Yard & Garden Line News
Volume 7 Number 10                                                               July 1, 2005
Features this issue:

Review and Update of Lawn Weed Control Products Available to Homeowners
Plant PMS
Stag Beetles Gone Wild
Larder Beetles
An Insect Pest on Tomatillos
July Garden Calendar
Editorial Notes

Review and Update of Lawn Weed Control Products Available to Homeowners
Bob Mugaas, Regional Extension Educator - Horticulture
Dr. Brian Horgan, Turfgrass Extension Specialist
Ronald Claussen, Horticulture Assistant

Dandelions.
Photo credit:
Beth Jarvis
At some point in our lawn care experience, there usually comes a time when there is a need for controlling weeds in our lawns. While plucking a few weeds by hand is sometimes all that is needed, there are other times when the aid of a weed killer (herbicide) may be more practical and effective. However, going to a local retail outlet for those weed killers often confronts one with a staggering array of herbicide choices. Not only are there a lot of choices, the extremely fine print on most labels can make it very difficult to determine whether or not this is the right product for our purposes.

The label on a herbicide container by law must provide the active ingredients and their concentrations (among other information). The active ingredients are usually listed by the chemical name of their actual chemical structure, (e.g., (±)-2-(4-chloro-2-methylphenoxy) propanoic acid). For most of us, the chemical name is of little help in knowing what is actually in the product. The common chemical name (e.g., dithiopyr) or an abbreviation (e.g., MCPP) is also listed below the active ingredient list, following the chemical name, or by itself. The common chemical name can be more helpful in knowing what's in the product. Nonetheless, most of the time, we depend on the label to tell us whether or not our weed in question is something that product will control AND be safe for the other plants that we don't want to destroy.

The remainder of this article will briefly discuss some of the old standby products as well as some of the new items to come on the market for weed control in home lawns. Common chemical names (e.g., dithiopyr, balan, MCPA) will be used throughout the article. This article does not specifically include lawn fertilizer products that contain an herbicide, often known as 'weed-and-feed' products. Nonetheless, the herbicides mentioned in the article are common to many of the weed-and-feed products. Materials not available for homeowner use but accessible to the commercial lawn care industry are also not included.

Following the article is list of the more commonly available lawn weed control products in the Twin Cities marketplace. Not all of the materials would necessarily be offered at one retail outlet. Rather these are the more commonly available materials offered for sale by various garden centers and stores in the Twin Cities area.

White Clover-weed or groundcover?
Photo credit:
Sid Jarvis
Getting started
When the determination is made that an herbicide is needed to control a population of weeds, it is always best to get the weeds properly identified such that an appropriate herbicide can be selected that is safe for surrounding vegetation. During the identification process, notice how the weed grows and spreads from one area to another. That information along with knowing the name of the plant is an important first step in choosing the correct product.

For lawn weed control applications, there are 2 major categories of herbicides: preemergence and postemergence. Preemergence products are directed at controlling the germinating weed seed before it emerges from the ground. These products are applied as either a liquid or granular and usually require a small amount of watering-in (1/4 to 1/2 inch) following their application to be effective. These products set up a "barrier" at the soil surface that kills the weed seedling as it contacts this barrier but before emergence. It is important to remember that these materials do not kill seeds that do not germinate. The seed must begin to grow and contact the material before it is killed.

Postemergence products are directed at controlling those weeds fully emerged from the ground and are easily visible. This group of materials is further divided into two other categories: selective and non-selective. Selective materials are able to 'selectively' remove certain weeds while not harming others in the same area. Examples include the ability to remove broadleaf plants (e.g., dandelions, white clover) from lawn grasses, or remove grass plants from broadleaf plants such as shrub borders or flowering perennial beds. Another form of selective control would be the use of preemergence herbicides to selectively remove annual weedy grasses (e.g., crabgrass) from existing lawns. Non-selective materials are used to destroy all of the vegetation in an area. Examples of non-selective control include killing off all of the weeds from an area prior to seeding or sodding or doing the same strategy but where a new perennial bed or shrub border is to be located.

Postemergence emergence products can also be divided into contact or systemic herbicides. Contact herbicides elicit their effect at the point contact with the plant. Hence, it is very important to get coverage of the plant such that all of the plant will ultimately be affected and destroyed. Contact products are usually non-selective as they do not discriminate between desirable and weedy plants. Systemic herbicides have the capability to be moved around in the plant to particular sites of activity. It is the effects produced by the herbicide at those sites that ultimately results in the death of the plant. Systemic products can be both selective and non-selective.

With weeds identified and an initial idea as to how our weed control is to be approached, (i.e., preemergence, post emergence - selective, etc.), we are now ready to face the task of selecting an appropriate product(s) to use. This need not be as daunting as you might think.

Pre-emergence Herbicides
Concern Weed
Prevention Plus
Photo credit:
Safer
Preemergence herbicides are most commonly recognized for warm season annual grass control, such as crabgrass in lawns. In recent years, most of the herbicides used for this purpose came from a family of herbicides with similar chemical structures but varying levels of longevity and effectiveness. Some of the commonly available homeowner products include balan, trifluralin, and pendimethalin. This family of preemergence herbicides has enjoyed many years of successful crabgrass control in home lawns. However, they must be applied prior to any emergence of crabgrass seedlings. Once crabgrass seedlings poke through the soil these products are ineffective in killing the emerged seedlings. Hence these materials have a very narrow window of effectiveness. If you miss that window of application time, you will have missed any chance at control.

Balan and trifluralin are combined together under the trade name of Team. This trade name is often listed on the product label. Trifluralin is packaged by itself under the trade name Preen but is not intended for lawn use.

Several years ago, the product dithiopyr was introduced as a preemergence material that also had some very early post-emergence effect as well. That is, even if the crabgrass seedling had emerged from the soil but only had 1 to 2 leaves, dithiopyr (Trade name: Dimension) would still be able to destroy the seedlings. While this gives a little bigger window of control, it too must be applied before the seedlings get much beyond the 1 or 2 true leaf stage. For homeowners, dithiopyr is usually packaged with granular lawn fertilizers and sold as 'weed and feed' products. The notable exception is Spectracide's Weed Stop Crabgrass Preventer, which is a liquid formulation of dithiopyr packaged in a hose-end sprayer ready to apply product. It too should be followed up with a light watering to move the material down to the soil surface from the grass blades above.

None of the above mentioned products can be used at the time of seeding a new lawn or overseeding an existing lawn. The problem is that they do not discriminate between the seeds of weedy grasses or the seed of desirable lawn grasses. These products will kill either one equally well. However, there is a product that will control crabgrass and other weedy summer annual grasses but will not affect seeds of our bluegrasses, fine fescues or perennial ryegrass. The product's chemical name is know as siduron and is sold under the trade name of Tupersan. This is the only preemergent that homeowners can access and be safely used at the time of seeding our cool season lawn grasses. Thus, if you need to do some seeding during the mid-May through mid-July period, using siduron will help provide some short term control of the annual weedy grasses while not interfering with lawn grass establishment.

Another newcomer to the preemergence scene is that of a natural organic known as corn gluten meal (CGM). This is a by-product of the corn processing industry and is used as a feedstock for some animals. In the early nineties, Dr. Nick Christians and his staff at Iowa State University discovered this material also had some weed control properties. This material destroys the seedling root system shortly after it emerges from the seed. Once the root system is damaged the plant cannot continue to grow and consequently dies. This material is available under several different trade names and is becoming more readily available for homeowner use. In addition, this product acts much like a traditional weed and feed material as it contains 10% nitrogen, all in an organic form. Its one downside is that control can be quite variable, especially the first year it is used. Therefore, it is important to have a little patience with this product as control usually continues to improve each year that it is used.

Post-emergence selective herbicides
Non-selective post emergent Ground Force Photo credit:
Abby
This is the largest group of herbicides that homeowners will have to choose from as they range from products to control dandelions in bluegrass lawns to controlling bluegrass encroachment into flower beds. Most of these are liquid formulations that are available as 'concentrates,' which need to be diluted with water prior to spraying, or ready-to-use (abbreviated RTU) products that can be applied directly from the container in which they are purchased.

There are two general types of ready-to-use packaging, those that can be applied with a spray bottle by simply squeezing a trigger while aiming the applicator at the target weed, or as a hose-end spray bottle that dilutes and applies the material as water flows through the hose and applicator nozzle. The hand trigger ready-to-use sprayers are best for spot treating individual or small groups of weeds whereas the hose-end sprayer is designed to cover much larger areas.

Postemergence broadleaf weed control products
Over the past several decades, products containing one or more of the chemicals 2,4-D, MCPP, MCPA, 2,4-DP(also known as diclorprop) and dicamba have been very popular and effective at controlling many different broadleaf weeds. One very popular combination was 2,4-D, MCPP and dicamba and came to be known as a three-way product for its three different ingredients. A common product name for a particular combination of these three ingredients is Trimec.

Amines & Esters
When reading the active ingredients portion of the product label, the long chemical name will often be followed by the term amine or ester. These terms have to do with the actual chemical structure of the ingredients. The important difference for weed control is that the amine formulations are much less volatile than the ester formulations. That is, they are not as prone to volatilize (vaporize) back into the air thereby increasing their risk of injury to other non-target plants. This is especially true as temperatures rise. The trade-off is that the ester formulations have better penetration into the plant and can be more effective in their control.

Products containing ester formulations often have that noted prominently on the label (e.g, Turflon-D Ester, (a butoxyethyl ester of triclopyr)). If you are still wary of using any ester formulation, you can restrict their use to the cooler spring and fall periods and use amine formulations during warmer spring and summer conditions.

A couple newcomers
Within the last year or two, a couple of new chemicals have been added to the typical three-way mixes. They are carfentrazone (available in Fertilome's Weed Free Zone) or sulfentrazone (available in Spectracide's Weed Stop for Lawns RTU). Both belong to a class of herbicides that disrupt chlorophyll synthesis causing foliage to quickly turn yellow and begin drying up. However, they are not transported in the plant and hence are better combined with the other broadleaf herbicides like 2,4-D, MCPP, MCPA and/or dicamba that are systemic in the plant meaning they are easily transported to target sites of activity within the plant. They do provide a somewhat quicker acting product with fairly rapid dieback of the foliage yet do not interfere with the movement and effects of the other materials in the plant such that the whole plant is ultimately destroyed.

Stubborn broadleaf weeds
When it comes to some of the more difficult weeds to control such as creeping Charlie, clover, chickweed, oxalis or violets in lawns, most of the homeowner products will contain a chemical known as triclopyr. This material is frequently combined with other weed control chemicals like 2,4-D or MCPP to give an even broader range of control. If you are having difficulty controlling some of those tougher weeds with products not containing triclopyr you may want to consider using one that does. It may just be the ingredient needed to obtain better control.

What about grasses?
There are also postemergence products to control crabgrass and other warm season annual grasses selectively in an existing home lawn. Early emerging crabgrass can usually be observed in the home lawn by its light green color and generally wider blade. These will be visible in mid to late June. Postemergence control is usually easier when crabgrass is still quite young. Most homeowner products contain one of the methanearsonates and work quite well when applied to young actively growing plants. These products can cause some temporary yellowing of the bluegrass and fine fescue plants. Treatment should be avoided during periods of drought stress and/or high temperatures.

The methanarsonates are frequently combined with other postemergence broadleaf herbicides thereby avoiding having to handle two separate products. However, only purchase the product for the weeds they intend to control. If the lawn is essentially free of crabgrass but has a few broadleaf weeds, then there is no need to include a crabgrass herbicide since the target weeds are broadleaf weeds. It will usually be a less expensive alternative as well.

Postemergence Nonselective Weed Control
RoundUp Photo credit:
Monsanto
In many instances it is often desirable to control all of the vegetation in an area when preparing a site for a new lawn or to remove perennial grassy weeds such as quackgrass from an existing lawn followed by seeding or sodding. This kind of weed control is termed non-selective as the desire is to eliminate all vegetation regardless of whether it is a grassy or broadleaf weed. One of the most common non-selective ingredients over the last couple of decades has been glyphosate. While originally developed by Monsanto Corporation there are many other formulations of this material by other manufacturers. Other recent additions to the homeowner non-selective arsenal include glufosinate - ammonium (an example trade name being Finale), diquat dibromide and pelargonic acid.

Glyphosate 'plus'
Another new twist to glyphosate has been combining it with a selective postemergence herbicide (e.g. glyphosate + triclopyr) or a second non-selective postemergence herbicide such as diquat dibromide or pelargonic acid. In either case, it would appear that the additions are either to improve glyphosate's effect on some difficult to control weeds and/or to create a somewhat more rapid injury/killing effect on the target weeds. Always read label precautions regarding how long after applying these materials prior to reseeding or resodding an area. When only glyphosate is used, reseeding or resodding can occur within several days following application. Again, always check the particular product label for specific directions.

Non-selective organic products
The area of non-selective control has been the one area where "organic" alternatives have shown some promise as weed control products. Ingredients include materials such as citric acid, garlic extracts, clove oil, and potassium salts of fatty acids or soaps. Our survey turned up even more products that are available for homeowner use. Most of them affect cell membrane integrity which is responsible for controlling the movement of materials into and out of the cell.

While weed control is always better done when the weeds are small and immature, this may be particularly true for these organic non-selective products as their damage is usually confined to the tissue where the product is applied (contact herbicides). These materials are not moved within the plant and hence their damage is to the immediate local area of tissue contact. Therefore, it is easier to control smaller plants as it is usually easier to get thorough coverage of a smaller plant than a large mature plant. Their control is likely to be less successful on weedy plants with the capacity to regenerate from underground structures such as crowns, roots or rhizomes. In that case, repeat applications may be necessary to achieve complete control. As with various Round-up formulations, always check for any time interval restrictions before seeding or sodding is done.

Other items
Sometimes, weed control is not so much a function of the chemical product itself as it is the ability to contact the tissue long enough for absorption into the immediate plant tissue. One of the major stumbling blocks to getting herbicides to 'stick' on a plant surface is the presence of a waxy surface layer on stems and leaves. This waxy layer tends to repel water droplets as they land on the surface ultimately running off with much of the weed control product carried along with it. Hence, very little weed control material may actually stick to the leaves and stems long enough to cause their intended effect. It can also make the material more vulnerable to washing off should a rain occur too soon after application.

In order to get around that problem, manufacturers have begun to add "stickers" to their products to help the product stick to the surface and also provide protection against runoff during rainstorms. These stickers have a more formal name in horticulture called surfactants, short for surface acting agents. You will often see the term 'rainfast' or 'rain proof' in a predetermined number of hours after application. This usually means the formulation has included some means of helping the material stick to the foliage more efficiently thereby increasing its effectiveness. If given the choice, it is usually better to select those products known to have better 'sticking' capability than those that do not. Most products will clearly indicate their ability to be rainfast as that is clearly an advantage. Stickers can also be purchased separately and added to a spray mixture prior to being applied.

RTU packaging Weed-B-Gon Photo credit:
Orthp
The addition of foams and colorants to liquid weed control products helps improve tracking of where the product has been applied and where it has not. This can also be very helpful when using ready-to-use products to spot treat individual weeds or small areas in a lawn or garden bed. Even though spraying a plant will leave it looking wet rather than dry, there are times where better detection may be required to avoid skips or over application of an herbicide. In those situations, foams and colorants can be very helpful. There is a formulation of Round-up that comes as a foam aerosol to help control drift and improve precision of where the material is applied.

Last but not least, probably the biggest enhancement in homeowner weed control convenience has been the development of 'ready-to-use' applicators. For small areas and limited numbers of weeds to be treated, they are an ideal solution for homeowner use. It avoids all of the hassles of mixing of the material, maintaining a sprayer or applicator, and disposing of any unused material left in a sprayer or applicator once the treatment has been completed.

Remember, it is against the law to dispose of any product or product container that is inconsistent with its label directions. Any unused product in a ready-to-use applicator can be stored in that container until needed again. In most cases, these materials have a relatively good shelf life. Always follow label directions for proper storage of the product. In general that means in a locked storage unit in a cool dry area. Never allow these products to freeze as it will usually render them ineffective.

The following table lists a number of commonly available weed control products at local garden centers/stores in the Twin Cities area.

The information given in this publication is for educational purposes only. References to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the University of Minnesota Extension Service is implied.

Product NameSel.Non-Sel.Pre-em.Post-em.Active Ingredient
Abby Ground Force Organic Herbicide . x . x citric acid + garlic extract
Ace Spot Weed Killer x . . x 2,4-D + MCPP + dicamba
Ace Lawn Weed Killer x .. x 2,4-D + MCPP + dicamba
Ace Weed and Grass Killer . x . x glyphosate
Acme Super Chickweed Killer x . . x 2,4-D + MCPP + dicamba
All Down Organic Weed & Grass Killer . x . x citric acid + garlic
Bayer Advanced All-In-One Weed Killer x . . x 2,4-D + MCPP + dicamba + monosodium acid methanearsonate(MSMA)
Bonide Chickweed, Clover & Oxalis Killer x . . x MCPA + dicamba + triclopyr
Bonide Lawn Spot Weeder x . . x 2,4-D + MCPP + dicamba
Bonide Weed Beater - Lawn Weed Killer x . . x 2,4-D + MCPP + dicamba
Bonide Weed Beater Plus - Crabgrass & Broadleaf Weed Killer x . . x 2,4-D + MCPP + dicamba + MSMA
Concern Weed Prevention Plus (granular) x . x . granulated corn gluten meal + potassium sulfate
Ferti-lome Crabgrass, Nutgrass & Dallis Grass Killer x. . x MSMA
Ferti-lome Weed Free Zone (Ready to use) x .. x MCPA + MCPP + dicamba + carfentrazone-ethyl
Ferti-lome Weed Free Zone (Concentrate) x .. x 2,4-D + MCPP + dicamba + carfentrazone-ethyl
Ferti-lome Weed-Out for broadleaf weeds x .. x 2,4-D + MCPP + dicamba
Ferti-lome Weed Out(granular) x .. x 2,4-D + MCPP + dicamba
Ferti-lome Weed-Out Plus for broadleaf weeds and crabgrass x .. x 2,4-D + MCPP + dicamba + MSMA
Finale Weed & Grass Killer . x . x glufosinate ammonium
Gordon's Trimec Lawn Weed Killer x .. x 2,4-D + MCPP + dicamba
Green Light Wipe Out, Broadleaf Weed Killer x . . x 2,4-D + MCPP + dicamba
Green Thumb Lawn Weed Killer x .. x 2,4-D + MCPP + dicamba
Green Thumb Spot Weed Killer x .. x 2,4-D + MCPP + dicamba
Green Thumb Weed and Grass Killer . x . x glyphosate
Greenview Preen Lawn Weed Killer (hose-end application) x . . x 2,4-D + MCPP + dicamba
Greenview Preen Weed and Grass Preventer (hose-end application) . x . x glyphosate
Greenview Spring Crabgrass Preventer (granular) x . x . benefin + trifluralin (this combination also known as TEAM)
Hi-Yield Crabgrass Control (granular) x . x . benefin + trifluralin (this combination also known as TEAM)
Hi-Yield Grass Killer x . . x sethoxydim
Hi-Yield Kill-Zall Weed and Grass Killer . x . x glyphosate
Hi-Yield Turf and Ornamental Weed and Grass Stopper (granular) x . x . dithiopyr
Maxide Weed & Grass Killer . x . x glyphosate
Monterey Crab & Spurge Preventer x . x . dithiopyr
Monterey Spurge Power x . . x MCPA + triclopyr + dicamba
Ortho Basic Solutions Lawn Weed Killer x . . x 2,4-D + MCPP + dichlorprop
Ortho Crabgrass & Nutgrass Killer x . . x calcium acid methanearsonate
Ortho Weed-B-Gon Chickweed, Clover, Oxalis x . . x triclopyr
Ortho Weed-B-Gon Max x . . x 2,4-D + MCPP + dicamba
Renaissance Organic Preemeergent Weed & Feed 10-0-0, granular x . x . corn gluten meal
Roundup Concentrate plus . x . x glyphosate + diquat dibromide
Roundup Plus - Weed & Grass Killer (ready to use) . x . x glyphosate + pelargonic acid
Roundup Super concentrate . x . x glyphosate
Roundup Sure Shot Foam . x . x glyphosate
Spectracide Weed Stop for Lawns x . .x MCPP + 2,4-D + dicamba + sulfentrazone
Spectracide Weed Stop Crabgrass Preventer x . x . dithiopyr
St. Gabriel Laboratories Burn Out II - Weed & Grass Killer . x . x clove oil + sodium laurly sulfat

Sel. = selective products
Non-sel. = non-selective products
Pre-em. = pre-emergence activity
Post-em. = post-emergence activity

 
The information given in this publication is for educational purposes only. References to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the University of Minnesota Extension Service is implied.

Plant PMS
Janna Beckerman, Extension Plant Pathologist

Serviceberry suffering from PMS.
Photo credit:
Janna Beckerman
Plant Powdery Mildew Syndrome (PMS) is a common problem of landscape ornamentals. Powdery mildew is probably the easiest group of diseases to diagnose, and one of the hardest to manage. The fact that they are fairly common, extremely conspicuous, and infect thousands of plants provides ample opportunity to put those diagnostic and management skills to work. Fortunately, the damage caused by powdery mildew is of minor consequence to healthy plants, but of great consternation to some gardeners! It is important to remember that plants are rarely killed by powdery mildew, but they may become so ugly that you wish they were dead, to minimize any guilt you might feel when you put them out of your misery!

It is important to remember that powdery mildew is not one disease, but a group of pathogens that cause characteristic symptoms of a variety of plants. The powdery mildew on your turfgrass (Blumeria graminis) is not the powdery mildew on your rose (Sphaerotheca pannosa var. rosae), or your lilac (Microsphaera syringae). Powdery mildews are fairly, but not absolutely specific. That is, some powdery mildews can infect closely related plants: The powdery mildew on your pumpkin IS most likely, the same powdery mildew on your squash, or melon. The powdery mildew on your rose may infect your peach (if you can even grow peaches here in Minnesota!). One powdery mildew, though, is fairly cosmopolitan: Erysiphe cichoracearum. This is the powdery mildew on your bee balm (Menthae, or mint family), your Rudbeckia (Compositae, or daisy family), and your Veronica (Scrophulariaceae, or snapdragon family), in addition to cucurbits, and a variety of weeds. All powdery mildews are obligate parasites, meaning they require a live host for infection to obtain their food. Killing their host plant would be tantamount to suicide, meaning your plants may be ugly, but they probably aren't dead!

Symptoms and Signs of PMS

The lovely, powdery coating characteristic of plant PMS consists of thousands, if not millions, of spores that grow on top of each other in columnar fashion. Strong winds break up the columns and disseminate the spores. Unlike other pathogens, powdery mildew spores germinate in the absence of free water, meaning high humidity in the absence of rainfall facilitates plant PMS. Upon landing on a suitable leaf surface, the germinating spore grows, inserting specialized food extracting structures called haustoria into the plant cells and feeds. Infected leaves and shoots often become yellow, and may curl. With severe infection, premature leaf drop can result and susceptible plants may fail to flower. Powdery mildews continue producing spores, particularly under humid, overcrowded, and shaded conditions. Eventually, round, black "koosh-ball" structures called cleistothecia may develop on the surface of powdery covered leaves of some host plants. These are the sexual state of the fungus, and serve as overwintering structures to begin the cycle the following year. Some powdery mildews do not produce a sexual state, and over-winter by infecting buds on susceptible plants. Budbreak and shoot expansion initiates both plant and powdery mildew growth.

Fighting the White Stuff

Proper cultural practices go a long way in managing plant PMS. Start with:

1). Resistant varieties. Numerous cultivars are listed as resistant to PMS. Although plants may still suffer from PMS, symptoms aren't as severe as the susceptible counterpart. The Master Gardener Plant Research Evaluation Program evaluated different cultivars of Veronica, bee balm, aster, phlox, delphinium, and coreopsis for several common diseases, including PMS. Their results, in movie format, can be seen at:

2). Sanitation. Yes, your mother was right: Cleanliness is next to godliness. Personally, I think it's next to impossible, but who am I to argue with your mom? Prune and dispose diseased and dead branches: This practice is critical when powdery mildew over-winters in infected buds (e.g., azalea, crabapple, and rose). Collect and dispose of fallen, infected leaves to reduce inoculum available to start infections next spring. See-I told you it was next to impossible!

3). Environmental Modification. When pruning plants, remove branches to improve air circulation and increase sunlight in the canopy. Never grow susceptible plants in shaded sites, or water loving plants under droughty conditions. Avoid over-fertilizing, especially nitrogen, as it encourages tender, succulent growth that is more susceptible to foliar diseases, including powdery mildew infection. 4). Scouting. Monitor susceptible plants during favorable disease development conditions. This is essential if you plan on using any sort of fungicide so you can protect plants before they are severely infected.

5). Chemical control. When serious damage is occurring, or if appearance is deemed important, proper cultural practices coupled with chemical management is recommended. It is important to note that any program with chemical management requires regular spraying on a 10-14 day rotation throughout the season. When spraying, be sure to coat both surfaces of all leaves to prevent infection. Some packaged fungicides come with an adjuvant, or spreader-sticker that improves coverage and adhesion to plant surfaces. When beginning chemical control, start with the lowest impact products, such as horticultural oils, like SunSpray, or Volck's. Studies performed by extension plant pathologists across the country have consistently found that mineral-based oils like SunSpray or Volck's provide better control than vegetable derived oils, like neem, jojoba or soybean. If these fail to provide effective control, fungicides containing active ingredients such as chlorothalonil (Fungonil, Daconil), thiophanate-methyl (Clearys 3336) or triforine (Funginex, Triforine), can be rotated as needed. Professional applicators have several fungicides not available to homeowners that spread through plants (systemic), or are readily translocated, to provide greater protection. Check the label directions for how often the material needs to be applied for specific host plants. Organic chemicals approved for control include the horticultural and vegetable oils, sulfur, or bicarbonates (Kaligreen, First Step-Note: Baking soda is only slightly more effective than water alone, and the sodium can become toxic to certain plants!). Do not begin spraying if PMS is severe, as fungicides prevent infection, they do not cure infected plants.

For information on Minnesota Perennials, and their performance, see:
http://www.extension.umn.edu/projects/yardandgarden/MGPREPWEB/index.htm

For information on PM resistant woody ornamentals, check out Mary Ann Hanson's publication at:
http://www.ext.vt.edu/pubs/plantdiseasefs/450-616/450-616.html

Please check out the diagnostics web pages at:
http://www.extension.umn.edu/projects/yardandgarden/diagnostics/

Stag Beetles Gone Wild
Jeffrey Hahn, Assist. Extension Entomologist

Stag beetles and quarter Photo credit:
Darrell Stave
Many people have recently encountered large, June beetle-like insects in their yards, sometimes in large numbers. These dark-colored beetles are stag beetles, probably Lucanus placidus. This species is a little larger than one inch in size and is reddish brown to dark brown in color.

Stag beetles are related to June beetles and other scarab beetles. However, stag beetles possess more conspicuous heads and mandibles (jaws). You can distinguish between male and females as male stag beetle mandibles are larger. In some stag beetle species, the males has impressively large jaws giving them a menacing appearance. Ironically, stag beetles possessing such large mandibles are not able to bite people.

All stag beetle larvae feed in dead or decaying wood, such as logs and stumps. Most adults emerge in May or June and are believed to feed on honeydew or sap from plants. Stag beetles are active at night and are attracted to lights. They can fly into a yard, land on the ground and remain there until the following morning. If someone sees stag beetles emerging from the ground that is because they have been feeding in old decaying roots.

Large numbers of stag beetles were reported in mid June this year in central Minnesota (Crow Wing county), eastern Minnesota (Chisago county) and in the Twin Cities (Anoka county). People have undoubtedly seen these beetles in other areas. Although a lot of stag beetles in a yard is annoying, they are harmless to people and property. Do not spray stag beetles, their control isn't necessary; Just ignore them until they go away on there own.

Larder Beetles
Jeffrey Hahn, Assist. Extension Entomologist

>
Larder beetle immatures (top) and adults
Photo credit:
Jeff Hahn
Larder beetles have been commonly reported in homes this year. An adult is an oval shaped insect, about 1/3 inch long. It is blackish with a yellowish or brownish saddle-shaped band across its wing covers. A larva is dark brown, cylindrical, hairy, and possessing a pair of curved horns at the tip of its abdomen.

These beetles overwinter outdoors as adults. Once the weather warms during spring, they search for a food source to lay eggs. If you find just one or two larder beetles in your home during spring, that usually doesn't mean you have a problem. However, as the season progresses and you find persistent numbers of adults or you find larvae, that is evidence there is an infestation in the building.

Larder beetles feed on foods that are high in protein, such as meats, cheeses, dry pet food, hides, feathers, and dead insects. The abundance of larder beetles this year has been associated with lady beetles entering homes, then dying in walls, attics, and other inaccessible areas. These dead insects then become a food source for larder beetles.

The first step in larder beetle control is to try to determine the source of the infestation and remove it. Look particularly in areas where you see the most larder beetles. If it turns out to be something straight forward, like spilled pet food forgotten in a corner, it will be an easy matter to eliminate these pests.

However, it usually isn't that simple. If the food source is suspected to be dead insects or dead animals in the walls or somewhere inaccessible, then control is much more challenging. As long as a food source remains, larder beetles will continue to be a problem. If you believe your infestation is associated with dead insects or dead animals in wall voids or similar areas, short of tearing open the walls to get rid of the food source, the best you can do is to physically remove larder beetles (e.g. with a vacuum) as you see them. Insecticides sprayed indoors will have little lasting effect on larder beetles as long as a food source is available.

If you have had a problem with overwintering insects, such as lady beetles, you can reduce the number that get into your home by treating them in the fall before they get inside. Their management is a two step process. First, seal as many cracks and spaces around your home that may allow insects to entry. Second, apply a residual insecticide around the exterior of your building. For more detailed information on controlling lady beetles, see the following fact sheet, http://www.extension.umn.edu/distribution/housingandclothing/M1176.html.

An Insect Pest on Tomatillos
Jeffrey Hahn, Assist. Extension Entomologist

Threelined potato beetle. Photo credit:
Eric Burkness
You may occasionally encounter an uncommon beetle in your garden. The threelined potato beetle is a little larger than 1/4 inch long, with cream colored to reddish yellow wing covers with three black stripes running down its back. It has a reddish orange prothorax (the area behind the head) with two small black dots on it. A threelined potato beetle can be confused with a striped cucumber although these two insects feed on different plants.

It is believed that threelined potato beetles overwinter as adults. In the spring and early summer, they move to host plants to feed on leaves and lay eggs. This beetle loves to eat tomatillos as well as potatoes and other plants in the nightshade family. Once larvae hatch, they also feed on foliage. The larvae have the odd habit of protecting themselves by cementing their own excrement on their back (don't try this at home!). Larvae probably pupate in mid to late summer with most adults emerging in August. It is unclear whether this insect has one or two generations per year.

Fortunately, threelined potato beetles are usually not a problem, although they can be numerous in localized areas. If you encounter theses beetles in your garden, just handpick them and throw them into a pail of soap water. In cases, when an pesticide is justified, use a garden insecticide, such as permethrin or esfenvalerate to reduce their numbers.

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm

July Garden Calendar
Compiled from conversations with Bob Mugaas, Nancy Rose, Patrick Weicherding Regional Extension Educators

Velvet gall on birch Photo credit:
Beth Jarvis
Trees and Shrubs:
Dutch elm disease really started to show up last week, the first week of hot weather this season. Trees not getting at least an inch of moisture per week will show symptoms quickly when stressed by warm weather. Call your city forester if you see wilting, yellowing in branches of elms.

Apple scab also bloomed on trees a week or so ago. Lawns all over are decorated with fallen, yellow leaves.

Lots of galls showing up. Velvet gall on birch is real common this year. Also maples and oaks are getting a lot of leaf galls. Ash flower gall is also very common.

Anthracnose is still a problem, as well. It shows up as dried patches on leaves on the lower branches first.

General maple decline is very common this spring. Many landscape maples around the state have simply had enough. Several dry falls and snow-free winters permitted soils to freeze deeply, adding freezing injury to dessication root injury that has finally taxed trees to a breaking point.

Lawns:
Hot, humid conditions promote pythium and brown patch disease. If the weather turns warmer and dryer the diseases are controlled. They're not common and willl be apparent on high maintenance turf like golf courses.

Keep mowing so you don't have to cut more than 1/3 of the plant off per mowing.

Given all the rain, it could be beneficial to put down some fertilizer, about 1/2 nitrogen per 1000 ft. sq. for lawns that are irrigated.

If it ever dries out this summer and you choose to let your lawn go dormant, so it in stages. Let it dry down and provide 1/2" of water weekly.

If the weather stays below 85 or cooler, you can still do broadleaf weed control. It's far too late for pre-emergent but you can use post-emergence for crabgrass. For best control of weeds, do not apply herbicide when lawn is drought-stressed and/or the temperatures are too high.

Prairie grasses are going to be in bloom soon.

Fruits, Flowers and Veggies
Strawberries have taken a horrible beating from root rot due to the wet soils. When temperatures increase, the plants need more water and can't get it through the rotten away root system so the plant collapse.

June-bearing strawberry plants need to renovated. Here's how in the July 1, 1999 Yard & Garden Line News. http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-July0199.html#strawberries

Raspberries are producing and blueberries are just starting to ripen. The gooseberries and black currants are also ripening.

Potatoes do NOT need to bloom in order to set tubers. Tuberization is triggered by short days and cool nights

Editorial Notes

'Pink Pixie' and friends. Photo credits:
Beth Jarvis
I bumped Nancy's article because Bob and Ron, thanks to some rainy days, managed to get their piece on herbicides done. There will be a part two on garden herbicides later.

Julie Weisenhorn will conclude the landscaping project story in a future issue. Patrick Weicherding thinks the article about their planting research will be done soon. And he will write about when to call an arborist. I have Nancy's piece on shrubs ready to go.

. Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.

Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. The program is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations. (Scroll down for map.)

The Yard & Garden Clinic closed December 12, 2003 due to budget cuts. Questions from the general public will no longer be accepted. Samples will not be accepted.

For plant and insect questions, visit http://www.extension.umn.edu/askmg. Thousands of questions have been answered, so try the search option in the black bar at the top left of the board for the fastest answer.

If you would like to receive an e-mail reminder when the next issue of the Yard & Garden Line News is posted to the web, just send an e-mail to: listserv@lists.umn.edu (note: the second E in listserve is omitted), leave the subject line blank, then in the body of the message, type: sub yglnewslist or to unsubscribe, enter: unsub yglnewslist

Happy gardening!

Beth Jarvis
Yard & Garden Line Project Coordinator


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