Abstract
The sweet potato weevil (Cyclas formicarius Fabr.) remains a serious threat to sweet potato (Ipomoea batatas Poir.) production and is considered the most destructive pest of sweet potatoes in the field and storagein the Philippines. Chemical control of the weevil is seldom practiced by farmers because they find it too costly, it may increase the chance for pesticide resistance, and because of public concern of its effectson non-target organisms. The use of biological controls such as entomopathogenic nematodes (EPN) could offer an effective, economical, and environmentally-friendly alternative management of the weevil. This study determined the occurrence and distribution of entomopathogenic nematodes in selected sweet potato growing areas in the Philippines. Using soil from 13 sweet potato growing areas, EPNs were recovered using the insect baiting method. Morbid insect larvae were suspended in sterile water for 48 h, and the suspension was examined under a stereomicroscope for the presence of EPN. Out of 47 samples collected from the 13 sweet potato production areas, 39 (82%) were positive for the presence of EPNs. Preliminary identification of the EPNs through morphological characters showed that they belonged to Rhaditida: Heterorhabditidae and Steinernematidae. This is the first report on the occurrence of EPNs in sweet potato fields in the Philippines, and their distribution strongly supports the possibility of utilizing them in an IPM management approach as biological agents against the sweet potato weevil. Morphometric and molecular-based identification and pathogenicity studies are underway.
Highlights
The sweet potato weevil (Cylasformicarius Fabr.) is a serious threat to sweet potato production, locally in the Philippines and globally
Reports indicated that losses in sweet potato production due to this pest ranged from 5% to 97%, especially in areas where the weevil occurs [1]
Results from 47 areas in 13 provinces showed the presence of entomopathogenic nematodes (EPN), with most found in sweet potato growing areas in Negros Oriental, Visayas (Table 1)
Summary
The sweet potato weevil (Cylasformicarius Fabr.) is a serious threat to sweet potato production, locally in the Philippines and globally. Reports indicated that losses in sweet potato production due to this pest ranged from 5% to 97%, especially in areas where the weevil occurs [1]. The insect attacks both the fleshy roots and the stems by tunneling into them and tainting them with a disagreeable odor and a bitter taste which renders them unfit for human and animal consumption. Infective juveniles can be applied with conventional equipment, and they are compatible with most pesticides [2] They find their host either actively or passively, and, in cryptic habitats and sometimes in soil, they have proven superior to chemicals in controlling the target insects [3].
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