Friday, January 27, 2012

Sample of the Week: Tomato Triple Whammy

Tomato Sample, notice the puckered leaves (Photo: E. Lookabaugh)
This week’s Sample of the Week came packing a triple threat! A client brought in two tomato plants from their greenhouse. As soon as we opened the bag, a cloud of whiteflies flew out, alerting us to culprit number 1. Whiteflies damage the foliage when they feed, resulting in yellowing and curling of the leaves. In heavy infestations, whiteflies can cause stunting of the plant, reduced vigor, and leaf drop. Prevention is the best management option for whiteflies. All incoming plants should be checked before they are introduced into the greenhouse. Once the whiteflies are established in the greenhouse, you can starve them out by removing all host plants for at least two weeks, or a more practical option is the use of sticky traps. Whiteflies are attracted to bright colors like yellow and white so hanging white or yellow sticky traps above susceptible plants can reduce population numbers. 
Whitefly damage, look closely and you can see the whiteflies (Photo: E. Lookabaugh)
Upon examining the foliage, we noticed the leaves seemed stunted and distorted. Some of the leaves appeared puckered. We also saw light green etching or mottling on some of the foliage. Distorted foliage in combination with stunted new growth and mosaic or mottling of the leaves usually points toward a virus infection. We ran assays for the common viruses associated with greenhouse tomatoes and determined Tobacco Mosaic Virus (TMV) was culprit number 2. TMV is a serious threat to greenhouse plants. It is spread through contact with tools, workers’ hands, or infected plants. Pruning, tying, and transplanting are great ways to accidentally spread TMV to healthy plants in the greenhouse. TMV has a very wide host range and can survive on root and plant debris for long periods of time. Virus particles can also survive in cigarettes or chewing tobacco so workers who smoke or dip should wear gloves when handling TMV-susceptible plants. Strict prevention and sanitation programs provide the only means of controlling the disease. Use disease-resistant varieties and disease free seed/ transplants whenever possible. Encourage workers to dip hands in milk, wear gloves, or wash hands with soap and water before and after handling plants. Do not touch healthy plants after handling infected plants. Remove any nearby weeds that could harbor the virus. Infected plants and plant debris should be removed immediately. 
TMV Symptoms (Photo: E. Lookabaugh)
TMV Symptoms (Photo: E. Lookabaugh)
Finally, we checked the roots to provide a complete diagnosis. Amazingly, we noticed swollen and knotted roots caused by root knot nematodes, culprit number 3! Above ground, root-knot nematodes can cause yellowing, stunting, and wilting. Usually root-knot nematodes are not a problem in greenhouse tomatoes and other plants grown in treated potting mixes. These particular plants were being used in a research study so they were being grown in soil intentionally infested with nematodes. 
Root knot nematode, notice the galls on the roots (Photo: E. Lookabaugh)
Unfortunately, these tomato plants probably won’t make it. Whiteflies, TMV, and root knot nematodes can pack a serious punch to tomato plants individually-- imagine having all three!

For more information, see links below:

Monday, January 23, 2012

"It's alive!" - Scorpion found in local basement.

Hentz's Striped Scorpion, Centruroides hentzi
This juvenile Centruroides hentzi (a.k.a. Hentz's striped scorpion, a.k.a. Florida striped scorpion) was found alive in a Raleigh basement last week. It would measure a little over an inch long with the tail extended. It presumably hitchhiked on luggage that had traveled to the scorpion's native range and back. This range includes Florida, southern Georgia, and the Gulf Coast of Alabama. Like most scorpions, the sting of this species is painful but not deadly, according to PDIC entomologist Dave Stephan, who made the identification and provided the information for this post. It is interesting to note that there is only one scorpion species native to North Carolina, but none to the Triangle area.

Friday, January 20, 2012

1 year Anniversary

Happy Anniversary to the PDIC Blog!  

This month, we are celebrating our 1 year anniversary in the world of social media! On January 21, 2011, we made our first post on Blogger, since then we have posted 47 more blog entries.   A year ago, none of the members of our staff had ever blogged or tweeted in their lives.  We hopped on the social media bandwagon and spent the last year figuring out how to keep the blog topics interesting and current enough to satisfy our reader's appetite for fast and easy information on plant diseases and insect pests. 

A few statistics...
To date, we have posted 47 blog entries, reaching 10 different countries, and accumulated over 16,000 page views. Not too shabby if you ask us! To some bloggers these numbers may not seem too impressive, but we are slowly gaining speed and expect to have an even bigger audience by the end of 2012! 

Our most popular blog topics include herbicide injury to tomatoes, geotrichum sour rot on shrink wrapped sweetpotatoes, and household molds: what hurricane Irene left behind.  We are always looking for new topics so be sure to let us know if there is a topic you want to see on our next blog.  

In addition to our blog, we also developed a new website that contains lots of great information.  Here you can find info on how to submit samples to the clinic, videos on how to take a proper sample, links to useful websites, disease factsheets, and pest alerts. To visit our website, click here.

The goal of the blog was to educate the public on plant diseases, insect pests, and other topics of interest in the world of plant diagnostics.  We hope that as time goes on, you will agree that we have, at least in part, achieved what we set out to do! We hope you have enjoyed reading our blog as much as we have enjoyed writing it!

The Plant Disease and Insect Clinic Staff

Be sure to follow us on Facebook and Twitter and check out our awesome twitpics!

Friday, January 13, 2012

Sample of the Week: INSV on Cyclamen

INSV symptoms on cyclamen (Photo: M.J. Munster)
A potted cyclamen is a nice way to brighten up a cool windowsill in winter, but a cyclamen sample we received from a greenhouse this week did not look so pretty. The grower noted that the problem started with light-green mottling of the leaf edges. Eventually, these mottled areas turned brown and the buds died.
Necrotic spots on cyclamen, INSV symptoms (Photo: M.J. Munster)
Upon examining the plant, we observed mottling of the foliage, necrotic lesions on the leaves, and necrosis and decay of the crown. PDIC entomologist Dave Stephan also found Western flower thrips present in low numbers on the sample. We suspected INSV (Impatiens Nectrotic Spot Virus) and confirmed the diagnosis with an Agdia Immunostip test.
Positive Immunostrip Test (Photo: M.J. Munster)
INSV attacks a wide variety of hosts and is vectored by Western flower thrips (Frankliniella occidentalis), a tiny insect that feeds on leaf and flower buds, petals, and pollen. Thrips breed all year in the greenhouse and the virus can spread quickly when thrips are present. Symptoms of INSV infection vary widely from hosts to host. Typical symptoms in ornamental crops include mottling, yellowing, wilting, stem death, poor flowering, ringspots, and sunken lesions on the foliage.
Sunken necrotic lesion, INSV symptom (Photo: M.J. Munster)

Necrosis/decay of the crown (Photo: M.J. Munster)
Controlling INSV is difficult and the best management strategy is prevention. Both INSV and thrips have a very broad host range, so weed removal in and around greenhouses is an important part of prevention. Greenhouses vents should have screens to exclude thrips. Insecticides are only partially effective against thrips and virus transmission. Most systemic insecticides do not translocate well to flower parts where thrips feed, while insecticides that “kill on contact” may not reach thrips hiding deep in blossoms and buds.

Inspect and monitor all incoming plant material carefully to prevent introduction of INSV and thirps on stock plants. Any plants with suspicious symptoms should be isolated and sent to the PDIC to test for INSV infection. The virus can be spread by vegetative propagation. Since infected plants cannot be cured, and cannot be used for propagation, they should be destroyed.

For more information on thrips control, click here
For more information on INSV, click here

Friday, January 6, 2012

Sample of the Week: Canker Rot on Oak

Fruiting body of Inonotus hispidus on the
trunk of an oak in Craven Co., NC. December
2011. Photos courtesy Tom Glasgow, NC
Cooperative Extension Service.
This sample actually came in last month, but we made the definitive identification this week. You might be seeing more conks (a type of fungal fruiting body) now that our deciduous trees have dropped their leaves.

Inonotus hispidus is one of many fungi capable of causing a white rot of the heartwood of trees. It is, however, one of only a few such fungi that can kill living tissues of the tree. The common name of "canker rot" is a reflection of this fact. It  is widely distributed in North Carolina and the United States, and occurs on hardwood trees, especially oaks. For a technical description of this organism, see its page among the Fungus Profiles on the web site of the Larry F. Grand Mycological Herbarium.

Fruiting bodies of Inonotus hispidus can occur much farther up the trunk than what is pictured here. Also please note that the presence of these fruiting bodies indicates decay within the tree, but wood decay can be present without any externally visible signs or symptoms in a given year.

Tuesday, January 3, 2012

Box Blight Webinar - January 5, 2012 11 a.m. EST

On Thursday January 5th at 11 am EST, NC State University will be hosting an ELLUMINATE LIVE webinar on box blight. Box blight is a disease new to the US and was recently found on boxwood in North Carolina, Virginia, and Connecticut (and now a few additional states).

This webinar will be geared towards County Agents and boxwood growers in North Carolina and adjacent states, but all interested parties are invited. There is no limit on attendance, so anyone can watch the webinar LIVE!

Dr. Kelly Ivors, who first diagnosed box blight in the US, will speak for 45 minutes, followed by questions from the audience. The session is scheduled to last an hour and a half but will be extended if necessary.  Representatives from VA and other box blight positive states may make additional comments and address concerns in their states.

The webinar will be recorded and made available for viewing at any time after the webinar at the same URL given below. 

Here's how to participate in the webinar:
Before the webinar, click on
The webinar will start EXACTLY at 11 am EST. Please log in a little early so that you can check your connection.  You will be able to enter the session starting at 10 am EST on the day it occurs.  All that you need is an up-to-date browser and internet connection. In order to test that your system configuration is acceptable, visit the Configuration Room at any time before the webinar. In addition, Elluminate tips can be found at