September IPM Insect Scouting Tips

Emily Zobel, Senior Agriculture Agent Associate | ezobel@umd.edu
University of Maryland Extension, Dorchester County

Soybeans: Continue scouting for corn earworm, stink bugs, and soybean looper in double-crop fields. Defoliation thresholds at R5 are 15% and between 20 and 30% at R6. Corn earworm pheromone trapping information for Maryland can be found at https://extension.umd.edu/resource/corn-earworm-pheromone-trapping. NC State Extension has a good CEW threshold calculator can be used to help decide if it is worth treating: https://www.ces.ncsu.edu/wp-content/uploads/2017/08/CEW-calculator-v0.006.html. Stink bug thresholds are 5 bugs per 15 sweeps until the soybeans reach the R7 stage, after which treatment for stink bugs is not necessary.

As the month progresses and fields get closer to harvest, sample stems in any field with a history of Dectes stem borer issues. If the field has a large stem infestation, prioritize that field for as timely a harvest as possible to reduce loss due to lodging.

Sorghum: Sugarcane aphids have been found on the Eastern Shore. This week’s cooler weather should slow down their reproduction rate, but if we get some warm days in September, that might change. To scout, check the 50 plants in 4 different locations at least 25 feet into the field. If honeydew is present, check the upper and lower canopy of 15-20 plants for aphids. Treatment thresholds are when the field has an average of 50 and 125 aphids per leaf or 30% infested plants with localized areas with honeydew present. David Owen from UDel recommends using Sefina, Sivanto, and Transform for control. See Texas A&M “Scouting Sugarcane Aphids” handout for more information.

July Insect Scouting Tips 

Emily Zobel, Agriculture Agent Associate
University of Maryland Extension, Dorchester County

Soybean: The usual defoliators are starting to arrive, including bean leaf beetle, Japanese beetle, grasshoppers, and caterpillars. Control may be needed if there is 30% defoliation during the seedling and vegetative stages and 15% defoliation once plants start to bloom through pod fill.

Adult Dectes Stem borer will be emerging over the next several weeks. Chemical control is not recommended since it would require multiple applications to reduce larval infestations, which is not economical. If a high number of adults are found, harvesting that field as soon as it matures will reduce losses associated with lodged plants.

Fields that have an open canopy, drought-stressed, or have recently had an insecticide applied are at higher risk for corn earworm (CEW). CEW larva can feed on flowers without impacting yields because soybeans overproduce flowers. However, feeding during pod development can affect yield. An economic threshold calculator is available to assist with management decisions: https://soybeans.ces.ncsu.edu/wp-content/uploads/2017/08/CEW-calculator-v0.006.html.

Field Corn:  As corn ears begin to form, check for stink bugs. Stink bugs will gather around the edges of fields, so scouting should be done at least 15 rows in. Thresholds are 1 stink bug per 4 plants when the ear is forming, and 1 stink bug per 2 plants from pollen shed to blister stage. Treatment is not recommended past the blister stage. Japanese beetles are minor defoliators and will clip corn silks, but control is not needed unless silks are cut back to less than ½ inch, and less than half the field has been pollinated.

Alfalfa: Once plants have hopper burn, there is no way to undo it, so continue scouting for leafhopper.  Since infestations are highly variable, individual fields should be scouted. If you are planning on selling your hay for horse feed, check for blister beetle as well since they produce cantharidin, which causes skin blisters on humans and can make horses sick.

Sorghum: Sugarcane aphids were found on the Eastern Shore last year and typically show up in fields late July and August. Check underside of leaves for insects.  Honeydew will turn leaves shiny and is an easy to see indicator that aphids are present.  Sugarcane aphids are light yellow with black cornicles, antennae, and feet. Thresholds depend on plant growth stage; at boot to milk, thresholds are 50 aphids per leaf on 25 – 30% of plants. There is documented resistance to resistance to pyrethroids.

 

Sulfoxaflor Registered for New Uses

The U.S. Environmental Protection Agency (EPA) has just issued a long-term approval for the insecticide sulfoxaflor, which the Agency has characterized as “an effective tool to control challenging pests with fewer environmental impacts.” The following information is from today’s EPA OPP Update.

“After conducting an extensive risk analysis, including the review of one of the agency’s largest datasets on the effects of a pesticide on bees, EPA is approving the use of sulfoxaflor on alfalfa, corn, cacao, grains (millet, oats), pineapple, sorghum, teff, teosinte, tree plantations, citrus, cotton, cucurbits (squash, cucumbers, watermelons, some gourds), soybeans, and strawberries.

EPA is providing long-term certainty for U.S. growers to use an important tool to protect crops and avoid potentially significant economic losses, while maintaining strong protection for pollinators,” said Alexandra Dapolito Dunn, assistant administrator for EPA’s Office of Chemical Safety and Pollution Prevention. “Today’s decision shows the agency’s commitment to making decisions that are based on sound science.”

Sulfoxaflor is an important and highly effective tool for growers that targets difficult pests such as sugarcane aphids and tarnished plant bugs, also known as lygus. These pests can damage crops and cause significant economic loss. Additionally, there are few viable alternatives for sulfoxaflor for these pests. In many cases, alternative insecticides may be effective only if applied repeatedly or in a tank mix, whereas sulfoxaflor often requires fewer applications, resulting in less risk to aquatic and terrestrial wildlife.

EPA’s registration also includes updated requirements for product labels, which will include crop-specific restrictions and pollinator protection language.

*Background*

In 2016, following a 2015 decision of the Ninth Circuit Court of Appeals vacating the registration of sulfoxaflor citing inadequate data on the effects on bees, EPA reevaluated the data and approved registrations that did not include crops that attract bees. The 2016 registration allowed fewer uses than the initial registration and included additional interim restrictions on application while new data on bees were being obtained. Today’s action, adding new uses, restoring previous uses, and removing certain application restrictions is backed by substantial data supporting the use of sulfoxaflor.

For additional information, please visit the EPA website.