Fruit diseases

Many gardeners are starting their fall garden and landscape clean-up - which is good and bad. Garden sanitation, if insects or diseases were a problem this year, is an important step to reduce problems next year. But we need to balance pest control with allowing habitat for beneficial insects and pollinators. So, how can that be done? 

It will be time to start pruning fruit trees later this month. As pruning begins, it's important to have a good skills at identifying fire blight symptoms and have a multi-pronged approach for control, especially in very susceptible trees. Pruning and sanitation are important control strategies, but improper cleaning of pruning equipment between cuts can easily spread the disease.

It's too early to begin fruit tree pruning now, but it's not too early to prepare. For homeowners with only a few fruit trees - who can choose the ideal time for pruning their trees - it's best to wait until just before new growth begins. This is typically late February into March. Wounds heal fastest when pruned at this time. This is especially important for tender fruit trees (apricot, peach, nectarine, sweet cherry); early pruning of these trees could lead to cold damage at the pruning sites.

Apple scab, caused by the fungusVenturia inaequalis, is one of the most important diseases of apples and crabapples in Nebraska. It causes decreased yield, lower fruit quality, thin tree canopies and reduced tree vigor. Nearly every year, the disease defoliates susceptible varieties of ornamental crabapple.

Fungicide control of apple scab on trees with a history of heavy infestation, begins at bud break, which is only a few weeks away.

As you begin pruning this spring, keep an eye out for a common problem found on plants in the stone fruit family called Black Knot. It's a widespread fungal disease that affects plum and cherry, and occasionally infects apricots, peaches and other plants in the Prunus genus, like chokecherry. Black knot is common throughout Nebraska in wild plum thickets.

Two odd diseases that may occur on home-grown peaches and plums are called peach leaf curl (photo above) and plum pockets. Peach leaf curl is common and widespread, and can be found in Nebraska wherever peaches are grown although it is usually not severe in the drier areas of western Nebraska. The disease is favored by the milder, wetter climate of eastern Nebraska.

Although leaf curl is principally a disease of peaches, nectarines also can be infected. Related fungi of the Taphrina genus cause similar diseases such as plum pockets and leaf blisters on oak, maple, and elm.

Fruit trees will soon be blooming, marking the beginning of another growing season. Many diseases become active during blooming, so it’s time to prepare to protect your trees and ensure a good harvest.

Last week we looked at winter drought and watering. But many gardeners also have questions about spring pruning. Specifically, is the time to prune affected by warm winter conditions? Here are a few pruning -related questions I have received lately.