Prime Source Chlorothalonil 82.5DF Select Fungicide

5 out of 5 stars 1 Reviews | 8 Q&A

Prime Source Chlorothalonil 82.5DF Select Fungicide

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1 Review | 8 Q&A

Product Overview

Prime Source Chlorothalonil 82.5DF Select is a distinguished disease control agent for a wide variety of plant diseases. It offers a contact, preventive, and multi-site mode of action to impede or stop the increase of resistance to single-site fungicides. Prime Source Chlorothalonil 82.5DF Select features an easy to use dry flowable formulation and has natural adhesion to the plant surface. It is labeled for use on cool and warm season landscape ornamentals, conifers, and turfgrasses. It effectively obstructs algae, anthracnose, brown patch, dollar spot, fusarium, leaf spot, rust and more.

Features and Specs

Active Ingredient Chlorothalonil 82.5%
Target pests Turf Diseases: Algae, Anthracnose, Brown Blight, Brown Patch, Copper Spot, Dichondra Leafspot, Dollar Spot, Fusarium, Gray Leafspot, Gray Snow Mold, Leaf Spot, Melting Out, Red Thread, Rust, Stem Rust

Ornamental Diseases: Flower Spots, Leaf Spots, Flower Blights, Foliar Blights
For use in Commercial: Golf courses (Cool & Warm-Season Turf-grass), Landscape Ornamentals and Conifers
Application See label for specific application instructions
Pet safe Yes, if used as directed on Label (Toxic to aquatic invertebrates and wildlife)
Yield Conifers: 1 acre (1.36 to 5 lbs)
Golf course fairways: 1,000 sq ft (1.8 to 5.0 oz)
Golf course tees and greens: 1,000 sq ft (1.8 to 5.0 oz)
Ornamentals: 100 gallons of water (0.9 to 2.5 lbs)
Formulation Professional Product
Group M5 Fungicide
Special Features No Resistance with Repeated Use
Long Residual
Shipping Weight 5.49 lbs
Manufacturer Prime Source
UPC 794504354065
EPA Registration 89442-6


Diseases controlled:

  • Actinopelte leaf spot
  • Algal scum
  • Alternaria leaf spot or leaf blight
  • Anthracnose
  • Anthracnose (Gnomonia, Glomerella, Colletotrichum, Discula)
  • Black spot (Diplocarpon)
  • Blights
  • Botrytis blights
  • Botrytis flower spot, flower blight
  • Brown patch
  • Cephalosporium leafspot
  • Cercospora leafspot
  • Cerosporidium leafspot
  • Copper spot
  • Corynespora stem and leaf spots
  • Curvularia flower spot
  • Curvularia leafspot
  • Cylindrocladium stem canker
  • Dactylaria leafspot
  • Dichondra leaf spot
  • Didymellina leafspot
  • Dollar spot
  • Drechslera (Bipolaris) leafspots, inkspot
  • Erysiphe cichoracearum (powdery mildew) Microsphaera spp.
  • Fabraea (Entomosporium) leafspot
  • Fusarium (Gibberella) leafspot
  • Fusarium (Microdocium) Patch
  • Gloeosporium black leafspot
  • Gray Snow Mold
  • Gray leaf spot
  • Gymnosporangium spp. (rust) Puccinia spp.
  • Leaf spot, Melting Out, Brown blight
  • Marssonina leafspot
  • Monilinia blossom blight
  • Monilinia blossom blight, twig blight
  • Mycosphaerella ray blight
  • Myrothecium leafspot, brown rot
  • Ovulinia flower blight
  • Phyllosticta leafspot
  • Phytophthora leaf blight, dieback
  • Pucciniastrum hydrangeae (rust) Puccinia spp.
  • Ramularia leaf spot
  • Red thread
  • Rhizoctonia web blight
  • Rhizopus blossom blight
  • Scab (Venturia)
  • Sclerotinia flower blight
  • Septoria leafspot
  • Shothole (Stigmina)
  • Sphaeropsis leafspot
  • Sphaerotheca fuliginea (powdery mildew) Microsphaera spp.
  • Stagonospora leaf scorch
  • Stem rust (bluegrass)
  • Tan leafspot (Curvularia)
  • Taphrina blister
  • Volutella leaf blight

Application Rates

  • Conifers: 1.36 to 5 lbs/acre
  • Golf course fairways: 1.8 to 5.0 oz/1,000 sq ft.
  • Golf course tees and greens: 1.8 to 5.0 oz/1,000 sq ft.
  • Ornamentals: 0.9 to 2.5 lbs/100 gallons of water

General Precautions and Restrictions

Do not apply this within 150 feet (for aerial and air-blast application); or 25 feet (for ground applications) from marine/estuarine water bodies unless there is an untreated buffer area of that width between the area to be treated and the water body.

Avoiding spray drift at the application site is the responsibility of the applicator. The interaction of many equipment-and-weather related factors determine the potential for spray drift. The applicator and the grower are responsible for considering all these factors when making decisions. The following drift management requirements must be followed to avoid off-target drift movement from aerial applications to agricultural field crops. These requirements do not apply to forestry applications, public health uses or to applications using dry formulations.

  1. The distance of the outer most nozzles on the boom must not exceed 3/4 the length of the wingspan or rotor.
  2. Nozzles must always point backward parallel with the air stream and never be pointed downwards more than 45 degrees.
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  • 5 of 5 Stars

    Prime Source Chlorothalonil 82.5DF Select

    By Edward on 06/19/2020

    I tried other fungicides from my local nursery over the last three years to treat red thread, brown spot and gray snow with no results. I am seeing great results after two applications of Prime Source Chlorothalonil 82.5DF Select. I am very happy with this product. Before buying read all instructions. You'll have to do some math to figure how much product to mix. I bought a small digital scale, a good quality pump sprayer and pesticide flags.

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    7 of 8 people found this review helpful

Questions & Answers

Have a question about this product?
What are the mixing directions when using a backpack sprayer to apply Prime Source Chlorothalonil 82.5DF Select?

I battle brown patch on my St. Augustine yard. I want to alternate Chlorothalonil 82.5DF with other treatments. I'm guessing 1 oz per gallon of water when mixing for a backpack sprayer. Is that about the correct amount? I realize it depends on several factors. Also can I mix in an insecticide such as Talstar or Bilfen when spraying? Thank you for your assistance.


To treat brown patch using Prime Source Chlorothalonil 82.5DF Select on turfgrass, you would use 1.8 - 3.25 oz per 1,000 square feet. Using 1 oz per gallon of water would be fine if that gallon is only covering about 300-500 square feet. Typically 1 gallon of solution covers 1,000 square feet in a hand pump sprayer.

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11 of 13 people found this answer helpful

Is the Prime Source Chlorothalonil 82.5DF distributed in fluid ounces or by weight?

Since this is a dry flowable, I assume when you need to apply 1.8 - 3.25 oz per 1,000 square feet, the 1.8 - 3.25 oz is by weight on a scale, not volume/fluid ounce. Correct?


Prime Source Chlorothalonil 82.5DF Select  is a dry flowable powder and is measured and distributed by weight in ounces.  

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5 of 7 people found this answer helpful

What is the setting rate of Prime Source Chlorothalonil 82.5 DF when using an Ortho Dial-n-spray?

I would be treating tall fescue in a residential lawn for brown spot control.


Prime Source Chlorothalonil 82.5 DF Select is not for use in any type of hose end applicator. It must be used in a tank sprayer and per the product label for brown patch is mixed at 1.82 to 3.25 ounces per 1000 sq/ft and can be reapplied every 7-14 days to maintain control of the disease and prevent it. 

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2 of 3 people found this answer helpful

Can Prime Source Chlorothalonil 82.5DF Select be used to control mild Volutella Blight of Pachysandra?

First: Thanks to the two ladies for answering my questions of about 10 days ago. I am updating my cheat sheet. Second: Have about 500 sq ft of pachysandra with approximately 1 in 100 leaves showing volutella blight. Am reading much conflicting information about what to use for control. Some say Daconil. Others say copper. Others say Daconil is a preventative and will not treat established fungus. The label suggests otherwise. Before I call a professional I would like to try myself. Can you recommend something? I prefer liquid concentrates but will consider anything. If you have something liquid, please advise mixture rate for a hand held 1 gallon pump up garden sprayer. Also, how long till the product is rain tight. I have a Solo hand crank spreader so granular product can be considered. Thank you.


Yes, Prime Source Chlorothalonil 82.5DF Select is labeled for Volutella Leaf Blight (Pachysandra). Per the product label you would apply at a rate of .125 oz per gallon to cover 1000 square feet. This product should be rainfast after about 6 hours. 

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2 of 4 people found this answer helpful

Can Prime Source Chlorothalonil 82.5DF Select be used as a drench?

I have Knock out Roses, Indian Hawthorns and Holly's in my shrub beds. Can this product be used as a drench? If so what is the rate?


Prime Source Chlorothalonil 82.5DF Select is not labeled to be applied as a drench. It offers a protective barrier so it should be applied directly to foliage. The foliar rate will vary depending on what you are treating.  Please consult the product label to find the appropriate rate for your needs. 

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1 of 1 people found this answer helpful

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