Stink Bugs

Classification and Description:  Stink bugs (Hemiptera: Pentatomidae) are true bugs with piercing-sucking mouthparts and incomplete metamorphosis.  The immature stages (nymphs) and adults of several species may damage cotton.  Predatory stink bugs may also be found in cotton. 

The green stink bug (Acrosternum hilare) is the most common species that feeds on cotton in Tennessee.  The brown stink bug (Euschistus servus) is another common component of the stink bug complex.

Hosts, Life History, and Distribution:   Both green and brown stink bugs are found throughout the state.  A third species, the southern green stink bug (Nezara viridula), is less common in Tennessee and often confined to the southernmost counties.  Stink bugs have a wide host range that includes many cultivated crops, including corn and soybean, as well as numerous uncultivated plants.  Overwintering adults become active in the spring.  Stink bug eggs are characteristically laid in a mass of 20-100.  Eggs hatch in 6-7 days during the summer.  Nymphs tend to remain aggregated until the third or fourth instar.  All species pass through five immature (nymphal) life stages,  which requires 23-25 days at optimal temperature, and the adults may live several weeks or months.  Several generations per year occur in Tennessee.

Pest Status and Injury:  Stink bugs have become a common pest problem in cotton.  Bt cotton and boll weevil eradication efforts have reduced the overall number of insecticide applications being made to cotton.  Because stink bugs are generally susceptible to many insecticides, this reduction in insecticide use has provided an opportunity for stink bugs to establish in cotton fields.  Plant-feeding species of stink bugs are typically seed feeders, and thus, injury to cotton bolls is the primary concern.  Economic damage in pre-flowering cotton is very rare.  Stink bugs target the seed inside developing bolls, preferring bolls between 7-21 days in age.  External signs of feeding injury include the appearance of circular black lesions on the surface of bolls (i.e., “catfacing”).  These sunken lesions are typically about 1/16^th of an inch in diameter.  The lint of bolls may be stained, seed may be destroyed, and feeding warts may be observed on the internal surface of boll wall.  Damaged bolls may rot because of secondary infection by plant pathogens, or lint production may be reduced in one or more locks.  Other true bugs, such as clouded plant bug and tarnished plant bug, may cause similar injury.  External feeding signs on bolls are not always associated with internal damage.

Management Considerations and Thresholds:  Adult stink bugs are strong fliers and typically migrate into cotton from alternate hosts outside the field, including adjacent fields of maturing corn and soybean.  Stink bugs are difficult to scout.  Adults tend to aggregate, and the distribution of stink bugs within a field may be highly concentrated, particularly along borders.  Despite being relatively large insects, they can be difficult to see.  Stink bugs can be scouted for visually, but most thresholds are based on drop cloth samples or the occurrence of internal symptoms of feeding damage to bolls.

Current UT thresholds call for a treatment when one or more stink bugs are found per drop cloth sample (6 row feet) or when 20 percent or more of thumb-sized bolls show internal evidence of stink bug feeding, including feeding warts or stained lint.  Insecticide options are listed in the Insect Control Recommendations for Field Crops (PB1768).  Brown stink bugs are relatively tolerant of pyrethroid insecticides.  Thus, organophosphate insecticides such as Bidrin, Orthene, or methyl parathion are typically preferred for stink bug control.  However, pyrethroid insecticides are effective on green stink bugs.

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