Toward the integration of an attract-and-kill approach with entomopathogenic nematodes to control multiple life stages of plum curculio (Coleoptera: Curculionidae)

Authors: PINERO, JAIME - University Of Massachusetts; Shapiro Ilan, David; COOLEY, DANIEL - University Of Massachusetts; TUTTLE, ARTHUR - University Of Massachusetts; EATON, ALAN - University Of New Hampshire; DROHAN, PATRICK - Pennsylvania State University; LEAHY, KATHLEEN - Polaris Orchard Management; Zhang, Aijun; Hancock, Torri; WALLINGFORD, ANNA - University Of New Hampshire; Leskey, Tracy

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2020
Publication Date: 6/17/2020
Citation: Pinero, J.C., Shapiro Ilan, D.I., Cooley, D.R., Tuttle, A., Eaton, A., Drohan, P., Leahy, K., Zhang, A., Hancock, T., Wallingford, A.K., Leskey, T.C. 2020. Toward the integration of an attract-and-kill approach with entomopathogenic nematodes to control multiple life stages of plum curculio (Coleoptera: Curculionidae). Insects. https://doi.org/10.3390/insects11060375.
DOI: https://doi.org/10.3390/insects11060375

Interpretive Summary: The plum curculio is a persistent, native pest of apple in eastern North America and has generally been managed using multiple broad-spectrum insecticide application beginning at petal fall. Here, we evaluated a multi-lifestage approach to manage this weevil and reduce insecticide inputs. For the adult stage, we baited border row apple trees with a combination of the plum curculio pheromone and benzaldehyde, an attractant. These so-called ‘trap trees’ were spaced 50 meters apart around the exterior of the orchard and served as attract-and-kill sites. Following a single full-block petal fall spray, only these ‘trap trees’ were treated with insecticide, reducing insecticide inputs significantly and managing plum curculio as well as full block sprays. Additionally, we targeted the larval lifestage with an entomopathogenic nematode species, Steinernema riobrave, in orchard trials and found they suppressed larval development better than another strain, S. carpocapsae. Overall, these studies provide mechanisms to manage plum curculio using advanced integrated pest management tactics and increase sustainability of orchard agroecosystems.

Technical Abstract: Efforts to reduce insecticide inputs against plum curculio, Conotrachelus nenuphar, a key pest of apples in eastern North America, include perimeter-row insecticide sprays applied after the whole-orchard petal fall spray to manage dispersing adults and more recently, insecticide sprays confined to odor-baited trap trees. The latter approach calls for baiting branches of selected perimeter-row trees with a synergistic lure to attract adult C. nenuphar to aggregate adult activity and fruit injury within the canopies of odor-baited trees. Entomopathogenic nematodes (EPNs) are virulent to ground-dwelling stages of C. nenuphar and may be applied to the ground underneath trap-tree canopies. Here, we (1) compared the efficacy of the odor-baited trap tree approach with grower-prescribed (= grower standard) sprays to manage adult C. nenuphar populations over a 6-year period in seven commercial apple orchards located in Massachusetts, New Hampshire, and Vermont; and (2) assessed the performance of the EPN Steinernema riobrave at suppressing ground-dwelling stages of C. nenuphar. In addition, the performance of S. riobrave was compared against that of S. carpocapsae and S. feltiae in one year. Across the six years, percent fruit injury on trap tree plots averaged 11.3% on odor-baited trees in trap tree plots and 1.4% on unbaited trees in grower standard plots, highlighting the ability of trap trees to aggregate C. nenuphar activity and subsequent injury. Mean percentage injury on fruit sampled from interior trees, the strongest measure of treatment performance, in trap tree plots did not differ significantly from that recorded on interior trees in grower standard spray plots (0.95 vs. 0.68%, respectively). Steinernema riobrave consistently reduced C. nenuphar populations as indicated by the significantly lower number of adult C. nenuphar that emerged from the soil, when compared to water control. Steinernema carpocapsae and S. riobrave performed similarly well, and both EPN species outperformed S. feltiae. Our combined findings indicate that an integrated pest management approach that targets multiple life stages of C. nenuphar has the potential to manage this pest more sustainably in a reduced-spray environment.