Pontential of bipolaris bicolor in combination with ametryn for inhibition of glyphosate-resistant goosegrass [Eleusine indica] biotypes / Nur Faqihah Ghazali

There are several studies on potential use of fungal pathogen, Bipolaris bicolor for biological control of goosegrass but there is still a limited study on compatibility of synthetic herbicide with B. bicolor for glyphosate-resistant goosegrass control. Thus, this study aimed to examine in vitro compatibility between B. bicolor and three herbicides under laboratory conditions and to determine the efficacy of a combination of B. bicolor and ametryn for inhibition of glyphosate-resistant biotype of goosegrass under greenhouse conditions. Spores of B. bicolor was treated with ametryn, flumiozaxin and sodium chlorate at one fifteen their respective recommended rates to determine the most compatible herbicide based on mycelial growth inhibition area in the petri dish. Then, a total four treatments including control plants (non-treated/sprayed) were subjected to goosegrass seedlings at the 3 to 4-leaf stage as follows: T1: Negative control plant, T2: ametryn at one fifteen recommended rate, T3: spore suspension of B. bicolor and T4: ametryn plus spore suspension of B. bicolor. The assessments was carried out based on plant height, leaf greenness, phytoxicity of ametryn, disease severity of B. bicolor and shoot dry weight reduction daily for one week. The results showed that the lowest inhibitory effect was exhibited by ametryn with 10% of inhibition, whereas flumioxazin and sodium chlorate showed 80 and 30% of inhibition, respectively, implying ametryn is the most compatible herbicide with B. bicolor. The most effective treatment for inhibition of goosegrass was B. bicolor in combination with ametryn where the height, leaf greenness and shoot dry weight of seedlings were reduced by 50 to 94%, thus leading to plant death at 7 days after treatment. These findings suggest that B. bicolor combined with ametryn could be a potential integrated strategy for controlling the glyphosate-resistant biotype of goosegrass.