Compatibility between entomopathogenic nematodes and crop protection products used in maize seed treatment

Chemical insecticides are widely used to control soil pests but not always effective. Entomopathogenic nematodes (NEPs) are found in the soil and depend on host insects to complete their life cycle, and therefore have the potential to control soil pests. Thus, we aimed to investigate the possible joint use of these control methods by assessing the compatibility of two nematodes (Heterorhabditis amazonensis GL and Heterorhabditis amazonensis MC01) with five crop protection products used for maize seed treatment (Maxim (R), Cruiser 350 FS (R), Fortenza 600 FS (R), Avicta 500 FS (R), and Amulet (R)), as well as one neem-based product (NeenMax (R)). The experimental design was completely randomized with five replicates, six treatments, and one control, in which only distilled water was added to nematode suspension. Each replicate consisted of a test tube containing 1 mL suspension with 2,000 infective juveniles (Us) and 1 mL of diluted product, following the manufacturer's recommendation. The evaluated parameters were viability, infectivity on Tenebrio molitor larvae and IJs production after exposure to products. Both nematodes were compatible with NeenMax (R) and Fortenza 600 FS (R) since they did not differ from the control and were classified as innocuous. Cruiser 350 FS (R) was also compatible with the nematodes since the effect value of the product was lower than 30%. Amulet (R) was classified as slightly noxious, reducing H. amazonensis MC01 and H. amazonensis GL infectivity by 17.5% and 28.5%, and production by 18.2% and 22.3%, respectively. Despite not having reduced viability, Avicta 500 FS (R) and Maxim (R) were considered harmful. This is because Avicta 500 FS (R) and Maxim (R) reduced productivity by 70.0% and 72.5% and production by 66.1% and 65.4% for H. amazonensis MC01, respectively. For H. amazonensis MC01, both Avicta 500 FS (R) and Maxim (R) reduced infectivity by 76.19%, and production by 63.7% and 62.3%, respectively.