What's Up at the USDA Office?
Upcoming Deadlines/Dates
May 15 - August 1: Primary Nesting Season
July 15: Spring Crop Reporting
July 14: ERP Phase 2
July 14: PARP
submitted by Ben Cottrell, District Conservationist
Lately at the NRCS office, we have been conducting a Conservation Reserve Program status review. We wanted to touch on a problematic weed that has been found during several reviews and how to manage it. The information below is from goodoak.com. Japanese Knotweed, this fast growing, aggressive perennial was brought from Japan to the United Kingdom and North America in the 19th century for ornamental purposes. It forms massive colonies and is extremely difficult to eradicate. The upright stalks often curve outward from the center of the colony, growing up to 4” in a day to a total height of 5’-12’. Each hollow stalk is 1/2” to over 1” in diameter with characteristic purple spots. There are also prominent nodes along the stem from which leaves sprout in an alternate arrangement. Creamy-white flowers also arise from these nodes in upright, multi-branching stalks. New growth often has a maroon color to it, and young leaves unroll as they emerge.
Japanese knotweed (JK) has a massive and extensive root system which can reach up to 10’ deep and laterally over 20’ from the nearest stalk. These robust roots can tear up pavement and even damage building foundations. This species spreads primarily when fragments, as small as a pea, are moved to a new site in soil or on mowers. The World Conservation Union lists this species as one of the 100 worst invasive species globally. It has potential to be a particularly hazardous weed along lake-shores and stream corridors. It should be aggressively eradicated wherever it is found to prevent further spread.
Control Methods:
Organic: Mowing the entire colony to the ground every 2 weeks for 2 or more years should starve the roots and kill the colony. Covering the entirety of a small colony with a tarp or thick black plastic for 2-4 years may be effective, especially if as much root as possible can be dug up first. Excavation of the of the entire root system down to 3-6’ depth should remove most of the root mass, limiting resprouts.
Contaminated mowing and digging tools is the primary means by which this species spreads, so take care to clean equipment after use. Plant waste must be disposed of in a landfill (can be placed in your trash as long as they are in a heavy-duty trash bag) or incinerated.
Chemical: For small colonies, cut down mature stalks close to ground level and then pour a “cut-stump treatment”, as directed on the label of glyphosate (Round-Up®, etc.) down each hollow stem. As new young leaves resprout, spray them with a foliar spray of glyphosate. Repeat this diligently until the plant is completely eradicated.
Our preferred method of control is to cut the knotweed down to about 18” in height in late summer, just as they begin to flower. Then wait 4-6 weeks for them to regrow before applying a 0.25% to 0.5% foliar spray of Milestone® or Perspective herbicide. This chemical is not approved for use in or near aquatic environments so try Habitat® in these areas and use as directed on the label. A foliar application of glyphosate can also be used but is generally less effective. Either way, a follow-up check 1 month later is recommended to treat stems that were missed with the first treatment. Re-treatment will be needed for 2-4 years until no resprouts are found. These recommendations are not a substitute for the pesticide label. The label is the law; read it and follow the instructions before applying any pesticide.
Native Alternatives:
Aggressive native shrubs such as grey dogwood, common elderberry, and hazelnut seem to be good competitors with JK and will also provide screening.
