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Tephritids are the major challenges for fruit and fleshy vegetable growers of the tropics and sub-tropics. Nepal also incurs huge losses of fruits and vegetables to the tephritids. This study was designed to identify the tephritid flies in Malepatan and Lumle of Gandaki Province. Bucket traps baited with methyl eugenol (ME) in Malepatan, and ME, cue lure (CL) and a mixture of ME and CL (ME + CL) with different releasers; tube, cotton and paper were installed at Lumle in 2020 summer. Three species of the fly (Bactrocera dorsalis, Bactrocera zonata and Bactrocera correcta) were recorded from Malepatan, dominated by B. dorsalis. The B. correcta count was negligible. While in Lumle, B. dorsalis was the most dominant, followed by B. zonata till July, after which, till August, B. tau followed the B. dorsalis. Seven species of the tephritids (B. zonata, B. dorsalis, B. tau, B. diversa, B. scutellaris, B. correcta and B. cucurbitae) were recorded from this region. Among the releasers, paper releaser was found more effective as compared to cotton and tube. However, the lures should be changed in a short interval, by two weeks, to acquire a satisfactory result. This study unveils that the study site already inhabits seven species of fruit flies. So, the monitoring with different cues could be an effective tool for species actuation. Additionally, the paper releasers could be recommended for further use in the traps for monitoring and mass trapping purposes.

Ethyl formate (EF) is becoming an insecticide of choice for protecting stored commodities. Along with EF, methyl salicylate (MS) is also naturally occurring, and both are generally regarded as safe fumigants for their higher threshold limit values (TLV) and residual status below minimum residue limit (MRL). Sub-lethal doses of EF and MS were evaluated to determine if there was a synergistic effect on fumigation against life stages of the adzuki bean beetle, Callosobruchus chinensis (L.) infesting adzuki bean grains. Based on lethal dose (LD) values, the C. chinensis eggs and adults were equally susceptible to EF followed by larvae and pupae. Adults were the most MS-sensitive followed by eggs and larvae, and pupae were the most tolerant stage. The mortalities of all the life stages of C. chinensis by combined fumigation with sub-lethal EF and MS doses were significantly higher compared to the sum of their separate fumigations revealing a notable synergistic effect. Moreover, the maximum doses of EF and MS tested for synergistic fumigation test did not hamper the germination potential of adzuki been seeds. The synergistic effect between EF and MS can significantly reduce the dose rate of flammable EF against C. chinensis thereby offering a good prospect for EF + MS formulation as an alternative to safeguard stored adzuki bean.

Japanese pine sawyer (Monochamus alternatus) (Coleoptera: Cerambycidae), a vector of pine wilt disease, produces male-produced aggregation pheromone called monochamol, 2-(1-undecyloxy)-1-ethanol (C11OEtOH). After the identification of unique nematicidal activity of the synthetic monochamol and its homologues (ROEtOH: R = C7-C11) against Bursaphelenchus xylophilus nematode, their acaricidal activities were evaluated against two spotted spider mite (TSSM, Tetranychus urticae Koch) (Acari: Tetranychidae). In a leaf disc bioassay method, 100 mgL−1 of monochamol and 2-(1-decyloxy)-1-ethanol (C10OEtOH) exhibited 100% adult mortality and zero fecundity. Along with C11OEtOH and C10OEtOH, 2-(1-octyloxy)-1-ethanol (C8OEtOH) and 2-(1-nonyloxy)-1-ethanol (C9OEtOH) were also 100% acaricidal with complete oviposition inhibition at increased concentration of 1000 mgL−1. When the TSSM eggs on leaf discs were immersed in 1000 mgL−1 solutions, none of the components were ovicidal. Egg hatching was completely inhibited by three components (C9OEtOH, C10OEtOH and C11OEtOH) at 6000 mgL−1 and by four components (C8OEtOH, C9OEtOH, C10OEtOH and C11OEtOH) at 8000 mgL−1. However, none of the compounds showed acaricidal effects in 0.5 h and 24 h residual toxicity tests at 1000 mgL−1. This study highlights the potential acaricidal activity of monochamol and its homologues. Notably, the monochamol and its C10-homologue could be listed as efficient acaricidal agents.

Azuki bean beetle, Callosobruchus chinensis (L.) (Coleoptera: Bruchidae), is a field-to-storage pest of legumes and its females produce sex pheromone components with two isomers: (2Z,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienal (2Z-homofarnesal) and (2E,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienal (2E-homofarnesal). Two-day-old virgin adults were treated with different doses (0, 200, 300, 400, 500, and 600 Gy) of gamma radiation and the effects on adult survivorship, fecundity, sterility, and pheromone production were studied. The longevity of both sexes and female fecundity were dose dependently affected by the gamma irradiation revealing that the fecundity was more reduced when the female adults were irradiated. Adults of both sexes were totally sterilized by the doses of gamma radiation tested in this study as depicted by the null hatchability of the laid eggs. The results from analyses by gas chromatography-mass spectrometry for solid phase micro-extraction revealed that both of the female sex pheromone components were significantly reduced by 300 Gy. Though significantly less, there was release of some amount of pheromone components by the irradiated female azuki bean beetles revealing the possibility of pheromonal attraction of males to the irradiated females. It is a pre-requisite for the successful sterile insect technology that the sterility of azuki bean beetle is induced without the total disruption of the calling behavior.

Use of synthetic pheromones is biologically and economically effective approach in insect pest management programs. The female adults of azuki bean beetle (Callosobruchus chinensis L.), a worldwide oligophagous pest of legumes including azuki beans, produce sex pheromone components known as homofarnesals with two isomer compounds; (2Z,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienal (2Z-homofarnesal) and (2E,6E)-7-ethyl-3,11-dimethyl-2,6,10-dodecatrienal (2E-homofarnesal). We used Z-selective method to synthesize 6:4 blend of 2E- and 2Z-homofarnesal and compared its attractiveness with two other blends; 9:1 and 1:9 using Y-olfactometry in laboratory and rocket traps in the field. Both laboratory and field experiments ascertained the higher attractiveness of synthetic homofarnesal with higher proportion of 2Z-homofarnesal. Among the tested blends of 9:1, 6:4 and 1:9 of 2E- and 2Z-homofarnesal in Y-olfactometry, the attractiveness pattern was found as 1:9 ≥ 6:4 > 9:1 blend. Under field condition also, the 6:4 blend was more attractive with the recapturing efficiency of 31.4 ± 2.6% as compared to 13.6 ± 0.4% of 9:1 blend of 2E-:2Z-homofarnesal. The result of this experiment provides an opportunity to synthesize pheromone rich in 2Z-homofarnesals with less sophisticated and economically feasible Z-selective method to incorporate it in eco-friendly alternative of azuki bean beetle management.

Essential oils (EOs) from different parts of some selected wooden plants (Illicium verum, Bursera delpechiana, Croton anisatum, Cinnamomum cassia and Aniba rosaeodora) and the major components, trans-anethole, trans-cinnamaldehyde, linalool and linalyl acetate, as well as the major component of Gaultheria fragrantissima, methyl salicylate were tested for adult repellence and oviposition deterrent effects on adzuki bean beetle (ABB), Callosobruchus chinensis L. in a Y-tube olfactometer assay and no choice assay, respectively. EOs of I. verum and C. anisatum as well as their common major component, trans-anethole and the major component of G. fragrantissima, methyl salicylate were effective repellents and had high degree of oviposition deterrent activity without affecting the seed viability. Linalool, the major component of A. rosaeodora and B. delpechiana EOs exhibited male repellency in higher concentrations but was not effective oviposition deterrent. From this study, two EOs: I. verum and C. anisatum and two major components; trans-anethole and methyl salicylate could be selected for use against C. chinensis for safe storage of adzuki bean.