Heterodera zeae
The Corn Cyst Nematode

  • Damage to Corn. Damage to corn by corn cyst nematodes may be considerable, as small

  •  numbers of the nematode have been found to cause serious damage.  Losses varying
     from 5.5% to 39.2% have been noted, depending on the cultivar. 
  • Biology.    Adult females are pear or lemon-shaped and pearly-white, turning light to dark brown as the cyst matures.  Eggs are generally retained in the cyst until they hatch. Temperature plays an important role in the biology of H. zeae. The life cycle is short, taking only 15-17 days if temperatures are optimally warm (about 27-39 C). It has been speculated that the nematode may complete six to seven generations during one crop season. Under conditions in Maryland, cysts with infective juveniles apparently only persist in fallow soil for about two years. 
  • Ecology.  Heterodera zeae was first described from India where it is widely distributed. It has also been reported from Pakistan, the Nile Valley, Egypt, and Maryland in the USA In Maryland, it is found primarily in heavy silty-clay soils. A cold, wet period in spring facilitates hatching of the nematode, and invasion of the root.
  • Symptoms.   Plants affected by corn cyst nematode are stunted, pale in color, with narrow leaves.  Stunting frequently occurs in irregular patches, and development of tassels may be noticeably delayed.  As with other cyst nematodes, the presence of cysts on the root surface is the most important characteristic used in the identificaion of H. zeae
  • Damage to other crops. Other economic hosts include millet, oat, rice, sorghum, sugar cane, and wheat. Several grass weed hosts have been identified in India and the USA 
  • Control.   After cyst nematodes have infested a field, it is practically impossible to eliminate them.  Crop rotation every 4-5 years with non-hosts helps maintain populations below threshold levels.  Susceptibility to Heterodera zeae  varies widely among corn cultivars,  providing the possibility of some resistance as well.
This nematode currently is or could potentially be an APHIS quarantine pest.