Planting cover crops outperformed both preventative and reactive use of pesticides in reducing pest damage during a three-year experiment in a corn-soy rotation.
Using either oats or cereal rye as a cover crop, scientists at Pennsylvania State University demonstrated that vegetation cover during May had significantly more of an impact on early-season damage caused by invertebrates to the cash crops than either using neonicotinoid seed coatings or applying a broad-spectrum insecticide when a pest threshold was met.
“Our goal was to understand whether a certain conservation practice—planting cover crops—increased predator activity and biological control and whether using neonicotinoid coatings disrupted these benefits,” they wrote in the journal Ecological Applications.
“Furthermore, we wanted to know whether deploying insecticides through an integrated pest management (IPM) framework was more compatible with conservation practices than preventative pest management (PPM).”
Predator provision
The success of the cover crops is likely to be linked to them significantly increasing the presence of potential predators of pests, and so improving the efficacy of biological control, they said. Such natural enemy populations are aided by the provision of varied habitat and alternative prey due to planting of the crops outside the main cash crop growing season.
In contrast, both the neonicotinoid seed coatings and the pyrethroid insecticide used in the PPM and IPM approaches reduced predator activity, and did not guarantee either effective pest control or greater yields. In fact, using the pyrethroid insecticide reduced yield for more than a year after it was applied, while having an effect on non-target insects for a similar amount of time.
“These results point to the importance of protecting and stewarding insecticides that are more targeted, such as neonicotinoids, so they can continue to remain effective and available; that is, use them within an IPM framework and deploy them only in response to economically significant insect pressure,” the authors said.
Season-long effects
While the seed coatings have a two-day window of protection after planting, effects of cover crops on predation were seen months after their growth period had finished. Additionally, there was greater yield of soy in the experimental plots using cover crops.
Despite the positive results, care should be taken to select the right cover species for the situation, and to continue effective monitoring of pests, the scientists stressed.