Efficacy of Horse and Donkey Manure Compost as an Economical Alternative to Commercial Biofungicides for Control of Phytophthora spp. Root Rot in Lavender Plants

Problem

Crown root rot (Phytophthora spp.) is known to infect and kill lavender plants in the local areas, based on reported experiences of two lavender farms in local region (Onederings Lavender Farm, Clarksville; Peaceful Acres Lavender Farm, Martinsville). Commercially available biofungicides are very expensive, particularly products that are OMRI approved.

Scientific evidence has been published on some compost formulations that perform as biofungicides, antagonizing specific plant pathogens, eg Phytophthora spp. responsible for causing lavender root rot. The appropriate compost components may act as a food source and shelter for beneficial microorganisms (Hoitink & Fahy, 1986; Phae et al 1990; Hardy & Sivasithamparam, 1991; Fiddaman & Rossal, 1993).

While several studies have reported on cow and chicken manure compost effects, there is no definitive specific study confirming the efficacy of horse manure compost in controlling lavender root rot. There is only anecdotal observations on the possibility of horse manure compost having protective effects on lavender plant survival reported in a previous project done by Peaceful Acres Lavender Farm in 2010 funded study (FNC10-819) to investigate increasing lavender production. There is no data on donkey manure and any efficacy in compost. Additionally, it is reported that consistency and stability of the animal waste compost affected its efficacy in ameliorating plant disease.

There are many horse farms and large number of horses in the local region with accompanying manure management protocols. From the listing information on equinenow.com, searching within a 100 mile radius of Morrow OH, there are 1472 horse farms and 5210 horses for sale. There are likely many more horses than those listed, and thus sources of manure.

Learnings from this project will help our local region address two problems together – appropriate disposal of small farm animal wastes and biocontrol for disease affecting many crops.

Solution

Project will investigate how to solve two problems in one study: (1) appropriate disposal of animal wastes on a small farm, while producing a stable and consistent compost; (2) effective biocontrol of Phytophthora spp in young lavender plants grown in the local region farms.

(A) Establish consistent protocol for making horse/donkey manure compost by using template from Manure and Pasture Management for Horse Owners (by Dr. Lori K. Warren and Christine Sweet, 2003, Alberta Agriculture, Food and Rural Development). Process designed for small operation in size with the modified passive-turned piles system over a minimum 4-6 months duration. Initial batches started in October 2016 (50:50 mixture of horse/donkey manure with grass clippings and stall bedding straw/hay; targeting 30-50:1 C:N ratio), will be ready for use by spring 2017. Multiple bin system was built using recycled wood pallets and minimal cost. Costs documented and monitored for later comparison to using commercial biofungicides vs farm made compost.

(B) To determine the efficacy of horse/donkey manure compost in controlling lavender root rot. Hypotheses:

1. Soil amended with horse/donkey manure compost prevents root rot in young lavender plants

2. Soil amended with horse/donkey manure compost reduces injury/loss due to root rot infection in young lavender plants

3. Horse/donkey manure compost biocontrol is cheaper than commercial biofungicides

4. Horse/donkey manure compost for use in soil amendments in local farms can be a viable business in integrated sustainable farming

Study Design:

1. Prepare horse/donkey manure compost (in process described above)

2. Plant lavender cuttings spring 2017 (test negative for Phytophthora)

3. Treatment Groups:
a. Control – no horse/donkey manure (0%)
b. Horse/donkey manure (10-20%) (25-50%)
c. Horse/donkey manure + infected plants soil (source from Onederings Farm)

4. Measure survival of lavender plants in first year; document injury/loss due to root rot; test for root rot