Pathogen Alert: Late Blight of Potato and Tomato

Late blight, a destructive disease caused by Phytophthora infestans, is a pathogen of tomato and potato plants that has recently been found in several states in the Northeast, including Maine, New York and Pennsylvania. The late blight has been identified on tomato transplants sold in big box stores and other garden centers under the brand name Bonnie Plants, and has also been found in a potato field in Pennsylvania. Because a few instances of late blight have now been detected on tomato plants in our state, the Massachusetts Department of Agricultural Resources (MDAR) is asking anyone growing tomatoes or potatoes to monitor them for signs of the disease, in order to prevent its further spread.

Late blight, the disease that was responsible for the Irish potato famine in the mid-19th century, is caused by a fungus-like pathogen that spreads through splashing rain or wind currents. Spores can disperse from one to several miles from the point of origin, with the infection spreading most efficiently in conditions of high moisture and temperatures ranging from 60° to 80°F.

Symptoms of late blight include small olive green or brown lesions on the upper surface of the foliage or the stems. Under moist conditions, there is a white, fuzzy growth on the underside of the leaves where the lesions occur, but the absence of this growth does not rule out late blight. Eventually the lesions turn black, leaves start to die, and then the entire plant dies.

This is a serious, destructive disease that can spread quite rapidly when conditions are right, infecting an entire field within days. Any gardeners who suspect they have tomato or potato plants infected with late blight should dig them up, place them in plastic bags, and dispose of them in the trash. Commercial growers wishing to control late blight should begin spraying fungicide immediately, even before symptoms are spotted. Spraying must continue regularly, using a product containing chlorothalonil, a state restricted fungicide which requires certification to use. Growers should be prepared to destroy the plants if the late blight starts to become severe.

For more information about late blight of potato and tomato, including diagnostic images, see the following websites:

• Breaking Info from UMass Extension
• Fact sheet from Cornell University Extension
• Photos for identification of Late Blight
• Information about systemic fungicides from UMass Extension

If you think you have seen late blight of potato and tomato, you can report here, or call the MDAR Plant Pest Hotline at 617-626-1779.

To sign up for pest and pathogen alerts from the Massachusetts Introduced Pests Outreach Project, visit this page.

(Photo by Rob Wick, Plant Pathologist, UMass Amherst)

The Eyed Click Beetle: Another ALB "Look-Alike"

The whitespotted sawyer is not the only species which is frequently mistaken for the Asian longhorned beetle. We have received several reports recently from concerned residents who thought they had ALB on their property, but it turned out to be another "look-alike" species: the eyed click beetle (Alaus oculatus).


Unlike ALB, the eyed click beetle is harmless. It is a native species, about 1 to 1 3/4 inches long, that gets its name from its unusual appearance and behavior. On its back are two large black spots surrounded by a white outline which look like eyes and serve to frighten predators away. When it falls on its back, it snaps or "clicks" a hinged joint between its head and thorax. This action springs the beetle into the air so that it can right itself.

The eyed click beetle habitat is dominated by different species of hardwood trees than that of ALB, including cherry, apple and oak. Unlike ALB, eyed click beetles do not attack live trees. Instead, larvae pupate in rotting logs or underground after emerging from eggs laid in the soil. The diet of the eyed click beetle is also different from that of ALB, consisting of grubs during the larva stage, and nectar or plant juices during the adult stage.

If you find an eyed click beetle, you can consider yourself lucky to see this interesting insect up close and can release it "back into the wild". As always, you can report any potential Asian longhorned beetles using our web form, or by calling 1-866-702-9938.

(Thanks to Helen Rosenberger for giving us permission to use her photo)

Emerald Ash Borer found in NY

The emerald ash borer (Agrilus planipennis, "EAB") has found for the first time in Western New York. The invasive, wood-boring beetle was discovered earlier this week when USDA employees noticed suspicious damage to ash trees off of a highway in the town of Randolph, located in Cattaraugus County. So far, about 30 trees have been flagged as infested. Surveys over the coming weeks will help determine the extent of the infestation.

To prevent the spread of EAB to other parts of the state, New York is asking its residents to avoid bringing firewood to campgrounds or parks, and to instead purchase firewood from local vendors with proof of that firewood source. Also, New York is one of several states that now ban untreated firewood from entering their state. For more information about the dangers of moving firewood and other untreated wood long distances, visit http://dontmovefirewood.org/

More whitespotted sawyer beetle images

Here is a another great whitespotted sawyer beetle image, sent in by Mary Malley:

This is a specimen we inspected earlier today, also whitespotted pine sawyer:

Note the distinct white half-moon shape at the top of the wing covers, behind the neck.

Here is an Asian longhorned beetle for comparison (this photo was taken in August 2008 - ALB is not expected to emerge from the trees until July):

Note that Asian longhorned beetle is a much shinier black than the whitespotted sawyer. It is also missing that distinct white half-circle at the top of its wing covers, and it has a bluish tinge to its feet.

Whitespotted sawyer beetles out and about

Over the past week or so, biologists across Massachusetts and other New England states have reported seeing whitespotted sawyer beetles, the beetle most often confused with Asian longhorned beetle (ALB). The whitespotted sawyer (Monochamus scutellatus), a native beetle that attacks diseased and damaged pine trees, emerges from trees earlier in the season than ALB, which is not expected to be seen in Massachusetts until July.

Similar reports have been coming in via our ALB reporting form this week. Below is a photo, sent in today from Whitman, Massachusetts by Scott Pelletier, showing a whitespotted sawyer. This is a great shot of the beetle, making it easy for an expert to determine the species. Using the notes we've added that point out the tell-tale signs that this is a sawyer beetle, not ALB, you too can learn the difference between these two lookalikes:

(Click on the image to see it in full size)

If you see a longhorned beetle and are concerned that it might be ALB, it is always better to report it. For more information, check out this comparison of whitespotted sawyer and ALB.

(Below, for comparison: ALB - The real thing)

(Thanks to Scott for giving us permission to post his photo)

Winter moth caterpillars

If you've noticed an onslaught of little green caterpillars devouring the leaves on your trees, you are not alone - winter moth caterpillar season has kicked into high gear. We are receiving many reports from our report-a-pest form of this pest attacking trees, particularly in the eastern and southeastern part of the state. Many of you seeing this damage now will remember the moth in its adult form, as it is one of few moths in flight during the winter months.

While there are a variety of treatments to protect trees from winter moth and other defoliating caterpillars, one of the most promising management techniques is the effort to develop a biological control for this pest. Biologists at UMass Amherst have been working on just such a program, but it will take several years for the biocontrol to establish, so expect winter moths to continue to be a problem. More information about winter moth is available on our fact sheet.

Now Hiring: ALB Outreach/Survey Technician

The Massachusetts Department of Agricultural Resources is hiring a Contracted Seasonal Employee for the position of ALB Outreach/Survey Technician. The ideal job candidate will have excellent communication skills, a background in biology, and a drive to educate the entire state about the Asian longhorned beetle. For details, click here. Deadline to apply is May 25, 2009.