Effects of ph aNd Inorganic Ions On Emergence of Heterodera Glycines 1)

Abstract

Experiments were conducted to determine effects of pH and inorganic ions on emergence of the soybean cyst nematode, Heterodera glycines. Emergence from cysts without egg masses was greatest at pH 3.5 but was depressed at pH 5.5. Hatching from egg masses was insensitive to pH. The influence of inorganic ions on emergence was determined in a factorial experiment in which the cations NH4+, Ca++, and Mg++ were used in combination with each of the anions NO3-, SO4=, and Cl-. Compounds containing NH4+ or NO3- inhibited emergence as compared to phthalate buffer control, whereas CaSO4 was stimulatory. Experimental results demonstrated the necessity of controlling pH in emergence experiments and suggested that inorganic ions applied as fertilizers may influence the inoculum potential of the soybean cyst nematode.