No abstract

Entomopathogenic nematodes are effective in controlling soil insects and they are used in agricultural systems. The virulence of entomopathogenic nematodes on crickets (Gryllus L.) (Orthoptera: Gryllidae) was evaluated under different conditions in order to select populations for application in the field. Virulence tests with Heterorhabditis amazonensis RSC05, H. amazonensis MC01, Steinernema carpocapsae All (Weiser) and H. amazonensis GL were performed. Evaluations were then made of the concentrations of infective juveniles (100, 200, 400 and 600 infective juveniles per insect); feeding preference with or without choice; and field tests using traps to evaluate insect sampling. All isolates were found to cause mortality in Gryllus sp., and H. amazonensis MC01 and S. carpocapsae All were selected; an increase in concentration resulted in increased insect mortality. Regarding the feeding preference tests, after 16 h there was no feeding in any of the treatments. In treatments with a chance of choice, it was verified that the crickets fed, independently of the presence of the nematodes. In the field tests, 19 live crickets were found in the traps, and, after application of entomopathogenic nematodes in aqueous suspension, 2 live crickets were found. Results suggested that H. amazonensis MC01 was promising in the control of Gryllus sp. under the tested conditions.

Biological control is a viable alternative to chemical control; however, some methods of releasing control agents still need to be improved in order to attract the attention of producers and to reduce costs. Therefore, this work was conducted to evaluate the effects of hydraulic spray nozzles on the viability and infectivity of entomopathogenic nematodes. The experiment was conducted using a completely randomized design with 37 treatments, of which there were three controls and 34 treatments using different spray nozzles with six repetitions. A spraying table was used for the applications. The working pressure was 400 kPa for all nozzles and the solution sprayed consisted of an aqueous suspension of the nematode Heterorhabditis amazonensis MC01 at a concentration of 400 infective juveniles (IJ) mL-1. The viability of the IJ after being sprayed, as well as the infectivity of Tenebrio molitor larvae were verified. The results indicated that nematode viability was influenced by the nozzles and the living nematodes sprayed did not lose their capacity to infect the insect.