Mines are starting to appear in birch, hawthorn and alder leaves where leafminer larvae are active. In another week or so leaves will start to turn brown from the tunneling damage. Right now is still a good time to spray, but it will soon be too late to apply insecticides for birch leafminer in Lansing.

Black vine weevil larvae have almost finished their spring feeding in southern Michigan and are now pupating. In two to three weeks, we will start to see the adult weevils walking around, especially in the evening after sunset. If you happen to dig some up this week you will find white pupae in the shape of an adult weevil with wing pads on its back. The pupae can wiggle their legs, but cannot crawl.

Oystershell scale, Juniper scale and Euonymus scale crawlers will be active in early June. The best time to apply a 2% horticultural oil for control of these scales is just after peak crawler emergence. Horticultural oils will still work when applied as long as three weeks after crawler emergence. To tell when crawlers emerge, clip off some infested stems and put them in a small glass jar or sealed dish on your desk. When you see crawlers all over the inside of the jar, you will know it is time.

Young honeylocust plant bugs can now be found on the new growth of honeylocust. It is easy to check for the small green plant bugs by sharply rapping a branch over a piece of white paper or cloth. If the damage is unacceptable, trees can be treated with an insecticide. The plant bugs are active in late May and June.

Eastern tent caterpillar tents (12 to18 inches-long) are now visible on wild cherry, crabapples and a variety of ornamental Prunus spp. trees. The caterpillars are a half to 1 inch long in the Lansing area. For eastern tent caterpillar and other spring caterpillars, insecticides are not needed unless more than 50 percent defoliation is expected.

European pine sawfly larvae are feeding on the old needles of pine trees at this time. Are your Mugho pines looking thin? Take a closer look and you may find that most of the old needles are missing from some branches. You will need to look close to find the caterpillar-like sawfly larvae themselves because they blend in perfectly with pine needles. The sawflies will feed for another two to three weeks in Lansing.

Fletcher scale can be a serious problem for nursery growers, but is inconsequential in the urban landscape. Recent tests have shown that this scale tends to disappear when infested nursery plants are moved to urban yards. Unfortunately, predators and parasites that keep Fletcher scale under control in the urban landscape are scarce in large nursery fields. Some growers with small, more diverse fields have not had a problem with Fletcher scale. This scale is only found on yews and arborvitae. It becomes a problem when scale populations build-up on nursery plants to the point that they are easily observed. Inspectors will not approve plants for sale that are heavily infested with scale.

Female scales grow rapidly in May, reaching a mature size of about 3.0 mm, by June 1. Crawlers emerge in mid to late June. Part of the population may undergo a second generation with crawlers emerging in September or early October. The scales are most easily observed from mid May to late June. Scouting should begin in yew fields two years before they are scheduled for sale, to allow adequate time to treat infested fields before they are inspected.

Nurseries have been very successful with spring and fall applications of Dursban 50N, Supracide, or Sevin. In our tests on the best timing of insecticide applications for Fletcher scale, we found that late June and late August were the best times, with a combination of both being the most effective. Alternative products are being evaluated each year.

The recent and continuing stretch of cold and very wet weather has resulted in soils that are water saturated and may remain cool and wet for several weeks. These conditions are particularly suitable for the development of root-rotting pathogens, for example, Phytophthora spp., Rhizoctonia, Pythium, Fusarium, Thielaviopsis and other soil-inhabiting fungi. Spores of these fungi and water-molds can remain dormant in the soil for many years, and it is likely that with current soil conditions and lack of root development, many plants are vulnerable. Infected plants may exhibit symptoms that start with wilt and apparent nutrient deficiencies and ultimately become necrotic and die. The roots lose integrity and adhesion to the soil.

Once the soil has dried out sufficiently (about 80 percent soil moisture), the appropriate fungicides may be applied. Use only fungicides recommended for the diagnosed pathogen and use label recommended rates and application methods (see accompanying table and web page). It is important that these are used as plants may respond differently to the fungicide and its formulation components. For example, grasses are prone to leaf-tip burning caused by EC formulations that contain, for example, xylene as a diluent. Other fungicides may not be able to be translocated to the root zone through the phloem and others may not be able to penetrate leaf tissue without adjuvants, which can be phytotoxic. Therefore, if a fungicide has been recommended for soil application only, try to avoid foliar contact. This, of course, is not always possible, especially if soil fungicides are being applied curatively after transplanting. For further information (Tables 2-6), please visit:

Included in this web page are tables referring to: pathogen targets for chlorothalonil and mancozeb on ornamentals and perennials, ornamental and perennial species listed on chlorothalonil and mancozeb fungicide labels, use of medallion on ornamentals and perennials, use of terraguard on ornamentals and perennials, and use of triazoles on ornamentals and perennials.

Many important floricultural crops are susceptible to botrytis with certain plants and plant parts being highly susceptible. In commercial greenhouses, geranium leaves, flowers, and leaf stipules; primula flowers; and the senescent leaves and true flowers of poinsettia are favorable for infection and reproduction of botrytis. The age of plants is also a factor in botrytis infection. For instance, geranium leaves one week old are more susceptible than leaves that are four weeks old. However, as geranium leaves mature at ten weeks, they are once again very susceptible to botrytis infection.

Botrytis reproduces via conidia (spores) that can be released into the greenhouse atmosphere during grower activity, including irrigating, spraying pesticides, and harvesting cuttings. When there is little or no grower activity in the greenhouse, botrytis conidia are released into the greenhouse atmosphere at approximately mid-morning and mid-afternoon and coincide with a rapid decrease in relative humidity. If a conidium lands on a plant surface but the environment is not favorable for infection, it may survive for at least three weeks and potentially be shipped from greenhouse to greenhouse. When healthy-appearing geraniums were evaluated for botrytis on the same day the shipments were received, botrytis was recovered most often from the stipules and flower buds. Botrytis blight can also occur when the threads (hyphae) of the fungus grow from infected plant parts (petals, senescent flowers) into nearby healthy plant parts.

Successful management of botrytis requires an integrated approach. Environmental control is the key.

Botrytis requires free water on the plant surface to cause disease. Preventing or limiting the occurrence and duration of free moisture on the plant's surface is critical to botrytis management. This can be accomplished by keeping the relative humidity below 85 percent and providing air circulation so that free moisture in the form of condensation (dew) will not form on plant surfaces if the temperatures drop quickly or the leaves cool rapidly by losing radiant energy to the sky at nightfall. Venting and heating late in the afternoon is helpful in removing humid air before sunset. If plants are being watered overhead, time the activity to allow plants to dry before evening. Plants watered in the late afternoon or early evening will likely remain wet throughout the night. Such an extended period of free water would ensure the occurrence and development of botrytis blight. Without the necessary wet and humid environment, botrytis will not be able to germinate and infect plant tissue and will be unable to reproduce.

Adequate spacing of plants is important in reducing the relative humidity of the microenvironment that forms within the plant canopy. Spacing plants closely together results in dense canopies that limit light and air penetration and promotes senescence of the lower leaves. Under humid and wet environmental conditions, botrytis readily infects these senescent leaves and sporulates, providing ample inoculum to infect nearby healthy plants.

Forcing heated air under lath, wire mesh, or expanded metal benches via perforated polyethylene tubes is an effective way of reducing the relative humidity within the plant canopy. A white plastic mulch on top of pots within a stock-plant canopy can also reduce botrytis blight but is not as effective as using forced heated air.

Long-wave, infrared-absorbing plastic film is available to cover greenhouses and may reduce relative humidity by reducing greenhouse cooling during the night. It has been reported that botrytis blight on tomatoes was reduced when a long-wave infrared-absorbing vinyl film was used. Greenhouse coverings that block the ultra-violet light and thereby increase the blue-UV ratio are also reported to inhibit the reproduction of botrytis. These commercially-available films can be used over the entire greenhouse or as a tent over an especially susceptible crop, and are reported to reduce botrytis reproduction by as much as 80 percent in experimental studies. It is important to keep in mind, however, that the effect of the light-absorbing plastics can vary with the strain of Botrytis present.

Sanitation is an important management tool in controlling botrytis. However, to ensure effectiveness it must be remembered that botrytis can infect and produce conidia on tissue that is dead or alive. Leaves and flowers senescent are often favored hosts for botrytis. Such tissue may fall onto nearby healthy plants resulting in disease spread. If plants drop petals or flowers onto benches or the floor, that tissue is still a suitable host for infection by botrytis and subsequent production of conidia as long as the environment is wet and humid. Even if infected debris is collected and put into a trash container, botrytis can produce conidia. If a trash container is kept in the greenhouse and is uncovered, air currents can pick up the conidia being produced by botrytis on this diseased tissue and disperse them to healthy plants throughout the greenhouse. To prevent this, trash containers should always be covered, emptied frequently, and preferably stored in an area other than the plant growing area.

Removing infected plants (roguing) is also an important component of sanitation. A plant may be so severely infected with botrytis and have a large load of conidia that the entire plant should be discarded so it does not contaminate neighboring healthy plants. In such a case, it is better to bring a covered container or plastic bag that can be sealed to the site of the infected plant to be discarded, rather than carrying the infected plant throughout the greenhouse to a trash container. When an infected plant has a significant amount of tissue covered with conidia, the air currents created by carrying the plant out of the production area will result in many conidia being released and "shaken" off en route.

The physical action of removing infected leaves with sporulating botrytis is sufficient to release conidia into the atmosphere, thereby putting healthy plants at risk. Removing the crop from the growing area prior to cleaning and packing could substantially decrease the exposure of nearby healthy plants to botrytis conidia and decrease disease potential.

Prior to workers "cleaning" plants in a greenhouse by removing the lower senescent leaves, blossoms, or infected plant parts, it would be wise to have a protectant fungicide on all of the plants in the greenhouse prior to the activity, and reduce the relative humidity (less than 65 percent) for three days following the cleaning. Growers can be sure that if botrytis is present, a cleaning activity will result in a high number of conidia being released into the atmosphere where they can be spread throughout the greenhouse and be deposited onto healthy plants. Since plants are often wounded during cleaning, the lowered relative humidity helps to make these wounds a less suitable entry point for botrytis.

Fungicides are often important in managing botrytis disease, but must be chosen carefully. Some botrytis strains have become "resistant" or "insensitive" and can grow and reproduce in the presence of some of the fungicides that used to offer effective control. For example, due to the frequency of botrytis strains resistant to benzimidazoles (Cleary's 3336), these fungicides are no longer recommended as the primary tool for controlling botrytis. Although resistance to the dicarboximide fungicides (Chipco 26019) has also been documented, resistance does not appear to be widespread and if these fungicides are used wisely should continue to be effective. Protectant fungicides (Daconil, Decree, Phyton 27, Exotherm Termil, Dithane, Protect T/O, and Mancozeb) do not appear to be at great risk of developing resistance but may vary in their ability to control botrytis blight.

Make sure your fungicide applications count by considering the following strategies and research studies.

Rotate dicarboximide fungicides (Chipco 26019) with protectant fungicides (Daconil, Decree, Phyton 27, Exotherm Termil, Dithane, Protect T/O, or Mancozeb).

Use protectant fungicides only. Since there is no documented case of botrytis developing resistance to protectant fungicides, they may be used with confidence. However, protectant fungicides may not equally be effective and should be chosen based on the magnitude of disease threat. Daconil and Decree are among the most effective protectants.

Use tank mixtures of systemic and protectant fungicides. Tank mixtures of systemic and protectant fungicides provide good control of botrytis. In most cases, reduced rates of fungicides, when used in mixtures, provide control comparable to full strength mixtures (Note: In some states it is illegal to apply a pesticide at a lesser concentration than recommended on the label). Growers who have the option of using less than the labeled rate of fungicides may consider mixing two botrytis-controlling fungicides together, each at one-half of the full rate. Mixing a dicarboximide fungicide such as Chipco 26019 with a protectant fungicide (such as Daconil 2787, Phyton 27, or Dithane) (each at one half the full rate) is effective in controlling botrytis and also addresses the concern about fungicide resistance. Daconil is especially effective in limiting the ability of Botrytis to reproduce. As long as the reduced rate fungicide combinations include Daconil, all tank mixtures investigated were effective in limiting botrytis reproduction. Remember, if botrytis cannot reproduce, disease cannot spread! Mixing three or four fungicides together at reduced rates is not more effective than mixing two fungicides together. Growers should always check fungicide labels carefully and treat a small number of plants to check for phytotoxicity prior to treating a large number of plants.

In many of our fungicide trials, plants that were not sprayed with botrytis conidia but maintained under high humidity had as many blighted leaves as those untreated plants that were sprayed with botrytis conidia. Apparently, naturally occurring botrytis conidia can hitchhike on plants and develop into disease once plants are held in a high relative humidity environment. The ability of botrytis conidia to travel on plant surfaces and be transported from greenhouse to greenhouse can mean that resistant strains of botrytis can be introduced to a greenhouse via plant material. It is wise for all growers to assume, therefore, that resistant botrytis strains are present, and manage their fungicide selection accordingly.

Biological controls are being actively researched. Investigations are needed to optimize strategies for timing applications of biocontrol agents to achieve commercially acceptable control. Microclimate and plant nutrition may impact the ability of the biocontrol agents to become established on the plant surface. The ability of botrytis infection to be delayed or latent may make using biocontrol agents difficult in some production systems.

If you have Scotch pine trees that had high densities of pine needle scale last year and your fields are in southwest or southeastern lower Michigan, you need to be scouting your trees right about now. The first generation of eggs will usually hatch around 300 degree days base 50. Most areas in the southern Lower Peninsula will have accumulated 300+ degree days base 50 by the end of this week or by late next week.

It's not necessary to apply an insecticide immediately after you see the reddish-colored crawlers. In fact, it's best to let the crawlers settle down and establish feeding sites on the needles. At this point, the immature scales are exposed and have not yet secreted the white, waxy protective armor. If you can apply your spray at this point and if you get good coverage, you should get good control.

Keep in mind that pretty much any registered, contact insecticide will be effective on pine needle scale. You do not need to use a systemic product. This scale feeds on sap from the parenchyma cells in the needle and systemic insecticides are not going to be anymore effective than contact insecticides. (In contrast, pine tortoise scale feeds on phloem sap and systemics are likely to be more effective than contact insecticides).

Also, you can use a 2% solution of horticultural oil instead of a broad-spectrum insecticide. Our research indicated that if your timing and coverage are good, the oil will be just as effective as a long-lasting chemical insecticide such as Lorsban. Oils have other advantages, too. They are not toxic to humans and they will conserve the predatory insects that attack scales and other plant feeders during the summer.

Just a reminder -- if you have pine fields enrolled in the Compliance Program, you can collect and destroy your trap logs any day now.

Asian longhorned beetle remains a serious issue in Chicago and especially in New York, where the infested area has increased in size. Asian longhorned beetle is also causing problems in Europe. An infestation in Branau, Austria has resulted in the destruction of over 900 trees in the past year or so. This eradication project included clearing all of the maple trees out of a strip of forested land that was roughly 20 yards wide and 2.2 miles long. A meeting on Asian longhorned beetle (ALB) is being held in Germany next week.

In Michigan, we remain concerned about the possibility of an ALB introduction. This beetle attacks live maples, poplars, horse chestnuts and other species. Such an introduction could occur if visitors (e.g. from Chicago) inadvertently brought infested firewood or other materials along during their trip to Michigan. Another potential pathway involves infested wood crating or other packing carried on cargo ships originating in Asia. Regulations implemented in China have hopefully reduced the risks of this type of introduction.

In some metropolitan communities and counties, mosquito abatement programs are in effect. This activity is usually supported through a millage or some other form of local taxation.

The mosquito population is constantly monitored. A management plan is

implemented each spring based on population monitoring data. Habitats containing high

populations are treated with B.t.i. (Bacillus thuringiensis var. israelensis), in the form of a toxin derived from this soil bacterium. B.t.i. is quite specific and causes no harm to vertebrate animals.

The goal of an area-wide management plan is practical; reduce the nuisance level of the mosquito to an acceptable human tolerance level.

One of the concerns I have about large scale mosquito control programs is that as nuisance levels are lowered the taxpayer expectations become that of zero tolerance. Often times, local governments add large scale adult mosquito control to the existing management efforts. This addition is usually in the form of spraying broad spectrum insecticides. Over the long term it is suspected (and proven by some studies) that this control practice eliminates many insect predators and parasitoids. This in turn allows other insect pests, previously kept in check by natural enemies, to flourish. End result can be replacing a nuisance problem with insect pest problems that have economic consequences.

There are several species of mosquitoes that thrive in people-made aquatic habitats. Clogged gutters, water-collecting trash, bird baths, ditches that no longer flow properly, and poorly drained landscaping are a few examples.

Care should be taken during spring and fall cleanup to reduce these breeding sites. Also, resting areas for adult mosquitoes such as weedy and brushy areas around yard

borders should be minimized.

Property owners that have small ponds or other permanently impounded water (natural or constructed) can obtain B.t.i. in the form of small, pressed cakes or granules from lawn and garden centers or other retailers that carry a lawn and garden line. This formulation is easy to use and safe to handle. However, not all retailers carry this product. I checked some of the wholesale supply firms and not all were familiar with this product. One, Mollema's in Grand Rapids, does carry the product and has an ample supply on hand for retailers interested in carrying this product.

There are also several different kinds of mosquito traps now available that use carbon dioxide to attract mosquitoes to their doom (See article in 5-3-02 LCAT).

Repellents. There are many insect repellents on the market. Most contain the active ingredient DEET. This is still a very effective insect repellent. DEET-based

repellents are formulated in many different concentrations of the active ingredient. The repellents are also formulated in skin lotion bases to minimize skin drying.

The many formulations available sometimes cause confusion to the consumer. Often times, the buyer doesn't read the label (surprise-surprise) and applies the same amount regardless of the DEET concentration in the repellent, the anticipated time to be spent out-of-doors, the type of outdoor activity, and the time of day. These are all

important considerations. Any store that sells a variety of repellants will offer products that contain DEET ranging in concentration of active ingredient from about 5% to over 90%. The chemical name for DEET is diethyl-meta-tolumide.

DEET-based products are not the only repellent products available. If you have concerns about DEET try some of the other repellants. Some of the products show promise. Their active ingredients include soy oil, garlic and lemon grass extracts, to name a couple. Products containing the natural compound citronellin (citronella candles and lotions) have some repellency. Citronellin comes from a species of grass called citronella grass

There is also a product sold that you sprinkle on your backyard. It is called Mosquito Beater. It contains naphthalene. The active ingredient is volatile and sensitive to atmospheric conditions. The research indicates that it shows some good results when the wind velocity is under 5 mph and rain is absent.

Many flying animals prey on mosquito adults. Most notable are bats. They don't feed on mosquitoes exclusively, but like most successful predators, once they identify a plentiful food source, they exploit it. Insect-eating birds are no different. The purple martin feeds on many flying insects and is particularly adept at capturing mosquitoes and midges. Many insects feed on mosquito adults. Top Gun award probably goes to dragonflies. Many small fish that feed on pond surfaces will really get after mosquito larvae.