Yews Sensitive to Wet Roots

Yews have very few serious insect or disease problems. When a yew does die, the common cause is "wet roots." And, people usually cause the problem. Anything that keeps the roots of the plant wet for an extended period of time will cause root rot and resulting death of the plant.

Plants located near a downspout or under a leaking gutter connection are usually the first to show symptoms of the problem. You can correct the problem by connecting a drain to the downspout to move water away from the plants. Proper sealing of gutter connections can protect the plant under a leaky area.

Planting the yew too deep is another common problem. Tight clay soils are usually poorly drained to start with. If you have good soil, plant the yew no deeper than it was in the nursery. If you have poorly-drained soil, consider raising the planting depth.

Do not use black plastic around the base of yews because it can keep the roots continually wet. Instead use a mesh-type material that lets water pass through and evaporate from around the plant. Professionals will plant on raised areas and alter soil conditions to provide drainage when using any material around the plant.

Occasionally in the spring, you may see that small twigs at the ends of branches have turned brown. This browning is winter damage. The brown branch tips should be pruned back.

Yews have few insect problems, but on occasion they do occur. Scale is the problem most likely to occur, and different types of scale infest yews. You need to know the type of scale to determine when controls should be applied. To control scale, chemical products must be applied while the scale is in the crawler stage. Once the hard, scaly shell begins to develop over the crawler, chemical control is not as effective.

The black carpenter ant and the termite occasionally infest the trunk of an older yew. Both are capable of excavating the trunk and nesting in the trunk. This infestation rarely occurs and can be controlled with a chemical application.

The black vine weevil, or taxus weevil, has also been found on yews in Illinois. The larva of the black vine weevil feed on the roots of the plant,consuming the smaller roots. The adults appear during early or late June. There is only one generation per year. The adults feed on foliage during the day and hide at the base of the plant at night. The adults make a crescent-shaped feeding wound on the leaf margin. This feeding damage can be an indication of root feeding damage by larva that may also be occurring. At the time feeding first occurs, you can apply a soil drench using an approved insecticide.

What about pruning? When yews are growing well, prune every spring and again in mid-June to maintain shape and compactness. Cut back the current season's growth to a cluster of side branches. Make angle cuts whenever possible. Minor pruning can be done any time during the growing season.

Orange Rust: One of the Worst for Brambles

Some plant diseases are worse than others, and orange rust of brambles falls in the worse category. Orange rust is the most important of several rust diseases that attack brambles and is caused by the fungus Arthuriomyces petkianus. All varieties of black and purple raspberries and most varieties of erect blackberries and trailing blackberries are susceptible to orange rust. Orange rust does not infect red raspberries.

The orange rust fungus grows systemically throughout the roots, crown, and shoots of an infected plant and is perennial inside the below-ground plant parts. Once a plant is infected systemically by orange rust, it is infected for life. Orange rust rarely kills plants but causes them to be stunted and weakened so that they produce little or no fruit.

Orange rust is easily identified shortly after new growth appears in the spring. Newly forming shoots are weak and spindly. Leaves on canes are stunted and misshapen and pale green to yellowish. Within a few weeks, the lower surface of infected leaves are covered with blister-like pustules that are initially waxy but turn powdery and bright orange. These "rusted" leaves wither and drop by early summer.

Although young, apparently healthy canes with normal leaves can be found toward the end of June, the plant is still infected. There are no fungicides available that control orange rust after a plant has become systemically infected. When the disease first appears in early spring, dig up and burn infected plants before the pustules break open and discharge spores.

There are two main periods during the growing season when fungicide sprays are effective in preventing infection of healthy plants. The first period is during the spring when the bright orange spores (aeciospores) are being produced, around mid-May through mid-July. Sprays at this time control the "localized" infection and prevent systemic infection (teliospores) later in the season.

The second period is during the late summer or fall as temperatures decrease and the threat of systemic infections occur. Unfortunately, the fungicides that are labeled for control of orange rust in brambles are only available on the commercial market and include Nova, Abound, Cabrio, or Pristine.

For more information on orange rust of brambles, refer to the Midwest Small Fruit Pest Management Handbook (http://ohioline.osu.edu/b861/) and University of Illinois Extension Report on Plant Disease No. 708, Orange Rust of Brambles (http://web.aces.uiuc.edu/vista/pdf_pubs/708.pdf).

Tips for Growing Azaleas and Rhododendrons

Rhododendrons and azaleas are some of the best-loved landscape plants. They belong to the Ericaceae family which includes some great, but less commonly used, plants like Mountain Laurel (Kalmia latifolia) and Mountain Pieris (Pieris floribunda). Although our native azaleas are deciduous, most of the plants in this family are broadleaf evergreens.

These plants require acidic soil, pH 4.5 to 5.5. They prefer a partially-shaded site that receives cooler morning sun rather than hot afternoon sun. The plants also need protection from wind. A moist, well-drained soil is essential for healthy rhododendrons and azaleas. Waterlogged soils contribute to root rot–the number one problem of these plants.

Phytophthora root rot is the biggest problem. Phytophthora is a soil-borne fungal pathogen that requires wet soil conditions to infect the plant. Symptoms of the disease include yellowing and dwarfing of leaves and stunted shoot growth. Typically, you will see shoots that begin to brown and die back at the tip. The leaves usually roll downward and inward, then wilt and brown. Infected roots are reddish-brown and brittle.

Since Phytophthora is a systemic disease, it moves within the plant. Once you see the symptoms on the shoots and leaves, it's too late to save the plant. Pruning out the diseased branch can slow the death of the plant. Be sure to sterilize pruners with bleach after each cut is made; that way, you don't speed up the spread of the disease. Some chemical control options are available, but most only slow the spread of the disease; they don't completely eliminate it.

How do rhododendrons and azaleas get Phytophthora root rot? The fungus can be present in the container when you purchase the plant from the nursery or garden center. When buying, choose only healthy plants. Also, inspect the root system of your new plants before you put them in the ground. A healthy plant has an abundance of white roots, good foliar color, and is free of leaf lesions.

The problem could also be in the soil. Often, people replace a dead rhododendron or azalea with a new one, not realizing that the fungus that killed the first plant is in the soil. A few years down the road, the new plant starts to show symptoms on its leaves. Drenching the soil with a fungicide labeled to control Phytophthora may kill the pathogen in the soil. But, the best option for that location may be to choose a different plant, one that is not susceptible to Phytophthora.

Poor site selection and lack of soil preparation can provide the ideal environment for Phytophthora. Waterlogged soils also contribute to the problem. You can improve soil drainage by amending clay soil with organic material. Sphagnum peat moss is a good amendment for plants in the Ericaceae family because it is acidic and can help lower the pH of the soil; it also has fungistatic properties, meaning it inhibits the growth of fungal pathogens like Phytophthora.

Say "No" to Identifying Mushrooms

During the past weeks, clients may have asked you to identify mushrooms they found in the woods.

But, remember that the University of Illinois does not make positive identification of mushrooms without determining the spore pattern/print.....which means letting the mushroom mature to the point where spores are released.Only at this point, can we safely determine whether the mushroom is edible.

This may take several days to a week or more, which means the mushroom will no longer be edible.

There are too many mushrooms that look alike.are edible while others are poisonous. As a Master Gardener, you are urged not to get drawn in by a client who wants "you" to actually put "their" life on the line. You can see the words "lawsuit" and "liability" all over misidentification.

If someone wants to send in the mushrooms to the University of Illinois plant pathologists, or take their mushrooms to a mycologist at a university or college, that is their choice. This policy protects U of I Extension and you as a volunteer Master Gardener.

So when asked to identify mushrooms, explain the University's policy and simply say,"I'm sorry...we can't make that determination.don't have the skills or ability."

- Martha Smith, David Robson, and Elizabeth Wahle