Weed Control for Grazed Pastures & Hay Fields

1. Weed Control for Grazed Pastures & Hay Fields Elizabethtown – ANR Update Session November 20, 2008 J. D. Green Extension Weed Scientist Plant & Soil Sciences University of Kentucky

3. Problematic Weeds* of Grass PasturesKY ANR agent survey (Nov 2007) • 69% Tall Ironweed • 64% Musk Thistle • 49% Buttercup spp. • 47% Spiny Amaranth (pigweed) • 38% Cocklebur • 24% Multiflora Rose • 22% Poison Hemlock • 20% Common Ragweed [also Lanceleaf Ragweed] • 20% Horsenettle • 11% Bull Thistle • Canada Thistle & Plumeless Thistle * Based on 5 most problematic weeds indicated

4. Reasons why weeds are controlled in pastures*KY ANR agent survey (Nov 2007) • 69% Reduced forage yield & carrying capacity • 40% Aesthetics • 38% Control weeds cows don’t eat • 38% Reduced forage quality • 11% Poisonous plants • 7% Spiny / thorny weeds * Agents requested to list top 2 reasons

5. Reasons why weeds are controlled in pastures*KY ANR agent survey (Nov 2007) • 69% Reduced forage yield & carrying capacity • 40% Aesthetics • 38% Control weeds cows don’t eat • 38% Reduced forage quality • 11% Poisonous plants • 7% Spiny / thorny weeds * Each survey participant listed top 2 reasons

6. Reasons why weeds are not controlled in pastures*KY ANR agent survey (Nov 2007) • 73% Do not want to kill clover • 60% Herbicides too expensive • 18% Why spray if cows eat weeds • 16% Land topography (steep terrain, etc.) • 13% Mowing too expensive • 11% Concern with grazing restrictions • 11% Poor / Low management • 9% Weeds are not a problem • 7% Spray equipment limitations * Each survey participant listed top 2 reasons

7. Target weeds for herbicide applications* KY ANR agent survey (Nov 2007) • 56% Thistles (musk thistle) • 29% Buttercup • 27% Tall Ironweed • 27% Broadleaf weeds • 13% Multiflora rose • 11% Spiny amaranth (pigweed) * ~16% Pasture acres sprayed with a herbicide

8. Herbicides Labeled for Broadleaf Weed Control in Grass Pastures - Kentucky 2,4-D [2,4-D (various products)] Clarity / Banvel [dicamba] Distinct / Overdrive [dicamba + diflufenzopyr] Weedmaster, etc. [dicamba + 2,4-D] Remedy / Remedy RTU[triclopyr] Crossbow [triclopyr + 2,4-D] Redeem R&P [triclopyr + clopyralid] Pasturegard [triclopyr + fluroxypyr] Milestone [aminopyralid] ForeFront R&P [aminopyralid + 2,4-D] Cimarron Max [metsulfuron+dicamba+2,4-D] Cimarron Plus [metsulfuron+chlorsulfuron]

9. Issues Which Limit Herbicide Use in Pastures/Hayfields Forages interseeded with legumes (eg. Clover) Time to wait before reseeding clovers 2,4-D products: ~ 6 to 8 weeks ?? Other herbicides: May be a longer waiting period after treatment ? Consult labels and other information sources

10. Cost of Herbicide Treatments *Does not include treatment cost for the application.

11. Issues Which Limit Herbicide Use in Pastures/Hayfields Timing of effective treatment Other crops have higher priority Failure to recognize the problem until after the fact

12. Poison Hemlock (Conium maculatum) Musk Thistle (Carduus nutans) Bull Thistle (Cirsium vulgare)

13. Issues Which Limit Herbicide Use in Pastures/Hayfields Sensitive crops growing nearby Tobacco, vegetable crops, grapes Rural home sites (ornamentals, home gardens)

16. Spray drift effect on tobacco from an application of Weedmaster (dicamba + 2,4-D) sprayed on a nearby pasture field Lesson Learned: Be cautious about where and when to apply herbicides (time of year, environmental conditions – wind direction and speed). Look for surrounding crops or other sensitive vegetation that may be nearby and know the characteristics of the herbicide product to be used.

19. Injury symptoms observed 2-3 weeks after tobacco was transplanted into the field Previous season field was pasture land Forefront R&P (aminopyralid) applied to pasture Lesson Learned: On land that will be rotated to tobacco or another sensitive crop do not apply aminopyralid [ForeFront R&P, Milestone], clopyralid [Redeem R&P], or other herbicides that may persist in the soil

20. ForeFront R&P(aminopyralid + 2,4-D) • Herbaceous broadleaf weeds • Including biennial thistles (musk thistle, bull thistle), Canada thistle, cocklebur, horsenettle, tall ironweed • Application rate: • Broadcast – 1.5 to 2.6 pt/A • Add surfactant (0.25 to 0.5% v/v) • Grazing and Haying Restriction • No restrictions for grazing • Do not harvest treated forage for hay within 7 days • Residues from aminopyralid-treated areas can remain in manure, compost, hay, or straw which can injury broadleaf crops (consult label guidelines) • Allow 3 days of grazing on untreated pasture before transfering animals to fields used to plant broadleaf crops

21. Roto-Wiper and Rope Wick Applicators

22. Tall Ironweed Control in Grazed PastureRockcastle Co, KY 2006-2007 Herbicide treatments applied September 12, 2006. All treatments applied with surfactant @ 0.25% v/v Source: J. D. Green and Tom Mills, Univ. of KY

23. Tall Ironweed and Horsenettle Control in Permanent Grass Pasture Breathitt Co., KY June 7, 2007 *Herbicide treatment applied August 31,2006 Source: J.D. Green and D. Ditsch, Univ. of Kentucky

24. Tall Ironweed Control • Mow pastures in mid- to late-summer • Allow tall ironweed to develop vegetative regrowth (12” to 20” tall) • Treat in the fall (August to early September) • Crossbow, PastureGard • [ triclopyr] • ForeFront R&P (Milestone) • [ aminopyralid ] • Reseed clover in the spring