Weeds as alternate hosts of plant pathogens and their chemical management

Abstract

Weeds in non-crop areas cause as much of a menace as in crop fields. They are known to provide food, shelter and reproductive sites for various pest organisms (plant pathogens, insects, mites, nematodes etc.) and serve as alternate hosts. Many plant pathogens (fungi, bacteria and viruses) have several alternate hosts on which they pass at least a part of their life cycle. Eliminating them from the margins of crop fields as well as non-crop areas is an important aspect for achieving higher crop productivity as well as better crop quality. These non-crop weed hosts can effectively be managed with the post-emergence application of total killer herbicide, glyphosate 41 SL at 1.5 kg a.i. ha-1, in combination with 2,4-D sodium salt 80 WP at 1.5 kg a.i. ha-1. As of current recommendation, the herbicides viz. 2,4-D dimethyl amine salt (58 SL), glyphosate IPA salt (20.2 SL, 41 SL or 54 SL), glyphosate ammonium salt (5 SL or 71 SG) or carfentrazone-ethyl+glyphosate (0.43+30.82 EW) should be used, depending on floristic composition of weeds, type of herbicide availability etc. Herbicide rotation is also to be in practice to prevent evolvement of super weeds. Furthermore, an integrated approach can be considered appropriate for the management of diverse weed flora in non-crop areas