Forecasting the seasonal phenology of Agrotis ipsilon in Oregon grass seed and vegetable agroecosystems

Authors: SLONE, EMMA - Oregon State University; GREEN, JESSICA - Oregon State University; KAUR, NAVNEET - Oregon State University; WALENTA, DARRIN - Oregon State University; ANDERSON, NICOLE - Oregon State University; Cruse, Casey; Dorman, Seth

Submitted to: Frontiers in Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2024
Publication Date: 1/17/2025
Citation: Slone, E., Green, J., Kaur, N., Walenta, D., Anderson, N., Cruse, C.E., Dorman, S.J. 2025. Forecasting the seasonal phenology of Agrotis ipsilon in Oregon grass seed and vegetable agroecosystems. Frontiers in Insect Science. 4. Article 1505524. https://doi.org/10.3389/finsc.2024.1505524.
DOI: https://doi.org/10.3389/finsc.2024.1505524

Interpretive Summary: The black cutworm is a serious pest in Oregon grass seed and vegetable crops. Effective management relies on timely insecticide applications when the crop-damaging larval life stage is immature before significant feeding damage is observed. Phenology models, which relate environmental conditions to development stages of the pest, are essential for effective areawide pest management plans to inform the timing of when pest monitoring and management actions should occur. Seasonal modeling of black cutworm phenology is complicated by their migratory behavior and limited knowledge of temperature-dependent development on affected crop hosts. Growth chamber experiments were conducted to determine the temperature-dependent development of black cutworm life stages on artificial and perennial ryegrass diets. The timing of migrant adults was predicted using non-linear regression with abundance data collected from pheromone-baited traps in 77 total commercial vegetable and grass seed production fields across 19 sampling years. Developmental parameters and predictions of adult arrival were used to develop general and grass seed specific phenology model projections for black cutworm populations in Oregon. Regionally validated phenology models can be incorporated into decision support tools that forecast the spatiotemporal occurrence of crop-damaging life stages of priority pests.

Technical Abstract: Agrotis ipsilon (Lepidoptera: Noctuidae), commonly known as black cutworm, is a significant pest in Oregon grass seed and vegetable production systems. Effective management of this species relies on timely foliar insecticide applications targeting immature A. ipsilon larvae (first to third instar) before crop damage is observed. Regionally specific phenological models can serve as a critical component of effective areawide pest management plans to inform the timing of pest monitoring and management action. Seasonal modeling of A. ipsilon phenology is complicated by their migratory behavior and limited knowledge of temperature-dependent development on affected crop hosts. Growth chamber experiments at five stable temperatures (12 to 32°C) were conducted to determine the temperature-dependent development of A. ispsilon life stages on an artificial and perennial ryegrass diet. The completion of one A. ipsilon generation (egg to adult) required 692, 965, and 795 growing degree days with a base temperature threshold of 10.47 for artificial diet, perennial ryegrass diet, and across both diet types, respectively. The timing of migrant adults was predicted using non-linear regression with abundance data collected from pheromone-baited traps in 77 total commercial vegetable (n = 20) and grass seed production fields (n = 57) across 19 sampling years (1996 to 2023). Developmental parameters and predictions of adult arrival were used to develop general and grass seed specific phenology model projections for A. ipsilon populations in Oregon. Regionally validated phenology models can be incorporated into decision support tools that forecast the spatiotemporal occurrence of crop-damaging life stages of priority pests.