Orange-striped oakworms make yearly appearance

This is a quick field note by PhD student Emily Meineke.

For the last few weeks, orange striped oakworms have been raining on my head as I work in the trees. They also drop a lot of

 

 

Large oakworms eat entire leaves except for the mid vein. Photo: EK Meineke

Large oakworms eat entire leaves except for the mid vein. Photo: EK Meineke

poop (entomologists call it frass) which is one of the major complaints by homeowners. Orange-striped oakworms congregate on branches to feed every year in late summer but usually do not cause enough damage to warrant treatment.

Young oak worms cause damage called 'window panning' in which they eat the surface of leaves and feed between tiny veins. Photo: EK Meineke.

Young oak worms cause damage called ‘window panning’ in which they eat the surface of leaves and feed between tiny veins. Photo: EK Meineke.

Young orangestriped oakworms are often light in color and darken as they get older. I have found some parasitized individuals, which means natural enemies are doing their part to reduce oakworm outbreaks. Caterpillars also make great food for birds. We have posted previously about orange-striped oak worm biology and management if you want more information.  

Large caterpillar poops around the base of a tree. Photo: SD Frank

Large caterpillar poops around the base of a tree. Photo: SD Frank

Azalea caterpillars hatching

Yesterday I found the first azalea caterpillars of the year. These tiny caterpillars had just hatched from the white eggs you see

Newly hatched azalea caterpillars. Notice white eggs on the leaves in the background. Photo: SD Frank

Newly hatched azalea caterpillars. Notice white eggs on the leaves in the background. Photo: SD Frank

in the background. You can scout for these bright eggs in August before the caterpillars hatch and remove them. I think these caterpillars are worth having though since they are very beautiful. Actually the caterpillars are prettier than azaleas tend to be this time of year and they will eat all the leaves stippled by lace bugs! You can read more about these caterpillars that feed on azaleas and blueberries in a post from last August.

Sycamore lace bugs cause yellow leaves

This week I have gotten three samples from the clinic with sycamore lace bug, Corythucha

Adult sycamore lace bug. Photo: SD Frank

Adult sycamore lace bug. Photo: SD Frank

ciliata. I had just taken some pictures of these beautiful critters last week when I was in Asheville. They really do a number on sycamore leaves and this time of year heavily infested sycamores look pretty bad. The other lace bugs that are important landscape pests are the azalea lace bug and hawthorn lace bug. Like these, the sycamore lace bug causes stippling damage by piercing the underside of leaves with its stylet and sucking out the fluids. Large yellow and gray areas develop on the top of the leaves. In some cases, most leaves on a tree can be entirely covered in stippling damage.

 

Yellow blotch of stippling damage caused by sycamore lace bugs. Photo: SD Frank

Yellow blotch of stippling damage caused by sycamore lace bugs. Photo: SD Frank

Sycamore lace bugs are a native insect. They overwinter as adults under bark or in other sheltered spots and become active soon after bud break. They lay eggs in leaves and complete their lifecycle in around 30 days. However, research from China, where this is an invasive pest, shows that at high temperatures this happens much faster, even twice as fast. This suggests that it could be more abundant in hot urban areas where sycamores are often planted in parking lots and along roads. Our research shows that lecanium scales and gloomy scales become much more abundant on hot urban trees than cooler trees nearby. My anecdotal observation is that this hold true for sycamore lace bugs too. Sycamores are wetland trees and probably are not very happy in hot, sunny, dry spots but lace bugs clearly are.

Sycamore lace bug nymphs. Photo: SD Frank

Sycamore lace bug nymphs. Photo: SD Frank

Management of sycamore lace bugs will be similar as for other lace bugs but you are typically dealing with large trees instead of small azalea bushes or cotoneaster. Thus systemic insecticides applied as a drench can be a good option. Applications of horticultural oil should also help keep abundance low just by killing adults and nymphs that are present.

Mimosa webworm

Mimosa webworms are active in Raleigh. I saw initial webbing just a week or so ago but

Small web in a mimosa tree. Photo: SD Frank

Small web in a mimosa tree. Photo: SD Frank

now they are in full swing. These are annual pests of mimosa trees which many people consider pests in their own right. However, if you are you of the many folks who love mimosa trees sans messy caterpillar webbing then it is time for action. The best way to prevent heavy infestations and extensive webbing is to prune out the nest when they are small. Moths overwinter as pupae attached to tree trunks, buildings, or other sheltered locations. The adults emerge in June or so to lay eggs on mimosa and honey locust trees. Caterpillars feed within the webbing for several weeks before pupating. There are multiple generations per year. Most insecticides available for caterpillar control will also control

Mimosa webworm. Photo: SD Frank

Mimosa webworm. Photo: SD Frank

mimosa webworm but remember that contact is difficult since they live in waterproof webs. In most cases mimosa webworms will not reduce the health or growth of their rapidly growing hosts. They also don’t seem to eat all the seedlings that pop up all over my yard from the tree next door. http://www.ces.ncsu.edu/depts/ent/notes/O&T/shrubs/note07/note07.html

Imported willow leaf beetle

Imported willow leaf beetle (Plagiodera versicolor) adults are metallic blue. This time of

Imported willow leaf beetle. Photo: SD Frank

Imported willow leaf beetle. Photo: SD Frank

year adults and larvae are feeding on willows. The adult beetles overwinter outdoors under bark or in leaf litter. They and emerge from hibernation sites in spring around the time willows start getting leaves since adults prefer new leaves. Females lay pale yellow eggs that hatch into voracious larvae. Adults and larvae skeletonize leaves which can give trees a brown cast as damaged leaves crisp in the sun. In some cases though they can eventually defoliate trees like the one I saw walking to work today. Insecticides labeled for leaf feeding beetles such as spinosad, imidacloprid, and chlorantraniliprole can be used if needed. Unfortunately, these beetles are here to stay so efforts to prevent any

Imported willow leaf beetle eggs. Photo: SD Frank

Imported willow leaf beetle eggs. Photo: SD Frank

damage to willows is in vain. High populations that cause complete defoliation pose a risk to tree health and may warrant management. Otherwise some damage is inevitable so go out and look at the beautiful beetles.

 

Tuliptree scale primer

If you haven’t met tuliptree scale, Toumeyella liriodendri, its high time you did. I found

Tuliptree scales on tulip poplar twig. Photo: SD Frank

Tuliptree scales on tulip poplar twig. Photo: SD Frank

dense patches of it at a local playground the other day. I was tipped off by honeydew, which can mean tulip poplar aphids, but also scales. Tuliptree scales feed primarily on tulip poplar, Liriodendron tulipifera, though it is occasionally found on other trees including Magnolia spp. It occurs throughout the eastern US from New England to Florida.

Unlike many other soft scales in our area, tuliptree scale produces crawlers at the end of summer and into fall. The scales overwinter as 2nd instars on twigs. In spring they develop to adults and produce lots of honeydew throughout the summer. In late summer honeydew production declines as female scale begin producing eggs and crawlers. A single female can produce over 3000 crawlers over three months. This could make control difficult since you cannot target a whole cohort of crawlers with a single application of oil or insecticide.

Honeydew from tuliptree scale supports dozens of other species. Researchers have recorded 93 hymenopteran species that collect honeydew of tuliptree scale and a dozen or so ant species. This is an amazing diversity of creatures that would not be in a tree if these scales were absent. This disproportionate effect of one species on the animal community

Distribution of tuliptree scale as of 1969 from Burns & Donlely 1970.

Distribution of tuliptree scale as of 1969 from Burns & Donlely 1970.

suggests a potential foundational or keystone role. Since these scale produce so much honeydew they can be heavily tended by ants. Ant tending can reduce scale mortality by predators and increase scale abundance.

Tuliptree scale cause considerable damage to trees. They can kill central leaders resulting in bushy plants with codominant leaders. They can kill trees or reduce tree growth rate. High densities of scales can remove more carbon than a tree produces. In this case trees are surviving on reserved energy that is gradually depleted.

Reference: Burns, DP, Donely, DE. 1970. Biology of the Tuliptree Scale, Tourneyella liriodendri (Homoptera: Coccidae). Annals of the Entomological Society of America, 63, 228-235.

 

 

Columbine leafminers

The first round of flowering is about over for my native columbine, Aquilegia canadensis. Columbine is a great early spring flower that flowers profusely and spread easily by seed. Spring bees and humming birds visit columbine flowers particularly in early spring when it is one of the only flowers present.

Heavily mined columbine leaves. Photo: SD Frank

Heavily mined columbine leaves. Photo: SD Frank

The columbine leafminer, Phytomyza aquilegivora, overwinters as pupae. Adults emerge in early spring and oviposit in new columbine leaves. Small white maggots mine the leaves creating white or grey serpentine pathways. Often entire leaves are discolored. Larvae pupate after about 10 days on the underside of leaves. Columbine leafminer has at least 4 overlapping generations per year in North Carolina. There are at least 13 species of parasitoids that become more abundant as the summer progresses.

Braman et al. (2005) reported that the native species, A. canadensis, is more resistant to leafminers than many other species of cultivars. Removing and destroying infested leaves before adults emerge may help reduce damage to subsequent leaves. Leafminer control is often best to left the parasitoids become established and just accept some damage. If you are a grower than there are several insecticides available to help reduce leafminer damage.