P&PDL Picture of the Week for
November 19, 2007

Fall Sanitation is Important to Reduce the Amount of Disease Carryover

Gail Ruhl, Sr. Plant Disease Diagnostician, Dept. of Botany & Plant Pathology, Purdue University

The parasitic fungi that cause leaf and fruit spots, powdery mildew, cankers, etc.  over-winter in the soil, in debris under the plants, in cracks in the bark and in ‘mummified’ fruit.  These fungi wait in a dormant state until the following spring when rains and warmer weather induce the production of spores which are then disseminated by wind and rain to infect plants during the growing season.

Sanitation is one of the most important methods of maintaining a healthy garden. Removal of infected plant material will reduce the amount of disease causing fungi present in the area, thus reducing the amount of potential disease for the next season.

Your sanitation regiment for ornamentals, trees, shrubs, fruits, and vegetables should include the following:

  • Prune out and destroy all dead and diseased branches.  Employ proper pruning techniques. (pdf file)

  • Remove fallen leaves and fruit to eliminate them as an over-wintering site of plant pathogens and insects.

  • Remove dried, mummified, fruits or vegetables, old flower heads and flower stalks. This plant material should be composted, buried or destroyed in some other fashion when removed from the garden.

  • If plants were severely infected, it is advisable to remove and destroy them.

  • Remove weeds.  They provide a winter habitat for fungi and insects, and seed for next year’s weed crop. 

In reality, sanitation is a year round process. Therefore, removal of infected leaves, flowers, fruit,and branches, as soon as problems appear, will reduce the spread of disease.

Click image to enlarge

Removal of foliage infected with black spot will help reduce the amount of fungal inoculum.

Pre-sanitation--Note flower stalks and weeds that will harbor diseases and pests over the winter

Post Sanitation--Garden areas cleaned of plant debris will provide an environment less
favorable to diseases and insects the following growing season.

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service