Composting & Compost Tea for Disease Control

Composting is the biological decomposition of organic material under controlled conditions. The heat generated by decomposer microorganisms during composting can destroy most pathogens, weed seeds, and invertebrates. Beneficial microorganisms inhabiting some composts control diseases. For disease suppression compost must have a diversity of bacteria, fungi, protozoa, and nematodes.

Compost Starting Materials

The greater the variety and size of materials the better the diversity of bacteria, fungi, protozoa and nematodes in your compost. Have a mix of particle sizes in the composting materials, from very small up to one square inch.

Nitrogen (N)

The amount of nitrogen determines the temperature of the pile. Turn while hot a minimum of three times. A temperature of 135°F for three days will kill the pathogenic bacteria, Escherichia coli, Shigella, and Salmonella. Root feeding nematodes will also be killed at 135°F. Beneficial nematodes are not as heat sensitive and will live through the 135°F temperatures.


Add water to the 50% level while making the pile. At the 50% level the surface of the material shines (glistens). To determine the 50% level reach two feet into the pile at different locations, remove a hand full of material at give it the hardest squeeze possible. IF:
A. water runs out, too wet, turn and leave the surface open to dry; do this several times;
B. if only a drop of water comes out, Goldilocks, just right;
C. if no water comes out and compost keeps the squeezed shape, it’s OK;
D. if no water comes out and compost does not keep the squeezed shape, the compost is too dry, open the pile and add water.

Materials for Bacteria Dominated Compost

Bacteria dominated compost is used for foliar compost tea and/or a soil drench for annuals, row crops, and most vegetables.

A. 35% high N: legumes; manure (know diet of animals, if pellet fed, high potassium salt [KCl] that will kill microorganisms and plants); most soils have an abundance of potassium;

  • If fresh manure: poultry 15%; pig 5%; biosolids 5%
  • old manure: if black, buyers beware!! Check by smelling, IF: vinegar smell (acetic acid); or sour milk (butyric acid); or rotten egg (hydrogen sulfide); or ammonia (NH3), or vomit (volaric acid) is has been anaerobic (without oxygen). DO NOT USE.
  • If black, probably N is gone as ammonia gas and probably sulfur is gone as hydrogen sulfide gas. First one or two cuttings of lawn in spring can be classified as high N after that cuttings are classified as green stuff.

B. 35% green stuff (bacteria food): greens & coffee grounds are classified as green stuff

C. 30% woody stuff (fungi food): shredded paper is ok, but not too small.

Materials Fungal Dominated Compost

Fungal dominated compost can be used as a soil drench for perennials, berries, conifers, Rhododendrons, azalea, tomatoes, strawberries, and deciduous trees.

  1. 25% high N: (See Above)
  2. 30% green stuff: (See Above)
  3. 45% woody stuff: (See Above)

Composting Process

Monitor the temperature with a long stemmed thermometer. Three days at 135°F will kill pathogens. If temperature goes to 155-165°F this will start to kill the beneficials. Turn pile to cool.


Compost Pile NOT Heating?

Increase the N content.

Still not heating? Check moisture.

Still not heating? Maybe you have pesticides or heavy metals that may be killing the microorganisms. Add an inoculate of microorganisms and bacterial food (molasses). Added food is required because it takes added energy to detoxify pesticides and heavy metals.

Observations of the Compost Process

  • monitor temperature and moisture
  • look for fungal hyphae (little white threads)
  • smell the compost, it should smell like fresh soil (actinomycetes)

Best Compost

Up to 6 months old, the compost has more diversity of organisms. Two-year-old compost is not different than topsoil.

Compost Tea: Bucket Method

Materials list: (estimated cost $40.00)

  • 1 five gallon plastic bucket
  • 1 fish tank air pump
  • 4-5 air stones
  • 1 gang distributor
  • plastic tubing for connections
  • compost (enough to half fill your bucket)
  • 1-cup molasses – non-sulfured
  • water at 65-72?F (dechlorinate before adding to fill bucket)
  • 1 stick for stirring
  • 1 thermometer
  • duct tape


Bucket Method

  1. duct tape 4-5 air stones to the bottom of the five gallon plastic bucket
  2. connect air stones to gang distributor and fish tank air pump
  3. add inch or two of water to bucket
  4. add compost to fill bucket half full
  5. add more water to fill the about 3 inches from brim
  6. stir with stick being careful not to dislodge air stones
  7. add cup of molasses
  8. turn on air pump
  9. stir occasionally

Let this brew for 24-48 hours, stirring occasionally. The brew should smell good, like molasses. As time passes the molasses smell will disappear, as the bacteria have consumed it. If the brew begins to stink, it is because is has gone anaerobic, lack of oxygen. Get more air to your brew

At the end of the brew cycle, turn the air bubblers off at the gang distributor. Let the brew settle for 15-30 minutes. Strain the tea through a tea sieve, cheesecloth or tea towel. This is your compost tea for spraying and it MUST BE USED RIGHT AWAY.

How Much to Spray?

All the tea produced will vary in composition but if the compost was “good” and the tea brewer functioned properly, about 5 gallons of teas will cover one acre (43,560 square feet). For most of us this translates to about 1 pint per 1000 square feet.

To this approximation, realize that for foliar disease control you must cover a minimum of 70% of the leaf and stem surface, upper and lower.

Some Foliar Diseases Controlled by Compost Tea

  • late blight in potato and tomato (Phytopthora infestans)
  • early blight on tomato
  • gray mold on beans and strawberries (Botrytis cinerea)
  • Fusarium wilt (Fuarium oxysporum)
  • downy and powdery mildew on grapes ( Plasmopara viticola and Uncinula neactor)
  • powdery mildew on cucumbers (Sphaerotheca fuliginea)
  • apple and pear scab (Venturia inaequalis and V. p;irina)
  • fireblight on apples and pears (Erwinina amylora)
  • black spot on roses
  • snow mold on lawn grasses
  • dollar spot on lawn grasses