Pathogenicity of Steinernematid Nematodes on the Sweet Potato Weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae) and Their Feasibility for Suppression of the Weevil Population

Abstract

Abstract:We evaluated entomopathogenic nematodes (Steinernematidae) as potential biocontrol agents to suppress the wild population of the sweet potato weevil, Cylas formicarius (Fabricius) as part of its eradication program. The pathogenicity of Steinernema carpocapsae ('All' strain), S. feltiae, S. riobrave and S. glaseri ('326', '328', 'Mungyeong' and 'Dongrae' strains) was checked against the sweet potato weevil under laboratory conditions. S. carpocapsae induced the highest mortality in both sexes of the adult sweet potato weevil (90%Ͻ). About 30-60% of pupae and larvae in the root of sweet potatoes were killed by S. riobrave, S. glaseri ('Mungyeong' strain) and S. glaseri ('Dongrae' strain). The efficacy of S. carpocapsae ('All' strain) on the suppression of the weevil population was then tested in a sweet potato field. Application of S. carpocapsae ('All' strain) successfully reduced the root damage rate and root damage index by approximately 60% and 40%, respectively, as compared with root damage in the control fields. These results suggested that S. carpocapsae ('All' strain) would be an appropriate and effective biocontrol agent for suppressing the weevil population.

Invertebrate pests and diseases of sweetpotato (Ipomoea batatas): a review and identification of research priorities for smallholder production

“…Recently there has been an increase in the number of papers published on this form of biological control (San-Blas, 2013), and despite early failures, advances in mass-production and formulation technology, and the discovery of effective isolates/strains, has re-invigorated interest in the use of entomopathogenic nematodes as biological control agents. In a Japanese trial, Steinernema carpocapsae achieved a 90% kill rate on C. formicarius under laboratory conditions and in the field reduced damage by 40-60% (Yamaguchi et al, 2006). In Kenya, trials with S. karii and Heterorhabditis indica, resulted in high mortality of larvae and reduced the adult population (Nderitu et al, 2009).…”

The Major Sweet Potato Weevils; Management and Control: A Review

“…Different classes of insect have been identified as predators of Cylas spp [16,22,33], in different geographical regions, but the cost and technical know-how associated with their biological controls remains a challenge in the small scale farming system (Table 3) [110][111][112][113][114][115][116][117][118][119][120][121].…”

“…Heterorhabditis found among different species was indicated to be most effective and pathogenic than Steinernematids [116]. Research on Heterorhabditis indica and S. karii in Kenya resulted in a high death rate of larvae and adults [117]. Steinernema carpocapsae has attained a damage rate of 90% on Cylas formicarius under conditions at the laboratory, but in the field, a decreased of 40%-60% damage on weevils [118].…”

Different Susceptibility in the Two Sympatric Sweet Potato Weevils, <i>Cylas formicarius</i> and <i>Euscepes postfasciatus</i>, to the Entomopathogenic Fungus <i>Metarhizium anisopliae</i>

“…(Hymenoptera: Braconidae), cause more than 30% mortality in immatures of E. postfasciatus [7]. Entomopathogenic nematodes (EPNs) substantially reduce the population of C. formicarius [8] [9] [10]. Both parasitoids and EPNs can parasitize immatures inhabiting inside both root and stem of the plant [10] [11], where effective doses of chemical insecticides are hard to deliver.…”

“…Entomopathogenic nematodes (EPNs) substantially reduce the population of C. formicarius [8] [9] [10]. Both parasitoids and EPNs can parasitize immatures inhabiting inside both root and stem of the plant [10] [11], where effective doses of chemical insecticides are hard to deliver. Despite the advantage in the use of these agents, their uses are not common or even not realized yet, primarily due to the costs of both mass production and the application to this low-valued crop.…”