Pesky Pest: the Hemlock Wooly Adelgid

     The Hemlock Wooly Adelgid (HWA), Adelges tsugae, is a small aphid-like insect that is infesting and seriously harming the Eastern (Tsuga canadensis) and Carolina (T. caroliniana) hemlocks in the eastern US. It was accidentally introduced into the US in 1924 and the first reported case of infestation was in 1951 in Virginia. The HWA is native to Eastern Asia where it has natural predators that keep the population in check; it is also believed that the Asian species of hemlocks have resistance to the pests.
     The HWA damages the hemlocks when it feeds. It has a piercing-sucking mouthpart, which it uses to suck the sap out of tender new branches. These wounds that they leave are openings for disease, and on top of that, it’s thought that the HWA injects some sort of toxin that causes further damage! As thousands of adelgids can congregate on one tree, these are mortal wounds. As a result, infested and infected hemlocks will look a silvery gray-green instead of the lush dark green that you’re used to seeing, and succumb in 7-20 years after initial infestation- faster the further south they are.

     The situation is dire: there are currently 11 states from Georgia to Vermont that have HWA populations. 50% of the range of the hemlock is compromised. The HWA has moved into Georgia as far south as Ellijay. If you have hemlocks, keep an eye on them to catch an infestation early – once on the tree, the HWA is not very mobile, so infected branches can be removed to save the rest of the tree. Notify your county extension office that you have a possible HWA infestation, take them a sample branch if you can to confirm your suspicions.
     There is no 100% effective treatment for the HWA. On a small tree horticultural oil, insecticidal soap and other insecticides can be used, but obviously as the trees grow to enormous proportions it is not feasible to spray an entire tree, also most pesticides cannot be sprayed within close proximity to water... which in the mountains is very limiting. There has been some luck with a pathogenic fungus that specifically targets the HWA, as well as some predatory insects: a beetle and another winged insect with a name that I cannot pronounce.
     Scientists have been crossing the American species with the HWA-resistant Asian species and have had some success maintaining the look of our hemlock while hanging on to the resistance. Hopefully this will prove to be a viable variety that can be available soon in nurseries or for reforestation of the northeast, where the hemlock is the 3rd most populous tree. Quarantines have also been established: no hemlock from a compromised area can be shipped outside that area.
     The outlook is grim for the Canadian and Carolina hemlocks in the Eastern US. Hopefully there will be a breakthrough in time to save this beautiful tree.

Jessica Watters, GCLP           Horticulture Technician, Chattahoochee Technical College

Pesky Pest: Japanese Beetles

     Japanese beetles, Popillia japonica, are probably the most frequent pest insect to harm our gardens and landscapes. Native to Japan they were first discovered in 1916 and were suspected to have hitched a ride in a shipment of iris tubers that arrived at a nursery in New Jersey. Since then, they have gone on to establish themselves in nearly all of the eastern United States as far west as Arkansas and north to Ontario Canada.  They are about a half inch long and have a greenish to brownish metallic sheen.

     Japanese beetles are not a problem in their native Japan because of natural enemies that keep their populations down, but here in the US that’s not the case. Here they tend to gather in large numbers and decimate plants. (see photo below, taken by D. Gordon E. Robertson). They eat the tender parts of the leaves between the veins so that they’re ‘skeletonized’. They love roses, filberts, Japanese maples, sycamores, and many, many other plants. They do tend to avoid evergreens, I guess the leaves aren’t as tender.

     Well, how do you get rid of them?  One form of control we’ve seen for years is that bag trap thing you hang in your yard with the pheromone/scent lure. Well, research has shown that yes they do attract beetles very well, but unfortunately, they do not trap that many. The beetles are attracted to your trap and eat your plants on their way to the trap and they eat them as they hang around not being trapped in the trap… So hanging one in your yard will actually cause more damage to your plants than not having one at all. So maybe sneak one in the yard of that mean guy down the street… (kidding!) Seriously though, there are many different chemicals to control Japanese beetle populations out there. Despite this they are still hard to control. You have to apply a chemical to your turfgrass in early spring to kill the grubs, and then you have to spray for adults repeatedly through the summer because they are so mobile they can come to your yard from anywhere. So to me, that sounds like an awful lot of chemicals that aren’t that effective. One old school way to kill them that works for small infestations or small yards is soapy water. You can just knock them off the plants early in the morning when they’re sluggish and drop them in soapy water.  Sraying soapy water is somewhat effective as well.

     Now the best Japanese beetle control, according to our esteemed Mr. Bishop is to make margaritas. His advice is to take the down-the-street-neighbor’s full trap, dump it in your blender, add some water and spray this delightful concoction on your plants. And of course, don’t use that blender again for actual margaritas. Having never done this myself, I can only say that research has shown that live beetles avoid dead of their own kind.

So, good luck!

Jessica Watters, GCLP Horticulture Technician, Chattahoochee Technical College

Pruning Azaleas

     Azaleas need to be pruned between the end of blooming in the spring and before the 4th of July. If you prune after this date you will risk losing next spring’s blooms! You can begin the pruning process before they’ve finished blooming- take some of your clippings inside and enjoy them!

     There is a school of thought that disagrees with this rule however. Some experts say that if you’ve got very overgrown azaleas and you want to prune them to dramatically lower their height, called rejuvenation, do it in the late winter or early spring before they bloom. You will lose the flowers for that year. (Rejuvenation means starting over: when a plant is rejuvenated it is cut back to structural branches, usually bare, that act as a base for the plant to come back from- it isn’t pretty and not all plants will tolerate this, azaleas will). The reasoning behind the timing of this theory is that the azaleas will need a significant amount of energy to come back from being pruned severely and they also require a significant amount of energy to produce flowers… so they will come back much better from the rejuvenation if they are spared the stress of producing blooms: this needs to be done before you see any color from the flowers. The photos below are of a rejuvenation project half way done- you can see that the azaleas have been lowered by about 2/3 of their height. The photo on the bottom is a year later; see how much of the fence is visible now?

                                                        

     These photos are courtesy of Rick Smith at The Pruning Guru, www.PruningGuru.com    

    
     Another way to significantly reduce the size of your azaleas but keep your blooms, and avoid undue stress to your plants, is to spread the pruning out over several years: remove a few of the tallest branches every year. Patience, Grasshopper.

     One other concern about the timeline is Encore azaleas that have a second, or even third, bloom later in the year. You’re pretty much sacrificing a bloom cycle by pruning them, anytime. Since the spring bloom is the showiest, prune immediately after that has tapered off. Your fall show may not be as good as last year but you should still have some blooms.

     As with pruning anything, cuts should be made just above a lateral branch, any branch coming out from the main stem, branch or trunk. Cuts made in the middle of a branch will cause several problems: the wood between the cut and the branch below it will die and be an entry point for disease, or a bud (or several buds) along that branch will produce a sucker that will grow straight up, way above the existing canopy- which means more pruning for you, and it will not conform to the regular growth habit, neither result is pretty. Be sure to remove any dead wood.

     While you’re up close and personal with your azaleas it’s a good time to check for any insect or disease activity goin’ on. The most common problem with azaleas is lace bugs. If you see splotchy discoloration on the tops of the leaves and dirty looking smudges on the back, the smudges are lace bug poo and eggs; the discoloration on the top is the damage they cause (below). You may see tiny fly-looking bugs with transparent wings about ¼ an inch in length, these are the culprit. There are a number of chemicals available to nuke ‘em, read the labels at your local supplier or big box store- be sure to spray the underside of the leaves (that’s where the buggies are) when applying the chemical. Read the entire label and follow the directions exactly; pesticides are not to be taken lightly. The damage to the leaves is permanent but future growth should hide the damaged leaves.

                      Photograph by: James Castner, University of Florida/IFAS, used with permission

Azaleas really require very little pruning and maintenance but with just the right amount they will astound you every spring. If you’re rejuvenating your azaleas or they’ve got lace bug damage they’ll appreciate a balanced fertilizer (10-10-10, or similar) in the spring.

Jessica Logan, Horticulture Technician, Chattahoochee Technical College