Submitted to: Journal of Nematology
Publication Type: Abstract Only
Publication Acceptance Date: 6/4/2016
Publication Date: 1/18/2017
Citation: Myers, R.Y., McQuate, G.T., Sylva, C.D., Mello, C.L. 2016. Potential of Heterorhabditis indica to control Cylas formicarius in field culled sweet potato roots. Journal of Nematology. 48:355.
Technical Abstract: Sweet potato weevil, Cylas formicarius, is one of the most destructive insect pests of sweet potato in Hawaii. The larvae feed and tunnel inside the root causing malformation and a bitter taste that makes the product unmarketable. During harvest, farmers leave off-grade roots in the field which serve as inoculum and infect the next planting. Sanitation by removing roots and vines is the current control measure but rarely practiced due to high labor costs. An indigenous entomopathogenic nematode, Heterorhabditis indica, was shown to infect and kill C. formicarius in laboratory studies. In petri dish assays, 90% of larvae and nymphs were killed in two days when inoculated with 1 – 25 infective juveniles (IJs). In tub bioassays, tuberous roots infected with C. formicarius were partially buried in sand and inoculated with H. indica. After one month, 89% and 100% of larvae and pupae from dissected root slices were morbid after inoculation with 1,000 and 10,000 IJs respectively. The remaining root pieces were placed on modified white traps and held for 25 days. An average of 60,000 nematodes was recovered from each tuberous root. Spraying these biological control agents on harvested fields has potential as a sanitation measure for reducing sweet potato weevil populations between plantings.