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North Hills Monthly

Keep an Eye Out for Devastating Garden Pests

Jun 30, 2016 08:57AM ● By Denise Schreiber

“By the pricking of my thumbs, something wicked this way comes”  – Macbeth

Unfortunately for gardeners, there are several wicked things coming toward us in our gardens. 

There is a leafminer that was discovered in Lancaster County in late 2015 that can be devastating not only to farmers but also to the home gardener. The Allium leafminer, also known as the Onion leafminer (Phytomyza gymnostoma Loew) is known to infect chives, onions, leeks, garlic, shallots, green onions and ornamental onions, as well as wild onions and other members of the allium group. It is native to Poland and Germany, but has since made its way west through Europe and across the sea. It is a tiny fly that lays its eggs from late winter to mid-spring at the base of the plant, causing distorted leaves that twist and curl. The larvae move through the leaf sheaths and into the bulbs where they pupate and can also move into the soil as well.

They are a dark brown color, which allows you to see them easily when you remove the sheaths of the leaves. These pupae will emerge in September and October, attacking the plants. They then overwinter, allowing them to emerge the following spring to attack more alliums. 

One of the best protection practices is to cover the bulbs and seedlings with a floating row cover which allows the plant to grow but excludes the adult fly from laying its eggs. If you suspect you have this leafminer, it is recommended that you either contact Penn State Extension or the Region Four office of the Pennsylvania Department of Agriculture so that they can confirm the infestation. 

Another pest that is causing major problems is a pretty but deadly little insect called the Spotted Lantern Fly (Lycorma delicatula) even though it isn’t a fly, but a plant hopper. It comes from Asia and it is devastating to more than 70 species of trees, shrubs, fruits and vines. It could easily wipe out the cherry crops in Pennsylvania, the hardwoods in our forests or the grape vineyards in northwestern Pennsylvania. Right now it is confined to locations in Berks, Bucks, Chester and Montgomery counties and quarantines are in effect in those counties to avoid bringing egg cases into other parts of Pennsylvania.

The egg cases hold 30 to 50 eggs, and aren’t just laid on trees but on campers, truck beds, rocks, grills and almost any other flat surface. Right now, the nymphs are out morphing into adults that are black and red with white spots; the adults also have a hind wing that is reddish orange and white. If you see the grayish brown egg cases covered in a waxy coating, which are about 1 to 1.5 inches long and a half- to three-quarter inches wide, scrape them into a plastic bag and again contact Penn State Extension or the local department of agriculture. In the fall, adults prefer Tree of Heaven (Ailanthus altissima), an invasive species itself, as a preferred food source and also for mating and an egg-laying location.

And just when you thought it was safe to go back into the woods, there is the Asian Longhorn Beetle. The adult beetle is three-quarters to one-and-a-quarter inches long, has a jet-black glossy body with white spots on each wing, and long, black and bluish-white curled antennae. It reminds me of the alien beetle in Men in Black and it is just as deadly. This beetle was first found in Brooklyn, NY, and to try and stop its spread, all of the trees within a one-mile radius were cut down—but it still escaped and moved on.

The beetle larvae tunnel through tree stems, blocking the trees’ uptake of nutrients and eventually killing them. Coarse sawdust is always found at the base of the infested parts of the tree. Adult beetles leave round exit holes as opposed to the D-shaped holes that Emerald Ash Borers make in trees after they emerge. There is no known practical control for this wood-boring pest other than destroying infested trees.

The beetles attack and eventually kill many species of trees, but they prefer maple species. Unfortunately, soft (red maple) and hard (sugar maple) trees make up more than 25 percent of Pennsylvania’s hardwood forests. The beetles also attack species of ash, birch, buckeye, elm, horse chestnut, poplar and willow trees. Billions of dollars are at risk of being lost through the destruction of these trees which include the hardwoods used in furniture and building supplies as well as in the maple sugar industry.