New herbicides labeled for blueberries offer growers more choices in their weed control programs. It takes time to learn about new products and understand how they are best used. Herbicide changes are updated each year in the Michigan State University Extension Bulletin E-154 “Michigan Fruit Management Guide,” consult this publication for details. Below is a review of some of the newer materials and label changes for 2020.

Labeled in the last five years

Alion (indaziflam) is labeled for late fall or early spring use in highbush blueberries established at least one year. Alion is a preemergence (PRE) herbicide that only controls weeds as they germinate. It has no effect on emerged weeds or established perennials. It should be applied before weeds emerge or tank-mixed with a postemergence (POST) herbicide such as Roundup Ultra (glyphosate), Gramoxone (paraquat), Rely (glufosinate) or Aim (carfentrazone) to control emerged weeds. Alion has activity on a broad range of annual broadleaf and grass weeds. Do not use Alion on soil classed as sand, or with more than 20% gravel. Do not apply to plants with exposed roots. Apply 3.5-5 fluid ounces per acre and not more than 10 fluid ounces per acre per year.

Fusilade 2E (fluzifop-P) is a POST grass herbicide, which has the same mode of action (MOA) as Poast 1.5E (sethoxydim) and SelectMax 0.97E (clethodim). To be effective, these materials need be applied to actively growing grasses. There are growth stages specified on product label (annual grasses less than 8 inches tall and actively growing perennial grasses with 8 to 10 inches of new growth), but the earlier these products are applied to actively growing grasses, the better they will work rather than later as active growth is shutting down. Fusilade at higher rates is very effective against quackgrass. Apply 1-1.5 pints per acre and not more than 3 pints per acre per year. Preharvest interval (PHI) is one day.

Embed-Extra 3.8L (2,4-D choline salt) is a new formulation of 2,4-D that is labeled for use in blueberries. This is the first time 2,4-D has been labeled in blueberries, which are fairly sensitive to 2,4-D, which easily volatizes so the plants are exposed to 2,4-D as a vapor or gas. Embed utilizes the choline salt of 2,4-D and has reduced volatility and drift compared to other 2,4-D amine or ester formulations. To avoid direct contact with your blueberry plants, use directed or shielded application equipment. 2,4-D is an auxin-disruptor POST herbicide with activity on several annual and perennial broadleaves weeds such as dandelions, field bindweed and common milkweed. A directed or shielded application with 3 pints per acre (not more than 6 pints per acre per year) may be made in the spring or after harvest. PHI is 30 days.

Quinstar 4L (quinclorac) is another auxin-disruptor POST herbicide with activity on several annual and perennial broadleaves and grasses. It is very effective against large crabgrass, barnyardgrass, foxtails, catchweed bedstraw, clover, morningglory, bindweeds, lambsquarters, ragweed, Canada thistle and Russian thistle. A banded application to highbush blueberry and broadcast to lowbush blueberry at 12.6 fluid ounces per acre (not more than 25.2 fluid ounces per acre per year) may be made from the end of dormancy, through the season up to 30 days before harvest. The PHI is 30 days.

Labeled in the last few years

Devrinol XT (napropamide) is a PRE herbicide labeled for both non-bearing and bearing blueberries to apply in spring. Devrinol is safe on new plants and provides good control of annual grasses and some broadleaves if applied to a clean soil surface before weeds germinate. Apply 8 pounds per acre. Do not repeat in the same growing season.

Surflan 4 AS (oryzalin) is another PRE herbicide labeled for use on both non-bearing and bearing blueberries. It is not registered to use in lowbush blueberry. Rainfall or irrigation is needed to activate the product. Oryzalin only controls weeds as they germinate. It has no effect on emerged weeds or established perennials. It controls most annual grasses and a few annual broadleaves. Do not use on soils containing more than 5% organic matter.

Trellis 4.16 SC (isoxaben) is now labeled for both non-bearing and bearing blueberries except in lowbush blueberry. Trellis will be most useful in new plantings for PRE control of annual broadleaf weeds such as common lambsquarters, ragweed, black nightshade, horseweed and smartweed. It does not control grasses. Apply Trellis at 16 to 31 fluid ounces per acre in fall or spring before weeds emerge. If Trellis is applied after planting, wait until the soil is settled by rain or irrigation. This product is stable on the soil surface for up to 21 days and requires rainfall or irrigation for activation and incorporation during this time period. PHI is 60 days.

Dual Magnum 7.62 E (S-metolachlor) is a PRE herbicide labeled for both non-bearing and bearing blueberries for control of annual grasses and broadleaves and nutsedge. Use 0.67 pints per acre on young bushes on sandy soils and 1.33 pints per acre on large bushes on heavier soils. Only one application is allowed per season and it has 28 days PHI.

Zeus XC (sulfentrazone) is a PRE herbicide that is labeled for 3-year-old blueberries or older. Apply 8-12 fluid ounces per acre and no more than 12 fluid ounces per acre per year. Do not apply after petal fall unless a shielded sprayer is used. Zeus controls selected broadleaf weeds (pigweeds, smartweeds and black nightshade) and grasses as well as sedges. Like all PRE herbicides, Zeus is sensitive to your soil type and weed control may be reduced in soils with very low pH or high contents of organic matter and clay. Best control is achieved if 0.5 inches of rain or irrigation is received after application. PHI is three days.

Chateau SW (flumioxazin) is a PRE herbicide, which has been labeled for use at 6-12 fluid ounces per acre in spring or fall on blueberries that have been in the field for three or more years. Chateau controls many broadleaf and grass weeds, including chickweeds, dandelion, common groundsel, lambsquarters, eastern black nightshade, pigweeds, ragweed, horseweed and most annual grasses. Chateau provides some burndown of small weeds if combined with non-ionic surfactant (NIS) or crop oil concentrate (COC). PHI is seven days.

Stinger 3L (clopyralid) is a PRE and POST herbicide that is strong on weeds in the composite and legume families, such as thistles, asters, dandelion, goldenrod, ragweed, horseweed, clovers and wild bean or groundnut. It also controls nightshades, smartweeds, wild buckwheat and plantain. Stinger has some odd timing restrictions (see chart). Stinger is a growth regulator type herbicide and is most effective when weeds are up and growing. Rates are 2.6 to 5.3 fluid ounces per acre and not more than 10.6 fluid ounces per acre per year. PHI is 30 days.

Sandea 75 WG (halosulfuron) provides PRE and POST control of nutsedge and many broadleaf weeds such as pigweed, ragweed and smartweed. Treat nutsedge when three to five leaves are present. Two applications with non-ionic surfactant are most effective. The second application may need to be after harvest. Rates are 0.5 to 1 ounces per acre and no more than 2 ounces per acre per year. Do not use on ‘Elliott’ bushes less than 4 years in the field. PHI is 14 days.

Matrix 25 SG (rimsulfuron) has the same mode of action as Sandea. Matrix controls a broad spectrum of annual grasses and broadleaf weeds. Do not use Matrix on sandy soils or on bushes less than a year in the field. In low bush blueberry, can only apply in the vegetative (sprout) year growth stage. Apply 4 fluid ounces per acre per year with non-ionic surfactant. Avoid contacting growing shoots and leaves. Because Matrix has the same mode of action as Sandea, don’t use these products together or sequentially. PHI is 21 days.

Callisto 4 SC (mesotrione) is PRE and POST herbicide that is labeled for use before bloom. It has activity on most broadleaves and large crabgrass. In low bush blueberry, Callisto may only be applied in the non-bearing year. Rates are 3 to 6 fluid ounces per acre and not more than 6 fluid ounces per acre per year.

Application timing

Most herbicide labels include specific application times, others are less specific. Best timings for weed control and PHI vary and are not always specified. This table was developed to describe when herbicides should be applied. Always check the most recent herbicide label to ensure application timing, rates and other restrictions and to make sure that all applications are safe and legal.

Herbicide modes of action

Herbicides kill weeds by disrupting specific plant processes and they are classified based on their modes of action. If herbicides with the same mode of action are used repeatedly, resistant weed populations may develop. This table groups the common blueberry herbicides by their modes of action. The Weed Science Society of America (WSSA) has numbered these modes of action to make it easier for growers to recognize the mode of action. To avoid resistance, rotate between or use combinations with different groups.