Behavior and effectiveness of adult Hippodamia convergens (Coleoptera: Coccinellidae) as a predator of Acyrthosiphon pisum (Homoptera: Aphididae) on a wax mutant of Pisum sativum

Adult females of the coccinellid predator Hippodamia convergens (Say) spent more time walking and less time grooming on a line of peas, Pisum sativum L., that has reduced waxbloom on all parts of the plant (due to the mutation wel) compared with a near-isogenic sister line with normal waxbloom. H. convergens walking was distributed over all parts of the low-wax plants, whereas on normal-wax plants walking occurred mostly on stems and the edges of leaves and stipules. The beetles were able to generate 30 times the adhesive traction force on leaf surfaces of low-wax plants compared with normal-wax plants. In cage studies, H. convergens (4 adults per plant) were more effective at reducing population growth of pea aphid, Acyrthosiphon pisum (Harris), on low-wax plants than on normal-wax plants, but only at initial aphid densities of 10 aphids per plant. At higher initial densities (20 and 40 aphids per plant), differential impact of H. convergens was not observed or disappeared after 4-5 d. The results indicate that reduced waxbloom in peas could improve the effectiveness of H convergens on peas at low prey densities.