Research Update: Trenching near trees

Ever eat a pine tree? I have a healthy, good-sized lacebark pine (Pinus bungeana), and I have noticed some holes in the trunk, sort of like the dots on dice. I assume it's some sort of bird. Is there something I can do about this? -- Illinois

I contacted an extension horticulturist from Illinois who stated that regularly patterned holes in tree trunks, especially pines, are virtually always caused by yellow-bellied sapsuckers. Woodpeckers can also create holes in tree trunks, but the holes tend to be isolated or random, not in rows.

Sapsuckers are migratory birds, spending their summers in Canada and their winters in warmer climates to the south. They pass north through Illinois in mid-April and May and return southward in mid-September through early November. Like many migratory species, they tend to follow the same path during each migration and may even return to the same trees (especially a good sap producer), sometimes bringing their offspring along with them.

Sapsuckers peck holes to create a flow of sap, on which they feed. The holes can be severe enough to reduce growth or even cause tops to die out, so this is not a harmless activity. Pines are not the only species on which sapsuckers feed, but they are a favorite because they can produce copious sap flows. Feeding typically occurs at dawn and dusk, so these birds often escape notice by those who are at a site only during usual working hours. Making them even more elusive is the fact that, even though the migration as a whole may last 4 to 6 weeks, individual birds may linger in one place for just a day or two.

Yellow-bellied sapsuckers are protected by law, so you must not intentionally harm them. To discourage feeding on trees, you can wrap portions of the trunk on which the birds feed in burlap, paper, screen or anything else you can think of that would make it more difficult for the birds to peck the holes. Another strategy is to use plastic inflatable snakes or owls. Because crows may attack the plastic owls, many people prefer snakes, but you may need several spread throughout a large tree to provide adequate protection.

Just doin' its job How do I get more life from the air filter on a Briggs & Stratton Vanguard engine on a Scag mower? The engine sucks up anything loose in the area of the filter. -- Indiana

Air filters provide vital protection to engines. If your air filter needs servicing more often than you like, it's only because it's doing its job.

George Thompson, vice president of corporate communications for Briggs & Stratton, explains that engine components are designed for conditions typical of the tasks for which the equipment is intended. In unusually dusty conditions, your filters will require more frequent servicing. There's nothing you can do about that. Just be thankful that the debris is in the filter and not inside the engine, and keep servicing the filter as often as needed. As Thompson states, it's a lot less expensive to pay for new filters than to pay for a new engine.

Thompson also cautions against altering the engine, filter or air intake in any way. An engine's design is a product of many factors, some of which may not be obvious to the user. Alterations may cause damage or excessive wear to the engine or create a situation that endangers the operator. Plus, manufacturers do not usually honor warranties when equipment has been altered. Some operators, weary of replacing filters, shake or blow them out and reuse them to delay putting in a new one. This may or may not be acceptable depending on the type of equipment you are using (your owner's manual should address this topic), but you should follow manufacturer recommendations, whatever they tell you to do. Service guidelines are intended to give your engine a long life. Chances are the manual is going to tell you to cope with severe conditions by replacing the filter more often, and that's exactly what you should do.>SBResearch Update: Estimating l abor

Last September, we asked Grounds Maintenance readers how they estimate labor needs for various maintenance tasks. This is a frequent topic of reader inquiries, and we thought that actual experiences of grounds-care professionals would be helpful. Thanks to our readers for their numerous responses.

Before getting to that, here's a resource that's relevant to this issue. It's a maintenance-estimating guide published by the Professional Grounds Management Society (PGMS). The cost is $30 for non-members. You can order a copy by calling 410-584-9754, or writing to 120 Cockeysville Rd., Suite 104, Hunt Valley, MD 21031.

Additionally, PGMS is developing similar guidelines in conjunction with the Association of Higher Education Facilities Officers and the American Public Works Association. These will be specific to these fields, but they are not yet ready for publication.

Finally, Grounds Maintenance offers an article pack that includes 6 previously published articles on the topic of estimating. The cost is $30 (+ tax) and you can order by calling (913) 967-1780. (Ask for No. P2.)

The trouble with any estimating formula or guideline is that every site is unique -- applying set formulas to varying sites inevitably leads to inaccuracies. This is reflected in the comments from most readers who, with few exceptions, said they did not use formulas to estimate labor needs. However, several important themes were apparent in the responses:

* Estimates depend on site factors and maintenance intensity. This, of course, is the problem, but there seems to be no getting around it. Nearly every respondent made note of this. A university groundskeeper from Massachusetts summed it up: "I have yet to see [a formula] that works."

* Individual productivity varies. A Pennsylvania contractor offers this advice: "Realize that no one is going to work as hard as you [and] be realistic about the task and the people who will accomplish the task." A Burlington, N.C., reader adds, "Each individual is different. No set rate [applies]..."

* Experience counts. When asked how they arrive at estimates, the most common response from readers was, in effect, "based on experience."

* Learn from others. From an institutional groundskeeper in California: "Be open-minded to other people in the industry who are operating successful businesses and learn from them. Don't be shy to ask for advice and critiquing."

* Keep records. From Pennsylvania: "Learn from experience and keep track of elapsed time." Sound advice. Another reader, also from Pennsylvania, concurred: "If it's a new area, we record how long [the task took] and how many employees it demanded..."

* Tip of the month. A respondent from Hawaii added this often-overlooked aspect: "Always factor in a small percentage of time for 'personal contact' with each client."

Perhaps the most frequently cited reason for needing a labor-estimating formula comes from park and institutional managers that need to justify labor -- existing or proposed. A grounds superintendent from Illinois who obviously is familiar with this quandary stated it well: "I kept an actual record of time used in most of the grounds-maintenance activities with the help of my computerized and (self-invented) codified system. By the end of one season (one full year is better), one gets ideas of how many hours it takes to maintain a known number of square feet, acreage or whatever. I had to mainly use this as a tool to justify extra labor due to additions. Do-gooders wanted more flowerbeds, not realizing the extra work involved and manpower required. In those cases, my records were a defensive weapon."

How can we sum this up? Experience, record keeping, learning from others and familiarity with the site -- these are the marks of a well-run operation, so it's not surprising that they are your best tools for solving the problem of estimating labor.

Every contractor, sooner or later, must trench close to a tree. Though everyone agrees this can't be good, it is difficult to ascertain how damaging this really is. Trenching often occurs on sites where other construction activity is occurring, and subsequent tree decline may be due to several factors -- compaction, grade changes or altered drainage patterns -- other than direct root loss. Gary Watson, a researcher from the Morton Arboretum (Lisle, Ill.), conducted a study to evaluate the effects of root loss from trenching.

Watson also examined compensatory crown pruning (to mitigate the effects of root loss). Though it still has adherents, many experts discourage the practice of compensatory pruning, noting that it removes foliage that the tree needs to manufacture resources for root growth.

Watson compared pin oaks around which trenching was performed on no, one, two or three sides, with and without compensatory pruning. The pruning treatment consisted of removing about 30 percent of the leaf area. Then, for several years subsequent to the treatments, Watson measured trunk diameter, twig growth, stored starch and dieback.

Not surprisingly, reductions in tree growth related proportionately to the amount of trenching. Trenching on one side resulted in no significant reduction in trunk growth, whereas trees with trenching on three sides showed reduced growth every year of the study except the last (year 6). Reduced twig growth and increased dieback followed a similar pattern, though each was significant only for trees trenched on three sides.

Did compensatory pruning help? Somewhat, but the effect was modest except for the 3-trench treatments, which responded to the pruning with significantly less dieback. Additionally, Watson noted that pruning did not appear to reduce growth or carbohydrate levels. Noting the similarity between trenching and transplanting (both reduce root systems), Watson suggests that moderate pruning to alleviate effects of root loss should not be detrimental to trees. However, he cautions that the same does not necessarily apply to severe pruning.

Watson stressed that the trees in this study were young, vigorous and growing in high-quality soil. Mature or stressed trees might not respond as well to trenching or other root disturbances. Thus, "all site factors should be taken into consideration to assess the potential for root system damage and the chances for survival," and "the results of this study should not be used to justify unnecessary trenching around trees."

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