Precision micro-spray tower for application of entomopathogens

Abstract

An inexpensive, portable and easy handling spraying device was developed for experimental application of water suspensions of entomopathogens and insecticides. The micro-sprayer was calibrated using different settings of pressure and time to apply a wide range of doses on a plain surface. Filter paper cards sprayed with dye solutions were used to examine the deposition uniformity (coverage). The relationship between conidial suspensions of fungal entomopathogens and deposition rate of conidia was also investigated. As a result, the combination of 10 PSI and 3 s provided the most uniform coverage at a volume application rate of 2.15 μL cm -2 (= 215 L ha -1 ). Conidial deposition rate was positively linear to fungal concentrations and regression lines were not significantly different among the fungal species tested. Hence, a single regression line was determined, which gave an estimate of 150 conidia mm -2 (= 1.5×10 12 conidia ha -1 ) based on a concentration of 1×10 7 conidial mL -1 . Once calibrated, this spray device can be used in a variety of bioassays testing efficacy of entomopathogens and chemical pesticides in small confined experimental arena.