Fruit Crops

Predators of Tarnished Plant Bug in Apple

Tarnished plant bug (TPB) is a significant pest of apple production in many areas. Overwintered adults feed on foliage and buds in the spring, and feeding on developing fruit can result in fruit drop or distorted fruit at harvest. Researchers in Quebec have studied the potential predators of TPB in an experimental orchard that had not been treated with insecticides for nearly ten years. Orchard habitats monitored included the tree canopy, the ground vegetation, and ground vegetation adjacent to the orchard; sampling was conducted twice weekly, from early May through October, for two years.

The potential predators found included 11 species of spider, 4 types of beetles, and 16 types of true bugs (Hemiptera). There were six species that were relatively abundant and well synchronized with either TPB, or another damaging hemipteran, Lygocoris communis. These consisted of four predatory hemipterans: the spined soldier bug, Podisus maculiventris (Pentatomidae), an assassin bug, Zelus socius (Reduviidae), an ambush bug, Phymata pennsylvanica (Phymatidae), and a damsel bug, Nabicula subcoleoptrata (Nabidae), and two spiders: Philodromus praelustris and Xysticus punctatus.

In laboratory studies, 17 species of the potential predators found in the orchard were provided TPB adults as food; 15 of the species killed and ate at least some TPB. The highest rates of predation were seen with the four hemipteran species listed above. When provided with an abundance of prey, these four species consumed on average 2-3 tarnished plant bugs per day.

The predation found in the orchard was inadequate to keep the numbers of TPB adults below the established economic injury level. The authors suggest that this probably resulted from, the fact that the predators were generalists and therefore not likely to respond to an increasing TPB population, especially in the presence of other abundant prey.

Source: Arinoldi, D., R. K. Stewart, and G. Boivin. 1991. Field survey and laboratory evaluation of the predator complex of Lygus lineolaris and Lygocoris communis (Hemiptera: Miridae) in apple orchards. J. Econ. Entomol. 84:830-836.

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