Extension Educator, Local Food Systems and Small Farms
Extension Educator, Horticulture
May 29, 2009
As anticipated for the past few weeks, the fungal leaf spot diseases are wreaking havoc on ornamental and fruit trees alike. The main culprits at this time are anthracnose on good quality shade trees, apple scab on production apple trees and crabapples, and leaf curl on peaches.
The common factors, as in any disease problem, are a susceptible host, weather favorable for the disease, the disease present, and time. The "photo shoot" blog from a couple weeks ago had early infection stages of many of these diseases. Now, the full blown effect is heavy leaf drop.
These diseases are preventable to some extent, but not curable. This doesn't mean you will lose the trees, but young or weakened ones might be at risk. Most healthy trees, especially shade trees, will put out a new set of leaves even this year. It just takes energy out of the tree's system to do this. Preventative fungicide treatments would have been put on even as early as bud swell to help prevent peach leaf curl. With the abnormal amount of rainfall, you may have needed many extra treatments to have had any success.
For further information on fungal infections of shade and ornamental trees, check out the Report on Plant Diseases at http://web.extension.uiuc.edu/forestry/publications/pdf/forest_health/UIUC_Leaf_Spot_Diseases_of_Trees.pdf
May 28, 2009
West Nile Virus (WNV) has, unfortunately, become a household phrase. WNV was first isolated in Uganda, Africa. It can harm humans, birds, and other animals. It is transmitted by infected mosquitoes, primarily the northern house mosquito. The mosquito becomes infected after biting wild birds that are the primary host of the virus. The mosquito is actually able to transmit the virus after 10-14 days after biting the infected bird.
The mosquito life cycle has four life stages (egg, larvae, pupa, and adult). The female mosquito lays eggs on water or moist soil. Most of the larvae hatch after 48 hours and the larvae and pupae live in the water. The females need a blood meal before they can lay eggs, so only the females bite. They bite every few days during their adult lives, which may last several weeks.
Preventing mosquitoes is a first step. Homeowners can best accomplish this by eliminating standing water. Tires and old containers are obvious places to start, drill holes in the bottom of recycling containers, clean clogged gutters, don't allow stagnant water in anything such as birdbaths, change landscape slopes to eliminate standing water, and use larvacides in standing water that can't be eliminated. B.t. Israeli is the strain that is effective against mosquito larvae – not the B.t. variety commonly used on trees and gardens! The mosquitoes have already begun hatching, so treatment time is at hand.
Also protect yourself from bites. Mosquitoes can travel up to three miles from their breeding sites! Make sure that screens and doors are tight, use proper outside lighting such as fluorescent lights, stay indoors at dawn and dusk when mosquitoes are most active, wear long-sleeved shirt and long pants when you must go outside, and use insect repellents properly applied. Exposed skin should be sparingly treated with a repellent containing up to 30% DEET (up to 10% for children), and make sure to treat thin clothing as well (since mosquitoes can bite through the thin clothing).
May 28, 2009
We are now in the middle of the correct planting time for the warm loving vegetables for our gardens. This would include lima beans, cucumber, eggplant, melons, peppers, summer squash, winter squash, and pumpkins. Pumpkins for use as fall ornamentals should be planted around Father's Day so they have less chance of rotting before fall display. Believe it or not, we're at the proper timing for fall garden plantings as of this coming weekend. That means potatoes, kale, and some others. Some of the planting dates overlap this time of year. That basically means plant it, but you can expect harvest to be closer to fall.
Keep pruning flowering shrubs after they complete bloom. That will allow for more flower buds for next year. Coming up the end of June will be the pruning time for evergreens.
Bagworm spray time will be coming up mid-June. We'll try and fine tune the date as we get closer. The cool spring has delayed things to this point, but warm weather could catch us back up to the book timing of June 15.
Last chance for the pour-on treatments for Japanese beetles on ornamentals using imidacloprid. Earlier application would have allowed for more translocation. These treatments do allow some damage to occur before a lethal dose is consumed.
May 21, 2009
With the type of weather we have had, it should have been expected many different diseases would come our way this spring. Well, they are here. Here are some shorts on the past week and some of the items found without looking too hard.
Peach leaf curl is caused by a fungus on trees in the stone fruit family. This would include mainly peaches and plums. It is rather striking with the bright red swellings on the green leaves. This disease can only be prevented with a dormant time application of a fungicide on your trees. Seeing it now means that you probably should have sprayed before the buds began to swell (meaning before leaves actually came out).
Anthracnose starts as dead leaf areas between leaf veins, or on the tips of leaves. When severe enough, leaves will fall. The good news is that it rarely harms trees. If enough leaves drop, a new set comes out in 4-6 weeks and we start all over. The next set of leaves may also get the disease, but they may not. Infection can continue with weather favorable to the disease, and when nighttime temperatures stay under 65 degrees. Treatments when you see the symptoms of this disease are simply wasted time and money. Apple scab is a disease similar to anthracnose, and can cause premature leaf drop in apples and crabapples. If you are on a regular spray schedule for fruit trees, it should prevent most of the problems. You could also spray crabapples this way, but you would have to weigh the cost and benefit since no fruit production is involved.
Many people are reporting holes in tree trunks. These holes are round and in a pattern either around or up and down on tree trunks. They are also usually found in a tree that has high sap flows such as maples, gums, or evergreens. These holes are caused by yellow bellied sapsuckers. About the time we notice the holes, the birds are gone. They migrate and only bless us with their presence about two months in the spring (around May) and again in the fall (around September). These holes can cause injury to the tree by allowing a place for insects and disease to get in, and death if they completely girdle trees. Control is very difficult, and consists of trying to scare the birds with pie pans, whirlybirds, rubber snakes, or other items that make sound or sight. If damage in an area of the tree trunk is severe, you can wrap burlap around that portion to protect it. The sticky type products, such as Tanglefoot would also have some effect, but might cause problems for some of the non-sapsuckers in the area.
Apple and pear trees are also having their problems. There is a large amount of tip dieback in some varieties , and this is probably fire blight. Look for a shepherd's crook at the tip of the affected areas as a clue it is fire blight. Fire blight is a bacterial disease, therefore there is little chance for you to treat it. The common treatment in commercial operations is streptomycin, but it has to be applied before symptoms appear. Bordeaux mixture can also help prevent the disease. Prune out disease cankers when dormant. This disease cost Illinois its pear industry.
May 12, 2009
May 12, 2009
Throughout the year I get several calls and samples brought in dealing with puffballs or toadstools. This year we have had an unusual amount of calls about dark green grass in rings that kind of looks like a target pattern. These rings are called fairy rings.
Fairy rings are caused by a fungus in the soil. Actually there are about 50 fungi that can cause fairy rings. These fungi feed on decaying organic matter such as large roots from trees that were in the area, or from buried lumber. The dark green circle part of the equation comes from extra nitrogen that comes available as the organic matter is broken down by the fungus.
Some prevention will help keep the problem from occurring. Simply removing stumps, large roots, and not burying lumber help prevent this type of problem. As for a cure, fungicide drenches have been successful on a very limited basis. One option is to mask the symptoms of the dark rings by fertilizing the surrounding grass with a high-nitrogen fertilizer to make that grass green also.
As for the puffballs, toadstools, or mushrooms, they are part of the same complex as fairy rings. They are part of the natural decay process that helps break down large wood items in the ground. There is no real control so mowing them off or knocking them loose with a garden rake is about the best thing going.
May 12, 2009
Here is a listing of common borers and their control times: Ash borers (early June and early July), Bronze birch borer (mid May and repeat two times at two week intervals), Dogwood borer (mid May and mid June), Flatheaded apple borer (late May and repeat in three weeks), Lilac borer (early June and early July), Locust borer (late August and mid September), Mountain ash borer (early June and mid July), Peach tree borer (mid June and mid July), Viburnum borer (early June and early July), and Zimmerman pine moth (April or August). The Emerald ash borer, although not confirmed in our area at this time, control time in Michigan begins mid May and runs through mid July.
The products of choice for many borers are now permethrin or bifenthrin. Imidacloprid is fairly new on the market, and one trade name is Merit (sold for homeowners as Bayer Advanced Garden Tree and Shrub Insect Care). This product use rate is an ounce per inch of circumference of the tree trunk. You then mix it with three gallons of water and pour around the base of the tree. It may take a few months for it to translocate though the tree. A good time to apply it is in early spring when the sap rises. These treatments need to be completed by late May to have a chance of getting the current season borers. Each treatment lasts about a year, and is more successful on younger trees. Fruit trees generally are treated differently, with Sevin or bifenthrin applied to the trunk, or just using the regular spray program due to the possibility of residue in fruit
Zimmerman pine moth is one of those "kind of borers." It generally affects only severely weakened trees, and goes just under the bark to girdle the cambium layer. It seems like older Scotch, red, and Austrian pines are favorites when they begin to decline. Permethrin is recommended for Zimmerman pine moth. Bird damage from yellow-bellied sapsuckers on trunks and main limbs also looks like borer damage to many. This bird damage is easily recognized by the evenly spaced holes in a straight line.
May 8, 2009
With the cool, damp spring we expected to have a problem. The great outdoors now seems like one of those commercials for mosquito repellent, where a brave person puts his arms into a tent full of hungry mosquitoes. We not only have mosquitoes, but also the biting midges. These also are called biting gnats, punkies, buffalo gnats, no-see-ums, and worse. Some of these names are specific for black flies, and others for sand flies. At any rate, it seems as though outdoor activities may be a little more exciting than we planned.
Let's start with the biting midges. Like anything in the biting fly family, they are hard to control. They don't need standing water to develop in, they aren't dawn and dusk feeders like mosquitos, and they don't "roost" in a particular area. They are also small enough to come through many window screens. And when they bite, they leave a painful welt. Smaller screen wire size will help keep them from entering the home, as will keeping windows shut. Using "bug light" bulbs will also attract fewer, as will using sodium lights outside. Insecticide treatments are hard to apply, but products such as malathion, permethrin, or bifenthrin will at least kill the ones you hit. Repellents with DEET in them, such as the mosquito repellents, will usually show some deterrent.
For mosquitoes, prevention is the first step. Homeowners can best accomplish this by eliminating standing water. Tires and old containers are obvious places to start, drill holes in the bottom of recycling containers, clean clogged gutters, don't allow stagnant water in anything such as birdbaths, change landscape slopes to eliminate standing water, and use larvacides in standing water that can't be eliminated. B.t. Israeli is the strain that is effective against mosquito larvae – not the B.t. variety commonly used on trees and gardens!
Also protect yourself from bites. Mosquitoes can travel up to three miles from their breeding sites! Make sure that screens and doors are tight, use proper outside lighting such as fluorescent lights, stay indoors at dawn and dusk when mosquitoes are most active, wear long-sleeved shirt and long pants when you must go outside, and use properly applied insect repellents. Exposed skin should be sparingly treated with a repellent containing up to 30% DEET (up to 10% for children), and make sure to treat thin clothing as well (since mosquitoes can bite through the thin clothing). The higher DEET percentages can work for four to six hours. The lower concentrations will work for about two hours. Mild products such as the active ingredient in cosmetic company non-DEET formulas may work for 15-30 minutes.
For that special occasion outside, you can reduce populations by spraying large areas with insecticides effective against flying insects, such as malathion, permethrin, or bifenthrin. Don't expect miracles, but you can greatly reduce populations for a few hours. Concentrate sprays in shrubbery, tall grass, and tree areas.
May 8, 2009
Roses - the "Queen of Flowers," should be in full glory in the month of June, said a University of Illinois Extension horticulture educator.
"The many colors, scents and flower sizes are all qualities the rose connoisseur craves," said Martha Smith. "Rose care is not difficult. What roses require, however, is consistent care.
"Roses are heavy feeders so a regular fertilizer program is essential. Disease problems can be controlled with a regular spray program."
Container-grown roses can be planted any time after mid-May. Choose a sunny area since roses require a minimum of six full hours of direct sun. Roses will not tolerate wet soil, so choose a site that has good drainage. Dig a hole deep enough and wide enough to generously accommodate the roots.
"If the rose is grafted, you need to consider how deep to set the graft union," she said. "In warmer climates, position the rose so that the bud union is at or just above ground level. In colder climates, position the bud union one to two inches below ground level and mulch over.
"If your garden soil is a heavy clay or very sandy, incorporate compost, peat moss or leaf mold into the backfill. Half fill the hole and water to allow any air pockets to settle out. Continue adding backfill to the hole until full and repeat the watering."
Smith said that if your roses are stunted, have weak growth, small flowers, pale or discolored leaves, premature petal fall and/or poor disease resistance, a regular fertilizer program may solve the problem.
"The Central Illinois Rose Society recommends adding compost or manure every year to the bed as well as following a fertilizer schedule," said Smith. "A complete fertilizer is recommended May 1, June 1 and July 1. A complete fertilizer contains nitrogen, phosphorus and potassium. Follow the recommended rates on the label. They also suggest a liquid feed between monthly fertilizing."
In past seasons, you may have had rose foliage turning yellow with large black spots this is called black spot and is a very common disease of roses.
Infected leaves may drop prematurely. Severe infection may cause some canes to completely defoliate. Fungicide sprays serve as a protectorant and must be applied before infection. As the leaves emerge, and the day temperatures are above 50 degrees F., begin applying a fungicide every two weeks.
"Powdery mildew can also be a problem," she said. "It is easily recognized by the white powdery patches that form over the foliage. Powdery mildew can be a problem in shady areas, or where there is very little air movement. Fungicide sprays are again recommended and should be applied when new growth appears and repeated every seven to 14 days."
Rake up and discard fallen diseased foliage to minimize further spread of black spot or powdery mildew.
Properly pruning roses is another important item to consider.
"A rose leaf is actually comprised of several leaflets," said Smith. "Starting at the flower, count the number of leaflets on each leaf. Some will have single leaflets, three leaflets or five leaflets. The five-leaflet leaves have mature buds at their base that will produce a new shoot.
"Choose an outward-facing, five-leaflet leaf in the middle of the stem and cut above it. Don't cut back to the lowest. By choosing a mid-level bud, you ensure that adequate foliage remains on the plant. An outward-facing bud directs new growth away from the center of the plant."
Bring cut flowers inside for your enjoyment. Also, prune off faded flowers.
"Any gardener can have success with roses if they follow these guidelines," she said. "Remember, rose care is not difficult, you just need to be consistent. For more information on rose care, visit Our Rose Garden (http://urbanext.illinois.edu/roses/)."