Weeds in Irrigated Pasture

Transcription

1 Weeds in Irrigated Pasture University of California Cooperative Extension All company names are used for educational examples put in common terminology and are not specifically endorsed by the University of California

2 Baltic Rush Cool Season Perennial Reproduces from seed & rhizomes Induced by wet and overgrazed conditions-indicates a disturbed site Occurs in soils that are not adequately drained Forage value is low Robert H. Mohlenbrock. USDA NRCS. 1995

3 Italian Thistle 2001 CDFA Br. Alfred Brousseau, Saint Mary's College

4 Italian Thistle cont.. Annual or Biennial Reproduce from seeds which can remain viable for eight years Found on road sides pasture and waste areas Induced by open space where seedlings have the opportunity to thrive

5 Bull Thistle Biennial Chokes out desirable forages Encouraged by overgrazed or barren land Grows from one to six feet Highly competitive 2002 Molly Elizabeth Bagley Br. Alfred Brousseau, Saint Mary's College

6 Henbit/Dead Nettle/Mint Annual, biennial, shortlived perennial Rarely grows over 12 inches Has square stems Cool season weed 2003 Michael Charters Induced by poor drainage and irrigation 2003 Michael Charters

7 Pigeon Grass/Green Foxtail/Wild Millet Annual Tolerates dry/moist/acidic and neutral soils Cannot grow is shade Requires well drained soils 2005 Louis-M. Landry 2005 Louis-M. Landry. Although Palatable before heading out, yield is greatly reduced

8 Sour/Curly Dock Perennial Known to produce oxalates which can poison cattle Commonly associated with over watering or weed infested irrigation ditches 2005 Louis-M. Landry Carol W. Witham

9 Velvetgrass Perennial grass Grows from feet tall Vigorous seedlings choke out more desirable grasses Induced by barren lands Charles Webber California Academy of Sci ences. Underground rhizomes make control difficult Monterey Bay Nursery, Inc.

10 Smut Grass Warm season perennial Normally unpalatable and grazing encourages the spread of seed Two species-1 is smaller and narrower Name comes from smut fungus which inhabits the plant in the humid south where it has been an ongoing problematic weed. technical/plants/pla49.html

11 Johnson Grass Perennial Reproduces from seeds and rhizomes Can cause nitrate and prussic acid poisoning if fed after stress from drought or frost 2001 CDFA 2001 CDFA

12 Barnyard Grass Summer Annual Can survive drought and flourish when moisture is present Grows from 6 inches to 6 feet 1 plant produces 40,000 seeds 2003 George W. Hartwell Conflicts with cool season irrigated pasture forages 2001 CDFA

13 Spiny Cocklebur Annual Difference between Spiny cocklebur (left) and the poisonous common cocklebur (below) is the lack of spines on common cocklebur The burs of each catch in the wool and tails of livestock Inhabits dry areas Beatrice F. Howitt California Academy of Sciences Br. Alfred Brousseau, Saint Mary's College

14 Chemical Control Postemergence Herbicides 2,4-D (Weedmaster, Weedone, Curtail, Grazon, etc) Dicamba (Banvel, Clarity,Vanquish, Weedmaster, etc.) Triclopyr (Redeem, Garlon 3A & 4, Remedy) Clopyralid (Transline)

15 Postemergence Herbicides cont.. Control broadleaf weeds (annual, biennial, & perennial) but not grasses, thus use of chemical can be related back to timing of tillage Dicamba and Triclopyr will also control woody plants such as blackberry and poison oak Glyphosphate (Roundup, and many variants) is not specific but can be used in various strategies

16 Postemergence Herbicides cont.. Strategies for herbicides Spot Spraying selective or non selective- takes time and inevitably will miss weeds Ropewick- economical, let cattle graze down the desired grasses then hit the weeds that are left Disc/Glyphosphate/Seed-more expensive, but effective

17 Detriments of Herbicides cont.. Withhold grazing times: 2,4-D-wait 7 days for dairy animals Dicamba/Banvel-do not harvest within 37 days of treatment Glyphosphate-wait 60 days Triclopyr/Redeem-see label Clopyralid/Transline-see label Water Quality Expense in time, labor, and product

18 It s Just Easier to Prevent Em Prevention Points Tillage: Timing Fall tillage encourages winter annuals Winter tillage encourages summer broadleaf weeds Type of tillage Plows/Discs-control annuals by burying them, but is not as effective on perennials

19 Prevention Points Type of tillage cont Harrows/Knives/Sweeps-work well in dry soil because they damage roots and separate roots from the shoots Harrows/Knives/Sweeps-have the opposite affect in wet soils. In wet soils the weed problem can even be enhanced

20 Mechanical Mowing Opens canopy for light to reach lower growing legumes and grasses Timing is critical To early and there is not enough biomass cut, which will trigger rapid growth by weeds To late and weeds will be allowed to go to seed

21 Water To little and we get weeds like star thistle, pigeon grass, spiny cocklebur, and barnyard grass To much and you get curly dock, henbit, and baltic rush 4 to 5 acre feet of water is sufficient per season 3 acre inches every 7 to 10 days

22 Open Ground Most grasses are actually more competitive so keep their numbers up Weeds such as thistles and other annuals take advantage of this opportunity because of their seed spreading ability Ideas to help are fall seeding/drilling clover seed fed in hay, correct stocking rate

23 Fertilizer Soil and plant tissue test Fertilizer isn t cheap so it s worth knowing what you need Fertilize to what you want to encourage Nitrogen to grasses Phosphorous to legumes

24 Questions??????? Forero, Reed, NRP-1193 (1993) Irrigated Pasture Production in the Sacramento Valley Baumann, Paul A., B-5038 (2004) Suggestions for Weed Control in Pasture and Forages DiTomaso, Joseph M., (1996) Yellow Starthistle: Chemical Control DiTomaso, Joseph M.,Principles of Weed Control Third Edition, Irrigated Pastures pgs University of California ANR, 4030-I, Growers Weed Identification Handbook Whitson, Burrill, Dewey, Cudney, Nelson, Lee, Parker,(2002) Weeds of the West 9 th Edition CalPhotos: Plants website University of California, Berkeley