It's summer, so the conscientious home gardener should be spraying, right? Not necessarily. Before you can prevent or control an insect, pest, or disease problem, you should identify the culprit. As a starting point, if a plant appears healthy, it probably is healthy, and there is no need to spray. If a plant appears unhealthy, the cause could be "cultural" and involve the care of the plant rather than an insect or disease: too much water, too little water, not enough fertilizer, too much fertilizer, poor drainage, root disturbance, hot drying winds, or cold can affect the health of the plant.
But the problem could also be due to insects or disease. Examine the plant carefully. Check both the top and underside of the leaves, the stems, and the branches. Look for adult insects, webbing, eggs, larvae or pupae. Are there obvious signs of its being "eaten"? If the culprit is nowhere to be found during the day, go out with a flashlight and check at night. Check around the roots.
Consider the frequency and amount of water the plant has been receiving. Generally it is better to water deeply (to the depth of the roots) and less frequently. Irrigation systems are great for turf but too frequent and too little for woody plants. Frequent, shallow watering will result in a shallow root system which is less able to withstand periods of drought.
Check for physical damage. Does the part of the tree or shrub which is wilted or discolored have a break or split lower down on the branch? Has it been girdled by a guy wire, rope or chain? Has a lawn mower injured the trunk? If a plant has a case history, such as birch leaf miner, you might want to take preventive measures. A heavy infestation last year might warrant the use of a systemic as a soil drench this year. When dealing with pesticides, keep in mind that some insect sprays (such as malathion) are "contact" insecticides. That means that they will only be effective in killing the insect if the spray makes contact with the insect at the time of application. Malathion cannot be used as a "preventive" at the beginning of the growing season when no insects are present. Nor can it be used once an insect has taken such protective measures as rolling itself up in a leaf, or forming a gall around itself. Malathion is not effective at temperatures below 20C. Also note that both malathion and carbaryl (Sevin) are extremely toxic to bees and are best not used when fruit trees are in blossom. They can kill the pollinating bees and prevent pollination. Using these chemicals at night or in the evening when bees are not present is also an alternative. Sevin also acts as a thinning agent and may reduce fruit set if applied to fruit trees during or soon after flowering.
Other insecticides, such as dimethoate (Cygon or Lagon) are termed "systemic." That means they travel through the system to all parts of the plant tissue, and when the offending insect chews on the plant he ingests the insecticide and is killed. Systemic insecticides (like all other pesticides) should be used with caution, and only according to the directions on the label. Also consider less toxic alternatives to pest problems such as insecticidal soaps and dormant oil sprays. Above all, READ THE LABEL!! DUTCH ELM DISEASEDutch elm disease was first found in the United States in Ohio in 1930. It has now spread throughout North America and has destroyed over half the elm trees in the northern United Sates. The disease has been reported in all states except the desert Southwest.
DUTCH ELM DISEASE
The fungus responsible for Dutch elm disease is thought to have originated in Asia. This site of origin is proposed because Asian species of elm demonstrate at least a moderate level of resistance to the fungus which causes the disease. Having co- existed for many generations with the fungus, susceptible Asian elms were slowly eliminated from the population and replaced by seedlings with greater and greater resistance. In this way, the elms of Asia established a natural equilibrium with the disease. Dutch elm disease only became an epidemic in the early part of this century when the fungus responsible for the disease was somehow transported from Asia to Europe. Once in Europe, where the elms had no previous exposure to the disease, an epidemic was at hand. The disease's arrival in Europe was marked by the sudden decline and death of millions of elms in the first two decades of the th century. In 1920, the fungus responsible for the mysterious death of Europe's elm trees was positively identified by a scientist working in Holland leading to the name Dutch elm disease.
After having decimated the elms of Europe, the fungus responsible for the disease was accidentally transported to North America in the early 1930's, when diseased elm logs were imported to America. Like the elms of Europe, the native American elm had no pre-exposure to the fungus, and was therefore highly susceptible to invasion. Soon after its arrival, decimation of elms in Eastern North America was begun. Since that time, the disease has proceeded along a steady westward course across the North American continent wherever elm trees grow naturally, or in cultivation. In the time since the first diseased logs arrived in this continent, over 40 million elm trees in the United States have been killed, with the worst devastation being found in those cities which ignored the problem. It was not uncommon for a city to lose 90% of its elms in as little as ten years leaving tree-lined streets suddenly transformed into empty wind-swept places. Property values dropped and municipal budgets ballooned to cover the cost of wholesale tree removals
Dutch elm disease is caused by the fungus Ophiostoma ulmi (syn. Ceratocystis ulmi) which is transmitted by two species of bark beetles or by root grafting. The American elm, Ulmus Americana, is the most seriously affected of all elms. The Siberian elm, Ulmus pumila, is tolerant but not immune to the disease.
More information on identification and management of Dutch Elm Disease is available at the US Forest Service website.
EMERALD ASH BORER In the summer of 2002, scientists detected a new exotic insect in six southeast Michigan counties -- Livingston, Macomb, Monroe, Oakland, Washtenaw and Wayne. This pest, known as the Emerald Ash Borer (EAB for short), is an invasive species originally from Asia and previously unknown in North America that attacks Ash trees. To date, it has killed or damaged millions of Ash trees in these affected areas. It has also been detected in Windsor, Ontario of Canada, and in small, isolated pockets in Berrien, Calhoun, Eaton, Genesee, Ingham, Jackson, Kent, Lenawee, Saginaw, Shiawassee and St. Clair counties.
EMERALD ASH BORER
The Emerald Ash Borer belongs to a group of insects known as metallic wood-boring beetles. Adults are dark metallic green in color, 1/2 inch in length and 1/16 inch wide, and are only present from mid May until late July. The larvae are creamy white in color and are found under the bark.
The borer's host range is limited to species of Ash trees (identified by their distinctive leaves, which are located directly across from each other on the leaf stem, and bark). In Michigan, most Ash trees are White, Black and Green Ash. Emerald Ash Borer does not attack Mountain Ash, which is not related to White, Black, or Green Ash trees.
Usually their presence goes undetected until the trees show symptoms of infestation. Typically the upper third of a tree will die back first, followed by the rest the next year. This is often followed by a large number of shoots or sprouts arising below the dead portions of the trunk.
The adult beetles typically make a D-shaped exit hole when they emerge. Tissue produced by the tree in response to larval feeding may also cause vertical splits to occur in the bark. Distinct S-shaped tunnels may also be apparent under the bark
More information on the Emerald Ash Borer is available at the following websites:
Insect Trap Targets Pine Tree Pest
The United States Department of Agriculture (USDA) will be installing a three foot tall insect trap in a Pine tree located on Madison at Woodward, adjacent to Poppleton Park. The trap is part of a detection process to monitor a Pine tree pest known as Sirex woodwasp. The USDA will install 13 traps in Oakland County as part of this program. The trap will be installed mid-June and will be monitored every two weeks by the USDA and removed sometime early October. This pest focuses on less healthy Pine trees and is moving from New York, Pennsylvania and Canada toward Michigan. Updates on this pest and/or project will be posted as they become available.
GYPSY MOTH
The species originally evolved in Europe and Asia and has existed there for thousands of years. In either 1868 or 1 869, the gypsy moth was accidentally introduced near Boston, MA by E. Leopold Trouvelot. About 10 years after this introduction, the first outbreaks began in Trouvelot's neighborhood and in 1890 the State and Federal Government began their attempts to eradicate the gypsy moth. These attempts ultimately failed and since that time, the range of gypsy moth has continued to spread. Every year, isolated populations are discovered beyond the contiguous range of the gypsy moth but these populations are eradicated or they disappear without intervention.
After a reprieve of 2 years of no treatment being necessary in Oakland County, gypsy moth numbers appear to be increasing in some areas of the county. This year treatment will be occurring in the following communities under the Oakland County Gypsy Moth Suppression Program: Addison Township, Auburn Hills, Oakland Township, Orion Township, Oxford Township, Rochester Hills, and Waterford Township. Treatment is an aerial application by helicopter of the bacterial insecticide Bacillus thuringiensis (B.t.). All homeowners in the impacted areas have been notified of the impending treatment. For more information on gypsy moth and other insects, call the MSU Extension Yard and Garden Hotline at 248.858.0902
EASTERN TENT CATAPILLAREastern tent caterpillars become a pest when they feed on deciduous trees and cause defoliation. They construct a tent of silk on one or more branches of a tree. The tent provides protection against weather conditions and predators. The caterpillars feed during the day, and at night, they return to the tent for protection. Eastern Tent Caterpillars are considered a great pest by many people. Actually, they are usually not very destructive. They are only fatal to young trees, where they eat all of the leaves quickly. Older trees will still have most of their leaves after the tent is gone, and the caterpillars have moved on.
The Eastern tent caterpillars are often confused for the Gypsy Moth. Gypsy Moths do not make a web tent like the Eastern tent caterpillar.
SYCAMORE ANTHRACNOSEAnthracnose in sycamores has been a major cause of concern with residents. It causes twig canker and die back, leaf and shoot blight, and often substantial defoliation. Infected leaves develop tan to reddish brown lesions that typically center on and extend along the leaf veins.
The disease is caused by a fungus that develops over winter in twigs of the tree. Dieback occurs when a canker forms, enlarges, and girdles the twig. Trees with high twig and bud mortality produce only thin crowns by late spring. Weather conditions, frequent rains and cool temperatures, typically influence the severity of the problem. In early spring, small black fruiting bodies are produced on dead one-year-old twigs. These fruiting bodies release spores that infect expanding shoots and leaves. Infected shoots suddenly wilt and appear scorched. When the mean daily temperatures are 50-55 degrees F between bud-break and early leaf emergence, anthracnose can be severe. The disease should be less severe if the mean daily temperatures during a susceptible stage of plant growth is 60 degrees F or above. This means that when the trees produce a second flush of leaves, typically from mid-June into July, there should be little to no anthracnose infection.
To help reduce infection, it is always a good idea to rake and destroy fallen leaves and twigs, since the fungus can develop over winter on these plant parts.
TAR SPOT
These dramatic but inconsequential diseases of numerous maple species cause small to almost one-inch diameter tar-like spots on leaves. The fungus develops over winters on fallen leaves then infects the upper surfaces of leaves in spring during moist conditions. Leaf spots are first a yellowish green but by mid to late summer a tar-like mesh of fungal and leaf tissue develops inside the yellowed area. Occasionally some leaf withering and drop occurs but this is not generally serious and fungicide sprays are not generally recommended.
CANKER WORMS
Loopers or canker worms eat the leaves of fruit trees and many ornamental shrubs and trees. They are a brown, black or green-striped worm with a dark head that makes a loop when it walks and if disturbed spins a web as it falls to the ground. These insects (if in large numbers) can defoliate a tree. Canker worm
Cankerworm populations go through 10-year cycles which often peak for two to three years. In much of the affected area, this is the second and possibly the last year of the cycle. Many will be eaten by birds and other predators. Canker worms remaining cankerworms will feed until mid-June and then will crawl into the ground to pupate. In October, they will begin to re-emerge as moths.
However, if there are only a few insects present and little damage is evident, apply tangle foot to the trunk of your tree. This sticky material prevents the wingless female from migrating to the upper branches to lay eggs for the next year's infestation. Tangle foot should be applied about September 1st for control of fall canker worms and mid April for the spring species.
ASIAN LONG HORNED BEETLE
Prior to 1996, there were no known infestations of the Asian Long Horned Beetle (ALB for short) in North America. The first infestation in the U.S. was discovered in New York City in 1996. This was followed by the report of a second infestation in Chicago in 1998. Within months of the initial discoveries, Asian Long Horned Beetles were found in several different urban and suburban settings in both cities. Millions of dollars have been spent trying to rid these areas of ALB and thousands of high-value shade trees already have been lost. ALB also has been found in dozens of port and warehouse locations nationwide. Such accidental introductions have the potential to develop into new infestations of trees. The ALB's favorite host trees are Maples, but it will also Horse chestnut Elm, Horsechestnut, Willows, and Poplars. The ALB does not attack conifers or evergreens. Adult females chew out small pits in the bark and lay their eggs in them. The eggs hatch and the young grubs tunnel into the cambium, causing branch die-back. The grubs tunnel deeper into the tree as they grow. This tunneling eventually kills the tree by cutting off the flow of water and nutrients. Tree death is caused by repeated attacks over several years. There are no known infestations in Michigan at this time.
More information is available at the US Department of Agriculture website.