Horticulture & Chemicals

Stressing out I recently transplanted a large B&B weeping Japanese maple that was shipped from Oregon to my location in Southern California. It keeps sending out new shoots, which then wither, and some entire branches are dying. I took great pains to plant it properly, but it's still declining. Could it have a root fungus? Should I try anti-transpirants? This is a very expensive specimen that I would hate to have to replace.-California

Extensive root loss always causes significant stress, which can lead to serious secondary problems. Thus, fungal pathogens are not out of the question. However, the symptoms you describe, by themselves, are likely due to simple transplant stress. Before concluding that pathogens are involved, check for other symptoms characteristic of fungal disease.

Your most immediate task is to ease the stress of transplanting. Dr. John Ball, an arborist with South Dakota State University, was not surprised that your tree was experiencing dieback, especially considering the drastic environmental differences between the tree's old and new homes. Ball recommends setting up an intermittent misting system in the crown of the tree. This will reduce transpiration as well as respiration rates. In addition to this, a shade cloth rigged over the plant will significantly reduce stress. Ball notes you may need to use the misting system throughout this summer, and the shade cloth perhaps into the following year until the tree's roots become established. This should enable the plant to recover from transplanting and tolerate its new, more-demanding climate.

Anti-transpirants are not Ball's first recommendation in this situation. Conceding that such products have their place in some circumstances, he notes that they also have drawbacks on actively growing plants in warm weather. They reduce transpiration by plugging stomates, which means that the plant will be unable to obtain much carbon dioxide. This, in turn, will reduce photosynthesis and food production. Further, by reducing transpiration, the foliage is at greater risk of overheating, if not burning, and will experience a higher respiration rate. Misting the canopy does not have these drawbacks.

Landscape math Could you describe a good formula for determining pounds of fertilizer to apply per 1,000 square feet?-Via the internet

Let's say you want to apply 1.0 pound of nitrogen (N) per 1,000 square feet. To determine the amount of fertilizer you should use, divide the pounds of N you want to apply per 1,000 square feet (1.0) by the percent N in the fertilizer. If, for example, you are using a product with a 24-5-12 analysis (the first number refers to the percent N in the fertilizer), then you would divide 1.0 by 0.24. The result is 4.2-the number of pounds of fertilizer you must apply per 1,000 square feet to provide 1 pound of actual N.

Typical fertilizer rates range from 0.5 to 1.0 pound of nitrogen per 1,000 square feet per application. The exact amount depends on the product, timing and the turfgrass. Be sure you have calibrated your spreader (or sprayer) to ensure accurate rates and that you have accurately measured the turf area you're going to fertilize.

Structural pest-control operators routinely advise homeowners to avoid applying wood mulch around their homes. They reason that wood mulch-which is wood, after all-is attractive to subterranean termites and could draw them closer to wooden structures. However, little research actually exists to support this concept, which may stem, in part, from the long-recognized fact that buried construction debris often harbors termites. To test whether termites actually consume wood mulch, researchers from Florida and Louisiana conducted a study to assess termites' appetite for this material.

The researchers tested termites' consumption and survival on six types of wood mulch: cypress, eucalyptus, melaleuca, pine bark, pine straw and chipped utility prunings containing a variety of woods. In addition, the researchers examined termite consumption of heartwood vs. sapwood of melaleuca and cypress.

The researchers found that termites consumed all the mulches except melaleuca. However, some woods were more attractive to termites than others. The researchers tested the various mulches for nutrient content and found that termites ate more of the mulches with higher nitrogen and phosphorus content. Thus, it was no surprise that the most desirable mulch to the termites was the utility mulch, which contained a variety of woods as well as some decomposed green tissue.

In addition, termites clearly preferred sapwood to the exclusion of heartwood. (Unfortunately, most wood mulches contain little heartwood.)

The researchers noted that termites require wood with a certain minimum amount of moisture (or else an alternate source of water). Owing to the prevalence of irrigation systems in landscapes, it appears that many mulches may, indeed, provide an attractive food source for termites. However, the discovery that certain woods-in this study, melaleuca and heartwoods-are not suitable food for termites provides hope that proper choice of wood mulch may reduce its potential to attract termites.

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