Scouting key to identifying yield-robbing soybean pests
While high heat and drought conditions last year controlled some yield-robbing insect populations, including soybean aphids, this season may reveal a different story, caution DuPont Pioneer experts. Moderate temperatures and delayed planting, combined with aphids’ ability to overwinter, could increase the risk of this insect’s infestation.
Insect specialists recommend scouting for aphids this season and taking action to prevent the pest from impacting soybean yields. While scouting, you may also find new soybean pests in your fields.
“Identified as strong fliers with the ability to hitchhike, both brown marmorated stink bugs and kudzu bugs continue to migrate and increase populations,” said Paula Davis, DuPont Pioneer senior manager for insect and disease resistance traits. “Along with soybean aphids, these pests will challenge growers to closely monitor their fields and keep tabs on current threat levels.”
BMSB have already been detected in a number of states, up to 40 in total, including every state east of the Mississippi. Kudzu bugs have rapidly spread across 10 southeastern states since the first detection four years ago.
Soybean yields are reduced as a result of feeding damage from BMSB and kudzu bugs. Kudzu bug infestations in Georgia and South Carolina show an average soybean yield loss of 18 percent, with ranges up to 47 percent. Growers in Maryland have estimated yield losses greater than 50 percent at field edges as well as delayed maturity due to early feeding by BMSB.
Pioneer experts encourage close scouting and use of insecticides to manage risk from pest infestations.
The distinguishing soybean aphid characteristic is cornicles, or black “tail pipes” projecting from the rear of the abdomen. The pests are typically light green and less than one millimeter in length with an oval or pear shape. Symptoms of infestations include shortened plant height, curled leaves with yellow edges, excessive honeydew on leaves and the presence of ants. Excessive honeydew may also promote mold growth, reducing photosynthesis.
For maximum effectiveness, apply insecticide when populations reach threshold levels. The economic threshold to justify insecticides is 250 aphids per plant. Insecticides should be applied before the R5 plant stage and populations reach 1,000 aphids per plant. Soybean aphids pose a threat to soybean yields if economic threshold levels are left untreated—reducing production by more than 10 bushels per acre.
To distinguish BMSB from the brown stink bug—the term “marmorated” means having a marbled or streaked appearance—look for a distinct double white band on the antennae, alternating light and dark bands around the abdomen and red eyes. Soybeans are vulnerable to seed damage by BMSB after the R3 stage leading to deformed seeds and pod loss. In addition, soybean plants retain green stems and improperly mature. The pest may also increase the potential for ear molds and negatively impact seed quality in corn due to ear feeding injury.
“Damage can be caused by BMSB as well as bean leaf beetles and other stink bugs, and we need to consider the problems caused by the complex of pests,” according to Ron Hammond, Ohio State University Extension entomologist. “The concern is the amount of yield and money staying in the field due to the BMSB-induced damage and simultaneous pod feeding by the bean leaf beetle. It only takes one or two seeds per plant not being harvested, and you have an economic loss.”
Many insecticides are labeled for stink bug control, although BMSB may be more tolerant of many pesticides than other stink bugs.
Smaller than a stink bug, but larger than an aphid, adult kudzu bugs are shiny, 3.5 to 6 millimeters in length and brown to olive green in color with light freckled spots. The pests have red eyes and a broadly round tail end. Kudzu bugs induce stress by feeding on soybean stems and leaves, reducing pods per plant, seeds per pod and seed size. The pest may also reduce yields and cause harvest problems by delaying soybean maturity and causing green stem syndrome. Insecticide treatment must penetrate the canopy to effectively control kudzu bugs.