Population dynamics and integrated control of the damson-hop aphid Phorodon humuli (Schrank) on hops in Spain

The hop aphid Phorodon humuli (Schrank) (Hemiptera: Aphididae) is a serious pest in most areas where hops are grown. A field trial was performed on a hop yard throughout 2002, 2003 and 2004 in León (Spain) in order to analyse the population development of Phorodon humuli and its natural enemies, as well as to determine the most effective integrated program of insecticide treatments. The basic population development pattern of P. humuli was similar in the three years: the population peaked between mid to late June, and then decreased in late June/early July, rising again and reaching another peak in mid-July, after which it began to decline, rising once more in late August; this last rise is characteristic of Spain and has not been recorded in the rest of Europe. The hop aphid�s main natural enemy found on the leaves was Coccinella septempunctata (Coleoptera: Coccinellidae). The multiple regression analysis showed that aphids are positively related with the presence of beetle eggs and mean daily temperatures and negatively related with maximum daily temperature integral above 27°C in plots without insecticide treatment. The most effective program of insecticide (imidacloprid) treatments consisted of an initial treatment in June and a second treatment in the second half of July or at the beginning of August. However, a single treatment in June would be sufficient when in this last period the maximum daily temperatures were higher than 27°C for at least 15 days, avoiding in this way the harmful effects of imidacloprid on predators