Scarlet Oak Sawfly

skeletonized oak leaf

“What’s up with the oaks?” or “Are my oak trees are dying?” were common questions from residents in the Hilltown/Perkasie/Bedminster area this year. Symptoms included whitening in the tops of pin oaks and, on closer examination, leaves that had been “skeletonized”. This means that all of the soft parts of the plant tissue were gone but the “bones’ remained… just the skeleton.


You might think, as I did originally, that the insect called Oak Leaf Skeletonizer was the culprit. But a conversation with Penn State entomologist Greg Hoover led to the conclusion that this was another insect, Scarlet Oak Sawfly. Both insects skeletonize leaves but Scarlet Oak Sawfly does not leave tell-tale pupal cases on the leaves as does the Oak Leaf Skeletonizer.



pin oak injury from sawfly feeding

 The clincher was speaking with arborists Craig Brooks (Bedminster) and Bob McMullin (Doylestown). Both reported diagnosing the problem in the past two years. Craig and Bob are International Society of Arboriculture (ISA) certified arborists and excellent tree men. If you are looking of tree care, an ISA certified arborist is a really good idea.

So, what will become of oaks infested with Scarlet oak sawfly? PSU’s Greg Hoover thinks that natural predators and parasites will begin to take control and reduce sawfly populations to levels that are almost harmless. Defoliation is the issue here. The question is: “How much foliage can a tree stand to lose?” Answer is: "Some, not too much, not too often." It is not a black and white situation. Many factors such as overall tree condition, amount of foliage loss and site factors come in to play. It is unlikely that partial defoliation in one year will be a life or death situation for an oak.



sawfly larva feeding

 However, major defoliation in consecutive years is a problem. Think about gypsy moth damage. Similar scenario here. Except that Scarlet oak sawfly has two generations, one in early summer and one in late summer. Insecticide options exist, but the bugs habit of feeding from the tops of trees downward can present logistical problems... how to get good spray coverage at the top of a 50 foot tree? If necessary, arborists have the tools to do the job. It is not a do-it-yourself situation.

Personally, I have my bet on Mother Nature to come to the rescue. Sure, She can be unpredictable and is habitually late, but population spikes of one bug eventually result in their enemies coming along to even things out. 

Fresh From Bucks County Farms

Summer has arrived … and so have seasonal fruit and vegetables. Blueberries are “in” and peaches are not far behind. Raspberries are about to ripen. Get them while you can! The first tomatoes, planted early in greenhouses, are about to become plentiful, too. Some local sweet corn for the 4th of July? You bet.



"New" potatoes and peas

You can find a source for all of these favorite produce items in the 2012 edition of Fresh From Bucks County Farms, a directory of local farms, farm markets and CSA’s published by Penn State Extension. Copies are available on request by calling 215-345-3283 or at this site. Copies are also available in any Bucks County library.


While peaches, sweet corn and tomatoes get all of the attention, there is a lot more to like in the local food scene. “Foodies” have been enjoying garlic scapes for the last 3 weeks. The strawberry crop was exceptionally early and delicious this year. If you have never enjoyed “new” potatoes and peas a visit to the local farmers market will introduce you to a June treat.

Looking of something special? European-style artisanal cheese? Champagne? Duck eggs? Lamb? Grass-fed beef? You will find it all in Fresh From Bucks County Farms.

Start Farming

High tunnel greenhouses extend the farming season

This is a gardening blog so you might think farming is not up your alley. But as gardeners, you have a lot in common with farmers. You watch the weather more closely than most people. You have an intimate relationship with insects… some friendly, some adversarial. You grow more of your own food than most folks. You know the names of beet varieties… because you grow them.


And I’ll bet that some of you have farming fantasies. You can see yourself selling stuff at the local farmers market rather than buying. You stare at tractors, longingly. The smell of manure is like perfume. As you might suspect, you are in a minority. So are farmers. Census data says that about one percent of the U.S. population identifies its occupation as farming. And that group is aging. About 40 percent are over 55. There is legitimate concern about where the next generation of farmers will come from.

What’s Penn State got to do with it? Well, as many of you know, we’ve been in the farming education business since about 1862. Many of today’s farmers were not born on farms. They followed a dream of farming and made it a reality. I can quickly name a Bucks County dairy farmer who grew up in Philadelphia, a vegetable grower who was an electrician and a commercial fruit producer who is a nurse. Each of them would tell you that Penn State has played a role in their success.

Recently, a federal grant was initiated specifically to help beginning farmers get started. Tianna Dupont, Penn State Extension Educator, is heading up the Start Farming program in Southeastern Pennsylvania. In the last two years, this program has reached more than 950 new and beginning farmers through 36 courses with names such as: ABCs of Beekeeping, Exploring the Small Farm Dream, Pasture School, Sheep Short Course, Introduction to Organic Vegetable Production and Small Scale Poultry. About half of the participants had no farm background or farming experience prior to taking the courses. These courses are ideal for working people, those between jobs, folks nearing retirement, and others who cannot devote time to full-time undergraduate course work, but still want to receive high quality education in agriculture.

For those who are ready to take on four years of study, Penn State has about 20 majors in agriculture. And they are popular! From the years 20005 to 2010, College of Ag enrollment at Penn State was up 42 percent. To see what the curriculum in agriculture looks like at Penn State see this.

It is interesting that at a time when concerns about where the next generation of farmers will come from, enthusiasm for food production is sky high….from both consumers and prospective producers. Want to start farming? See what Penn State has to offer.

Yes, Kiss Your Ash Goodbye

Emerald Ash Borer larval feeding injury

About nine months ago, this blog described purple traps hung throughout the Delaware Valley which are designed to detect an important pest … Emerald Ash Borer (EAB). The traps were not successful in detecting this insect but a sharp-eyed arborist was. Last Friday I got a call to look at some ash trees that were ravaged by woodpecker feeding. Beneath the bark, signs of larval tunneling were obvious. A few days later, Pennsylvania Department of Agriculture entomologists visited the site and verified that this was indeed Emerald Ash Borer.

Bad news for ash trees.

You can read the blog of June 11 last year and get the story … nothing has changed except that a detection has been made about 100 miles east (Warrington, PA, Bucks County) of the leading edge of the Pennsylvania EAB infestation. About the only good news is that a tremendous amount has been learned about this insect in the last 10 years. See this Penn State site or this National EAB site for solid, research-based information. The PSU “Frequently asked questions” feature is a good starting place.

For tree owners, the time has come to consider the fate of your ash. Depending on who’s counting, this insect has killed between 40 and 50 million trees between Michigan and….. Warrington. It is in 15 states and two Canadian provinces. It’s a tree killer. Infested ash die.

Individual trees can be protected with insecticides. Some can be applied by homeowners but, from what I read, the best product is available to arborists only and has to be injected. Upside? Two years of control.

Another hopeful thought is that entomologists now have several parasitoids, (bug killing bugs) that may provide some control of EAB… and perhaps the site recently detected would be a release site for them. That would be nice. Cross your fingers.

But don’t expect predators to catch up to EAB in Bucks County before a lot of damage is done. For now, learn to recognize ash . Think about whether it is really important to preserve those that you see. It is not practical to treat every ash tree. Remember, treatment provides only temporary protection, not immunity or a cure.

Those considering do-it-yourself treatment will find instructions here

Anyone following the story of Emerald Ash Borer knew that it was only a matter of time before this insect would be found killing ash trees in eastern Pennsylvania. Maybe this knowledge lessened the blow a bit. Also, those who closely observe tree and pest interactions know that this is one of many associations between an insect (or disease pathogen) that results in catastrophic impact on a species. See Dutch Elm Disease, Chestnut Blight or Hemlock Wooly Adelgid. More recently, Thousand Cankers Disease of Black Walnut.

I never paid much attention to ash trees until EAB arrived in Pennsylvania five years ago. Now I see them everywhere. Not for long.

The Raised Bed Club

My pal Harry called recently to tell me that he had located some rough cut, white oak boards to build raised garden beds. We discussed board dimensions, how to fasten them together, what to fill the new beds with. I knew that Harry was about to become a member of the Raised Bed Club. I have been a member for about 15 years and it is probably the single most productive gardening step I’ve ever taken. I’ll outline some of the benefits and details here. If you want to take your vegetable gardening to another level, consider raised beds.

So, what’s the big deal with raised beds? For many of us (and certainly my original motivation) it is to gain the ability to garden in poorly drained soils… or to get access to garden soil earlier in the season. Raising the soil profile even a few inches creates gravitational pull on water that leaves it better drained. Many folks think that it is the media in the bed that is creating all of that drainage, and to certain extent, it does play a role. But even raising the existing soil on a site improves drainage dramatically. And if you are worrying about the task of importing a lot of stuff to fill you new raised bed… stop. You can accomplish a lot by simply using the existing soil.

Now, to talk out of both sides of my mouth, as they say…. let’s not ignore the potential to really improve soil texture and structure by amending that stuff we’ll fill those beds with. If you can add good organic matter to your existing garden soil in a raised bed you will see additional benefits. Where do you go for good organic matter? It’s everywhere. If you live in Southeastern Pennsylvania you are within an hour’s drive of some of the best compost money can buy. And sometimes it’s free! Spent mushroom compost is a beautiful thing. Many garden centers sell it. As you get closer to Kennet Square in Chester County it becomes more plentiful and cheaper. Since this stuff is often a waste product of the mushroom industry, there are mountains of it. It is simply the growing medium that several crops of mushrooms have been living in. It is high in organic matter and nutrients. Mix about 25 % mushroom compost, by volume, into even the crummiest soil and you have a decent growing media. Sure, do a soil test after you make this mix and adjust as necessary but that mushroom soil is nutrient rich and near neutral pH.

Composted leaves are stockpiled in many communities. While these will be less nutrient rich than mushroom compost, they do provide wonderful soil textural qualities. Again, adding about 25 %, by volume, is a good start.

Manure is magnificent. Find one of those old barnyard piles that has been ageing like a fine wine and you have hit the jackpot.

OK you get the idea. Find some organic matter. Amend your existing soil by incorporating about 25 % of what you can find with the existing soil. Then soil test and adjust fertility as needed. This will get you started. As time goes by you will fine tune that media in the beds. It will settle and shrink over time so yearly additions are needed.

Some garden centers and mulch suppliers sell a garden soil mix in bulk, by the cubic yard. Most will deliver. Tell them your bed dimensions and they will tell you how much you need. A bed that measures 8 feet by 3 feet by 9 inches will require 18 cubic feet… less than a cubic yard (27 square feet).

Rock raised bed

Wooden boards are probably material most people use to construct beds but many things can do the job. Rocks work. So do concrete blocks. I suppose you could use the fancy fake rock wall materials that are so popular. Metal, plastic, you name it. In fact, a raised bed can be borderless if you’d like. But the tidiness of wooden raised beds is nice. What kind of wood? Since there will definitely be contact with soil, a rot resistant wood is important if you want the beds to last more than a couple of years. Pressure treated wood sold these days does not contain arsenic.

Borderless Bed

Copper is used instead to resist the rots. Got old pressure treated wood with arsenic? There is pretty good evidence that this does not pose a great threat, but if you are going to spend one moment worrying about it (or trying to convince someone else who eats from your garden that all is fine by explaining the chemical qualities of arsenic) maybe it is a better idea to make a set of stairs out of those old pressure treated boards.

Black Locust Beds

Or… you can use naturally rot resistant wood. Black Locust is probably the most rot resistant species you can find locally. White oak is OK. If you have unlimited funds, Cedar and Redwood are sold. You’ll find locust and white oak at Pennsylvania sawmills. Yes, there are still sawmills around. I have 15 year old white oak beds that are just now breaking down. I expect the locust beds to be heirlooms.

Warped bed Board

The bed length is up to you but the longer board the more expensive they get. You can butt ends of individual beds together, as needed, if you have a big garden and want lots of gardening capacity. Bed width… you want to be able to reach across the bed from either side. Three feet wide is good. Wider is a stretch. Literally. If you don’t mnd working from both sides of a bed make them five feet wide. Board width…a full one inch board width will serve you well.

Locust is like concrete and must be pre-drilled in order to fasten end together. Screws are better than nails. Exterior grade screws are best. Plan to assemble you beds immediately after purchasing the boards at a sawmill, unless the boards have been properly dried, otherwise warping will make this impossible later.

How deep should the bed boards be? Six to eight inches is enough. More is a better but the boards will get expensive. Want deeper beds? Make them the identical dimensions and stack them on top of each other.

Hoops and Plastic make a Mini Greenhouse out of a Raised Bed

It is hard to believe that raising your garden surface less than a foot would yield huge benefits…. But it does. You’ll find gardening gets easier and your efforts are more productive. Your fingers are all you need to plant and weed. You will probably find yourself making low covered tunnels to extend the growing season and seeding crops like lettuce in solid beds instead of rows. You’ll make a cold frame instantly by covering a raised bed with a discarded window. You’ll be gardening earlier and later in the season… harvesting lettuce for Thanksgiving… or Christmas!

Ready for a new gardening adventure? Make a couple of raised beds.

Disarded window makes a cold frame out of a raised bed!

For a nice publication on the subject, see this from Missouri xtension.

Plan and Plant



Winterberry holly bent badly in the October snow storm. It recovered.

 What to do in the yard and garden in December? While we might putter around with the compost pile, rake up the last leaves or finish clean up from that October snow storm, the list of possible gardening tasks is pretty short. Now is a great time to begin planning for next year’s spring planting…..especially tree and shrub planting.





Japanese Zelkova after the storm... beyond repair

  Many of us have been forced to think about tree replacement as a result of the late October Snow storm. Six to eight inches of snow applied to trees full of leaves was devastating. On the other hand…the weaklings were weeded out!

Southeastern Pennsylvania certainly could use more trees. In fact, research done in 2002 showed an alarming loss of tree cover in the metro Philly area. In response, Tree Vitalize was born. This private/public partnership has the goal of establishing one million new trees. Quoting from the Tree Vitalize website... “An additional goal is to train 10,000 volunteers in basic tree biology and tree care to assist their communities in establishing and maintaining new plantings. Ultimately, the goal of TreeVitalize is to establish strong urban forestry partnerships in all 14 Pennsylvania metropolitan areas and to build local capacity for sustaining the urban forest resource.” If I am reading the website correctly 296,952 trees have been planted so far. It is a wonderful program. Check it out at http://www.treevitalize.net/ . The volunteer portion of the program is called Tree Tenders and training is ongoing in many communities. See this for details.

Tree Vitalize and Tree Tenders are great programs for communities that want to establish trees. They are not designed to assist private property owners.



Bucks County Master Gardeners plant bare-root Tree Vitalize trees

 Penn State Master Gardeners have planted about 75 Tree Vitalize trees at Neshaminy Manor Center, home of the Penn State Extension office. We’re calling our planting The Almshouse Arboretum and it consists of Tree Vitalize trees, some existing trees, as well as specimens we have added on our own. Most of the trees are labeled so you can do a self-guided tour. Or, contact us to have a Master Gardner give you or your group a personalized tour.

OK. Back to your yard….Maybe you have other reasons to plant trees and shrubs. Still trying to sell that house? Realtors will tell you that well landscape properties have exceptional value. Whatever your motivation, tree planting is a good idea. So where to start….

Penn State has lots of help. Trees for Pennsylvania Landscapes and Shrubs for Pennsylvania Landscapes are two excellent references. They describe great plants and categorize them by size and other characteristics such as flowering habit, fall foliage, etc.
Now is a great time to consider where to locate new landscape plants. Your local garden center/nursery usually has a landscape designer on staff to talk this through with you. Check out the Penn State publication Landscaping Home Grounds for some basic principles of landscape design and you’ll be a step ahead when you begin this conversation.


Finally…the actual planting. You can let the professionals do this or tackle it yourself. Planting and After Care of Community Trees will give you good guidance. Or, for a great, short video on the tree planting process, just watch the video produced by the Penn State Master Gardeners of Berks County at this site.
Alright, you’ve got all winter to read, study, talk and plan for tree and shrub planting this spring. Unique, beautiful, long-lived, wildlife-supporting plants are ready and waiting for new homes. It’s up to you to do your part.

Thousand Cankers Disease threatens Black Walnut.. and some businesses

A species is at stake. Businesses are at stake. Both may survive but damage has already been done and the future is uncertain.




Black Walnut, Juglans nigra, is an important tree species in the eastern United States. In July of this year, Thousand Cankers Disease (TCD) was detected in Pennsylvania for the first time. We now join two other states east of the Mississippi with confirmed cases of a disease which is deadly to black walnut. A quarantine has been established by the Pennsylvania Department of Agriculture in an effort to slow the spread of the disease. The quarantine prohibits the movement of walnut out of Bucks County, the only county in Pennsylvania where detection has occurred. All firewood and wood chips are also subject to the quarantine since segregation of walnut from these potential infection sources cannot be assured.


Here are some questions and answers about Thousand Cankers Disease


Q. Where did it come from?


A. New Mexico, California, Colorado, Oregon, Washington and a few other western states began detecting the disease about ten years ago. In 2010 it was found in Tennessee... in 2011 Virginia and Pennsylvania. It is likely that movement of walnut logs or other walnut wood brought the infestation from the west to the native range of black walnut…. the eastern United States. Both the walnut twig beetle, Pityophthorus juglandis and the fungus Geosmithia morbida which are involved in the disease, are thought to be native to the southwestern United States where they originally infested/infected other Juglans species.


Q. How are black walnut trees affected?


A. A beetle about the size of a sesame seed, called the Walnut Twig Beetle, bores into trees. Actually thousands of beetles infest individual trees. The beetle’s larvae tunnel in the bark and at the same time infect the tree with a fungus which kills the plant tissue. These dead areas are called cankers. Many cankers combine to girdle and kill the stems. The numerous feeding sites and cankers give rise to the name Thousand Cankers Disease. Infested walnut trees exhibit yellowing, wilting and dieback in the crown or upper branches of the tree. Within 10 year of infestation, and three years from the time symptoms develop,  the tree dies. The best diagnostic sign will be numerous tiny (2 mm) holes in the bark of branches. Beneath the bark, darkly stained, cankered, wood indicates the activity of the fungus. Most Juglans species are susceptible to TCD but Black Walnut appears to be most severely affected.


Q. Are there treatments to cure affected trees or prevent infestation of healthy trees?


A. Not at this time. The nature and habits of the beetle present a great challenge to those who want to control this pest. For instance, adults are active from March through October and can fly 1-2 miles. Even if beetles are partially controlled, the fungus may still cause damage. Research is underway to better understand both the beetle and the fungus involved in the disease.


Q. Why has quarantine been established?


A. The quarantine is an attempt to slow the spread of the disease and preserve this important tree species, both within Pennsylvania and also in states that are currently uninfested.


Q. What businesses are affected by the quarantine?


A. It is unlawful to move any walnut wood (except kiln dried lumber or finished furniture) out of Bucks County. Since it is impractical to distinguish walnut from other wood in loads of firewood or wood chips, they are subject to the quarantine and may not be moved out of Bucks County. Walnut lumber is also quarantined unless it meets certain requirements including kiln drying.


Q. What is being done about the problem?


A. A task force involving regulatory and research experts is creating an action plan to manage TCD in Pennsylvania. Compliance agreements with those affected by the quarantine are being investigated in an effort to find a way to allow them to continue business activities without presenting a threat to walnut outside of Bucks County.


Q What do I do if I think my walnut trees have TCD?


A. Collect a sample of branches with wilting and dieback symptoms. If they exhibit many tiny holes in them, contact Pennsylvania Department of Agriculture 1-866-253-7189 or Penn State Extension.


Q. How can I learn more about the disease and its symptoms?


A. Call  (215-345-3283) for a fact sheet or see this website.


In summary, a new disease of Black Walnut threatens an important tree species. Sadly, we’ve seen situations like this before…. Chestnut Blight, Dutch Elm Disease (DED), Hemlock Woolly Adelgid. Perhaps Dutch Elm Disease is most similar because in both cases a beetle vectors a fungal pathogen. Decades after Dutch Elm Disease was introduced, we still have some elms, but the once loved American Elm has been seriously impacted. Many differences exist between DED and TCD but its probably a good place to start as we contemplate the effect of TCD in Pennsylvania. How the story of Thousand Cankers Disease of Black Walnut will play out remains to be seen.