Peter J. Dittmar and Jeffrey G. Williamson2
Blueberry growers use a system of turf and weed-free strips under the bushes. A weed-free zone under the bushes reduces the impact of weeds on blueberry bush growth. For the first 2–3 years, a strip 2–3 ft. wide is maintained weed free. After 3 years, the weed-free strip is widened to 4–5 ft. Turf strips are mowed or growth is chemically controlled on a regular basis. The turf minimizes erosion and provides an area for machinery and picking crews.
Nonchemical weed management practices are part of a complete weed management program. Cultivation was once a common practice for weed management in blueberries. This management practice is not as widely used now because of bush root pruning, erosion, and reduced radiant heat in the spring. Reduce the spread of weed species by controlling the plants before seeds are produced and by cleaning mowing equipment. Polyethylene or landscape fabric mulches provide weed control but can be cost prohibitive.
Herbicides available for weed control in blueberry are included in Tables 1 and 2. Because soil types in Florida vary, consult the labels for application rate restrictions based on soil type. Bearing bushes are blueberry bushes that are currently producing fruit. Nonbearing bushes are blueberry bushes that will not produce fruit for a year after application. The tables include preharvest intervals (PHI).
All herbicides should be directed to the base of the bushes; this method provides coverage of the weeds while minimizing the contact to the bushes. Young bushes should be protected with nonporous wraps or growth tubes to minimize uptake of the herbicide. This is especially important for systemic postemergence herbicides (for example, glyphosate) and contact burndown herbicides (for example, paraquat, diquat, and glufosinate).
Tank mixing can broaden the spectrum of weed control. A preemergence herbicide may only control the most problematic weed in the orchard and leave some weed species unaffected. A preemergence herbicide can be tank mixed with another preemergence herbicide that controls several weed species but not the most problematic weed in the orchard.
The most common method of tank mixing is a postemergence herbicide with a preemergence herbicide. This method provides control of the weeds that are above the soil surface and controls weeds for a longer period. Consult the label for compatible tank mixing partners. If concerned, use a jar filled with the herbicides and water then agitate the jar to see if the herbicides mix.
Practices for improving weed control with herbicides are as follows:
Herbicide selection. Preemergence herbicides control the weeds before they emerge from the seed or break the soil surface. Postemergence herbicides control weeds that have emerged through the soil surface.
Optimal timing. Preemergence herbicides should be applied in the early spring or fall before annual weeds emerge. Postemergence herbicide efficacy decreases as weeds grow. Consult the label for the correct size of weed to control.
Sufficient coverage. Herbicide labels require certain nozzle types or applications of a certain number of gallons per acre (GPA) or nozzle types forto ensure proper coverage. Before spraying, check that all nozzles have a correct spray pattern and correct output.
Adequate activation. Preemergence herbicides require rainfall or irrigation to move the herbicide into the soil profile where the weed seeds are present. Postemergence herbicides require a nonionic surfactant, crop oil concentrate, or methylated seed oil for increased herbicide uptake.
Herbicide-resistant weeds are a continuous and growing concern for farmers. Methods for reducing the chances of herbicide resistance include the following:
Rotate herbicide'sherbicides’ mode of action. Each herbicide's mode of action (MOA) is assigned a numerical group. Tables 1 and 2 list the MOA for each herbicide. Rotate between modes of action/numerical groups.
Include multiple MOA. Many herbicides allow for tank mixing herbicides. It is often suggested that preemergence herbicides be tank mixed with a postemergence herbicide. This method controls weeds that will emerge as well asboth weeds that have already and have not yet emerged.
Managing known resistance. If an area of the field is known to have a resistant weed species, use mechanical weed removal and prevent the weed from producing seeds or other methods of propagation or otherwise propagating itself. Please contact your county Extension agent to have the weed resistance confirmed and documented.
Preemergence chemical weed control in highbush blueberry
Common name (lb. a.i./acre) |
Trade name (product/acre) |
MOA |
Crop age |
Comments |
Dichlobenil 4–6 1.96–3.9 |
(Casoron®) 4 G 100–150 lb. (Casoron®) 1.4 CS 1.4–2.8 gal. |
20 |
Bearing / nonbearing |
|
Diuron 1.2–1.6 |
(Diuron, Karmex®, Karmex® XP) 80 WDG 1.5–2.0 lb. (Direx®) 4 L 1.2–1.6 qt. |
7 |
Bearing / nonbearing |
|
Flumioxazin 0.188–0.38 |
(Chateau®) 51 WDG 6–12 oz. |
14 |
Bearing / nonbearing |
|
Isoxaben 0.5–1.0 |
(Gallery®, Gallery® T&V) 75 DF 0.66–1.33 lb. |
12 |
Nonbearing |
|
Isoxaben + Oryzalin 2.0–4.0 + 0.5–1 |
(Snapshot®) 2.5 TG 100–200 lb. |
12 + 3 |
Nonbearing |
|
Mesotrione 0.09–0.19 |
(Callisto®) 4 L 3–6 fl. oz. |
27 |
Bearing / nonbearing |
|
Napropamide 4 |
(Devrinol®) 50 DF 8 lb. (Devrinol®) 10 G 40 lb. |
15 |
Bearing / nonbearing |
|
Norflurazon 2–4 |
(Solicam®) 80 WDG 2.5–5.0 lb. |
12 |
Bearing / nonbearing |
|
Oryzalin 2–4 |
(Oryzalin, Surflan®) 4 AS 2–4 qt. |
3 |
Bearing / nonbearing |
|
Pronamide 1–2 |
(Kerb®) 50 W 2–4 lb. |
3 |
Bearing / nonbearing |
|
Simazine 2–4 |
(Princep®) 90 WDG 2.2–4.4 lb. (Princep®) 4 L 2–4 qt. |
5 |
Bearing / nonbearing |
|
Terbacil (5) 0.4–1.6 |
(Sinbar®) 80 WP 0.5–2 lb. |
5 |
Bearing / nonbearing |
|
Postemergence chemical weed control in blueberry
Common name (lb. a.i./acre) |
Trade name (product/acre) |
MOA |
Crop age |
Comments |
Carfentrazone 0.016–0.031 |
(Aim®) 2 EC 1–2 fl. oz. (Aim®) 1.9 EW 1–2 fl. oz. |
14 |
Bearing / nonbearing |
|
Clethodim 0.07–0.13 |
(Select Max®) 2 EC 9–16 fl. oz. |
1 |
Bearing / nonbearing |
|
Diuron 1.2–1.6 |
(Diuron, Karmex®, or Karmex® XP) 80 WDG 1.5–2 lb. (Direx®) 4 L 1.2–1.6 qt. |
7 |
Bearing / nonbearing |
|
Diquat 0.7–0.9 |
(Diquat) 2 L 1.5–2.0 pt. |
22 |
Nonbearing |
|
Fluazifop 0.25–0.375 |
(Fusilade® DX) 2 EC 16–24 fl. oz. |
1 |
Nonbearing |
|
Glufosinate 1.0–1.5 |
(Rely® 280) 2.34 SL 48–82 fl. oz. |
10 |
Bearing / nonbearing |
|
Glyphosate 0.5–1.5 |
(Various formulations) |
9 |
Bearing / nonbearing |
|
Halosulfuron |
(Sandea) 75DF 1 to 4 yr. bushes 0.5-0.6 oz. >4 yr. bushes 0.5 to 1 oz. |
2 |
Bearing / nonbearing |
|
Mesotrione 0.09–0.19 |
(Callisto®) 4 L 3–6 fl. oz. |
27 |
Bearing / nonbearing |
|
Paraquat 0.56–1 |
(Gramoxone Inteon®) 2 SL 2–4 pt. (Firestorm®) 3 SL 1.3–2.7 pt. |
22 |
Bearing / nonbearing |
|
Pelargonic Acid |
(Scythe®) 3%–10% v/v |
27 |
Bearing / nonbearing |
|
Rimsulfuron 0.063 |
(Matrix®) SG 4 oz. |
2 |
Bearing / nonbearing |
|
Sethoxydim 0.3–0.5 |
(Poast®) 1.5 EC 1.5–2.5 pt. |
1 |
Bearing / nonbearing |
|
This document is HS90, one of a series of the Horticultural Sciences Department, UF/IFAS Extension. Original publication date October 1993. Revised June 2015. Reviewed January 2019. Visit the EDIS website at https://edis.ifas.ufl.edu for the currently supported version of this publication.
Peter J. Dittmar, assistant professor; and Jeffrey G. Williamson, professor, Horticultural Sciences Department; UF/IFAS Extension, Gainesville, FL 32611.
The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label. Use pesticides safely. Read and follow directions on the manufacturer's label.
The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.
U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.