Hemp dogbane

One increasing problem in forages – hay stands in particular – is Hemp dogbane. A perennial, Hemp dogbane grows to three to five feet tall and is confused with milkweed species due to similar appearance and presence of milky sap (NOTE: only fresh plants will show sap). Stems have a reddish tint at maturity and become woody at the base.

Long, horizontal rootstocks result in plant colonies. Plants start as a single taproot, but have been found to grow to a depth of almost six feet and spread laterally as much as ten feet in one season. This vigorous growth and a long growing season (it flowers from May to September) makes it a formidable foe in forage stands. The term dogbane is said to refer to the plant being poisonous to dogs. The same plant resins can also harm cattle under the right conditions.

If plants are few and forage stands are competitive, Hemp dogbane might not be a significant weed of concern. If any production “hiccup” (or combination of) occurs, Hemp dogbane can become a significant problem. From a cultural control standpoint, make sure stands are healthy, with good fertility and appropriate harvest management. A competitive grass stand is your best weapon against allowing Hemp dogbane to gain a foothold.

If pressure is increasing, mowing is an option. Missouri research suggests a mid-August mowing could help to reduce the size of weed patches the next season while frequent mowing throughout the season could reduce plant vigor and seed production. Unfortunately, even repeated mowing isn’t likely to eliminate this perennial.

Chemical control options include many of our common active ingredients: 2,4-D, dicamba, fluroxypyr and triclopyr. Missouri research suggests 2,4-D or fluroxypyr. Limited research in Kansas shows an advantage to products containing fluroxypyr. 

Monitor forage stands post-harvest for Hemp dogbane with an eye to a control program if warranted. For identification aids, check out the Hemp dogbane page at the Kansas Wildflowers and Grasses website at https://www.kswildflower.org/flower_details.php?flowerID=112 .

Japanese Beetles

Japanese beetle feeding damage is again evident across Northeast Kansas. Most easily identified by their metallic green color with coppery brown wing covers and small tufts of white hairs along the edge of the abdomen, they feed through upper leaf surfaces, leaving leaves looking lace-like or skeletonized. They love warm days, starting at the tops of ornamentals and vegetables (mainly) and moving downwards.

Control starts by minimizing plant stress. Water appropriately and remove smartweeds attractive to Japanese beetles. Physically remove (every other day) adults on cool mornings when movement/feeding is slowed and collect beetles in a container of rubbing alcohol or soapy water. Traps work, (not recommended) but may lure more adults to an area than would occur normally.

Chemical control options are effective, but repeat applications when high numbers are present, will be needed. Find a list of products in the most recent Kansas Insect Newsletter at https://entomology.k-state.edu/doc/extension-newsletters/2022/KSInsectNewsletter%2011.pdf. Always read and follow label directions, making any applications in early morning or late evening to avoid harm to pollinators. Natural enemies of spider mites will be harmed by these applications resulting in possible spider mite outbreaks as well. 

David Hallauer60 Posts

David Hallauer is the Meadowlark Extension District agent in the areas of horticulture and crops and soils.

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