J. Ferrell Extension Weed Specialist of Onsite PPTs...Don’t assume your herbicide will kill every...
27
Why herbicides fail J. Ferrell Extension Weed Specialist
Transcript of J. Ferrell Extension Weed Specialist of Onsite PPTs...Don’t assume your herbicide will kill every...
Why herbicides fail
J. Ferrell Extension Weed Specialist
Where we are today
• Herbicides are more potent and forgiving than ever before.
Why do herbicides fail?
• Generally speaking, applicator error.
• Not going to discuss improper calculation, rain-off, or forgetting to add the herbicide to the sprayer.
Don’t assume your herbicide will kill every weed
• Milestone VM controls many weeds, but not all of them:
Tropical soda apple - yes Blackberry - no
James H. Miller. USDA Forest Service. Invasive Plants of the Eastern United States CD-ROM
Plant Size
Application timing
• Annuals – germinate from seed, produce seed, die within 1 yr. – Spanish needles, ragweed, etc.
• Perennials – emerge from rootstock, produce seed, go dormant. – Blackberry, trees, etc.
Annual
Control of Annual Weeds
0
20
40
60
80
100
120
Emerg. Seed. Veg. Flower Mat.
Wee
d C
ontr
ol
Perennials Control of Perennial Weeds
0
10
20
30
40
50
60
70
80
90
100
Dorm. Veg. Bud Flower Fruiting Fall
Wee
d C
ontr
ol
Drought
• Slow plant growth. More time for the plant to disassemble the herbicide.
• Cuticle thickness.
Adjuvants
• Can greatly improve herbicide uptake
Leaf Surface
No adjuvant
adjuvant
Reduction of Droplet Surface Tension
Surfactants vs Oils
• Surfactants simply flatten out the droplet.
• Oils (methylated seed oils) will partially dissolve leaf waxes.
Why not use MSO all the time?
• Surfactant - $5 per 100 gal water
• MSO - $10-20 per 100 gal water
Application technique
• More is not always better.
More is not better
100% spray retention 30% spray retention
Why do they fail?
• Misidentified the weed • Wrong herbicide • Weed size • Application timing • Adjuvant selection • Drought • Improper spray technique
