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In the Spotlight ...
In this section of the Vermont Apple Newsletter, a different arthropod or disease will be featured. This information is part of "Key Arthropods, Diseases, and Vertebrates affecting Apples: A Synopsis" by Jessica Reardon and Lorraine Berkett and which appeared in the Back to Basics Resource Notebook, March 22, 2000.
The Tarnished Plant Bug (TPB)
Lygus lineolaris (Palisot de Beauvois)
Description: Adults are approximately 1/4 inch long, oval, and slightly flattened. They are brown in color with a white or yellow Y on the thorax. Nymphs are green in color with black spots.
Life Cycle: Adults overwinter in protected places such as under leaf litter, stones, logs, and in cracks in tree bark. They become active in the spring and move to fruit trees as buds begin to open. They are most abundant and active in the orchard from green tip through petal fall.
Damage: TPB feeds on buds and flower parts in the spring. Buds or flowers which have been injured will abort or fail to develop normally. Early feeding on the fruit occurs later in the season and results in depressions which deepen as the fruit grows. Egg laying punctures are deeper and are most often found on the calyx end. Feeding and ovipostition on the fruit by adults is most noticeable at harvest. Fruit which is attacked when very young may abort.
Monitoring
Key times for monitoring: silver tip-bloom
Monitoring method: Sticky coated 6x8" white rectangle traps should be set out at silver tip at one per 3-5 acres, near the block periphery or two rows in from the outermost row. Place a minimum of 5 traps/block. Traps should be hung vertically from an outer branch at just below knee height. Each week, the number of TPB captures should be recorded, and that week's captures removed from the trap.
Action Threshold: Action threshold during tight cluster for apples that will be sold wholesale is a cumulative average of 3 TPB/trap, while the threshold for retail apples is a cumulative average of 5/trap. Action threshold during late pink for apples that will be sold wholesale is a cumulative average of 5/trap, while the action threshold for apples that will be sold retail is a cumulative average of 8/trap.
Management:
Cultural controls: Reduce or eliminate broadleaf weeds, especially chickweeds, dandelion and clovers, from orchard sod. Do not mow from bloom through petal fall to prevent the flying of adults into trees. Avoid the placement of orchards adjacent to alfalfa hay or strawberry fields (which house alternative hosts).
Biological Control: TPB has many natural enemies, including other true bugs, ladybird beetles, spiders, and parasitic wasps. These biological controls may lower TPB numbers, but are not able to achieve complete control of the insect.
Chemical: See New England Apple Pest Management Guide
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