weed control in carrot pnva, pasco rick boydston usda-ars prosser, wa
TRANSCRIPT
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Weed Control in Carrot PNVA, Pasco
Rick Boydston
USDA-ARS
Prosser, WA
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Carrot Weed Control
Carrots are very susceptible to competition from weeds (reduces carrot size, may cause malformed carrots, harvest losses)
eg. volunteer potato reduced carrot yield by 22 to 91% depending on potato densities.
Weeds can also act as hosts to insect pests, nematodes, and diseases of carrots.
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Cultural and Mechanical Weed Control in Carrots
Pre-sowing: • Various types of tillage implements and bedformers • Weeding implements for first flush of weeds
After sowing – pre-germination of carrots: • Flame or steam weeder • Harrow for blind weeding
After germination of carrots: • Various types of tine cultivators • Brush weeder • Steerage hoe (cultivator)• Hand hoe**Early weeding most critical on carrot yield (first 4-6 wks)**
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Stale seedbed – a fresh start
• Till soil and form beds• Allow weeds to germinate (irrigate)• Remove/control germinated weeds
– Manual removal – shallow tillage– In dry months, withhold irrigation– Flame– Herbicides
• Plant desirable species (minimal tillage)
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Alternative Strategy
• Prepare seedbed just 5-7 days prior to planting carrots to promote weed emergence prior to carrots – followed by flaming before carrots emerge.
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Flame weeding• Propane fueled burners• Idea is to just break cell membranes (dark
green color after flaming)• Controls primarily young, emerged annual
broadleaf weeds that have exposed growing points
• Grass and perennial weed control often poor, with re-growth after treatment– Grass weeds: growing point often below-ground– Perennial weeds: re-grow from root tissue
• Energy costs are high
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Prototype II in carrot:
–80-90% weeding effectiveness against annual weeds at 800C
–tendency for a higher marketable yield
–fuel consumption < 400 l ha-1
Band steamed
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Reduction in numbers of carrot seedlings and weeds by three different weeding implements (Mildura 2002)
Goosefoot tine cultivator
Finger-tine harrow Power rotary harrow
Carrots Weeds Carrots Weeds Carrots Weeds
67% 83% 33% 82% 0% 80%
Power rotary harrow
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Herbicides Registered for Carrot
Lorox (linuron) Poast (sethoxydim)Treflan (trifluralin) Fusilade (fluazifop-butyl)Sencor (metribuzin) Select (clethodim)Nortron (ethofumesate)
Prowl H2O (pendimethalin)
Roundup (glyphosate)Gramoxone (paraquat)
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Roundup, Gramoxone, Flaming
Prior to crop emergence – stale seedbed
Nonselective
Aim 2EW – carrot stand loss and yield loss when applied at rates of 1 or 2 fl oz/a
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Trifluralin (Treflan, others)
Preplant incorporated treatment for control of annual grasses and broadleaves
Soil Texture Treflan 4EC (pints)
Coarse 1
Medium 1.25 – 1.5
Fine 1.5 - 2
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Lorox 50DFStatus: Primary carrot herbicide “Do not apply to sand or loamy sand. Do not use
on soils with less than 1% organic matter”Use: PRE and POST control of most broadleaves
and annual grasses; Max. 2 lb ai/a/yrConcerns: POST applications at temp >85F can
burn carrots; some weeds have developed resistance to PS II inhibitors
POST - Wait 2 wks or more after first applicationCarrots must have 2 lvs or more (~3 inches tall)
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Sencor 75DF
Triazine, PS II inhibitorUse: POST control of annual broadleaves
when carrots have 5-6 leavesConcerns:
May burn carrots at temp <55 or >85FSensitive varietiesDo not tank mixWeed resistance
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Fusilade, Poast, Select
Use: POST grass control; volunteer small grains
Avoid tank mixes with Lorox or Sencor
Avoid applying to water stressed grasses
Always use adjuvants according to label
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Prowl H2O (3.8 CS)
Use: 2 pts/acre (max. 2 pts/season)
- Postplant, preemergence w/in 2 days of planting
- Layby as a directed spray before weed emergence.
Chemigation – only prior to carrot emergence.
Possible substitute for Treflan
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Prowl H2O (pendimethalin)
Kochia Lambsquarters
Purslane Pigweed sp.Annual grasses
Spotted spurge
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Nortron (Ethofumesate)• Labeled in OR and WA• Bayer - sugarbeet, grass seed herbicide• 1.5 – 2 lb ai/a (48 – 64 fl oz/a)• PRE 48 oz coarse soils
64 oz med and fine soils• Early POST (PRE to weeds) – 64 fl oz
(2-4 leaf carrot)
Max 128 fl oz (1 gal) per season
• Rotation crop interval – 12 month• Some carrot leaf fusion at higher doses
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Nortron (Ethofumesate)
Kochia Lambsquarters Chickweed
Russian thistleBlack NightshadeSmartweed/ladysthumb
Purslane Redroot Pigweed Volunteer Potato
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Nortron –grass weed control
• Barnyardgrass• Green foxtail• Yellow foxtail• Large crabgrass• Downy brome• Wild oat• Volunteer grains
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Volunteer potato height (inches) at time of weed removal
0 5 10 15 20 25 30
Ca
rro
t yi
eld
(%
)
20
40
60
80
100
120
Volunteer potato density (number per 100 square feet)
0 20 40 60 80
Ca
rro
t yi
eld
loss
(%
)
0
20
40
60
80
100
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• Nortron applied PRE delayed potato emergence, stunted potato growth, and caused epinastic growth on potato.
May 15, 2003 – Delayed potato emergence
Carrot Trial 2003
Nortron also applied POST at 2 leaf stage of carrot (potatoes had 6 leaves).
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0
20
40
60
80
100
120
Etho1.5/2
Etho 2/2 Etho 4.0 None
Yield of Carrot treated with Nortron - 2003
Yield (% of HW Check)
PRE/POST
POST/POST POST
aa a
b
Reduced due to potato competition
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Summary
• Nortron applied PRE delayed potato emergence and applied POST reduced potato growth in carrots.
• Sequential applications of Nortron 1.5/2 lb ai/a (PRE/POST) reduced number and weight of potato tubers and prevented carrot yield loss from volunteer potato.
• Sequential applications of Nortron and Caparol applied POST also provided good potato control without reducing carrot yields.
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Caparol 4F – NOT Labeled
Status: Possible label in 2008
PRE or POST control of broadleaves. Use as a substitute for Lorox (controls many
similar weeds as Lorox)
Volunteer potato - single or sequential POST applications of Caparol at 1 to 2 lb ai/a, were safe on carrot and suppressed volunteer potato.
Mode of action similar to Lorox (PS II inhibitor); potential crop stunting
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Dual Magnum – NOT labeled in WA
Status: 24c label in Oregon; growers must Indemnify Syngenta before use
Use: PRE control of nutsedge, annual grasses, pigweeds, and nightshades.Keep rates low to avoid crop damage
Concerns: Stand thinning on sandy soils
Future: Use with Lorox for nutsedge and crabgrass, and resistant pigweed control
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Summary
• Organic systems: stale seedbed, flame, cultivation, hand-weed
• Prowl H2O – pre or post directed, 2 pts/a
grass and small seeded broadleaf weeds• Nortron – pre (48-64 fl oz), post (64 fl oz)
volunteer potato suppression, grasses, and selected broadleaf weeds
Future labels?? Caparol – pre and post
Dual – pre for nutsedge, grasses
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Crossing paths Crossing paths on their on their respective respective journeys of journeys of destiny, destiny, Johnny Johnny Appleseed and Appleseed and Irving Irving Ragweed nod Ragweed nod “hello.”“hello.”