Assessing the potential of entomopathogenic Isaria javanica for management of the greenhouse insect pests

Organic nontoxic sustainable agroecosystem is the goal of perspective agriculture management. To fulfill this purpose, integrated pest management (IPM) is compulsory. Previously, Isaria javanica isolated from caterpillar (Lepidoptera), after host range and enzymatic study showed a potential to control small insect pests, particularly in greenhouse. To further test its biocontrol efficacy, experiments on pathogenicity, physiological, characteristics and formulation were conducted. Pathogenicity tests in laboratory, I. javanica led to a mortality 88.15% and medium lethal time (LT50) in four days toward green peach aphid (Myzus persicae Sulzer); 85% mortality in 5 day against southern yellow thrips (Thrips palmi Karny); and 79.62% in 8 days toward tea bug (Andraca theae Matsumura). Of the nine cultural media tested, I. javanica grew and sporulated best on Czapek’s yeast autolysate agar (CYA) at 25℃ in the dark, capable of producing 3.29 x 109 conidia/plate. However, I. javanica showed slow growth and lower germination rate under 95.9% RH. In carbon and nitrogen source test of I. javanica, sorbital was the best for colony growth, by contrast, maltose for sporulation. For growth and sporulation, potassium nitrate was better than other nitrogen source. On the other hand, I. javanica was somewhat more tolerant and compatible toward Acetamiprid, Abamectin and Pyriproxyfen insecticides, thus perhaps can be integrated use for pest control. On polish rice alone I. javanica produced 2.94 x 1010 conidia g-1, better than brown rice or amended with rice bran or soybean meal. The emulsified conidia formulation exhibited a 98% mortality rate toward aphids on cabbage in 8 days at 25℃ compared with 22% mortality rate at 30℃ in greenhouse. Overall, I. javanica was characterized with high conidia production capacity and moderate to high virulence toward many notorious greenhouse micro-insect pests, hence posed a high potential for commercialization as mycoinsecticides. However, the low tolerances to stressed environments, such as desiccation, UV-radiation etc., need to be overcome by protectants or via genetic engineering approach.