Research Update

Pruning sealant I've heard that pruning sealant is not recommended anymore. Is this true? -- Kansas

Your question demonstrates the power and persistence of myth. While it may be true that some "experts" used to recommend pruning sealant, arborists have been in general agreement for many years that pruning sealants are, at best, of no benefit. At worst, they can increase the risk of infection by wood-decay fungi.

Although it may be possible to speed wound closure to some degree, (see "Researching Maintenance," November 1996 Grounds Maintenance) with proper pruning practices and correct timing, a healthy, vigorous tree will heal pruning wounds adequately on its own.

PGRs and water use Do PGRs cause turf to use more or less water?-Colorado

Dr. Tom Fermanian, a turfgrass scientist at the University of Illinois, states that the few studies he has seen on this topic found either no change or a small decline in water use. Fermanian stresses that this is not a well-researched subject but notes that such a reduction in water use, if it occurs, could be due to decreased leaf area (resulting in lower transpiration) or lower metabolic-water needs.

According to Fermanian, PGRs are not an effective tool for reducing water use-the effect is just too small. If you treat turf with a PGR and find that the turf uses less water, consider it a bonus.

2-stroke oil and overheating Is there a special oil for 2-stroke mixes that prevents overheating? -- California

According to Eric Nolin of John Deere Consumer and Professional Products (formerly Homelite), oil-related overheating can result from insufficient lubrication. This causes increased friction which, in turn, results in overheating. However, the type of 2-cycle lubricant you use actually has little direct effect on operating temperatures.

According to Nolin, inadequate lubrication often is due to an insufficient amount of oil mixed into the gas. Lean running conditions (low fuel:air ratio) also cause inadequate lubrication. This often results from improper carburetor settings or an air leak in the crank case.

To avoid overheating, Nolin suggests the following guidelines: Regularly inspect and clean fan housings and cylinder air fins. Always mix fuel and 2-stroke oil according to manufacturer instructions. Adjust the carburetor settings to manufacturer specifications. If your equipment is still overheating, have it inspected by a 2-stroke-engine technician.

Keeping grass greener in fall How can I fertilize turfgrass to make it stay greener longer into the fall? -- Texas

Extension-service recommendations in Texas suggest applying a 3:1:2 fertilizer at 1 pound per 1,000 square feet just after the turf has started to go dormant. This will encourage warm-season turfgrasses such as St. Augustinegrass and bermuda-grass to stay green longer in fall. Dr. Douglas Welsh, extension horticulturist with Texas A&M University, explains that nitrogen stimulates the plants to retain their green tissue longer, while potassium may increase cold tolerance. Plus, late-season fertilization increases carbohydrate reserves, which encourages earlier and stronger spring green-up. Thus, Welsh says that this is more accurately thought of as "shortening the brown period," not just staying green longer into the fall. Welsh stresses that the fall-applied nitrogen should be a quick-release form but recommends slow-release forms for other times of the year.

In much of Texas, the time for this type of fertilization is around mid-October. The key determinant is waiting until the turf's growth slows, which happens after the first one or two cold snaps. After this, turfgrass plants will store resources rather than expending them to create growth. So this will vary by region and year. Welsh cautions that fertilizing too early, such as in August or September when temperatures are still warm, can cause excessive growth tender to frost damage.

Too much glue What is the correct amount of glue for joining PVC pipe and fittings? -- California

This is a seemingly simple subject, but one worth paying some attention to. Too little glue can cause joints to fail, as most irrigation installers are well aware. So, you want to use enough to ensure uniform and complete coverage of all adjoining surfaces within the union. But can you use too much glue? According to George Blanco of IPS Corp., the answer is yes.

If you use too much primer or glue, the excess tends to run past the union and into the interior of the pipe. Because virtually no air circulation occurs there, glue and primer will remain in a liquid state longer than when exposed to the outside atmosphere. This can soften the walls of the pipe, possibly causing it to split under pressure. Blanco states that this tends to be more of a problem with pipe with walls thinner than schedule 40.

Installers sometimes encounter fittings that are out-of-round or fit loosely. Blanco says that while using sufficient cement may fill in the gaps, a better and stronger joint will result with an interference fit-the surfaces are in intimate contact and will fuse together as the joint dries, creating an integral joint. That's why fittings are made with a taper-this helps ensure that the surfaces are in intimate contact and will fuse solidly after gluing.

Blanco points out that glue manufacturers usually print detailed instructions on their labeling. These will tell you how much glue to use, when to use primer and other information that can help you avoid pipe-union failures.

The gypsy moth is one of the great pest-control problems of our time. Since its accidental release in the United States in 1869, the gypsy moth has spread through most of the Northeast and continues to infest new regions, wreaking destruction on forests. Despite the introduction of several parasitic insects, outbreaks continue to occur with catastrophic results.

Mating pheromones are scents many insects use to lure mates from a distance. Agricultural and forestry officials have used the gypsy-moth pheromone disparlure in monitoring traps for many years. However, beginning in 1983, a product called Disrupt II was registered for gypsy moth control through mating disruption. Disrupt II consists of plastic flakes impregnated with disparlure, which permeated the atmosphere of the treated area. Males in treated areas become confused and unable to find females with which to mate. In U.S. Department of Agriculture trials conducted over the last several years, mating disruption has been highly effective in preventing mating and egg laying.

This method has advantages over other controls. For example, it is highly selective, with few or no non-target effects. However, the consistency of the formulated product has made it difficult to apply aerially. Taking a cue from a company that produces a similar product for pink-bollworm mating disruption (in cotton fields), the ARS researchers tried using plastic beads instead of flakes. In laboratory studies, it appeared that the beads were more efficient pheromone emitters than flakes. Unfortunately, the beads turned out to be more difficult to apply.

In spite of the drawbacks thus far encountered, the advantages of disparlure warrant further research, which is ongoing. Other controls such as Bacillus thuringiensis, diflubenzuron and conventional insecticides remain important. But, especially in isolated or sparse populations, pheromones can be a significant tool. Application difficulties notwithstanding, field treatments actually have met with some success.

Unfortunately, in dense populations, gypsy moths sometimes encounter one another simply by blind chance. Thus, a mating disruptor cannot eradicate heavy populations. Still, Kevin Thorpe, a researcher who works on gypsy moth control for the U.S. Department of Agriculture's Agricultural Research Service, notes that even in areas where the infestation is well-established, disparlure can significantly slow the rate of spread into uninfested areas, delaying the costly damage wrought by gypsy moths.

The Packaging/Container System Management Task Force of the Responsible Industry for a Sound Environment (RISE) recently conducted a survey of users of specialty chemical products. The purpose of the survey was to determine "end-users' attitudes, preferences and activities" regarding pesticide containers.

Among their findings: Most respondents (55 percent) said that no pesticide-container recycling or collection program existed in their area. Related to this, end users indicated that the most desirable aspect of refillable containers was that they eliminated container-disposal problems.

Respondents felt that difficulty pouring liquid products was one of the most troublesome characteristics of liquid containers. They expressed a similar attitude about opening and pouring dry products from bags.

Water-soluble containers are the favorite type of packaging among end users. However, end users want such packaging to dissolve more quickly. Many respondents indicated that incompletely dissolved soluble packaging often clogged their spray equipment. Also, respondents noted that manufacturers should improve outer packaging to protect water-soluble containers from moisture and humidity.

The task force concluded with several suggestions, including: Vendors should be required to accept used containers for recycling.

A zip-lock-style bag would make safe handling of dry products easier.

More liquid containers should incorporate splash-resistant or "no-glug" spouts.

Packaging should better protect water-soluble containers.

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