Long-term study of Bacillus thuringiensis application to control Tirathaba rufivena, along with the impact to Elaeidobius kamerunicus, insect biodiversity and oil palm productivity
2018
Zommick, D. H. | Lopez, J. A. | Susanto, A. | Prasetyo, A. E. | Eldridge, J. R.
A long-term study of commonly used insecticides for Tirathaba rufivena control was conducted in Riau, Indonesia. Treatments included fipronil, Bacillus thuringiensis subsp. kurstaki (Btk), and a rotation of Rynaxypyr and Btk applied every two weeks for a nine-month period. Assessments were monitoring of T. rufivena attack, quantifying the number and activity of E. kamerunicus, insect biodiversity, and analysis of oil palm fruit set and productivity. Despite overlapping pest stages, all insecticides were effective in reducing Tirathaba larvae within four months for Btk-containing treatments and two months for fipronil, while Tirathaba attack in the untreated control initially increased and then remained persistently high. Fipronil reduced the numbers of E. kamerunicus weevils visiting inflorescences one month after application while Btk-containing treatments did not reduce weevil populations resulting in <70% and >75% fruit set, respectively. Average bunch weight in treatments, which included Btk, was 11.7% higher than the fipronil treated blocks and 64.5% higher than the control block resulting in a yield increase of 14.4% and 55.5% over fipronil treatments and controls, respectively. Btk treatments were effective in controlling Tirathaba, did not impact E. kamerunicus or overall insect biodiversity and positively impacted oil palm fruit set, bunch weight and productivity.
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