Effects of insect tripping on seed yield of common bean

insect tripping might enhance seed production in common bean (Phaseolus vul garis L.). The effect of flower visits by insects on seed production was st udied during 3 yr, 1992 to 1994, in Riverside, CA, using four cultivars wit h different growth habits: Linden, Pindak, PI 164778, and Ferry Morse 53 (F M 53). Each year, a factorial experiment in a randomized complete block des ign with four replicates was used. Each cultivar was grown under three trea tments: (i) exposed to open visitation by all insects, (ii) in insect-proof cages, and (iii) in cages with bumblebees. All pods produced by bean plant s were collected and counted, and seed yield was determined. Year-to-gear v ariation had significant impact on cultivar performance and treatment effec ts. The bean Lines were significantly different for seed yield. The treatme nt effects were not consistent across years. The old cultivar FM 53 and Lin e PI 164778 had no clear trend for seed yield response to insect visits acr oss years, whereas Linden and Pindak showed a more defined and positive res ponse to visits. Seed yield of Linden was similar in the open visitation an d caged-with-bumblebees treatments but was significantly higher than that o f caged plants, by 13% in 1992 and by 35% in 1994. Pindak show ed a 9% incr ease in seed yield when plants were visited by insects in the open or in ca ged treatments compared with caged plants in 1992. The results indicate tha t cultivars such as Linden and Pindak, which behave as determinate plants, may respond to bumblebee tripping by increasing seed yield.