Termite biocontrol on cacao seedling: Vetiver grass application
Just in the last decade, cacao (Theobroma cacao) has been introduced to the agroforestry systems in some upland provinces of southern Vietnam, especially in cashew plantation for improving the income of local farmers. However termite attack on cacao seedlings is the main constraint to the development of this crop in these systems. Chemical application is the only method available for farmers to protect their cacao crop. So far there is no study on non-chemical termite control method. An experiment on natural termite control using vetiver grass was established by Nong Lam University (NLU) team from August to December, 2007 in Nghia Trung (site 1) and Nghia Binh (site 2) communes of Bu Dang district, Binh Phuoc province. The experiment aims to test the hypothesis that the natural oil compounds and some of its constituents in composted vetiver grass biomass can repel termite and its organic matter can enhance the growth of cacao seedlings. In each site, the trial was carried out with 6 month-old cacao seedling in a randomized complete block (RCB) design with 4 treatments and 3 replications. The 4 treatments were T1 (control treatment with manure only, no chemical, and no vetiver compost), T2 (farmer's practice with chemical termite control), T3(mixture of manure and lime), and T4 (mixture of manure and vetiver grass compost, and planting 6 vetiver clumps surrounding each cacao seedling). Manure, lime and vetiver compost were spread in the holes one week before planting. A total of 72 cacao seedlings were used in each site. Two months after planting, the rate of seedlings damage in site 1 were recorded to be 66%, 22%, 39%, and 17% but rate of seedling death due to termite were only 44%, 11%, 23%, and 0% for the treatments T1, T2, T3, and T4 respectively. The result shows that, no cacao seedling was damaged by termite in T4 (vetiver compost). The height of cacao seedlings after 4 months planting were recorded to be 61, 51, 58 and 80cm; the trunk diameter by 12, 10,14, 17mm per plant; and the number of primary branch were 3, 3, 3, and 4 per plant in the treatments T1, T2, T3 and T4 respectively. In site 2, the rate of seedling death by termite in the treatment T1, T2, and T3 were 72%, 61% and 61% respectively, while only 27% were recorded for the treatment T4 indicating that damage due to termite attack was lowest when applying vetiver compost. A large number of seedlings died in site 2, so some characteristics of cacao growth were monitoring only in site 1. The initial findings suggest that vetiver grass can be used not only as a tool for soil erosion control, but its biomass can used as a compost form for termite control also, instead of chemical, in cacao development in agroforestry systems.