Potential of entomopathogenic nematodes against the pupal stage of the apple maggot Rhagoletis pomonella (Walsh) (Diptera: Tephritidae)

Authors: USMAN, MUHAMMAD - Ayub Agricultural Research Institute; GULZAR, SEHRISH - Ayub Agricultural Research Institute; WAKIL, WAQAS - Ayub Agricultural Research Institute; PINERO, JAIME - University Of Massachusetts; Leskey, Tracy; NIXON, LAURA - US Department Of Agriculture (USDA); Hofman, Camila; WU, SHAOHUI - University Of Georgia; Shapiro Ilan, David

Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2020
Publication Date: 7/28/2020
Citation: Usman, M., Gulzar, S., Wakil, W., Pinero, J., Leskey, T.C., Nixon, L., Hofman, C.O., Wu, S., Shapiro Ilan, D.I. 2020. Potential of entomopathogenic nematodes against the pupal stage of the apple maggot Rhagoletis pomonella (Walsh) (Diptera: Tephritidae). Journal of Nematology. 52:1-9. https://doi.org/10.21307/jofnem-2020-079.
DOI: https://doi.org/10.21307/jofnem-2020-079

Interpretive Summary: The apple maggot is a key pest of apples. The insects attack fruit directly. However, a part of the insect’s life-cycle, particularly the pupal stage, occurs in the soil. To control the insect, broad spectrum chemical insecticides are sprayed. Due to regulatory and environmental concerns, research to develop alternative measures to control the pest is warranted. Entomopathogenic nematodes (also known as beneficial nematodes) are potential alternatives to chemical insecticides for control of apple maggot. Nematodes are round worms. Unlike harmful plant parasitic nematodes, entomopathogenic nematodes only attack insects and thus they are used as environmentally-friendly biopesticides to control a wide variety of economically important insect pests. The objective of our research was to determine if entomopathogenic nematodes can kill apple maggot pupae and to assess which nematode species is the most virulent. We tested seven different nematode species and found that three showed significant promise for controlling apple maggot pupae (the three nematodes are called Steinernema riobrave, Steinernema carpocapsae and Steinernema feltiae). This research opens up new avenues to explore for developing safe alternative pest management approaches. The next step will be to test the promising nematode species for their ability to kill apple maggot under field conditions.

Technical Abstract: The apple maggot, Rhagoletis pomonella, is considered a key pest of apples and is native to the eastern United States. The virulence of seven different species of entomopathogenic nematodes (EPN) was assessed against pupae of R. pomonella under laboratory conditions. Nematode species and strains included Steinernema carpocapsae (ALL strain), Steinernema feltiae (SN strain), Steinernema riobrave (355 strain), Steinernema glaseri (VS strain), Heterorhabditis bacteriophora (VS strain), Heterorhabditis indica (HOM1 strain) and Heterorhabditis megidis (UK211 strain). We conducted three bioassays: (a) short-term exposure cup bioassay (7 d), (b) long term cup bioassay (30 d), and (c) pot bioassay (30 d). In the short-term exposure bioassay, all nematode strains (applied at 54 infective juvenile nematodes (IJs) cm-2) significantly reduced (range: 42.9-73.8%) insect survival relative to the control, but no differences were observed among the treatments. For the long-term exposure bioassay, using the same EPN application rate as the short exposure assay, all treatments reduced adult R. pomonella emergence compared with the control. Steinernema riobrave was the most virulent (28.3% survival), and S. glaseri and H. megidis were the least virulent (53.3% survival). In the pot experiment, S. riobrave and S. carpocapsae (applied at 27 IJs cm-2) had the highest virulence (23.3% and 31.7% survival of R. pomonella, respectively), while H. bacteriophora was the least effective (68.33% survival). Our results indicate that S. riobrave, S. carpocapsae and S. feltiae have substantial potential to attack R. pomonella pupae, and their field application under the tree canopy (prior to adult emergence) in the spring when temperatures are conducive might be a good option for successful IPM of apple maggot fly.