Potential Application of Entomopathogenic Nematodes for Management of Stable fly, Stomoxys calcitrans (L.) under Laboratory Conditions

Abstract

The stable fly (Stomoxys calcitrans) is an important insect pest of livestock because it causes annoyance and vector-borne diseases to livestock. Farmers deploy several methods to control stable flies. Entomopathogenic nematodes (EPNs) are used to control stable fly as they are soil-borne insect pathogens. In this study, eight substrates including 0–12 hours old fresh cow manure (FCM12), seven days old cow manure (CM7), seven days old cow bedding (CB7), manure (Man), seven days old fermented timothy hay (FT7), seven days old fermented cow manure (FCM7), seven days old cow manure and fermented timothy hay (CMFT7) and water-soaked cotton (WSC = control) were performed for the preference of larvae and gravid female of S. calcitrans. Stomoxys calcitrans larvae showed the highest preference for substrate CM7 with 26.70%. The highest preference of gravid female was FCM12 with 55.00%. The pathogenicity of six EPN isolates (Steinernema scarabaei EPNKU60, Heterorhabditis indica EPNKU64, H. indica EPNKU67, H. indica EPNKU82, H. bacteriophora, S. carpocapsae and S. siamkayai) at the rates of 0, 25, 50, 100, 200 and 400 Infective Juveniles /cm2 were tested against second, third instar larvae and pupae of S. calcitrans in filter paper bioassays. Heterorhabditis bacteriophora killed 100.00% of the second instar larvae at the rate of 200 IJs/cm2. Heterorhabditis bacteriophora and H. indica EPNKU82 showed 80.00% and 100.00% mortality of third instar larvae at the rate of 400 IJs/cm2 while mortality of insect larvae was less than 30.00% for other EPNs. Low efficacy of EPN infection on pupae of S. calcitrans was observed and only 56.00% pupal mortality was found at the rate of 400 IJs/cm2. Persistence of three selected EPNs (H. indica EPNKU82, H. bacteriophora and S. siamkayai) was estimated at 1, 3, 5, 7 and 9 days of exposure on eight substrates where water-soaked cotton was replaced by 10% moist sand by baiting larvae at the last instar larvae of Galleria mellonella. Heterorhabditis indica EPNKU82 showed high persistence on SAN and FT7 causing 83.33–100.00% and 90.00–100.00% mortality at 1–9 days of exposure. Similarly, H. bacteriophora showed high persistence of EPN on SAN and CB7 and the insect mortality ranged from 93.33–100.00% and 90.00–100.00% at 1–9 days of exposure. Only on the 1 day of exposure S. siamkayai still had 90.00% mortality of the last instar larvae of G. mellonella.