Warmer weather can bring some unwanted visitors.

Insects and diseases that attack trees often show up this time of year, much to the dismay of homeowners.

Kayben Farms landscape designer and arborist Alexis Ference says one of the most common problems, affecting plum and cherry trees, is black knot. Affected branches swell and turn black, making this fungus easy to spot.

She says the best defense against black knot is proper pruning and that includes ensuring cuts are made in the right place. Improper pruning can leave the tree vulnerable to further disease and pests, she says.

Once diseased branches are removed, Ference stresses it's important to dispose of them properly.

"That wood, once it's been cut, it's really important that it gets buried or burned right away because those spores can be released from that knot up to four months after it's been cut," she says.

Another tree pest lays its eggs inside the leaves of birch trees. Normally, Ference says damage from birch leafminer is mostly aesthetic but it can cause more serious harm if it happens year after year and affects the whole tree.

"The birch leafminer lays her eggs between the two layers of the leaf," she says. "And that's where they hatch and the larvae actually eat in-between the two layers of the leaf."

Ference says there's a yellowish-brown worm that can cause problems for spruce trees. The spruce budworm can leave deformed needles and end twigs and destroyed flowers and cones in its wake. Plus, the damage can leave the tree weakened and vulnerable to other pests and diseases. Ference recommends picking the worms off or, for a larger spruce, a high pressure spray with a garden hose should knock them from the tree.

When it comes to preventing tree pests, Ference says homeowners have options besides pesticides. Ensuring trees are healthy, properly pruned and not drought-stressed will help prevent insect or disease infestations. She says arborists can help diagnosis tree problems and, if pesticides are used, they also have the know-how to apply them properly.

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