REPRODUCTION OF HETERODERA-ZEAE AND ITS SUPPRESSION OF CORN PLANT-GROWTH AS AFFECTED BY TEMPERATURE

Reproduction of the corn cyst nematode (Heterodera zeae) and its effect on growth of corn (Zea mays) was studied in plant growth chambers at 24, 27, 30, 33, and 36 C. Reproduction of H. zeae increased directly with increase in temperature from 24 to 36 C. Fifteen-cm-d pots of corn seedlings inoculated with a mixture of 5,000 eggs + J2 and maintained for 8 weeks in growth chambers contained an average of 7,042 cysts + females at 36 C, but only 350 cysts + females at 24 C. Fresh weights of plants without nematodes were highest at 27 C and lowest at 36 C. Nematodes suppressed plant fresh weight by an average of 30% at 27 C and by 27% at 33 C but did not suppress plant weight at 36 C. Heterodera zeae has the highest reported temperature optimum for reproduction of any cyst nematode.