Beauveria Bassiana as Fungal Endophyte for the Potential Control of the Potato Tuber Moth Phthorimaea Operculella on Potatoes

The potato tuber moth, Phthorimaea operculella, is the most damaging potato pest in the world and is difficult to control as the larvae are internal feeders in the foliage or tubers. Entomopathogenic fungi (EPF) which colonize plants as endophytes, have lethal and sublethal pathological effects on insect pests. Experiments showed that Beauveria bassiana colonized the aerial parts of potato plants endophytically after inoculation through soil drenching. The colonization rate reached 100% for both upper and lower foliage parts one day after inoculation, and endophytic B. bassiana remained present for more than 21-day post inoculation. Mortality experiments indicated that B. bassiana and B. bassiana-inoculated potato plants were pathogenic against 2nd instar larvae of P. operculella. Development experiments showed that the weight of P. operculella pupae reared on B. bassiana-colonized potato leaves (4.25 mg) was significantly lighter than of those reared on uninoculated control plants (8.89 mg). Sublethal experiments indicated that B. bassiana negatively affected the growth, development and reproduction of P. operculella. Compared to newly eclosed larvae fed on control plants, those fed on B. bassiana-inoculated plants had significantly lower survival, with only 17.8% developing to the adult stage. Oviposition of P. operculella females reared on B. bassiana endophytically-colonized plants was significantly lower (35 eggs/per female) than of those reared on uninoculated plants (115 eggs/per female). This study demonstrates that endophytic B. bassiana can be a potential biological agent for the control and management of P. operculella.

Potential of Entomopathogenic Nematodes versus Alpha-cypermethrin Against Potato Tuber Moth, Phthorimaea operculella Zeller 1873 (Lep.: Gelechiidae) in Storage Conditions

The potato tuber moth PTM, Phthorimaea operculella, is one of the most economically important potato pests worldwide. In the present study, the potential of Steinernema feltiae and Steinernema carpocapsae for controlling PTM in potato tubers was evaluated compared to alpha-cypermethrin. Steinernema carpocapsae in both concentrations (12.6×106IJs and 6.2×106IJs) showed a lower number of emerged insects than alpha-cypermethrin (10 mg ai l-1). Alpha-cypermethrin (20 mg ai l-1) showed the highest efficacy against PTM (81.17%), S.carpocapsae (12.6×106IJs), and alpha-cypermethrin (10 mg ai l-1) showed similar efficacy (72.53%) while S. feltiae (6.2×106IJs) showed the lowest efficacy (39.04%). The results showed that S.carpocapsae in both concentrations and S. feltiae (12.6×106IJs) were efficient the same as alpha-cypermethrin (10 mg ai l-1) having no environmental and health adverse impacts issued in the chemical insecticides usage. Both concentrations of alpha-cypermethrin and S. carpocapsae showed the least tuber damage with no significant differences, while it was as high as the control (59.26%) in both concentrations of S. feltiae. This promising finding introduces EPNs as a part of the potato tuber protection program in storage. Accordingly, EPNs can be considered as an appropriate alternative to synthetic chemicals for PTM control without any residue and health problems.

Identification and Functional Characterization of Two Putative Pheromone Receptors in the Potato Tuber Moth, Phthorimaea operculella

Pheromones are a kind of signal produced by an animal that evoke innate responses in conspecifics. In moth, pheromone components can be detected by specialized olfactory receptor neurons (OSNs) housed in long sensilla trichoids on the male antennae. The pheromone receptors (PRs) located in the dendrite membrane of OSNs are responsible for pheromone sensing in most Lepidopteran insects. The potato tuber moth Phthorimaea operculella is a destructive pest of Solanaceae crops. Although sex attractant is widely used in fields to monitor the population of P. operculella, no study has been reported on the mechanism the male moth of P. operculella uses to recognize sex pheromone components. In the present study, we cloned two pheromone receptor genes PopeOR1 and PopeOR3 in P. operculella. The transcripts of them were highly accumulated in the antennae of male adults. Functional analysis using the heterologous expression system of Xenopus oocyte demonstrated that these two PR proteins both responded to (E, Z)-4,7–13: OAc and (E, Z, Z)-4,7,10–13: OAc, the key sex pheromone components of P. operculella, whilst they responded differentially to these two ligands. Our findings for the first time characterized the function of pheromone receptors in gelechiid moth and could promote the olfactory based pest management of P. operculella in the field.