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.


Thrips vs. Mites: an Epic Fight

This is a guest blog by Post-Doctoral Researcher Sarah Jandricic, who specializes in Greenhouse Entomology. You can read more about our greenhouse research program here.

The fight is about to begin! In one corner of the ring we have the number one pest of greenhouse crops in the world: the western flower thrips.

Western flower thrips and damage on petunia leaf. Photo: SD Frank

Western flower thrips and damage on petunia leaf. Photo: SD Frank

This nasty little insect might look like a lightweight, but it’s in the heavy-weight class when it comes to damage. By sucking out the contents of individual plant cells, thrips cause a scratched, or “silvered” appearance to leaves and flower petals. Adding insult to injury, thrips can also transmit lethal plant viruses like Impatiens Necrotic Spot Virus.

In the other corner, we have the fan favorite – the predatory mite! Cucumeris are notorious for killing and eating 1st instar thrips (the life stage that hatches directly out the egg), and are sold commercially for control of thrips in greenhouses. Adult mites can eat 4 to 10 of these 1st instar thrips each day. But Cucumeris has yet to face its current opponent: the older and larger 2nd instar Western flower thrips.

Ding Ding Ding! The fight has begun!

The video of our fight (Sarah Jandricic and Matt Bertone, NCSU), shows Cucumeris making repeated attacks to the flank of Western flower thrips! But what’s this? The thrips is using its abdomen to land repeated blows to the head and body of Cucumeris! Despite a valiant effort from our plucky predator, it just can’t seem to find an opening. After several rounds, it’s clear that our 2nd instar Western flower thrips has won the fight.

But hold on, folks. Breaking news is coming from the post-fight interview…

It turns out that defending itself from the mite has cost our 2nd instar thrips dearly. Thrips engaging in this sort of battle spend less time feeding, cause less damage to plants, and ultimately are less successful in completing development into adults.

So, the story is clearly not over. The Frank Lab at NCSU is currently investigating ways to capitalize on effects of mite “intimidation” on 2nd instar thrips for better control of this pest in greenhouse crops.

Stay tuned for more updates on this big battle occurring in the tiny world of insects!



Impatiens Necrotic Spot Virus

In the last month we have had several samples come into the Plant Disease and Insect Clinic with impatiens necrotic spot virus (INSV). These have primarily been greenhouse crops like impatiens and mums but the virus can infect over 200 plant species. It is a lethal virus spread by thrips feeding.  Managing INSV is critical because it can easily over run your crop and cause you long-term problems.  Thrips become infected with the virus while feeding as larvae. After they pupate thrips spread the virus to new plants when they feed as adults.

Robert Wick, University of Massachusetts,

Robert Wick, University of Massachusetts,

Thus, INSV management starts with thrips management. You can read more about thrips management in a Insect Note and recent article in GrowerTalks. The essence though is to start with sanitation. Thrips can feed on hundreds of plants so any weeds growing in or near your greenhouse can support thrips feeding and egg laying. Get rid of pet plants and mother plants. Maybe you or you grandmother want to overwinter last years peppers or begonias but don’t. Its not worth it. These can serve as reservoirs for thrips and virus and keep your house constantly infected.

If you have INSV in the greenhouse get rid of all plants that show symptoms and consider get rid of all plants that thrips have fed on. Plants do not immediately show symptoms but they can still infect thrips. So even if you get rid of plants with visible spots thrips may continue to get infected and spread the virus. Get rid of thrips with insecticide applications or ramp up an existing biological control program to get thrips under control. Now is not the time to start a biological control program.

Keep an eye out for tell tale rings and spots on leaves so you can keep ahead of this virus and of course monitor for thrips with sticky cards to keep ahead of them.

Urbanization is good for pests and bad for trees

My wife is from a neighborhood outside Baltimore called Lawyer’s Hill. This is where, in the 18th century, lawyers (and I assume doctors and other gentlemen) had country houses and could escape the summer heat. Lawyer’s Hill is only 3 miles from Baltimore but, based on their significant investment in houses and land, it must have provided significant relief. So what was (and still is) the difference between Baltimore City and Lawyers Hill? Trees.

Historic Lawyer's Hill (left) and downtown Baltimore City. Images from Google Maps.

Historic Lawyer’s Hill (left) and downtown Baltimore City. Images from Google Maps.

Trees cool the environment by shading houses, roads, and sidewalks that absorb heat. If

Damage by gloomy scales. Notice dead branches and sparse canopy. Photo: SD Frank

Typically shabby red maples with damage by gloomy scales. Notice dead branches and sparse canopy. For more (better) pictures visit Adam’s picture gallery featured in the Bulletin of the Ecological Society of America. Photo: SD Frank

you have every walked barefoot from the pool (or wherever you spend time barefoot) to your car you know that pavement is hot and that you scurry from one patch of shade to another. All the heat absorbed by pavement that does not radiate into the soles of your feet radiates into the air. Trees also cool the environment by evaporative cooling called transpiration in which they release water vapor through their leaves. Of course there are other reasons cities are hot. Air conditioners, industrial processes, and vehicles all generate heat. An unshaded bus stop is hot but even hotter when the bus is idling next to it.

All this heat can be bad for people. Heat alone poses a risk to human health as does exposure to solar radiation and pollutants that become more concentrated in hot areas. So why don’t cities plant more trees? Many of them do and try to preserve the trees they have. Unfortunately, arthropod pests are more abundant on urban trees and urban tree survival is low.

In two papers released today, Adam Dale, PhD student extraordinaire, has tackled the questions of why herbivores are more abundant on urban trees and what are the consequences for urban tree health. Adam works on gloomy scale, Melanaspis tenebricosa, an armored scale that feeds on almost every red maple within city limits (go look at the closest red maple, then get back to work).

All the gray bumps on this trunk are gloomy scales sucking nutrients from the tree. Photo: SD Frank

All the gray bumps on this trunk are gloomy scales sucking nutrients from the tree. For more (better) pictures visit Adam’s picture gallery featured in the Bulletin of the Ecological Society of America. Photo: SD Frank

In his first “Urban warming trumps natural enemy regulation of herbivorous pests” published in Ecological Applications he shows that urban warming seems to be the primary factor associated with gloomy scale abundance on urban trees. He supports this by identifying an amazing physiological mechanism: scales at warm sites can have 3 times as many babies as scales at sites just 2.5 degrees cooler!

Adam came up with a way to count gloomy scale embryos to determine that warm scales produce more babies. Photo: AG Dale

Adam came up with a way to count gloomy scale embryos to determine that warm scales produce more babies. For more pictures of scale embryos visit Adam’s picture gallery featured in the Bulletin of the Ecological Society of America. Photo: AG Dale

Adam’s next question was: So what about the trees? Do scale insects and temperature increase plant stress or reduce tree growth? This is what urban foresters need to know if they are going to make management decisions. Why manage scales if the heat kills trees anyway? Adam’s second paper “The effects of urban warming on herbivore abundance and street tree condition” in PloS One shows that both scale insects and heat are associated with poor tree condition. This means trees with scales and particularly hot trees with scales are more likely to have dead branches, sparse foliage, and generally look worse that cool trees without scales.

Urbanization is increasing and a new paper from Adam Terando and colleagues from NCSU and the USGS Southeast Climate Science Center suggests urbanization will expand more than previously thought. See a piece on The Rise of Charlanta by Rob Dunn. You notice in the image of Lawyer’s Hill that subdivision construction is underway. Each of these house will get a lollipop tree, probably a red maple or worse an ornamental plum, but the canopy will never be restored. To conserve trees and their valuable benefits for human and environmental health we need to understand even more about why pests become more abundant on urban trees and which trees should be planted to establish resilient urban forests. Its clear from Adam’s work that red maples are not a good choice for hot southern cities.

A gallery of photographs of Adam’s research was featured in the Bulletin of the Ecological Society of America.

Retailers to label neonic-treated plants

Scientific American is reporting from Reuters that Home Depot, BJ’s Wholesale, and other smaller retailers will soon require vendors to label plants that have been treated with neonicotinoid insecticides. Neonicotinoids are among the most commonly used insecticides on ornamental crops and all crops. This class of chemicals includes imidacloprid, dinotefuran, thiamethoxam, acetamiprid, clothianidin, and others. Controversy around neonics revolves around their potential to harm bees and other pollinators. Like most insecticides, neonics are acutely toxic to bees on contact. Since neonicotinoids move systemically within plant tissue they can also contaminate flower pollen and nectar that bees consume. Though this can negatively affect individual bees the effects on bee populations is not yet known (and very hard to measure).  Information about this was recently reviewed in two extension publications and a scientific paper. Of course there is no news that these outlets will stop selling neonicotinoids to consumers. Nursery and greenhouse growers who produce crops for retail outlets should start figuring out alternative insecticides as this trend is likely to spread.

Potato leafhoppers crinkle maple leaves

This time of year the results of potato leafhopper feeding show up particularly in nurseries.Potato leafhoppers are a native insect but mimic retired folks because they spend winters in Florida and the Gulf coast. From there adult potato leafhoppers, Empoasca fabae, migrate between late April and early June. Female potato leafhoppers oviposit along leaf veins and clustered at the base of leaves near the petiole. There are five to six overlapping generations per year.

Potato leafhopper. Photo: Steve L. Brown, University of Georgia,

Potato leafhopper. Photo: Steve L. Brown, University of Georgia,

Injury is caused by salivary phytotoxins injected into the plant phloem during feeding. Damaged leaves can have necrotic margins and severe cupping or stunting referred to as ‘hopperburn’. Leafhopper feeding on buds and meristems causes loss of apical dominance and a witch’s ’broom’ can develop in which many stems grow from the apical tip of nursery trees and may require extra pruning to improve aesthetics and train a central leader.

Host plant resistance can play an important role in managing potato leafhopper damage. In general, red maple cultivars that break bud earliest in spring sustain the least feeding injury by the conclusion of the growing season. Higher levels of foliar nutrient content, particularly nitrogen, will also predispose maples to injury due to increased oviposition, nymphal survival, and development rate so don’t go crazy with early fertilization. Mites, aphids, and other pests also appreciate high nitrogen provided by fertilizer.

Potato leafhopper arrival can be monitored in spring using yellow sticky cards deployed above the canopy of young maple crop or in close proximity to outer canopy foliage. Arrival of migratory potato leafhopper adults usually corresponds to around 600 degree-days. Pyrethroids can be applied bi-weekly starting at peak trap catch. However, many applications of pyrethroids may be needed to reduce leafhopper populations and damage. Pyrethroids can also cause outbreaks of other pests like mites by killing predators in the canopy. Alternatively, recent research indicates that systemic neonicotinoid insecticides applied as a drench can provide effective leafhopper control for two years. Systemic insecticide drenches need to be applied before leafhopper arrival and can help protect natural enemies within the nursery. Even though neonics can in some cases induce mite outbreaks I think it is still a less intensive approach in terms of both labor, active ingredient, and effects on non-target organisms. More information about maple pest management can be found in a recent Journal of IPM paper and free iBook IPM for Common Deciduous Trees in Southeaster US Nursery Production.

Japanese maple scale

Japanese maple scale, Lopholeucaspis japonica , is active now and much of the summer. It is a small, oystershell-shaped, armored scale introduced to the U.S. from Asia. Japanese maple scale is found in several eastern U.S. states, including CT, DE, GA, KY, MD, NC, NJ, PA, RI, TN and VA, as well as Washington D.C.. Japanese maple scale has a wide host range that in addition to maples (e.g., Japanese maples, Red maples, Paperbark maples, and sugar maples), includes Amelanchier, Camellia, Carpinus, Cercis, Cladrastis, Cornus, Cotoneaster, Euonymus, Fraxinus, Gledistia, Ilex, Itea, Ligustrum, Magnolia, Malus, Prunus, Pyracantha, Pyrus, Salix, Stewartia, Styrax, Syringa, Tilia, Ulmus, Zelkova, and others.

Brian Kunkel, University of Delaware,

Brian Kunkel, University of Delaware,

Although the lifecycle of this pest has not been fully examined, two generations a year are expected in the mid-southern U.S. First generation crawlers emerge in mid-May, and the second generation in early August  but there may be more. Management efforts are complicated by the extended crawler emergence that results in first and second generational overlap. Thus, the most recent sample we received had every stage – egg to adult- present at the same time.

Adult scales and crawlers are very small and most readily observed on bark of dormant deciduous host plants, but can also be found on foliage. The waxy coating on the body of male Japanese maple scales is white and females, eggs, and crawlers are lavender. The most work on this scale has been done by Paula Shrewsbury and Stanton Gill at the University of Maryland. There is also information on JMS and other maple pests in our new book here:

A link to the UMD fact sheet is here: