Research to Curb Cutworm

Cutworms are a pest complex of many different species that pose different risks to a range of crops at various times throughout the year. The unpredictability of cutworm arrival and population density each year makes it challenging for producers to prevent outbreaks and extensive crop damage, especially in organic vegetable production systems.

As a result, lead researcher at Research and Development Institute for the Agri-environment inc. (Québec) Dr. Maxime Lefebvre and his team are working to increase the understanding and capacity to forecast the movement and abundance of cutworm species under different climate scenarios. Supported in part by Organic Science Cluster 4 funding, they are studying the biotic and abiotic factors that impact population dynamics.

Over 20 species of cutworms exist across Canada. They are generalist herbivores and can impact such crops as cabbage, carrot, celery, lettuce, onion, tomato and cucurbits. Some feed on the roots while others attack the foliage and fruit of vegetable crops.

Lefebvre is focusing on the migratory black cutworm and resident dark-sided cutworm, which are common pests in Eastern Canadian market gardens.

“For the migratory species, we want to study the risk of the migration for the black cutworms and the other experiments that I have are more related to the dark-sided cutworm. We will try to study its development according to the temperature and humidity of soil,” Lefebvre says.

The research team will use historical trapping data from Québec and Ontario, dating back to 2010, meteorological data and wind trajectory models to build migratory black cutworm models. For the dark-sided cutworm, researchers will use phenological modelling, which uses mathematical models to emulate and predict plant and animal life cycles.

“We will make an experiment where we expose the larva to different soil temperature and humidity regiments and see how they develop,” Lefebvre says. “In doing so, we will be able to know how much time it will take for a larva stage to reach a specific stage according to temperature accumulation, for example.”

The team will then validate their models, with the help of agronomists and other collaborators, through field observations across Ontario, Quebec and New Brunswick. 

Indeed, cutworm populations are largely impacted by weather. For example, cold and harsh winters with little snow cover may reduce egg and larvae survival of some species while a mild or snowy winter may result in higher survival. However, some species migrate from the southern US and winterkill does not contribute to population control.

“We have feedback from growers and agronomists where some years the infestations are higher than other years and we don’t know the mechanisms behind that,” Lefebvre says. “This is one of my research questions – to understand the outbreak phenomenon.”

Generally, cutworms inflict the most damage in May and June when the larvae are large and hungry, and crops are vulnerable as seedlings. That said, the increasing variability in weather due to climate change could impact the pests’ range, life cycle and winter survivability. As a result, the predictive models and forecasting tools from this research will help organic vegetable producers optimize cutworm management before, during and after the growing season.

In addition to the predictive modelling piece, the research team is going a step further to test preventative and curative measures for cutworm control in vegetable production.

At the Organic Agriculture Innovation Platform in Quebec, researchers will examine larvae susceptibility to mechanical weeding. During the day, the pest often rests in the top 5 centimetres of soil and soil disturbance could increase mortality. The team strives to identify the most susceptible larval stage and effective tools as well as how soil type may impact mortality. For no-till growers, Lefebvre hypothesizes that promoting agroecosystem services focused on pest control could help with cutworm control. For example, such best management practices as cover crops and flower strips will be studied for their effectiveness in promoting beneficial insect populations and improving natural mortality of eggs and larvae.

“I want to look into the natural enemies,” Lefebvre says. “If you’re using a flower strip, then you choose your flowers according to which species of parasitoids or predators that you want to attract. We are lucky because the organic growers are really aware of the ecosystem benefits and all the natural enemies that can work with them. So, it probably won’t be that hard to convince them that we can build that agroecosystem focused on the cutworm control.”

So far, the team has studied the correlation between weather and black cutworm moth counts. This data will be used to identify weather systems that aid the long-range dispersal of the migratory species. Researchers have also conducted a literature review to learn more about pathogens and parasitoids of the dark-sided cutworm.

This year, Lefebvre and his colleagues will work on the first iteration of the phenological modelling for the dark-sided cutworm as well as establish their pest control plots for 2026 observations. Through this five-year project, Lefebvre looks forward to helping growers solve a persistent production problem using the most sustainable methods possible.

“If our model works and the experiment gives us really important information, growers can be more aware of what they can do to reduce their risk of infestation and understand the outbreak patterns of cutworm damage,” he says. “They can prepare better and reduce their damage from cutworms. If I’m able to help them get rid of the cutworms at some point, I will be absolutely thrilled!”

Visit the Organic Science Cluster 4 website to watch a new film featuring Dr. Lefebvre’s research: Tracking the Elusive Cutworm.