Herbicides Used Preemergence, before weeds germinate
prometryn (Caparol 4L): PHI 40d, REI 12h, Group 5. Make a single broadcast application to established rhubarb when plants are dormant, before leaves have emerged from the crown. Apply 2.0-3.2 pt/A on coarse-textured soils and 3.2-4.0 pt/A on fine-textured soils. Apply in a minimum of 20 gallons of water per acre. Within the rate ranges given, use the lower rate on relatively coarse-textured soils and soils low in organic matter; use the higher specified rate on relatively fine-textured soils and soils high in organic matter.
s-metolachlor (Dual Magnum): PHI 62d, REI 12h, Group 15. Apply as a broadcast spray to soil surface in early spring prior to crop emergence. See label for specific rates on different soil types and organic matter content (0.67 to 1.33 pt/A). Will not control emerged weeds.
Herbicides Used for Pre- and Postemergence
halosulfuron (Sandea): PHI 60d, REI 12h, Group 2. Apply a single broadcast treatment of 0.5 to 1 oz/A in a minimum of 15 gal of water per acre to dormant rhubarb. The timing of the application should be as late as possible, or just prior to the breaking of rhubarb dormancy. Sandea may cause significant crop stunting. It is recommended that the user begin with a the lower rate to determine potential sensitivity to its use along with speed and degree of recovery. Provides both preemergence and postemergence control of many weed species, such as nutsedge and many broadleaf weeds. See the label for other precautions and a list of weeds controlled. For best results use a NIS if labeled weeds are emerged.
linuron (Lorox DF): REI 24h, Group 5. Apply as a single application of up to 3 lb/A as a dormant application (before leaves emerge from the crown). Make application as a broadcast or banded over-the-row treatment. Do not use on soils with less than 1% organic matter. Preemergence can control annual weeds as they germinate. Postemergence can control up to 2 inch tall annual grasses and up to 6 inch tall broadleaf weeds. See label for list of susceptible weeds.
mesotrione (Callisto): PHI 21d, REI 12h, Group 27. Can make a single application of up to 6 fl oz/A to dormant rhubarb (established beds only) prior to crop emergence. Applications to rhubarb that is not dormant may result in a temporary bleaching symptomology. Rainfall or irrigation after the Callisto Herbicide application may increase the risk of injury to emerging rhubarb. If weeds are emerged at the time of application it is recommended to add an adjuvant (crop oil at 1% v/v or NIS at 0.25% v/v).
quinclorac (QuinStar 4L): PHI 30, REI 12h, Group 4. Not registered in VT. Apply up to 12.6 fl oz/A as a foliar application. A second application may be made at least 30 days later. A crop oil concentrate at a rate of 2 pints per acre may be included in the spray mixture. Crop oil can cause injury if used under hot and humid conditions (do not use if temp (F) + humidity exceeds 150). May control field bindweed, hedge bindweed and Canada thistle. Do not apply to stressed crop or injury may occur. Do not plant any other crop other than Spring or Winter wheat or grain sorghum for 10 months following application. For alfalfa, clover, dry beans, flax, peas, lentils, safflower, Solanaceous family crops (and other sensitive species listed in PRODUCT INFORMATION section of label) do not replant for 24 months and conduct a bioassay prior to planting any of these crops.
Herbicides Used Postemergence, after weeds germinate
clethodim (Select Max): PHI 30d, 24hr REI, Group 1. Will control grass weeds only. Apply to actively growing grasses. See label for rate selection. Up to 4 applications permitted of 9 to 16 oz/A per application, minimum 14-days between applications, not to exceed 64 oz/A per year. Add 0.25% v:v nonionic surfactant (1 qt per 100 gal of spray). Can also be used as a spot-spray by mixing 1/3-2/3% (0.44 to 0.85 oz per gallon) Select Max and 0.25% v:v nonionic surfactant (0.33 oz per gallon). Spray to wet, but do not allow runoff of spray solution.
fluazifop (Fusilade DX): PHI 14d, REI 12h, Group 1. Will control grass weeds only. Apply up to 16 fl oz/A per application, minimum 14 days between applications. Maximum of 2 application permitted (not to exceed 32 oz/A per year). Apply to actively growing grasses (see product label for susceptible stage). Add either crop oil concentrate (0.5-1%, 0.5-1 gallon per 100 gallons of spray) or nonionic surfactant (0.25-0.5%, 1-2 qt per 100 gal of spray).
sethoxydim (Poast): PHI 30d, REI 12h, Group 1. Will control grass weeds only. Apply to actively growing grasses (see product label for susceptible stage). Maximum 1.5 pt/A per application, minimum 14-days between applications. Do not exceed 3 pt/A per year. Use with crop oil concentrate (2.0 pt/A) or methylated seed oil (1.5 pt/A). Note that crop oil can cause injury under hot and humid conditions. Can also be used as a spot-spray by mixing 1-1.5% (1.3 to 1.9 oz per gallon) Poast and 1% v:v crop oil concentrate (1.3 oz per gallon). Spray to wet, but do not allow runoff of spray solution.