Galls on Trees and Other Plants are Common and Need No Treatment

Galls on Trees are Common and Need No Treatment

Bill Sevier: April 26

Q: What are these blister-like things on the leaves of my oak tree? Will it harm them? P.T., Tulsa

A: The structure on your leaves is a common oak leaf gall and will not harm a mature tree.

Galls are abnormal growths on plants and come in many different shapes and colors. Several types of pests cause galls, including insects, mites, bacteria, fungi and viruses. These pests specialize and almost always cause galls on a specific plant type — oak galls on oaks and ash galls on ash trees and so forth.

Galls may affect any part of a plant but most commonly are found on stems and leaves. Any time you see a bizarre, abnormal growth on a plant — round, flat, fuzzy or irregular and of one of many different colors not belonging to the plant — it is safe to assume you have found a gall. There are many hundreds of gall types and have been the subject of much folk lore in the past.

Many types of oak galls, such as oak leaf gall, are produced by a tiny wasp about the size of a mosquito. In spring, the wasp lays eggs as the plant is putting on new growth. The egg-laying process produces a growth hormone, which stimulates the plant’s system to grow a protective shell. This shell is the gall, and once formed, it completely seals off the larvae, protecting them from predators and insecticides.

The galls almost never affect a tree’s growth and survival; most homeowners’ main concern is the appearance of the tree when it is heavily infested.

Some types of galls can be detrimental to fruit trees, and insecticidal sprays may be recommended as the wasp is laying eggs in early spring. However, spraying is not suggested for shade trees in the landscape. If the tree is small enough where one can reach the galls, they may be cut out. The infested leaves should be raked and placed in the trash, but otherwise, galls are best ignored.

One unique problem significant to homeowners, which is associated with oak leaf galls, is the “oak leaf itch mite.” There was an outbreak of this mite in the Midwest two years ago, and Tulsa had its share of the mites. The mite has a bite like a chigger, but the bite area tends to be a bit larger and may contain a pustule. As the name indicates, itching is a prominent feature of the bite.

Oak leaf itch mites are produced by a female mite laying eggs in a “marginal oak leaf gall,” where its larvae feed on the galls larvae and reproduce. They are then released by the many thousands. Because of their size, they are spread widely by wind and are able to pass through screens of windows and doors. At present, these mites have no solution other than letting nature control them, which seems to have happened. They may return in the future, but there is no predicting this.

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Garden tips

·        Lace bugs, aphids, spider mites, bagworms, etc. can start popping up in the landscape and garden later this month. Keep a close eye on all plants and use mechanical, cultural and biological control options first.

·        Remove any winter-damaged branches or plants that have not begun to grow. Prune spring-flowering plants as soon as they are finished blooming.

·        Proper watering of newly planted trees and shrubs often means the difference between success and replacement.

·        Do not spade or till wet soil; it will destroy the soils structure and eliminate air spaces which takes a very long time to recover.

Planting Disease Resistant Elm Trees

Master Gardener: Elm hybrids are good choice for shade trees

 Brian Jervis: Master Gardener

 Tuesday, April 18, 2017

Q: I am looking to plant a large shade tree and wonder what my choices are. Is it too risky to plant elm or ash trees due to their diseases? J.C., Tulsa

A: Several species of our great shade trees in the U.S. have suffered from the impact of imported pests and disease, and the process is still ongoing.

Most of our stately chestnuts that were so common in the past were killed due to chestnuts bark fungus, imported from Asia in 1904. In the following 40 years, more than 30 million acres of chestnuts were destroyed in the eastern U.S. However, some hybrids are now available that have excellent resistance to the fungus.

Ash trees are being decimated by the Emerald Ash Borer, an insect introduced into the country in 2002. Until recently, it was found only in states surrounding Oklahoma, but now has been reported infecting ash trees in the northeast part of Oklahoma. It is now found in most every state from Colorado eastward. To date, it has killed many millions of ash trees, no control is developed and will likely kill most of the 8 billion-plus ash trees in the U.S.

The majestic American elm tree, which had covered many of the streets in the U.S. with beautiful canopies, have mostly been destroyed by Dutch elm disease (DED), a fungus introduced in the U.S. around 1930. Elms were used so much in the past that most towns and cities still have an “Elm Street.” Of the 77 million elms in North America, is was estimated that 75 percent had been lost to the disease by 1989. The fungus is spread by the Elm Bark Beetle, and all of the native U.S. elm species are susceptible to the infection.

Since the disease began, horticulturists have been involved with selective breeding of elm survivors of the disease. Now there are several hybrids that have shown good to excellent DED resistance and are a great source of high-canopy shade trees. All are hardy into the USDA zone 4, which may have temperatures as low as -30 degrees.

The best of these hybrids are listed below.

Princeton: Selected years ago for its resistance, fast growth rate and a canopy similar to the original American elm.

Valley Forge: A USDA-recommended cultivar that has excellent disease resistance and form. It also is a rapid grower.

New Harmony: Another USDA selection of an American elm hybrid that appears to have superior form when compared to Princeton and Valley Forge.

St. Croix: Selected from a massive elm in Minnesota. It has good disease resistance.

Prairie Expedition (“Lewis and Clark”): A recent selection from North Dakota State University. Classic vase-shaped American elm form and growth rate, outstanding autumn gold color.

These trees may be difficult to find, but some, such as Princeton, may be found at local nurseries. Most others are available online. You will find no better tree to plant for shade and an aesthetic addition to your landscape.

Garden tips

·       Don’t spray insecticides during fruit tree bloom or pollinators may be killed. Disease sprays can continue according to schedule and labeled directions.

·       Mowing of warm-season lawns is beginning now. Cutting height for bermudagrass and zoysia grass should be 1 to 1½ inches high, and buffalograss 1½ to 3 inches high.

·       Harden off transplants outside in partial protection from sun and wind prior to planting.

·       Hummingbirds arrive in Oklahoma in early April. Get your bird feeders ready using 1 part sugar to 4 parts water. Do not use red food coloring.

For Best Production Fruit and Nuts Need Thinning

Fruit, nut trees benefit from thinning

Bill Sevier Ask a Master Gardener

Tuesday, April 11, 2017

Q: The production of apples on my tree goes in cycles — lots of apples one year and fewer the next. Is there anything I can do to prevent this? S.G., Sand Springs

A: Yes, there is. Every year, you should thin out the apples when they are the size of a quarter so that there are 6-8 inches between each young fruit.

Thinning fruit is important for optimal production in most all fruit and nut trees. There is a reason for this, and it relates to basic plant biology.

Any fruit or nut produced by a tree is dependent on an adequate supply of water, nutrients and energy (mostly sugars). Water and nutrients, such as nitrogen, phosphorus, potassium and others are absorbed from the soil by the roots. To do this, there must be ample amounts of nutrients and water in the soil. Energy comes from photosynthesis. This is the production of sugars, an effect of sunshine on the trees leaves. So for fruit production, a tree needs healthy roots, plenty of leaves and sunshine.

There is a limitation of the amounts of nutrients and energy a plant can supply for growing fruits and nuts. When the demand is greater than the tree can deliver, fruits and nuts are not only small but also do not have the sweetness and flavor expected from that particular variety of tree.

Thinning not only improves quality of fruit, but there is also less chance of unwanted fruit drop, cold injury and limb breakage. Be aware that all fruit trees do not need to be thinned; some varieties will thin themselves of excess fruit early on in development.

The cycling of fruit and nut production (large crop one year and small or no crop the next) is usually due to depletion of energy stores in the tree during a heavy crop year, followed by a need to replace energy supplies and produce little fruit the following year.

Thinning fruit can be painful. For some fruits, such as peaches, upwards of ¾ of the total fruit crop may need to be removed to produce a quality product. Commercial growers of fruits and nuts (mainly pecans) have several ways of thinning their trees. This involves a variety of chemical sprays, as well as some mechanical shaking of trees.

Most homeowners thin what they can reach by hand. When thinning, one should look not only for proper spacing between fruit, but also select the largest and healthiest fruit in a cluster to keep on the tree.

Some of the recommended spacing between fruit when thinning are: Apples 6-8 inches, apricots and plums 4-6 inches, peaches 6 inches. Cherries are not likely to need thinning. Most pear trees also need no thinning unless that variety is prone to cyclic production.

As stated, thinning can be painful but is essential for full-sized tasty fruit and nuts.

Garden tips

·       Termites and ants are swarming now and will be into May. It is essential to identify whether the flying insect is a termite or ant. To tell them apart, one may need a hand lens, but the essentials are this: Termites have no waist — the waist is the same size as the chest — while ants have a tiny waist. Termites have straight antenna; ants antenna are bent. Each have two pairs of wings, the termites are of equal size, while ants have a shortened pair.

·       Termites flying inside your home is significant and an exterminator should be consulted. Termites outdoors could be important, but most are feeding on woody material (old stumps for example) and are doing natures work in breaking down dead organic material. Nevertheless, if you see termites outdoors nearby, your home needs inspection for signs of invasion.

·       March is the second best time of the year to seed cool-season turfgrass; however, fall is the best time to plant.

·       Let spring-flowering bulb foliage remain as long as possible before removing it.

Selecting Vegetables to Grow

Picking the right veggies to grow in Oklahoma

Brian Jervis Ask a Master Gardener

Tuesday, April 4, 2017

Q: What are the best varieties of vegetables to grow in Oklahoma? T.M., Tulsa

A: Our weather extremes present a challenge for many varieties of vegetables. Fortunately, there are some good resources from OSU and elsewhere. OSU fact sheet F-6032, “Vegetable Varieties for the Home Garden in Oklahoma” is a good place to start.

In addition, OSU conducted a vegetable trial in 2014 obtaining information on a wide assortment of vegetables. This is available online by searching for Oklahoma States’ “2014 Vegetable Trial Report.” In particular, this report has a review of the best tomatoes for heat tolerance and taste, which would be of interest to Oklahoma tomato growers.

Another resource worth looking into is the All America Selections website, all-americaselections.org. This organization evaluates a host of new cultivars of ornamentals and vegetables and submits a yearly list of its winners. A partial selection of vegetable cultivar winners and the judges’ comments are below.

Candle Fire okra: This okra has bright red pods that are round, not ribbed, on red stems. The Candle Fire okra was graded not only for productivity, taste, texture and tenderness, but also for ornamental value. It was noted to be tolerant of heat and disease resistant, which is particularly pertinent to gardeners in our area. It was recommended for its fruit and ornamental value.

Mad Hatter Pepper: This pepper has several assets, not the least of which is its unique shape. The plant is described as a vigorous early producer with high yields. It is a large pepper, with a good taste, according to AAS judges. They describe the taste as “a citrus floral flavor, which remains sweet, only occasionally revealing mild heat near seeds.” Its origin is South America, but this cultivar has been bred for North America. This pepper is worth consideration for appearance and for a healthy food.

Winter Honeybaby squash: This plant is productive and is compact. The vines grow to 2-3 feet in a semi-bush habit and would be great for a container garden. The squashes are short and wide and are meatier than most squash. The taste was described as sweet and nutty, and it was recommended to be used steamed, baked or made into soups and stews.

Chef’s Choice Yellow tomato: This is a beefsteak type indeterminate (produces all season) tomato with a nice yellow color and a great taste. The plant is productive, with 30 or more 10-ounce tomatoes on a 5-foot vine per season. It has multiple disease resistances.

Patio Choice Yellow tomato: This tomato is a compact determinate (produces one crop) cherry tomato; the vines grow to 18 inches and are ideal for containers or limited-space gardens. The plant is said to be productive, with more than 100 fruit per season, and having a favorable mild flavor. This tomato would work in a hanging basket and you would have the fruit at your finger-tips.

There are other vegetables and a host of ornamentals in this group of AAS winners; consider looking them over.

Garden tips

·       Most bedding plants, summer-flowering bulbs and annual flower seeds can be planted after danger of frost. This happens around mid-April in most of Oklahoma. Hold off mulching these crops until spring rains subside and soil temperatures warm up. Warm-season annuals should not be planted until soil temperatures are in the low 60s. The Oklahoma Mesonet website has information about soil temperatures.

·       Harden off transplants outside in partial protection from sun and wind prior to planting.

·       Don’t plant tomato sprouts too early. The soil temperature is key and should be above 60 degrees before planting. If the soil is too cool, the plants will sit there and not grow. Remove the blossoms from any tomato plant at the time of planting, it needs roots before making tomatoes.