Ground Moving with Tiny Migrating Insects

Whenever I give my ‘General Insect Pest’ presentations I include a couple of photos of chinch bugs and their nymphs.  Usually I say something like “These are not pests every year in Indiana but can become troublesome in years when we have a drought.”

Guess what?  That is now! The dry conditions we are experiencing in much of the state are perfect for chinch bugs and false chinch bugs to thrive and we are beginning to receive reports of chinch bugs by the gazillions.  Some reports are that the ground appears to be moving due to the migration of these insects.

These bugs belong to a family of true bugs known as the seed bugs (Lygaeidae).  Adults chinch bugs are small (about 1/8 inch in length), narrow, and are gray-brown (if they are false chinch bugs), or black and silver (if they are true chinch bugs). They deposit eggs in cracks in the soil or on various plants in late winter or early spring. Small reddish-brown nymphs (immatures) feed, go through a series of molts, and reach the adult stage in approximately three weeks. Several generations may be produced per year, especially when dry conditions abound.  

False chinch bug nymphs with gray brown mottling and dark developing wing pads. Adult (bottom right) with silvery grey wings (Photo credit Surendra Dara)

True chinch bug nymphs in thatch with reddish body separated by distinct white band (Photo credit John Obermeyer)

Chinch bugs have piercing-sucking mouthparts and feed by removing fluids from their host plants. Some sources report the possibility of the injection of a toxin during the feeding process. Damage symptoms are usually restricted to a general wilting of the plant and heavy feeding may cause leaves to turn brown and die.

During droughty years large populations develop primarily on weeds especially in the mustard family and on clump grasses in rangelands, waste areas, and other uncultivated land. As the vegetation in these areas begins to dry up, the bugs migrate in large numbers to other more succulent food sources.

Agronomic crops, such as corn, soybeans and alfalfa, may be damaged by the feeding of chinch bugs.  Ornamental plants, including turfgrass can also become damaged. Damage is most likely to occur in fields, lawns or golf courses that are adjacent to the uncultivated areas the bugs are migrating from. Populations are extremely high along the migration "front" and damage may occur until the bugs disperse over a wider area.

Sometimes chinch bugs get into homes that are in their path of migration. Rest assured that they are a nuisance only and that they will not damage the structure of the building and are harmless to people and pets.  Excluding them by sealing up cracks, broken windows etc. will be helpful.

Chinch bugs should only be controlled if they are causing damage.  Effective chemical control generally requires that the bugs be contacted with the insecticide. Residual control is not likely during migration periods as bugs may not stay in treated areas for a sufficient period of time to accumulate lethal doses of the pesticide and any insects that are killed are merely replaced by other migrants.

Timothy J.  Gibb

Purdue University Insect Diagnostician