Horticulture Newsletter
June 2002

A Look Inside. . .	Archived newsletters

Upcoming Activities Perennial Plants With Fasciated Growth Zonal Geraniums Summarized from Northeast IPM Notes Commercial Berry Production Guide Update Early Season Pests Induced Resistance: Revving Up Plant Defenses Throw and Grow Mushrooms Should You Fertilize Trees?

Swimming Pool Pesticide Recertification Training and Pesticide License Examination for Private and Commercial Applicators

Tuesday, June 18, 8:30 a.m. to 5:00 p.m. at the Elk County Emergency Management Center in Ridgway. Call 776-5331 (Elk) or 486-3350 (Cameron) for more information or to register.

Commercial Horticulture

Greenhouse

Perennial Plants with Fasciated Growth
By Alan H. Michael

I am seeing more herbaceous perennials with odd growth at the soil line resembling a small witches broom or cauliflower-like growth (fasciation). It is caused by the bacterium Rhodoccus fascians (synonym Corynebacterium fascians) which stimulates rapid cell division by producing plant growth hormones. The pathogen stimulates reapid cell division by producing plant tissues. It is spread by water, cuttings, tools and workers hands and it has been reported that sweet peas and nasturtium can be sources. My experience is, if you see the problem, it is best to discard and destroy the plants, then sanitize the area, tools and wash hands.

Its host range includes many herbaceous and woody ornamentals: geranium, petunia, baby's-breath, coralbells, veronica, larkspur, Shasta daisy, marigold, etc. For more information check out University of Illinois Report on Plant Disease RPD No. 619 at http://www.ag.uiuc.edu/~vista/abstracts/a619.html

Zonal Geraniums
By Alan H. Michael

I had the opportunity to visit a number of local greenhouses these past weeks and have been seeing zonal geraniums with "Funky Leaf Symptoms" my name for an otherwise unnamed and undiagnosed geranium leaf disorder. Symptoms are some combination of distorted, light yellow, dwarfed and mottled new growth. Additionally the outer ¼ inch of the leaf margins are often turned upward. The problem tends to be most severe on some of the newer geranium varieties in the dark red and lavender colors.

It is not a widespread geranium problem, but is increasing and when it develops can be devastating. I have seen 100% of a geraniums variety affected, making them unsalable. The first report was in Chester County, Pennsylvania spring of 1998 and we have seen it, in various amounts, every year since then and now we are hearing reports from other states as well.

The problem is often noticed in early February and continues through March and April. No cause has yet been determined, but we do see some similarities between affected crops. Most are on flood benches, pH have dropped to below 6.0, many to 5.5 and fertilization tends to be a soilless feed like 21-5-20. Soil tests often show high nitrogen, and/or high micros nutrients and occasionally high ammonia. We have looked at soil and tissue tests from the various growers whose plants have symptoms, but test results for other macro and micro nutrients, like iron and manganese, lack consistency. Some folks have speculated that it may not just be a pH problem, but many be associated with a pesticide or fungicide breakdown product that is activated by low pH in saturated soils.

Control or reversal is possible if plant symptoms are slight to moderate, if severe the plants will recover very slowly (Salable by the 4th of July, maybe!). The most successful control has been to raise pH with flowable lime (4 quart /100 gal.*) or potassium bicarbonate (2 pounds/100 gal.*) and use a calcium nitrate based fertilizer when possible.

(* rates from Paul Fischer et.al. Univ. of New Hampshire, "Iron-Out: A nutritional program for geraniums and other crops prone to iron and manganese toxicity at low media pH, February 22, 2001)

It is my understanding that a grower in North Carolina has observed similar geranium symptoms and attributes it to something in their irrigation water. We in Pennsylvania have not been able to confirm a cause due to water contaminates and continue to look at low pH and sub-irrigation as key ingredients. Drs. Bob Berghage and Jay Holcomb at Penn State, University Park are trying various experiments in hopes of duplicating symptoms.

Since this is a new problem and as of yet undiagnosed I am asking your help! If you have observed the geranium leaf and growth symptoms that I've described in your own greenhouse please let me know. Our goal is to document cultural techniques and try to look for similarities. If you have information call me, Alan Michael at 717-921-8803 or email ahm4@psu.edu. Thanks.

Summarized from Northeast IPM Notes

Many houses are crowded, so maximize light and air movement by proper crop spacing. Avoid excessive numbers of hanging baskets. Keep air moving with horizontal airflow and avoid overwatering crops during cloudy, damp and cool conditions. Be sure watering crews irrigate according to crop needs, not by a schedule. Overwatering promotes algae and infectious diseases.

INSV: Check New Guineas closely when arriving and as they grow. Look for stem blackening, stunting and distorted foliage and necrotic leaf spots that often have dark colored margins. Isolate suspicious plants and have them tested at a good testing lab.

BACTERIAL BLIGHT: Be on the alert for bacterial blight caused by Xanthomonas pelargonii or Southern wilt caused by Ralstonia solanacearum. Only the Xanthomonas causes leaf spots; but both diseases may cause wilting. Prompt rouging out is the best remedy for both of these problems, so aim for early detection. Get a confirmation from a lab and notify your supplier before throwing plants away. Don't take chances with these diseases!

THIELAVIOPSIS: Thielaviopsis (black) root rot on pansies (and fuchsias) has been reported and may be common this year. If your pansy or viola plugs are growing unevenly, with a number of stunted plants, they may be suffering from Thielaviopsis. The foliage of affected plants may be yellowed or purpled. Several fungicides are labeled for drench applications. Those with thiophanate methyl (Banrot, Cleary's 3336, Fungo Flo, Domain) have been consistently effective. For crops that don't mind, keep pH on the low side-about 5.5 to 5.8: Lower pH hinders Thielaviopsis.

DOWNY MILDEW: Downy mildew was seen on strawflower. Yellow spots and some necrosis was observed on the tops of leaves, and white downy mildew growth on the undersurface. Sporulation occurs when the humidity is high. Many areas of the U.S. have been reporting troubles with downy mildew so keep an eye out! Locally it is getting common on snapdragon and pansy. Effective fungicides include the mancozeb products Protect T/O, Junction and Dithane along with the strobilurans Heritage and Compass. Stature MZ is very effective, but check to be sure it is labeled in your state (not legal yet in New York).

POWDERY MILDEW: Powdery mildew is common on Verbena, petunias, pansies, gerbera daisies, non-stop begonias, hydrangeas, kalanchoes, roses, etc. Some kind of leaf spot has been found on verbenas-possibly caused by a fungal pathogen Cercospora. However, INSV and Xanthomonas can also cause leaf spots. Stay tuned for further updates.

CYCLAMEN AND BROAD MITES: Cyclamen and broad mites were reported on various crops, such as English ivy. Look for abnormal, distorted growth. Sometimes crops, including gerberas and begonias, will show bronzed tissue running adjacent to and along veins. Avid has been effective for both-Thiodan for cyclamen mites. Dan Gilrein, Cornell Cooperative Extension Entomologist, has initiated a trial comparing at various treatments.

THRIPS: Thrips continue to threaten almost all greenhouse ornamentals. Remember they can quickly spread the tospoviruses (INSV and TSWV) which have caused devastating losses in recent years. See the following site for a free downloadable fact sheet on thrips management: http://www.rce.rutgers.edu/pubs/pdfs/fs887.pdf

Small Fruit

Commercial Berry Production Guide Update

PSU's Commercial Berry Production and Pest Management Guide, 2002-2004 is available. There are a number of changes in this version. One is that the guide, as you may have noticed, is a 3-year version this time around. This will put it on a production schedule that will make future versions available earlier in the year, with the intention of having them available for sale in time for winter meetings. Additions to the current version are a table of small fruit pesticide chemical and trade names with information on preharvest and reentry intervals of each one. Brief overviews of protected (high tunnel and greenhouse) culture are included in the strawberry and bramble chapters. The pesticide table that covers fungicides used on strawberries includes information on chemical class of each fungicide so that growers can tell which ones have different modes of action for purposes of resistance management. Information on production, pesticides labeled for each crop and rates, and cultivars has been updated. Information on nurseries and other sources of production supplies have been updated and expanded to include sources of biocontrol supplies, promotional supplies, high tunnels, and more in addition to the information on irrigation, fumigation, row covers and plastic mulch, specialized equipment and packaging that was already there.

Pest Management

Early Season Pests

The warm winter will probably result in high rates of survival of overwintering pests, giving us a fairly high rate of pest pressure early in the season. Here's a review of some early season pests. Chemical control options for seed treatments have been improving and have been incorporated into the 2002 Commercial Vegetable Production Recommendations.

Corn Flea Beetle: The corn flea beetle is 2 mm long, has an oval-shaped black body tinged with bronze or bluish-green and yellow markings on its legs. Adults overwinter in dead vegetation and litter at the base of plants. They are active on weeds in the spring, then move to corn and feed during May and June. Infestations are more severe during a mild winter followed by a cool spring. Adult beetles leave small circular feeding holes and spots or long stripes along the leaves. Because the beetles develop on weeds, keeping fields free of weds helps in their control. Delayed planting may also reduce populations. The economic importance of this insect is that it transmits the bacterium in preventing disease. This pest is typically more of a problem in earlier plantings-if at all possible, we recommend planting resistant cultivars for the early plantings. Seed commercially treated with imidacloprid is also effective in both controlling the beetle populations, typically until the four to five leaf stage, and in controlling disease. Soil-applied insecticides can be used, but are less effective during cooler temperatures; foliar materials may be necessary during this period. Treatments can also be based on scouting after plant emergence. Begin checking plants at the spike stage, especially during sunny calm days when the beetles are more likely to be active. Examine ten plants at each of ten sites and determine the number of plants infested. Record the percent plants infested. If varieties susceptible to Stewart's wilt are grown, apply foliar treatments when 6% or more of the plants are infested with beetles, and repeat if beetle activity remains high

Seedcorn Maggot: The adult seedcorn maggot is a fly similar to a housefly, but you are unlikely to see it. The adult is only 5 mm (~ ¼ inch) long, and is more gray in color than a housefly. The damaging larvae or "maggots" are the immature larval stage. They grow from a newly hatch larva up to ¼ inch long, they are yellowish white, legless, cylindrical and tapered at one end. This tapered end contains a single hook-like appendage that is part of the mouth. There are no other readily visible mouthparts. Pupa are inside a puparium (a hardened skin) which starts as an ivory color and hardens into a reddish brown color. Pupae are also ~ ¼ inch long.

These insects overwinter as a pupa in our soils (farther south all life stages can be found during the winter). Adults emerge in early spring and lay an average of 270 eggs per females in moist soil. Soil containing abundant decaying vegetation is also attractive to the ovipositing female. Exposed peat or potting soil mix of transplants can also serve as attractive sites for females looking for a place to lay eggs. Larvae hatch and crawl to germinating seeds or plant roots and complete their development within two to three weeks. Several generations per year may occur. The maggots burrow into the seed causing seed death or poor germination. Damage tends to be spread throughout the field. The larvae feed on peas, beans, corn, cabbage, turnip, radish, onion, beet, spinach and sprouting potato.

Damage can sometimes be avoided by delaying planting until the first generation larvae have pupated. This date varies with locality but is approximately June 10. it takes about 450 degree-days to complete a generation, which is a bit fast for an insect species. In field corn, it you have passed 450 degree-days, you are typically past the first generation and after that soil conditions make it unlikely that seedcorn maggot would be a serious problem. However, in vegetable crops the later plantings of multiple crops can be attacked. Cultural controls include:

• Thorough incorporation of organic matter into the soil,
• Preparation of seedbeds for rapid germination,
• Shallow planting (encourage rapid plant growth and minimize the time the germination seed is sitting in the soil),
• Covering rootball of transplants when transplanting,
• Planting when soil temperatures are warm.

This last recommendation is especially effective for transplants. Studies in Indiana with melon transplants have shown that root damage is directly related to soil temperature.

Seed treatments applied at planting should give effective chemical control with minimal amount of pesticide. There are many new options and formulations. Current options are on page B54 of the 2002 Commercial Vegetable Production Recommendations. For some crops, we have the option of transplant application of Admire. For example, transplant application of Admire can be applied which also effectively controls seedcorn maggot. There are also several materials available for preplant incorporation that control can be applied. Post-applications, soil drenches after the damage is present, are not effective. See the Commercial Vegetable Production Recommendations for specific materials. We try and provide specific recommendations for each crop, but for all crops we review soil pest issues in the introductory material (called Soil pests - their detection and control, which is on B51-B54 in the 2002 Production Guide).

Wireworms: Wireworms are long, slender, hard-bodied, wirelike larvae of "click beetles." They are about 1.25 inches long by 1/8 inches in diameter. The larvae are the damaging stage, not the adults. The adults are called click beetles because of their habit of snapping and flipping their bodies when turned upside down. Wireworms have variable life cycles, depending on the species. Most species take two to five years to complete their development, so there is considerable overlap of larval sizes; the larger larvae do more damage. One species that is troublesome in potato (Melanotus communis; there is no common name) takes six years to complete it's life cycle. Wireworms overwinter as eggs, larvae or adults.

Wireworms do more damage during cool wet springs, especially in fields following sod or other grasses. They damage crops by devouring seeds in the soil, cutting underground stems and roots, and by boring into the larger stems and roots. Often the seed is hollowed out, leaving only the hull. All crops are susceptible to attack to one degree or another, and particularly susceptible are potatoes, carrots, peas, onions, corn, sweet potatoes, lettuce, melons, beans, cowpeas and sugar beets.

Plowing or cultivating infested soils in the late summer or fall exposes wireworms to natural enemies. Crop rotation helps reduce wireworm populations; continuous planting of vegetables and field crops, especially potatoes and wheat, tend to increase wireworm abundance. No-till fields may allow wireworm populations to increase.

A number of materials are available for wireworm-control (see the Commercial Vegetable Production Recommendations). Insecticides can be applied either in the spring or fall when the soil temperature at six inches deep is at least 50 degrees F. In general, seed treatments with only lindane or permethrin protect only the germinating seed from wireworms; commercially treated seed with imidacloprid provides longer control.

White Grubs: White grubs are the immature stages (larvae) of June beetles, May beetles and Japanese beetles. There are over 100 species of white grubs. They have a C-shaped body, a brown head, three pairs of legs and a slightly enlarged abdomen. Full grown grubs range from 0.75 to 1.75 inches long.

Adults feed on leaves of trees, whereas the larvae feed on roots, particularly bluegrass, other lawn grasses, timothy, corn, soybeans, tubers of potatoes and other crops. Grubs feeding on roots of corn cause wilting and stunting and death of the plant if enough feeding occurs. Similar to wireworms, cool, wet springs and areas previously in sod may have heavier infestations.

The life cycles of the more abundant and injurious species may extend over three years. Eggs are laid one to eight inches deep in the soil, especially near woodlands; after three weeks the larvae hatch and begin feeding on roots. During the winter the larvae migrate to deeper portions of the soil.

Crop rotation helps reduce populations. It is best to plant deep-rooted legumes (alfalfa, clover) in rotation with susceptible crops. In some regions a rotation of oats, barley or wheat with clover and corn has been satisfactory. Corn or potatoes may follow clovers but they should not follow grasses in the year of a heavy beetle flight. The most severe damage occurs on crops that follow grass sod. Late summer or early fall plowing destroys many larvae, pupae and adults in the soil and exposes these stages to predators, which includes many vertebrates, as well as parasitic wasps. Soil insecticides applied for wireworm control may also effectively reduce grubs.

Black Cutworms: As opposed to early-season pests like seedcorn maggot and wireworms, which may be found on many crops, black cutworms are primarily pests of corn, but they can also attack tomato, pepper and eggplant. The adult moths of this species become active in April and May in Pennsylvania. Females lay eggs in dead vegetation on the soil surface and in weeds, where moisture is high. The larva is greasy gray to black with a light stripe down its back. Full grown larvae are about 1.75 inches in length. Young larvae feed on the leaves of emerging corn, whereas the older larvae cut the plant off at the base (hence the name "cutworm") or bore into the plant. After four or five weeks of feeding in May and June, the larvae pupate in the soil. Two more generations may occur, but no damage occurs from these.

A number of cultural controls may help control cutworm populations: good weed control, fall plowing, spring cultivation after weeds have started some growth (height of 2 inches). Also avoid planting hill or row crops after grassy sod. No-tillage or reduced tillage may increase the amount of damage. Pre-planting or at-planting treatments for black cutworm can be used, but post-planting treatments based on scouting during the leaf stages are effective. Blacklight traps can be used to monitor moths, but it is as effective to monitor for feeding damage. In sweet corn, check each planting weekly during the spike through the five-leaf stage. Check for small irregular holes in the leaves, as well as missing or cut plants. If cutworms are present, examine ten sets of 20 plants throughout the field and record the percent of cut or damaged plants. Look under clods of dirt and vegetation and the bases of plants for the larvae; if you see the larvae, record the average size of the cutworms and the number per 100 plants.

In sweet corn during the two-leaf stage, apply a treatment if more than 10% of the plants show fresh signs of feeding. At the three to four-leaf stages apply treatment at a 5% level. Also, use your judgment based on stand count: if you are at the minimum stand count, you may need immediate treatment, whereas more feeding can be tolerated if the stand is heavier than needed. During drier condition, treatments may be less effective because cutworms may be feeding below the soil surface; in these cases, rotary hoeing or cultivation, as well as using higher spray volumes, may help increase the chances of contacting the insects with the pesticide.

Asparagus Beetles: There are two species of asparagus beetles: asparagus beetle and spotted asparagus beetle. The life cycles are essentially identical, except that the spotted asparagus beetle feeds on or in the berries and thus does not cause economic damage. The adult asparagus beetle is about 0.25 long, with a blue-black underside and a reddish-brown prothorax (the area immediately behind the head). The wings have a blue-black base color, are bordered with reddish-brown and have four creamy-yellow circular to rectangular spots. Larvae are about 1/16 of an inch long, with dark gray bodies and black heads. Eggs are slate black in color, elongate oval in shape and attached by one end to the stems of the host. The spotted asparagus beetle has a blue-black underside and a reddish back with 12 small black spots. Larvae are orange.

Hibernating adults emerge and feed about the time the spears are cut for market. Asparagus beetles chew the green shoots, causing the tips to scar and turn brown. The presence of the black eggs on the shoots also makes them unfit for market. The eggs hatch in about one week and the larvae may then cause additional damage. If enough damage occurs, the next year's crop may be affected because of lower root reserves.

There are not many reported cultural controls for these beetles. One, which may be useful to homeowners, is to harvest the spears regularly and the wash the eggs off the spears. Foliar materials are available and post-harvest treatments are also effective in reducing the number of overwintering beetles.

Induced Resistance: Revving Up Plant Defenses

Plants respond to attacks by insects and diseases by mobilizing an array of compounds that inhibit plant diseases or reduce feeding by insects. Often, plants in which resistance is induced by one pathogen or insect will also be resistant to some other pathogens or insects, but not necessarily the entire spectrum of potential pests. It is also possible that mobilizing resistance to one pathogen could increase susceptibility to another pathogen. Various ways of inducing resistance in plants are currently being studies as possible pest management tools in the field. In this article are some of the ways that plant resistance can be induced in the absence of pests, rendering plants more resistant to future attacks by insects or pathogens.

Composts: The application of mature composts to soil or potting mix has been shown to induce a resistance response in above-ground parts in several crops including cucumber and tomato. The exact mechanism by which composts and compost extracts induce resistance is not well understood and not all composts are able to cause an induced resistance response. One study that looked at 25 different composts for induction of resistance to bacterial spot in radish found that only two of the composts induced strong resistance (Krause et al. 1998). Resistance induction by composts may depend on the composts being recolonized by specific organisms during the curing phase (Hoitink and Boehm 1999). Induced resistance responses may also be variable from one batch of compost to the next and the response may be different when different types of soils are amended (Abbasi et al. 2001).

Isolated Plant Growth Promoting Rhizobacteria: One of the known mechanism for the induction of resistance by composts is the presence of certain plant growth promoting rhizobacteris (PGPR). Researchers have isolated a number of species of bacteria that have plant growth promoting properties and tested them in specific crop/pest situations. They have found that particular species of bacteria work better in particular plant/pest situations.

Zehnder et al (1997) found that plant growth was enhanced and feeding by striped cucumber beetle and infection by bacterial wilt were reduced in cucumber plants treated with a mixture of species of PGPR's compared with untreated controls. PGPR's have also been shown to protect cucurbits from anthracnose andangular leafspot (Raupach and Kloepper 2000) and tomatoes from viral diseases (Zehnder et al. 2001).

Other Microbials: Microbial products that are sold for biological control of soil-borne pathogens may also induce resistance to diseases of above ground parts. It is suspected that induced resistance to is involved because of cases in which the product was applied only to the soil and the effect was seen in the above ground parts of the plants. In a trial conducted on an organic farm in western New York during the summer of 2001, tomatoes drenched with a suspension of Plantshield (Trichoderma harzianum) at transplanting showed the lowest levels of early blight at the end of the season compared with other treatments.

In a greenhouse trial, Mycostop (Streptomyces griseoviridis) applied as a soil drench provided control of gray mold comparable to foliar fungicide (Bravo) applications (Lamboy et al.).

Chemical Induction: A number of compounds have been shown to induce resistance in when applied to the foliage. Among the compounds shown to have this effect are salicylic acid, potassium phosphate, a water solution of NPK fertilizer, plant extracts and extracts of microbial metabolites. Specific plant/compound combinations seem to be necessary to induce resistance; e.g. a given compound will induce resistance in some plants but not others. Commercial products that act as resistance inducers are currently on the market. One product is called Messenger. The active ingredient of Messenger is a protein called harpin which occurs on the cell wall of the bacteria that causes fire blight, and is recognized by plants as a sign of pathogen attack. Harpin application also has the beneficial side effect of increasing plant growth. Another product, called Actigard, is a synthetic chemical that induces a resistance response in plants. A third product, called Milsana, is an extract from the giant knotweed plant.

Nonpathogens or Weak Pathogens: Weak or nonpathogenic strains of plant pathogens can induce a resistance response if they have surface proteins detected by the plant as those of pathogens. Weak strains of viruses have been used to induce resistance that helps protect plants from later infection by virulent strains. Cucumber plants inoculated with anthracnose were found to have fewer striped cucumber beetles feeding on them in cage studies (Zehnder et al. 1997).

Induced Resistance on the Farm: Although research on induced resistance has been conducted since the mid 1970's, there is still a lot to be learned before it can be used predictably in the field. Growers who regularly add compost or other organic matter to their soil may already be taking advantage of the benefits of induced resistance because of the increased microbial activity that results from additions of organic matter. It's not clear at this point how much additional advantage the use of resistance inducing products would add to plants growing in a very microbially active soil. Those who are still working to build their soil may get some benefits from the use of microbial or other products that induce resistance. Microbial products have also been found to be effective in a greenhouse situation where sterile potting mixtures are being used. Products sold for biological control of certain pathogens may also have more generalized induced resistance effects. They include products such as Serenade, Plant Shield, and Soilgard. These products and the chemical resistance inducers listed above will probably not provide complete control of plant diseases, but may delay the date or reduce the number of times that a field reaches threshold, saving some sprays. Keep an eye on this emerging area of research as specific products and practices are developed for field use. In the meantime, regular additions of compost and/or other sources of organic matter to your soil may induce some resistance in your crops while providing other benefits to the soil.

Home Garden

Throw and Grow Mushrooms

Mushrooms growing is an interesting activity that can be as simple as inoculating a pile of wood chips with an easily prepared slurry or complex enough to require a state of the art growth chamber with total environmental control. Perhaps the simplest method of growing some delicious mushrooms is the so-called "throw and grow" technique. This procedure is not always successful, but neither are some of other gardening endeavors!

The process begins by finding and positively identifying a desirable species of mushroom. Many people who regularly gather wild mushrooms are happy to teach newcomers how, when and where to locate good edibles. Once you have located the desirable mushrooms, make detailed observations of the habitat you find them in. if the mushrooms are gathered in a forest, note the type of trees they are growing under, the approximate amount of shade they are in and the type of leaf duff or other organic material they are coming up through. Many species of fungi are always associated with certain types of trees because they colonize the roots of those trees. Other species may grow out of piles of woodchips, bales of hay or straw, manure or even manicured lawns. Mushrooms are generally considered undesirable in lawns, so it is not a good idea to inoculate lawn areas unless you don't particularly care about the grass.

The next step is to locate similar habitat in an area you can visit regularly. This is the area where you will be "planting" mushroom spores. To obtain mushroom spores for planting, remove the caps from the ones you originally found and identified. Use only healthy looking mushrooms that have not begun to decay and are still somewhat fresh. Throw a few to a dozen or more caps into a five-gallon pail of water that is at room temperature. Let the caps float in the water for at least five hours or overnight. Remove the caps, stir, cover the pail and let it sit for another 24 hours. The spores will disperse throughout the water creating a slurry that you can simply pour on the ground in a similar habitat. With luck, the spores will germinate and the resulting mycelia will begin to colonize the surrounding area, eventually producing mushrooms for you to gather and eat.

Paul Stamets, perhaps the most famous mushroom grower in the United States and author of several excellent mushroom-growing books, suggests adding a pinch of salt and two ounces of molasses to the five-gallon pail of water. The salt inhibits bacterial growth while the molasses "feeds" the dispersed spores. With luck the area you planted (a better term is inoculated) will produce mushrooms within a year and, in some situations, you may plant and harvest mushrooms during the same growing season. Just make sure that the mushrooms that appear are the same species you inoculated before you eat any!

Should You Fertilize Trees?
By Jerry Bond

It was this question from an arborist named Leo that got me started. "What kind of fertilizer are you recommending these days? A client of mine has a young sugar maple that isn't growing too good and I want to give it a shot of something." Good business, bad question. I told him how research indicated that the only limiting nutrient for most young trees on most soils is nitrogen. I added that because nitrogen is so mobile in the soil and because trees only need it for certain periods during the year, that we highly recommended that the nitrogen be provided in slow-release form. Good science, bad answer. When I stopped later to think about that exchange, I realized that I had failed to explore all sides of the question he asked me. In doing this, I had made him and presumably his customer, happy without addressing the actual problem. There were two better answers I should have given. A tree not growing well needs either to have growth inhibiting factors identified and removed, or to have growth promoting factors identified and supplied. The number of possible growth inhibiting factors is, of course, very large. Diagnosing tree problems in the field can be tricky stuff, as anyone who routinely tried can attest. In an urban setting we usually look first to abiotic stress caused by soil, water, temperature, mechanical difficulties or human disturbance. When I didn't explore these factors on the phone, I gave up on understanding the real problem. To make it worse, the answer I gave ignored the important distinction between "tree growth promotion" and "tree fertilization." Factors important for improving tree growth have been well established, though it seems to me that we often ignore them.

Light is an important factor. To promote sugar maples growing in forests some forest owners cut down some of the surrounding trees, in order to increase their ability to gain from photosynthesis. In second place is water. When sufficient light is present, adequate water keeps the tree from stopping photosynthesis during summer or other droughts. In that way, more photosynthates (including carbohydrates that provide energy for defenses against decay and pests) are produced over the growing season, and the tree is both growing and strong. Controlled studies have demonstrated that there is no difference in many cases between simply adding water, and adding water plus fertilizer. Surprisingly, air is third in importance, soil air, that is. Urban soils frequently lack air, they are compacted, because their macropores are either crushed (from traffic of some kind) or filled (with water). Without sufficient air, most tree roots cannot get the oxygen they need to burn sugar through respiration providing energy for defense, carbohydrate storage and growth. For people who care about a declining tree's health and growth, soil aeration is a professional service well supported by research and well worth its cost.

Fourth, finally, is fertilization. But even here, mineral fertilization is less important in the long run than organic fertilization. Organic matter, such as provided by mulch, in addition to bettering soil texture by adding air, promotes the microbial life that is crucial to a healthy soil ecology. Also, it supplies organic acids that hold nutrients, especially micronutrients, in a form available for uptake by tree roots. A wide layer of composted mulch is a good start here. Don't get me wrong: mineral fertilizer has its place. But nitrogen is the element that primarily limits tree growth, especially for deciduous trees. Deciduous trees with high nutrient demands but planted (why, Lord?) on a soil with high sand content may need annual fertilization along with supplemental watering. A number of trees grown on a soil with light pH levels have trouble getting the micronutrients they need, because the high pH of the soil solution renders nutrients like nitrogen and maganeze unavailable to the trees. Without the application of an acidifier (such as EDDHA) such trees will grow weakly at best. But without sufficient light, water and soil air, mineral fertilizer is unlikely to promote healthy tree growth by itself. And if it does, it will probably be the watering or soil aeration accompanying it that actually brings the benefit.

Sincerely,

Gregory K. Burns
Elk-Cameron Extension Director

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