Authors: Buyung Hadi, Robert J. Whitworth, J. P. Michaud and Phillip E. Sloderbeck
Pillbugs are not insects. These creatures are more closely related to shrimp and crayfish. To survive, pillbugs require high humidity and moisture. Normally feeding on decaying organic matter, pillbugs can feed on the tender plant parts of soybean.
Identification
Pillbugs are wingless, with seven pairs of legs. The body is gray to black. Fully grown adult is about 0.75 inch (19 mm) long. When disturbed, pillbugs usually roll into a ball.
Life Cycle and Seasonal History
Pillbugs need high humidity to survive. Pillbugs may thrive in greenhouses due to humid conditions provided by the protected environment. In the field under hot weather they usually remain in dark humid places (e.g. under crop residue) and feed at night. They survive the winter as inactive adults. Mated female pillbugs carry their eggs in a brood pouch on the underside of the body. The pouch can store up to 200 eggs. Eggs hatch in about two months. Upon hatching young pillbugs, similar in appearance to adults but smaller, stay within the brood pouch for six to eight weeks. It takes a year for a young pillbug to develop into a fully reproductive adult. Up to three generations are produced per year. An individual pillbug can live up to three years.
Plant Injury and Damage
Pillbugs feed on tender portions of soybean seedling stem just above the soil line. Pillbugs may also feed on plant roots.
Management Approaches
In Kansas, pillbug is noted to be a perennial early season problem in no-till soybean planting. Reduced or no-till cropping system provides ample crop residues which act as pillbug habitat. Higher survival provided by this habitat translates into higher pillbug field population, to the point where crop-damaging levels may be reached. Pillbug problem is less apparent in conventional soybean as the conventional cropping system provides less moist habitats for pillbugs.
Cultural Methods
Tilling the field every other year may break the population development cycle of pillbugs in a given year, thus maintaining the pillbugs population under the crop damaging level.
Chemical Control
Pillbugs are susceptible to insecticides. Nevertheless some features of pillbug biology may render chemical control ineffective. Some insecticide seed treatment will kill pillbugs, but only after the pillbugs consume enough plant tissues for the toxin to be effective. High pillbug population may still damage soybean seedlings.
Planting time insecticide application may not be effective because pillbugs do not normally eat near the seeds at the time of planting. Only after the seedlings germinate are pillbugs attracted to them.
Foliar insecticide application may not reach pillbugs hiding under crop residues. Nevertheless, pillbugs that are active at night may be exposed to insecticide residue on the soil surface.
Other Online Resources
For information regarding labels of chemical control options, please visit Agrian.com
