ALLEGANY CO., N.Y. — At this time of year homeowners are inundated with information dealing with the pros and cons of fall yard and garden cleanup. Some experts advise complete removal of fallen leaves, twigs, grass clippings and other plant debris before the onset of winter. Other authorities’ advice is to leave these materials in place to retard soil erosion and to recycle nutrients into the soil.
From a plant pathologist’s perspective, a few hours spent outdoors now, raking and carting, spading and pulling, bagging, burning or burying dead plant parts, may prevent or greatly reduce a number of potentially serious insect and disease problems during the next growing season.
Farmers and serious gardeners know that the fall cleanup of dead or dying leaves, vines, decaying fruit, and other plant parts is the single most important pest-control step they can take. By destroying weeds and removing corn stubble, for example, farmers can prevent serious infestations of next year’s crop by corn borers and cutworms. Potato, pepper, and tomato growers completely remove and dispose of decaying plant parts to protect next season’s investment from such devastating diseases as late blight, stem canker, and several bacterial diseases.
The importance of fall cleanup is often not stressed enough for homeowners whose ornamental plants can also benefit from proper sanitation. One of the most common leaf and twig diseases of trees are caused by the anthracnose fungi. They affect sycamores, white oaks, maples, birches, tulip poplars, and many other trees. These fungi rarely kill trees, but foliage in mid-summer is often severely infected, causing leaf spots, blotches, early leaf fall, and reduced tree vigor. While there are many different anthracnose fungi, they all have similar life cycles. After maturing on infected leaves, spores overwinter in fallen leaf litter. In the spring the spores are wind-carried or are rain-splashed to young tender leaves and shoots of susceptible trees. Raking and destroying infected leaves in the fall often prevents or severely reduces the recurrence of these pathogens. The same is true for the fungus that causes “tar spot” of maples, and several other foliar diseases of trees.
Other examples of agents that damage leaves, flowers and fruit include fungi that cause black spot of roses, apple scab, and powdery mildews of lilacs and other ornamentals. The life cycles of a number of insect pests also can be disrupted by disposal of fallen leaves, twigs and other plant parts. Elm leaf beetle, clover mite and boxelder populations can be greatly curtailed by proper yard sanitation. And let’s not forget those gutters, where fallen needles, leaves, bark, etc. not only clog drain pipes, but also serve as attractive material for carpenter ants which, then, may find their way into the house. Sanitation is a particularly effective control measure for those pests whose initial population size in the spring will determine the severity of the problem during the growing season. It is less useful, but still important, for those diseases and pests that have many so-called secondary cycles that repeatedly increase their population sizes during the crop’s active growth phase.
The collected leaf material and other debris may be burned or buried. Burning may not be an acceptable choice for everyone because it may not only invite the wrath of the fire marshal, but it also contributes to air pollution. Home composting is typically not recommended because the average home compost pile does not heat up enough to destroy pests or pathogens. That leaves burying of wastes, which, for some homeowners, is not a workable solution. However, many municipalities will haul away curbside-placed (bagged or unbagged) yard wastes and compost them properly in their large facilities.
Fall cleanup can be a small but significant part in an integrated approach to controlling pests and pathogens on farms, in gardens or in the landscape. Collectively, natural management methods can reduce the need for increasingly costly and environmentally unsafe pesticide use.
—Steven Jakobi, Master Gardener Volunteer
Cornell Cooperative Extension of Allegany County
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