Master Gardener Newsletter July 2006
Aphids Are Here!
They're here, they're there, and they're everywhere. Aphids, sometimes referred to as plant lice, can be found in most gardens. Aphids appear each year, but current populations are unusually high due to the warm, dry weather.
Aphids are awkward, usually slow-moving insects with somewhat pear-shaped bodies. They range in size from 1/16 to ½ inch and come in a wide variety of colors. Some may have relatively large, transparent wings while others are wingless. A pair of cornicles, or tubes, that resemble tail pipes can be found projecting from the rear of the abdomen.
Aphids are sucking insects that feed by thrusting a long beak into plant tissue. As they feed, they withdraw large quantities of sap, often resulting in curling and distortion of leaves. Succulent, new growth may wilt, or growth may be arrested by dense colonies.
Aphids are often found on the undersides of leaves or along the stems. As aphids feed, they excrete a sticky substance called honeydew. The honeydew falls to the upper surface of surrounding leaves and makes these leaves look shiny. When trees are heavily infested with aphids, sidewalks and automobiles may become wet with honeydew. A sooty black mold often grows in the honeydew and blackens stems and foliage. This fungus is unsightly but is not harmful to the plant.
The life history of aphids is somewhat complicated and varies with the species. Usually, overwintering eggs on branches and stems hatch in the spring to produce a wingless form known as the stem mother. The unfertilized stem mother gives birth to living young in great numbers. Several generations may occur in this fashion; but in due time, some individuals will develop wings and migrate to another host. Here they may deposit eggs for the winter or, after a few generations, migrate back to the original host to lay eggs.
Because of their efficient reproductive ability, aphid populations seem to build up overnight. Normally, a wide variety of predators, parasites and rain keep populations in check. But, this year is an exception. Numbers continue to increase, and in many cases, control measures are warranted.
If infestations are confined to a branch or stem, hand pruning can be done to selectively remove the branches. Several strong blasts of water with a garden hose will sometimes reduce numbers. Either of these methods will not harm lady beetles, aphid lions and syrphid flies which are helpful in naturally keeping aphids under control.
Insecticidal soaps can be used to reduce aphid populations. The soaps break down the cuticle covering of the soft body aphid, making it susceptible to drying out.
Small, heavily infested plants may need to be treated. Aphids on large trees usually do not cause sufficient damage to warrant any control measures. Instead of spraying large trees, time and money would best spent watering and fertilizing to promote recovery.
Be On The Watch For Emerald Ash Borer
As you have most likely heard by now, a non-native, destructive pest that feeds on ash trees has been found in northern Illinois.
On June 13, the Illinois Department of Agriculture announced that in Kane County a beetle was identified as an emerald ash borer.
Emerald ash borer (EAB) had been confirmed in the Midwest during the summer of 2002 and, since then, more than 20 million ash trees are dead or dying. The emerald ash borer, Agrilus planipennis, attacks and kills healthy ash trees. It is a small, metallic-green beetle whose larvae burrow into the bark of ash trees, causing the trees to starve and eventually die.
The EAB is closely related to the bronze birch borer, so its damage, appearance, exit holes, and biology are similar to that pest's except that it attacks healthy ashes rather than birches. Its native range includes China, Korea, Mongolia, Japan, the Russian Far East, and Taiwan. In the U.S., the EAB was first identified in the Detroit area. Since then, it has also been found in other areas of Michigan and in Ohio, Indiana and Maryland, and Toronto, Canada.
Local, state and federal agencies have been preparing for EAB. Now that it has been found in Illinois, a response plan will begin the task of eradicating it.
The first step is to conduct an extensive survey of ash trees in the Kane County subdivision to determine the extent of damage. Then, boundaries for a quarantine will be established to stop the movement of potentially contaminated wood and nursery products out of the area and prevent the spread of EAB.
Inspectors think EAB may have been transported to Illinois in contaminated firewood from a quarantined area in Michigan. The emerald ash borer typically moves only short distances by flying, but moves long distances on ashnursery stock, ash logs, branches and firewood. To avoid bringing the beetle to new areas, we are advised to purchase only locally-grown nursery stock and locally-cut firewood.
As a Master Gardener, you can play a vital role in watching for this pest–in your own landscape and as you assist clients.
If you suspect EAB, contact the U of I Extension horticulture educator who covers your county. The Illinois Department of Agriculture also has a toll-free hotline, 800-641-3934, for Extension-confirmed infestations.
Signs of infestation include the presence of metallic-green beetles about half the diameter of a penny on or around ash trees, thinning and yellowing leaves, D-shaped holes in the bark of the trunk or branches, and shoots growing from the base. Options for treating infested trees are limited. In most instances, they must be removed.
Common Tomato Problems in the Home Garden
July is here and tomato problems will start. There are a number of diseases that Illinois tomato growers face, but the most common are Early blight, Septoria leaf spot and Late blight.
Early blight, also known as Alternaria leaf spot, can affect plants at any stage of development. All above-ground parts are susceptible. Spreading spots, ¼ to ½ inch in diameter, form on lower or older leaves. These spots have dark edges, and they are usually brown to black in the center. These spots frequently merge, forming irregular blotches. Concentric rings often form, creating a target or bulls-eye effect. Affected leaves develop yellow areas around the lesions. Spotted leaves soon turn yellow, whither and drop off. The fungus may cause lesions on the fruit around the stem end and shoulder. The lesion is usually dark brown to black, up to 1 inch in diameter, and with distinct concentric rings.
Septoria leaf spot can also affect plants at any stage of development. Numerous small, water-soaked spots first appear on the lower leaves. These spots soon become circular to angular with dark margins and grayish centers, often bearing one or more tiny black bodies called pycnidia which are spore-bearing structures. Individual lesions are seldom more than ? inch in diameter and are usually quite numerous on an infected leaf. Heavily diseased leaves turn yellow, wither and drop in large numbers, starting at the base of the plant. Defoliation can be severe during prolonged periods of warm, wet weather.
Late blight in garden tomatoes usually appears in mid- or late August. A primary source of this disease can be from leftover potatoes from last year's garden. Ideal conditions for development are warm, humid days followed by cool night temperatures with heavy dew, fog or light drizzly rain that persists through morning. A heavy overcast sky during the morning prevents temperatures from rising rapidly, and the foliage remains wet. In moist weather, this fungus can be carried 20 miles or more by strong winds and rain. On older plants, the fungus causes small to large, irregular, rapidly enlarging, water-soaked, pale green to greenish-black lesions which usually start at the margins or tips of the leaves. In dry weather, these lesions turn dark brown, dry, and wither. A pale green halo often surrounds affected leaf areas. The spot may enlarge until entire leaflets are killed. Lesions can expand rapidly and result in extensive, if not complete, defoliation within two weeks. Severely affected plants may appear as if damaged by frost. Infection of both green and ripe fruit starts at the stem-end or the side of the fruit. It soon spreads over the entire fruit. Infected areas are dark green, brown, or brownish-black and "greasy," with a rather firm but slightly wrinkled surface.
Successful disease control involves several steps. These guidelines should help to insure a healthy crop.
·Crop rotation is recommended every year. Do not plant
solanaceous crops (tomatoes and potatoes) in the same area more often than once every three or four years.
·Destroy any volunteer plants. This will prevent buildup of disease
organisms in the soil.
·Purchase only disease-free plants from a reliable grower.
·Allow adequate space between plants to increase the rate of evaporation of water, whether it's rain or dew.
·Harvest all ripe fruit at each picking. Ripe fruit left in the garden may decay and infect the remaining fruit.
·Don't cultivate or work plants when foliage is wet with dew or rain. The organisms spread under these conditions.
·When the above measures fail to provide adequate control, apply recommended fungicides according to label directions.
Contact the Extension office for current recommendations.
·After harvest is completed, spade or plow under, compost, or burn all tomato vines. Destroy all
potato cull piles, volunteer plants, and solanaceous weeds such as groundcherry, horse nettle, night- shade, and Jimson weed.
A Note from Sharon
Hi everyone,
Summer is upon us! The field crops are growing inches every day and my vegetable garden is progressing–I know some of you have had green beans already, but mine won't be ready until late this week (I'm writing this on the 5th). Can't wait---it is so easy to follow nutrition guidelines for meals this time of year. The fresh fruits and vegetables can't be beat!
Thanks to all of you who assisted with the Mattoon and Charleston area garden walks. It is great to have a U of I Extension Master Gardener presence at those community events. I saw some of you with your MG manuals hard at work answering questions in Mattoon and I heard about plant samples and questions coming into the library at Charleston.
The details about 2006 State Conference are in the latest issue of Imagine. If you haven't received a copy of it, we have one posted on the bulletin board at the office and it is also on our county web site on the Master Gardener quick link. If you haven't attended the conference before, you might want to check out the schedule. It is a great opportunity to learn new gardening techniques, share master gardener experiences and learn about projects across the state. The Quad Cities is a great place to visit---the spring Unit Leader Conference was there in 2005 and the facilities were great---very close to the John Deere complex with museums and stores. Find out who else is interested in attending and make plans to car pool with some of your MG friends.
I also want to thank each of you who taught, assisted, coordinated, demonstrated, or contributed in some way to the JMG day camp held in June. We had 12 youth who participated in the 4-day camp. I know Lake Land College is appreciative of this partnership. The committee will be discussing some possible changes before submitting for the 2007 summer program.
It's not too early to be thinking of the fall plant sale at the Farmer's Market in Charleston. If you have ideas or possibilities of plants/bulbs for sale discuss it with Kate and the committee. I'm sure we will spend some of the August and September business meetings discussing details.
The education committee has planned 3 opportunities for you to obtain some of your education hours during July/August. If your January – June hours are short on the education line, be sure to stay for the program tonight, attend the Whiteside garden walk later in July and attend the garden tour with the August meeting at Cheri Sims.
Happy gardening and eat those veggies while they are at their peak!
Sharon
Sharon Kuhns, County Director
