Every year, dry bean growers struggle with insects and their impact on yield and quality. Some pests arrive early in the season, others later. Some do damage above ground while others do their business underground.
In this episode of RealAgriculture’s Edible Bean School, OMAFRA Canola and Edible Bean Specialist Meghan Moran highlights the big yield stealers in edible beans and offers tips on how growers can identify and better manage these pests.
As for insect damage, Moran says aboveground pests that arrive later in the season tend to have a bigger impact on grain quality, but there can be situations where belowground pests cause significant damage.
“I certainly saw fields with significant seedcorn maggot damage that needed to be replanted,” she notes. “The majority of the fields have CruiserMaxx seed treatment, so there is some protection against soil bugs and early season insects.
Moran divides edible insects into two categories: chewers and suckers. She says chewing insects can cause plant defoliation, which can impact yield, but this is less common than other insect problems. She adds that bean plants can withstand up to 35% defoliation before flowering and 15% during or after flowering.
Belowground pests lead to a reduction in plant stand, which may or may not lead to replanting or reduced yield. The most common chewers that growers see are the bean leaf beetle, western bean cutworm, European corn borer and Japanese beetle.
Chewers can cause yield loss by completely removing pin pods and small developing pods. They may chew whole beans in the pods, causing some yield loss; or they may just take a small bite out of a bean, creating a quality issue. Chewers can also cause quality problems by leaving a hole in the pods where diseases can enter and damage quality – some beans change color or discolor when exposed to oxygen.
Sucking insects have a syringe-like stylet or mouthpart which they insert into plant tissue and feed by sucking. These insects can feed on leaves and cause damage that results in yield loss, or they can feed directly on pods and beans, causing damage and loss of quality, including deformed, shriveled, or discolored beans. .
The suckers include potato leafhoppers which inject a protein that blocks the plant’s vascular tissue. This causes the edges of the leaves to turn yellow and wrinkled, with a characteristic yellow “V” shape beginning at the tip of the leaves. When severe, leaves appear scorched or necrotic, a condition commonly referred to as “hopper blight”.
In the video, Moran and host Bernard Tobin discuss the growing season and identify some key pests growers need to watch out for. They also review thresholds and identify the best way to control pests to minimize the impact on yield and quality.
Click here for more Edible Bean School videos.