Received for publication 3 June 1983. Michigan Agricultural Experiment Station Journal Article No. 10887. We wish to thank Pioneer Hi-Bred International of Tipton, Ind. for providing maize seed. We also thank A.R. Putnam W.F. Meggitt, and M. Barrett for the use of their experimental sprayers. We also appreciate the cooperation of our colleagues in the PRC, particularly Ching Zhong, Shan Kun Chen, Fen-Tin Song, and Yi Dong Wang. We thank Mathew Zabik for assistance in obtaining mass spectral data, which was supported by NIH grant P41 RR00480-15. This research was supported by a grant from the Buckeye Cellulose Corp., Memphis, Tenn. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.