for Aphis gossypii (Hemiptera : Aphididae) on Citrus clementina

Different levels of Aphis gossypii Clover were maintained on clementine tre es by means of isolation inside mesh cages. Clementine yield loss was corre lated with the number of aphids per square meter of canopy, obtaining the c orresponding formula. Starting from this formula, the economic injury level (ELL) was calculated as follows: [218,333C + 11,130.6 . VP0K]/[57.08 . VP0 K - 100C] = EIL (aphids/m(2)), where C = total insecticide cost per hectare , V = fruit price per kilogram, P-0 = yield per hectare of a minimum pest l evel orchard, and K = reduction of injury due to treatment. Starting from t he EIL, the economic threshold, the environmental EIL, and the environmenta l economic threshold were obtained. Formulae relating the number of aphids per square meter with other simpler indices er;pressing these thresholds (p ercentage of infested shoots, infested shoots per 0.25 m(2) ring, index of infestation, percentage of occupied rings, and number of weekly captured ap hids in a yellow trap) also were calculated.