Christmas Tree Weed Control TREE SCHOOL 2012 Paul Borgen Agronomy Manager Pratum Co-op Salem, OR

Resources PNW Weed Control Handbook PNW Weed Control Handbook Weeds of the West Weeds of the West Extension Publications Extension Publications

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

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

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

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

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

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

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

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

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

Ground Covers B enefits Reduces soil erosion Reduces soil erosion Improve traffic conditions in wet weather Improve traffic conditions in wet weather Aids in harvest Aids in harvest Reduces mud on trees at harvest Reduces mud on trees at harvest

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

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

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

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

Triazines Atrazine Atrazine Simazine Simazine Velpar Velpar

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

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

Post-emergent Grass Killers Arrow Arrow Poast / Vantage Poast / Vantage Envoy Plus Envoy Plus

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

DNA’s Surflan Surflan Barricade Barricade Pendulum Pendulum