Those leaves are falling in some parts of the country, and others are still waiting for peak foliage season. But no matter where you are, the autumn harvest of apples and pears, along with the frost on the pumpkins, is evoking thoughts of winter. But the orchard isn’t quite ready for a long winter’s nap, and neither are you. There are important chores to be done!
The end of the growing season doesn’t mean the end of concerns, as every orchard grower knows. After the fruit is picked, much work remains. When the leaves have fallen, protection against diseases such as apple scab, cherry leaf spot, powdery mildew and peach leaf curl can begin. By taking steps in autumn, the volume of overwintering fungal spores or other inoculum can be significantly reduced. It’s also a good time to attack aphids, borers and other pests which overwinter in the orchard.
In order to keep the orchard healthy and the trees in top form, here are some of the basic task needed to prepare for next season:
Dormant pruning of cankered wood – It will take several repeated passes through the orchard over autumn and winter to ensure all the dead wood is removed properly. Look for darker bark, split bark, sunken spots and fungal spores or white protrusion indicating the wood is dead.
Check for signs of fire blight, and remove any cankers and about 12 inches of wood, pruning back to older, more resistant wood. Leaves will remain attached to branches with fire blight. Any pruned wood should be removed from the orchard and burned.
Removal of significantly diseased trees should also occur now, to prevent diseases from overwintering and spreading.
Fruit, leaves – Remove any fruit from the branches and clean up all drops. Fruit left in the orchard can harbor pests and diseases. Leaves should be removed, shredded or flail mowed to speed up decomposition. In addition, urea can be applied in autumn, either before leaf drop or onto fallen leaves. Urea applications assist in the rapid decomposition of leaves, and inhibits bacterial canker in nuts and stone fruits. It’s also effective against apple scab. Marssonina blotch, a problem for growers in regions such as Pennsylvania, New York and New Jersey this year, as well as in warmer climates, is also controlled with urea applications to fallen leaves.
In order to speed up sanitation chores, some growers defoliate trees using urea, copper or zinc. The leaves need to produce carbohydrates for the trees to store in the winter. Penn State pomologist Dr. Jim Schupp advises that growers wait until after the first frost – to allow the leaves to do their jobs – before defoliating trees.
Fall foliar urea applications can also help increase spur leaf size and total leaf area and have been shown to increase next season fruiting in apples and cherries.
Remove bins – Wooden bins, crates, wood piles and stumps make a cozy home for plum curculio, coddling moth and other insect pests. Remove these habitats from the orchard (and nearby areas) and your overwintering population will be reduced.
Mow weeds – Keep rodents and the tree damage they cause at bay by mowing down weeds around the tree trunks, for about a three feet radius. This also reduces deer rubbing.
Physical barriers – Young trees may benefit from a protective guard to prevent rodents from girdling the trunks. Guards should extend down into the soil several inches, and up the trunk several feet.
Water – Trees should be kept adequately (but not too) moist to support root growth until the ground freezes.
Apply protectants – Dormant oil spray, applied in autumn and winter, also protect from a variety of culprits, both microbial disease agents and insect pests.
Pear psylla adults migrate to leaf litter or protected areas in the tree to overwinter. A dormant oil spray in autumn can control these. Aphid and mite eggs, peach tree borer and scale can also be controlled with dormant oil sprays.
Coryneum blight spores land on leaf scars, which occur after the leaves fall. Knocking off remaining leaves after 50% have fallen naturally, and spraying copper sulfate (among other options), will prevent the fungus from infecting trees via the scars.
On cherries, bacterial canker also enters the tree via leaf scars. Applications of fixed copper or Bordeaux Mixture in mid-autumn can decrease inoculum.
Peach growers can only manage peach leaf curl in autumn, when the fallen leaves expose the spores, Dr. Kari Peter, Penn State, wrote in a recent post. When the leaves drop, an immediate application of control products is needed.
“Spray the trees with a fungicide, such as copper, ziram, lime sulfur or chlorothalonil. If you are unable to apply your spray this fall, fungicides can be applied during late winter before bud swell and before any drastic warm ups during late winter,” Peter advised.
Prevent sunscald – When bark warms up in the sun, but the temperatures drop at night, sunscald occurs and can kill the bark. Tree wraps or white paint on young trees offers protection. Cytospora canker can occur following sunscald, due to bark damage.
Cleaning up the orchard each autumn is the best way to ensure a healthy start for next season.