Tarnished plant bug: Lygus lineolaris (Palisot de Beauvois) Pale legume bug: Lygus elisus Van Duzee Mullein bug: Campylomma verbasci (Meyer) Hemiptera: Miridae
Lygus sp. plant bugs have a very wide range of hosts, particularly legumes. Economic damage in Colorado is most common to tree fruits.
Damage and Diagnosis:
Plant bugs feed on developing leaves, fruits and flowers, killing the areas around the feeding site. This can cause abortion of young flowers, seeds, or buds. Older tissues may continue to grow but be deformed. Leaf curling and corky 'catface' injuries to fruit are common distortions due to lygus bug feeding injury. Peach, apricot, strawberry, and beans are among the garden plants most commonly damaged.
Some flower abortion of most plants is normal and plant bug feeding injuries have little effect on plant yields unless the insects are abundant.
Adults plant bugs are generally oval in shape, being about twice as long as wide, and 1/4 inch in length. Most common species of Lygus in Colorado are pale green, but brownish and mottled forms occur. The nymphs are more rounded in general form and usually dark green, often with dark spotting.
Life History and Habits:
Lygus bugs spend the winter in the adult stage, under the cover of piled leaves, bark cracks or other sheltered sites. They emerge in early in spring and feed on emerging buds of trees and shrubs. Most then move to various weeds and other plants, and females insert eggs into the stems, leaves, and buds of these plants. The young hatch, feed and develop on these plants becoming full-grown in about a month. There are several generations produced during the year.
Lygus bugs also occasionally feed on insects, and can contribute to the biological control of aphids and other small, soft-bodied species. This habit is particularly well documented with the mullein (campylomma) bug, which can damage fruit during spring, but later is an important predator of orchard insects. Furthermore, there is one group of plant bugs (Deraeocorus spp.) that are strictly predators of insects and mites.
Legumes, particularly alfalfa, are important host plants for lygus bugs. If these plants occur around a garden, they should not be cut during times when fruits and vegetables are in susceptible stages, such as fruit set. Cutting can force migrations of lygus bugs.
Lygus bugs, and most other 'true bugs' are fairly difficult to control with insecticides. Since most injury occurs during early fruit development, insecticide sprays are best timed either immediately before flowering and/or immediately after petal fall. Insecticides should never be sprayed during flowering to avoid killing beneficial pollinating insects.
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.