Number of rice water weevil larvae (Coleoptera: Curculionidae) and rice plant growth in relation to adult infestation levels and broadleaf herbicide applications

摘要

We conducted experiments to determine the numbers of rice water weevil (RWW, Lissorhoptrus oryzophilus Kuschel) larvae and the growth of rice (Oryza sativa L.) plants resulting from combinations of adult-RWW-infestation levels and broadleaf herbicide (bensulfuron or MCPA [2-methyl-4-chlorophenoxyacetic acid]) applications. In the greenhouse, bensulfuron (applied either before or after adult RWW were added to rice plants) did not affect the number of immature RWW or rice plant growth. In field plots, herbicides did not affect the numbers of immature RWW produced from various adult-RWW-infestation levels in either 1989 or 1990, but affected various measures of plant growth. In both 1989 and 1990, adult-RWW-infestation levels afffected the number of immature RWW in plots and affected all (1989) or most (1990) rice growth characteristics. In 1990, rice plant growth measurements and yield generally declined sharply between 0 and 12 adult RWW added, but they declined gradually at higher infestation levels. Interaction between herbicides and adult-RWW-infestation level was not significant in either year, suggesting largely independent action of herbicides and RWW on plant growth and no moderating effect of herbicides on numbers of immature RWW. Our results underscore that RWW and broadleaf weeds are each important pests of rice in California, but the potential interaction from their management on immature RWW and corresponding rice plant growth appears to be of little relevance.