New ambrosia beetle marching across the US

Nursery growers have been struggling with ambrosia beetles for decades. In the southeast it is

Scopes-eye view of camphore shot borer fresh from a trap mixed in with granulate and other ambrosia beetle species. Photo: Andrew Ernst, NCSU.

Scopes-eye view of camphore shot borer fresh from a trap mixed in with granulate and other ambrosia beetle species. Photo: Andrew Ernst, NCSU.

primarily the granulate ambrosia beetle, Xylosandrus crassiusculus. In the Northeast and Midwest the predominate species is Xylosandrus germanus. These are tiny beetles that make tiny albeit lethal holes in trees. 

In the past several years a new species has been detected in several states including Florida, Tennessee, North Carolina, and just last month Virginia. This is the camphor shot borer, Cnestus (used to be Xylosandrus) mutilatus, and it is BIG. At least by ambrosia beetle standards this one makes holes as big as a pencil instead of then tiny 2mm holes made by other species. You can find out all about it in a thorough publication from University of Tennessee.  

We trap at 5 -10 nurseries every year around Johnston County, North Carolina. In 2011-2013 we captured 1 or 2 camphor shot borers each year. This year we captured about a dozen from at least 3 different nurseries. So it is here to stay and will probably become more of a problem over time. 

Camphor shot borer in a twig photographed by Matt Bertone, NCSU.

Camphor shot borer in a twig photographed by Matt Bertone, NCSU.

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, Bugwood.org

Robert Wick, University of Massachusetts, Bugwood.org

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.

New banker plant paper!

Sarah Jandricic, a postdoc in the lab, just published a paper titled “The effect of banker plant species on the fitness of Aphidius colemani Viereck and its aphid host (Rhopalosiphum padi L.)” in Biological Control.

Effects of grain species on wasp abundance.

Effects of grain species on wasp abundance.

The paper describes the effects of different grain species on aphid and parasitoid wasp development and fitness. The goal was to identify which gain species would make the best banker plant for greenhouse growers. Each grain, barley, wheat, rye, and oats, had different effects on aphid and parasitoid development time, fecundity, abundance, and other measures. However, wheat and barley consistently produced parasitoids with high fitness and in great abundance. Importantly, cultivar within species had little effect so whatever cultivar grows best in your region should work.