M. Grabowski, UMN Extension
Photo 1: Dead daylily leaves with visible dark spots from daylily leaf streak
The ground is cold, trees have dropped their leaves, and perennial and annual flowering plants have died back to the ground. Yet there is still time for a garden clean up that will reduce the number of pathogens and insect pests that survive from this season to the next. Sanitation, the removal of a infected plant material, is one of the basic steps of integrated pest management. It is a chemical free way to reduce pest damage in future growing seasons.
For sanitation to work you must remove the part of the plant that is infected with a pathogen or insect pest completely from the area and destroy it. Disease infected plant material can be burned, buried or composted. Check with local laws about burning plant material. Composting will kill pathogens and insects only if the pile gets hot. If your backyard compost pile is a slow pile of cold rot, consider taking infected material to a municipal compost site. These sites have so much plant residue to work with they manage the pile to heat up so the material breaks down quickly. It is important to realize that it might take a few years of good sanitation to truly get ahead of a fungal or bacterial plant disease. Fungi are known to survive 2-4 years in buried plant debris, bacteria typically can survive 1-2 years.
Here is a list of a few plant problems that would benefit from fall sanitation efforts.
M. Grabowski, UMN Extension
Photo 2: Fallen leaves at the base of this rose shrub should be cleaned up and removed from the garden to prevent overwintering of black spot
Trees and Shrubs
Apple Scab on crabapple or apple trees
Black Spot on rose
Any leaf spot disease like tar spot on maple, anthracnose or linden leaf blotch
Rake up and remove those leaves or they will produce fungal spores to start next years epidemic!
In the Flower Garden
Fungal and bacterial leaf spot diseases on perennials like Botrytis leaf spot on Peony, Daylily leaf streak, Iris leaf spot. Sorry, but sanitation will not help reduce powdery mildew.
Remove plants at ground level. Clean up all stems and fallen leaves. The pathogens survive in any infected plant material.
Four Lined Plant Bug
These insects lay eggs on plant material late in the growing season. In spring the new insects cause damage on these plants.
In the Vegetable Garden
Septoria Leaf Spot on tomato
Early Blight on Tomato
Bacterial leaf spot on pepper
Remove plants at ground level. Clean up all stems, fallen leaves, and rotten fruit. Infected plant material can be removed from the garden or tilled under.
These insects spend the winter as adults under plant debris. By removing plant debris in general the number of overwintering sites for these insects is reduced.