Christmas Tree Weed Control TREE SCHOOL 2012

1. Christmas Tree Weed ControlTREE SCHOOL 2012 Paul Borgen Agronomy Manager Pratum Co-op Salem, OR

2. Resources • PNW Weed Control Handbook • Weeds of the West • Extension Publications • http://eesc.oregonstate.edu

4. Why control weeds? • Ease of harvest • Weed cover harbors pests • Compete for water and nutrients

5. Why control weeds? • Remember that control does not mean elimination • Benefits of leaving some vegetation

6. Keys to success • Know your weeds • Properly calibrated equipment • Know the proper rate

7. Keys to success • Start clean • Keep good records • Expect to do more than spray once and forget it

8. Weed Shifts • Weed infestations change depending on cultural practices • Cultivation promotes deep rooted plants • Mowing promotes prostrate weeds • Use of the same chemicals promote tolerant weed species (e.g. false dandelion, field bindweed, rattail fescue)

9. Preventing Weed Shifts • Combine a variety of cultural practices and chemical treatments • Understand the effect each practice or product has on your particular weed population • Alternate or combine chemicals effectively • Use different modes of action or chemical families • Target specific weeds or get broad spectrum

10. Preventing Weed Shifts • Keep records of how your practices affect weeds • Note how each herbicide affects each weed then tank-mix or alternate to achieve desired results • Reduce chance of promoting resistant species

11. Preventing Weed Shifts • Combine or rotate practices; • mechanical • hand removal • spot treatment • Band spray • broadcast spray • wipers • Provide cost effective, year-round control

12. Ground Covers • Remove unwanted weeds • Plant sub-clover or dwarf plant varieties • Regulate vegetation height with with sub-lethal rates of chemicals (chemical mowing) • Spot spray is necessary to keep unwanted weeds in check

13. Ground CoversBenefits • Reduces soil erosion • Improve traffic conditions in wet weather • Aids in harvest • Reduces mud on trees at harvest

14. Ground CoversDrawbacks • Monitoring and management is necessary during much of growing season • Frequent mowing is necessary to regulate height if chemicals are not an option • Still provides competition for tree and harbors pests • Difficult to maintain around tree bases

15. Soil Active Herbicides • Residual weed control • Pre-emergent activity, Post-emergent activity or both • Apply late Winter/early Spring • Most need rain to activate chemical in soil • Can combine with contact herbicides • Apply March through April

16. Foliar Active Herbicides • Leaf or stem contact control only • Little or no soil residual qualities • Apply to actively growing plants • 2 days to several weeks needed to show results • May be tank-mixed with some soil residual products

17. Product Review • Always read and follow label directions • Obtain specific directions for rates, timing, and application • The label is the law!

18. Triazines • Atrazine • Simazine • Velpar

19. Atrazine • Root absorbed • Water solubility 33 ppm (Simazine 3.5ppm) • Inhibits photosynthesis • OK on newly transplanted conifers

20. Velpar • Also inhibits photosynthesis • Water solubility 33,000 ppm • Not restricted use…except in WA • Better on perennial grasses

21. Post-emergent Grass Killers • Arrow • Poast / Vantage • Envoy Plus

22. Post-emergent Grass Killers • Inhibit the growing point • Very slow to show symptoms • Surfactants a must • Summer annual grasses

23. DNA’s • Surflan • Barricade • Pendulum