Integrated weed management: effect of herbicide choice and timing of application on the survival of a biological control agent of the tropical wetland weed, Mimosa pigra

Herbivory by Neurostrota gunniella stunts mimosa (Mimosa pigra) plants, which should diminish seedling survival during wet-season floods, reduce competition with regenerating grasses and, therefore, reduce the need for repeated herbicide applications to control mimosa regenerating from the seed bank following clearance of dense stands. Few or no mimosa plants may survive the use of fire to control dense thickets, so N. gunniella populations will be unable to persist. Therefore, for damage to regenerating seedlings to be maintained over subsequent seasons, N. gunniella populations must be rapidly reestablished. Results presented in this manuscript indicate treating regenerating mimosa seedlings with herbicide does not necessarily prevent N. gunniella larvae from completing their development, and optimal timing of herbicide application during ground spraying operations can minimize the negative impact on N. gunniella. Delaying application until approximately 2 weeks from the first appearance of leaf mines should ensure that a high proportion of N. gunniella emerge and can infest any surviving mimosa nearby. The data do not indicate any major differences in the choice of herbicide and N. gunniella survival. However, 33% of seedlings treated with tebuthiuron survived.