Feeding of Lygus Bugs (Hemiptera: Miridae) on Developing Carrot and Bean Seed: Increased Growth and Yields of Plants Grown from That Seed1

Abstract

To determine the effect of lygus bugs, Lygus hesperus Knight and L. elisiis Van Duzee, feeding on developing carrot seed on the plants grown from that seed, adult lygus bugs were caged on carrot umbels. Some of the seed was then germinated and growth of the shoot was measured. Other seed was planted in the field, growth of the plants was measured, and weight of the roots was determined. Bean seed was sorted as to the number of lygus punctures per seed, then weighed and planted. Growth of the plants and seed yields were determined. Shoot growth from carrot seeds exposed to feeding by lygus bugs during development is reduced and varies inversely with the bug population. Plants grown from such seeds later surpass plants from seeds protected from lygus bugs during development and produce heavier roots. Bean plants grown from seeds with lygus bug punctures surpassed plants from seeds not fed on by lygus bugs. Although bean seeds were significantly lighter in weight when fed on by lygus bugs, they produced plants which grew significantly faster and yielded significantly heavier amounts of seed. Three possible explanations are discussed: (1) destruction of an inhibitor (possibly dormin) present in the seed; (2) injection of a plant auxin (possibly beta-indolyl acetic acid) into the developing seed during the feeding process; and (3) change of the protein-carbohydrate ratio in the seed as a result of feeding by lygus bugs.