It is time to revisit our post on bagworms! Over the weekend, I was notified by the National Phenology Network that bagworm caterpillars will be emerging in our area in the next six days. If you need to treat a tree that has been infested with bagworms in the past, it is important to do so soon after emergence when the caterpillars are small, as treatments are not effective against larger caterpillars.
Have you ever noticed one of these structures hanging on a Colorado blue spruce or an arborvitae? They kind of look like pine cones, but not exactly. Well, they aren’t pine cones, but silken bags spun and decorated by bagworms (Thyridopteryx ephemeraeform).
Bagworms are moths whose larvae feed on evergreens such as spruce, juniper, pine and arborvitae. The larvae can also feed on deciduous trees such as maple, elm, birch and sycamore. Bagworms defoliate the trees and shrubs they infest. In large numbers, bagworms can cause significant defoliation, which can lead to the death of the plant.
In late spring, bagworm eggs, which overwinter in their mother’s silken bag, hatch and caterpillars emerge. These caterpillars begin to form new silk bags, and as they eat, they cover it with bits of leaves. As the caterpillar grows, it expand its bags. Then in late summer the caterpillar firmly attaches its bag to the plant and pupates.
Complete metamorphosis from caterpillar to moth takes about four weeks. Adult male bagworms emerge from their bags as clear winged moths and begin to search for a mate. Adult female bagworms are wingless moths and never leave their bags. After mating females produce 500-1000 eggs before dying. Their eggs overwinter inside their mother’s silken bag and the whole cycle begins again.
Because bagworms are protected by their silken bag, management can be tricky. For smaller trees and shrubs the best tactic is to remove and destroy the bags by hand. Unfortunately, this is not possible in all instances, especially on larger trees and shrubs. Insecticides are most effective right after bagworm eggs hatch, when the caterpillars are small.
But how does one know when the eggs are going to hatch? Well, it turns out that there is a “Bagworm Forecast” that you can check in the spring to determine the best time to apply insecticide. The maps provided by this forecast are updated daily and available six days in the future, so you can plan ahead.
For recommendations on pesticides, check out the resources below. And as always, make sure you read and follow all the instructions on the pesticide label including the use of personal protective equipment. The label is the law!
As females don’t fly, you may wonder how bagworms spread. Bagworm caterpillars can balloon, or use their silk threads to catch the wind and travel long distances.
Despite relatively little protection for overwintering bagworm eggs, research at Purdue University found that it takes a 24 hr period at -0.6 ° F or below to kill the eggs. So if you live in Orange County New York don’t expect a cold winter to kill off your bagworms.
Hopefully you’ve spent some time outside enjoying the beautiful spring weather we had last weekend. Did you noticed any ash trees that look like they have been completely stripped of their bark? Did you wonder what happened? Did you think it was a disease, an insect or maybe a deer? This damaged is actually caused by woodpeckers. They are searching for emerald ash borer larvae which can be found just below the bark.
The emerald ash borer (Agrilus planipennis) is an shiny emerald-colored jewel beetle. Native to Asia, it was first discovered in North America near Detroit, Michigan in 2002 (most likely hitching a ride here in solid wood packing materials used in the transportation of goods).
Despite its beauty, the emerald ash borer is an invasive insect and has killed hundreds of millions of ash treesthroughout North America. As of April 2020, it has been found in 35 states and 5 Canadian provincescostingmunicipalities, property owners, nursery operators and forestry product industries hundreds of millions of dollars.
Emerald ash borers, like all beetles, undergo complete metamorphosis. Usually in June and July, adult females lay 60-90 eggs on the bark of ash trees (Fraxinus spp.). The eggs hatch and the larvae bore through the outer bark and begin feeding on the inner bark or phloem of the ash tree. The larvae feed for several weeks growing to rough 1 to 1.25 inches in length. The larvae then overwinter in the bark. In the spring they pupate and finally in May and June emerge as adults and exit their host tree by creating a D-shaped whole in the bark. The adults feed on the leaves of the ash tree, mate, and females lay eggs starting the cycle over.
As mentioned before, the larvae of the emerald ash borer feed on the inner bark or phloem of the ash tree. The phloem is part of the vascular system of the plant and is responsible for transporting the sugars produced by photosynthesis in the leaves to the rest of tree. Damage to the phloem cuts of the nutrient supply and eventually leads to the death of the tree.
One of the first symptoms produced by an emerald ash borer infestation is a thinning canopy. With fewer leaves the tree’s ability to produce food through photosynthesis decreases and as a result the tree may produce lots of shoots that sprout from the roots and trunk. The leaves on these shoots are often larger than normal as the tree tries to compensate for its loss of photosynthetic capability. The tree’s canopy will continue to thin eventually leaving the tree bare.
Many people do not notice that the canopy of their ash tree is thinning. For many people, the first symptom that they notice is the woodpecker damage on the trunk. At this point the tree is usually heavily infested by emerald ash borer and will soon succumb to the infestation.
The emerald ash borer was first detected in New York State in 2009 over in Cattaraugus County. Two years later, in 2011, it was detected here in Orange County. As of right now the majority of trees in Orange County have been infested by the emerald ash borer and are showing signs of decline or have died. Once you notice that the canopy of your ash tree is thinning there has already been extensive damage to the vascular system of the tree and even with treatment there is little chance of recovery.
Deciding whether or not to treat your ash tree is up to you. The first thing to do is make sure you properly identify your tree.
Once you have properly identified your tree there are three option: cut it, treat it, or leave it.
Ash trees that create a potential hazard (i.e. proximity to a building) need to be removed. If you cannot safely remove the tree yourself, look for a certified arborist near you at www.treesaregood.org. Many ash trees are being turned into firewood. Keep in mind that New York State law prohibits the movement of firewood more than 50 miles (linear distance) from its source, specifically to prevent the accidental movement of invasive species like the emerald ash borer. Don’t Move Firewood!
Remember that that if you tree is already showing signs of decline it is probably too late to save it through treatment.
If you decide you want to treat your ash tree(s), it is not just a one time investment. Most treatments only last one or two years before they wear off leaving the tree susceptible to infestation. This means trees need to be treated ever couple years since at the moment the emerald ash borer looks like it is here to stay.
If your ash tree poses no potential hazard, consider leaving it. Although the emerald ash borer has killed millions of ash trees here in North America, there is hope the identification of “lingering ash” or an ash that stays healthy after nearby trees have overwhelmingly succumbed to the emerald ash borer. The identification of “lingering ash” could help achieve ash species conservation. Click here to learn more about how you can become a citizen scientist with the Lingering Ash Search through the Monitoring and Managing Ash Program.
Let’s start with the parasitoid wasps. Three species of parasitoid wasps found in the emerald ash borer’s native range were were considered potential biological control agents. These parasitoids are natural enemies of the emerald ash borer and have long ovipositors that allow them to drill into the ash trees and lay their eggs on the emerald ash borer larvae. Once the eggs hatch the wasp larvae consume the emerald ash borer larvae alive. (Note: In order to get permission to release these parasitoid wasps in the United Stated, it took four or five years of research to make sure that they were host specific to emerald ash borer and wouldn’t impact any other similar species.) Of the three species released, two are showing promise, although research is still being done regarding their dispersal, spread, and ability to overwinter.
Many things in nature are governed by the weather, such as the hatching of bagworm eggs and in this case the emergence of emerald ash borer adults. You can track this year’s emergence using the “Emerald Ash Borer Forecast“. This forecast is updated daily and available six days in the future. Emerald ash borer adults are rarely seen. Once they emerge, they fly up into the canopy to feed on the leaves. But if you know when they are emerging you can be on the look out and might be lucky enough to find one.
The ash tree is a member of the Oleacae Family and researchers have found that the emerald ash borer can also complete its life cycle in another well-known member of the Oleacae family, the olive tree (Olea europaea). Although this has only been shown in a laboratory project, there is a possibility that the emerald ash borer could become a problem for olive growers.