Disease Management for Greenhouse Strawberry in Kentucky

 

Disease Management for Greenhouse Strawberry

 

Plug production, Greenhouse:

·         Drench or dip: Aliette/Rampart (33) for Pythium root rot

·         Drench: for fungal root and crown rots

o   Switch (9+12)

o   Captan (M)

 

 

Crop production, Greenhouse:

·         At Planting (Fall)

o   Dip/drench: Aliette/Rampart (33) or LalStop K-61* or
RootShield PLUS* for Pythium root rot

o   Dip: Switch anthracnose crown rot

·         Vegetative, apply on 14-day intervals, rotate among at least 3 of fungicides listed below, adhere to maximum applications for each FRAC group.

o   Captan (M) + Elevate (17)

o   Fontelis (7)

o   Luna Sensation (7+11)

o   Luna Tranquility (7+9)

o   PhD/OSO (19)*

o   Quadris Top (3+11)

·         Vegetative phase, as needed

o   Powdery mildew, as needed: Torino (U6)

o   Pythium root rot, as needed: Aliette/Rampart (33) or LalStop K-61* or RootShield PLUS*.

·         Fruiting (mid-late Spring), apply on 7-to-14-day intervals, adhere to maximum applications per season for each FRAC group.

o   Captan (M) + Elevate (17)

o   Fontelis (7)

o   PhD/OSO (19)*

o   Quadris Top (3+11)

 

FRAC groups in parentheses.

OMRI approved with asterisk*
Biologicals that are living organisms (LalStop K-61 and RootShield PLUS) can be deactivated by fungicides. Do not apply with Switch or other fungistat.

Limited options for Pythium root rot in greenhouses; maintain strict sanitation.

Refer to efficacy guide and other information in ID-232 Midwest Fruit Pest Management Guide.

UK Plant Pathology disease management resources can be found at https://plantpathology.ca.uky.edu/extension/publications#SMALLFRUIT 

Using Resistant Cultivars to Manage Strawberry Diseases

From the Midwest Small Fruit Pest Management Handbook
http://www2.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/MwSmFruitPMHandbook.pdf


In any IPM program, the use of resistant cultivars is an important consideration.  Many commercial cultivars have resistance and/ore tolerance to leaf spot, leaf scorch, red stele, and powdery mildew.  The more resistance within a program, the better.  Table 21 (page 27) lists ratings for disease resistance in several of the more commonly grown strawberry cultivars.

 

Skimpy Spruce – Defoliation from the Bottom Up

Rhizosphaera needle cast, the most common disease of spruce in Kentucky, causes needle drop in lower branches, resulting in a distinct thinned appearance.  The fungal pathogen Rhizosphaera kalkhoffii primarily infects spruce but can also affect some pine species. 

Figure 1 – Needles infected with Rhizosphaera turn purplish brown during summer.

Symptoms are often noticed during summer when needles on lower branches turn purplish or brown (Figure 1).  Within a few weeks, needles fall and lower limbs are left bare (Figure 2).  Small, dark fruiting bodies called pycnidia form in stomata (pores in needles) and can be used to confirm diagnoses (Figures 3 & 4).  Pycnidia can easily be recognized with a hand lens or with the naked eye. 

Figure 2 – Needle drop and thinning of lower canopy are classic symptoms of Rhizosphaera needle cast in spruce.

The life cycle of the fungus extends over a 15-month period.   Infection takes place as spores (conidia) within these pycnidia are rain splashed from needle debris onto foliage.  This infection process occurs primarily during spring, but it can continue as long as conditions are rainy, such as this past summer.  During the winter or following spring, pycnidia develop in infected needles, plugging stomata.  Needle discoloration and needle drop occur during summer of the second season, resulting in thinning of lower canopies.  If defoliation occurs 3 to 4 consecutive years, branch death is likely.  Stressed trees are more susceptible to infection by R. kalkhoffii than healthy plants. 



Figure 3 – Fungal pycnidia are often visible without a hand lens.

Disease management should consist of good cultural practices such as improved vigor and reduced plant stress, proper spacing to improve air circulation, and most importantly, good sanitation habits.  During rainy seasons or in plantings with a history of disease, fungicides may be applied two consecutive years during spring when fungi are most active.  Fungicides that include chlorothalonil, copper, or mancozeb are effective when applied during needle emergence (mid-April) and again four weeks later.  For more information, see Homeowner’s Guide to Fungicides. 

Figure 4 – Fungal pycnidia protrude from stomata.

Downy Mildew in Grape – Secrets to Successful Disease Management

Experienced grape growers saw it coming.  New growers hadn’t a clue.  Regardless, my crystal ball told me that with months of rain would come severe outbreaks of downy mildew in vineyards. 

Grape downy mildew has reached epidemic levels in some vineyards in Kentucky and possibly the Midwest.  The pathogen that causes the disease (Plasmopara viticola) is a water mold, which warrants special considerations for disease management.  Let’s begin with a quick overview of water molds (oomycetes, to be exact). 

Water Molds

Water molds are different from true fungi.  In fact, they are not related.  Most importantly, water molds require free water to complete their life cycles.  Initial infections often occur during rainy spring weather as temperatures begin to warm.  After infection, pathogens release large numbers of “swimming” spores (zoospores) that move in films of water (damp leaves or moist soil).  This is the repeating stage of disease that leads to epidemics if wet conditions persist.  Spores are spread by splashing water and wind-driven rain.  In addition to downy mildew pathogens, many root rotting pathogens (Phytophthora and Pythium) are water molds. 

Figure 1 - Early symptoms of grape downy mildew include yellow spots on upper sides of leaves.

 

Downy Mildew

Downy mildew symptoms are quite distinct.  Upper leaves are the first to develop noticeable symptoms.  Yellow circular to blotchy spots can quickly enlarge and become bright yellow (Fig 1).   As disease progresses, leaf tissue becomes reddish brown, and centers of spots becomes necrotic (dead tissue) (Fig 2).  Extreme disease conditions result in a coalescing of spots into large necrotic areas.     

Figure 2 - As downy mildew spreads, leaf tissue becomes necrotic.

 

The most characteristic symptom of downy mildew is the “downy” fungal masses that develop on undersides of leaves (Fig 3).  If weather remains rainy or humid/foggy, pathogens will begin producing spore capsules (sporangia) on microscopic branched structures (sporangiophores).  This branching gives the disease its fluffy, downy appearance.  Sporangia can spread to healthy plant parts by wind or rain, and then open to expose infective, swimming zoospores.  This repeating cycle is dependent upon temperature and availability of free water. 

Figure 3 - The most characteristic symptom of downy mildew is the "downy" fungal masses on undersides of leaves.

Downy mildew pathogens also produce another spore type, thick-walled overwintering spores (oospores), at the end of the season.  These spores drop to the ground and overwinter in leaf debris or in soils.  In spring, they germinate just as grape begin to bloom.  Thus, early fungicide protection is critical in order to combat the initial phase of disease.  Moreover, an effective disease management program (described below) will help eliminate some of the inoculum (oospores) that before they overwinter. 

Damage Caused by Downy Mildew

Effects of infection are two-fold.  First, diseased leaves fail to properly photosynthesize, while severely infected leaves drop, leading to inadequate energy production (Fig 4).  Secondly, grape berries may become infected, leading to yield and quality losses (Fig 5).

Figure 4 - Advanced symptom development can lead to reduced photosynthesis and leaf drop.

 

Fruit are susceptible to infection from bloom until 3 or 4 weeks after bloom.  After that, they become resistant to infection.  Berries may not develop symptoms until several weeks after infection.  Affected fruit become soft and brown and do not mature.  Like foliar infections, infected berries become covered with downy fungal growth when conditions are wet or humid.  While fruit become resistant to infection as they mature, cluster stems (rachis) do not.  Thus, infections in these cluster stems can spread internally to berries.  Additionally, young shoots, leaves, and tendrils remain susceptible to infections throughout the growing season.

Figure 5 - Grape berries become infected between bloom and 3 to 4 weeks after bloom.  Symptoms, however, may not develop until several weeks after infection. 

 

Disease Management

Growers must combine cultural and chemical practices to effectively manage downy mildew in grape vineyards. 

Cultural practices are important for both conventional and organic growers.  Maintaining dry foliage is important.  Plant spacing, pruning, tucking, and other practices that improve air circulation will help foliage dry faster, and thus, conditions become less conducive for disease development.  Surface and internal vineyard drainage can also help reduce moisture levels within canopies.  Next, sanitation should not be overlooked.  To the extent possible, remove diseased leaves, fruit, and other plant parts from vineyards.  This will help to prevent fallen debris from becoming a home for overwintering pathogens.  Some species and cultivars have some resistance to downy mildew.  See page 36 of the Midwest Small Fruit and Grape Spray Guide ID-94 for a partial listing of tolerant grapes. 

Fungicides are a vital part of management of downy mildew.  Protectant sprays should begin at bud break and continue throughout the growing season.  Keep in mind though, that fungicide applications between bud break and 3 to 4 weeks after bloom are the most critical.  When selecting fungicides, remember that the downy mildew pathogen is a water mold, not a true fungus.  Therefore, not all fungicides will be effective against infection.  Refer to Effectiveness of Grape Fungicides PPFS-FR-S-18 or the Midwest Small Fruit and Grape Spray Guide ID-94 for up to date fungicide information.

Additional information on grape production and disease management can be found online at the UK Department of Plant Pathology’s website.  http://www2.ca.uky.edu/agcollege/plantpathology/extension/pubs.html#Smallfruit

Two New Strawberry Viruses Detected in Kentucky.

Two New Strawberry Viruses Detected in Kentucky. The viruses (strawberry mottle virus, abbreviated SMoV; and strawberry mild yellow edge virus, abbreviated SMYEV) originated from a plug producer in Nova Scotia. In the aforementioned case,... three growers shared a shipment of plants, but only one of the growers has seen symptoms. The other two growers have not.

We encourage strawberry growers to contact their brokers to determine the source of his/her plants. Those with high risks may need to take some of the precautionary steps outlined below.

An article describing the two viruses in more detail is available at http://extension.psu.edu/plants/tree-fruit/news. Briefly, SMoV and SMYEV are transmitted by aphids. SMYEV infects only strawberry, but SMoV can also infect the weed common lambsquarters. Therefore, we encourage high-risk growers to scout for aphids and to implement a solid weed management program.  

 

 

 Finally, remember that virus diseases cannot be cured. We recommend that symptomatic plants be destroyed to prevent spread to healthy plants. If you determine that your plants originated from the Nova Scotia area, please do not hesitate to contact me for more specific information.

Sanitation is the First Step to a Disease-Free Greenhouse

Greenhouse Sanitation

Diseases are a major concern for greenhouse growers and can be a key limitation to profitable plant production.  Disease management in greenhouses is critical because the warm, humid environment in these structures provides optimal conditions for reproduction of many fungal and bacterial pathogens.  When disease management is neglected, pathogen populations build-up and continue to increase as long as there is susceptible plant tissue available for infection and disease development.  Infected plant tissue, infested soil, and pathogen inoculum all serve as sources of pathogens that can later infect healthy plants.  Removal of any material that can harbor pathogens is the basis for disease management using sanitation practices.  This prevents spread of pathogens to healthy plants or reduces survival from one cropping cycle to another.

(Kara Keeton, Kentucky Farm Bureau)

Importance of Sanitation.  Reduction of fungal and bacterial pathogens by various sanitation practices can reduce both active and dormant inoculum (infective pathogenic tissue).  While actively growing plants can provide host tissue for pathogen multiplication and sporulation, dead plant material can harbor overwintering propagules (fungal spores and bacterial cells) for months or years.  These propagules can travel through wind/fan currents, stick to shoes or tools, or move with contaminated soil or water droplets.

Sanitation is one of the most overlooked disease management practices.  Often, growers presume that fungicides are the most important disease management tool at their disposal.  However basic cultural practices such as sanitation help reduce pathogen numbers and eliminate infective propagules that cause disease.  Poor sanitation practices allow pathogens to spread to healthy plants or to survive from one cropping cycle to another.  Elimination and reduction of pathogens can help prevent “overwhelming” of spray programs in which surviving propagules cause disease epidemics within greenhouses.

Sanitation should be considered by both conventional and organic growers. 

Water mold pathogens are often spread by contaminated soil or water.  They can also overwinter in plant debris under benches or on containers and trays that are not properly sanitized (C. Kaiser).

 

Disease Management.  Elimination and/or reduction of pathogens from greenhouses results in fewer fungal propagules.  The following sanitation practices can reduce amounts of infectious pathogens:

·        Discard plants that are heavily infected and those with untreatable diseases (e.g. root rots).  Some diseases (e.g. leaf spots) can be managed using fungicides; isolate infected plants until disease is eliminated.  Fungicides won’t bring dead tissue back to life, but using fungicides will help protect new growth, allowing plants to overcome disease outbreaks.  Contact your local Extension agent for more information.

·        If infected plants are to be treated with fungicides, prune or remove infected tissue (flowers, leaves) to eliminate sources for spore production or propagule multiplication before fungicide application. 

Leaf spot fungi often produce hundreds or thousands of spores that are carried by wind currents or on clothing.  Many leaf spot diseases can carry over from one crop to the next on weeds that are left under benches or on alternate crops on nearby benches (J. Hartman).

 

·        Discard prunings and culled plants.  Never leave cuttings in greenhouses, as pathogens may continue to multiply by producing spores or other propagules.  Do not compost cuttings or soil because incomplete composting (temperatures below 160 F may result in survival of propagules.

·        Remove weeds and volunteer plants to prevent establishment of a “green bridge” between crops.  A green bridge allows pathogens to infect alternate hosts until a more suitable one becomes available.

·        Do not reuse soil or potting media.  Do not bring outside soil into greenhouses.  Use sterilized potting mix only.

·        Disinfest pots, benches, floors, and tools to remove spores and propagules.  Use a commercial disinfectant such as Green-Shield®, 10% bleach, or 10% Lysol® concentrated disinfectant.  Note:  bleach is corrosive, so tools must be rinsed after 5 to 10 minutes of exposure.

Many soilborne pathogens produce overwintering or survival structures (in this case, the tan spherical structures) that can remain dormant for months or years (D. Hershman). 

 

·        Clean excess soil and plant debris from floors and benches.  Soilborne pathogens can remain dormant in soil for months or years, becoming infective when temperature and humidity increase or when susceptible plant material becomes available.

·        Do not drag hoses and other tools along floors, where infested soil and plant debris can stick and be moved to clean surfaces.

·        Use pathogen-free irrigation water – either municipal water or sterilized.  Install a water-treatment system if using recycled pond water.

·        Ideally, a sanitation regime should begin with an empty greenhouse.  Clean and sanitize all surfaces to insure that pathogens are not carried over from one season to the next.

·        Use foot baths containing sanitizers to prevent carrying propagules to clean areas.

 

Additional Resources

Controlling Phytophthora Root Rot in Greenhouse Ornamentals, PPFS-OR-H-9

http://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-OR-H-9.pdf

 

Managing the Greenhouse Environment to Control Plant Diseases, PPFS-GH-1

http://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GH-1.pdf

 

Damping-off of Vegetables and Herbaceous Ornamentals, PPFS-GEN-3

http://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-GEN-3.pdf

Apple Rots Common This Time of Year: Bitter Rot is the Most Prevalent

As apple harvent gets into full swing, many growers and backyard orchardists are encountering a variety of fruit rots.  Some of these rots are initiated by insect entry wounds or hail, and others are caused by fungal pathogens.

The most common of the fungal fruit rots is bitter rot.  

Initial infections begin as early as bloom and continue until about one month after petal fall.  Early symptoms are small, slightly sunken lesions that eventually develop concentric rings (bulls eye pattern).  Under moist conditions, spores turn a distinct salmon color.  Cutting into infected fruit reveals a V-shaped internal rot.

The fungus overwinters in mummified fruit, crevices in bark, and dead wood such as fire blight damaged tissue.  Removal of mummified fruit, cankers, and dead wood helps reduce inoculum for the following season.  Diseased fruit should be discarded immediately.  Fungicides are only effective with good sanitation, so these cultural practices are a necessary step in disease prevention and control.

Current recommendations indicate fungicide applications soon after petal fall (no later than first cover) and continue until harvest.  Fungicides  captan, mancozeb (dithane, manzate, penncozeb), polyram, and ziram are recommended on 10-14 day schedules.  Note:   Symptoms do not always occur immediately after infection, and it is sometimes late in the season before symptoms appear.  However, fruit should be protected in the early stages of development.

 

Some cultivars are more resistant or tolerant of bitter rot disease than others.  Cultivar susceptibility table available at http://www.caf.wvu.edu/kearneysville/tables/bitterrotsus.html .

More information at http://nicolewarduk.blogspot.com/2012/04/homeowner-apple-spray-schedule-low.html ,  http://www.uky.edu/Ag/IPM/appleipm/appleipm/frot.php , and http://www.ca.uky.edu/agcollege/plantpathology/ext_files/PPFShtml/PPFS-FR-T-2.pdf

Blueberry Mosaic Virus Detected in Kentucky

Blueberry mosaic virus was confirmed in a blueberry orchard in central Kentucky this summer.  This is the first report of blueberry mosaic in the state.  The virus has not previously been found in southern states, but it has been reported in Michigan, Indiana, New Jersey, New York, Oregon, Washington, and British Columbia. 

Formerly considered a “disorder,” blueberry mosaic has only recently been classified as a virus.  Not much else is known about it.  Highbush cultivars ‘Bluecrop,’ ‘Pioneer,’  ‘Concord,’  ‘Earlibule,’ and ‘Jersey’ are among the susceptible cultivars.  Virus symptoms have not been reported in rabbiteye blueberry.  Limited research has been conducted thus far, but it is under evaluation by a team of researchers at the USDA-ARS Marucci Center in New Jersey.

 

Symptoms

Foliar symptoms include mottling and mosaic-patterned characteristics on leaves.  Patterns range from mild to brilliant with yellow, orange, and/or red colorations (see photos).  Mosaic symptoms are not always produced each year, and environmental conditions may affect symptom development.  It is possible that during cool seasons, symptoms are more pronounced.  Thus, under ideal conditions, symptoms may appear suddenly, and it may appear that spread is rapid.

Infected plants often result in reduced fruit load.  Yield losses of 15% have been reported on ‘Bluecrop’ in Michigan.  Fruit on infected plants have been shown to ripen later than noninfected fruit, and fruit quality is low.

 

Spread

The vector (carrier) of the virus is not known.  Researchers report that blueberry mosaic is not transmissible by mechanical means (i.e. pruners).  However, the virus is graft transmitted.  Because virus particles are systemic (dispersed throughout the vascular system), once infected, all plant parts are infected, even when symptoms are absent.  Thus, cuttings should never be taken from a virus-infected plant.

As mentioned above, the vector of blueberry mosaic virus is not known.  Therefore, growers are encouraged to destroy infected plants until it is clear on how the virus spreads.  Whether an insect vector is involved is yet to be determined.

Current research indicates that the virus is slow-spreading (if at all) under field conditions.  However, in Michigan, spread is rapid. So far, the reason is unknown.

 

Treatment

There is no cure for plant viruses, including blueberry mosaic.  Growers should remove infected plants and destroy them by burning or burying.  Remove all roots within soil, as well.  Scout orchards, especially nearby plants, several times during the growing season.  Contact a local extension agent if a plant appears suspicious.

Most importantly, purchase plants from a reputable grower.  Visit nurseries before plant purchase and ask to inspect parent plants.  Furthermore, a virus-free certification is always worth the extra cost. 

 

 

Fungicide-Resistant Downy Mildew Detected in Kentucky Vineyard

This summer, a grape grower in central Kentucky reported persistent downy mildew in his vineyard.  He noted that regular applications of Abound and Pristine fungicides failed to manage the disease.  After laboratory analysis, the pathogen was deemed completely resistant to the two fungicides at the lowest recommended rates and 85% resistant at the highest recommended rates. 

 

What is fungicide resistance?

In the simplest terms, pathogens become resistant to fungicides when the chemical no longer manages disease symptoms.  However, even the most effective fungicides fail to completely eradicate a pathogen population.  There are always a few fungal spores or other fungal inoculum that survive the pesticide application.  Those survivors may be the result of ineffective spray coverage, but individual pathogens may have a trait that provides some type of resistance to the fungicide.  Think back to high school biology when we learned the theory of “survival of the fittest.”  Unfortunately, a single survivor can multiply into thousands of individuals while passing that resistance gene onto its offspring, much the way our parents passed on eye color to us. 

 

How did resistance develop?

Consider that it is highly unlikely that a fungal population will incur resistance to more than one chemical type, at least over the short term.  As a fungal population can become resistant to a single chemical, growers should rotate sprays with a different chemical group.  These chemical rotations can become confusing, and many growers do not fully understand the concept of chemical groups. 

 Chemical groups are classified by biochemical mode of action, not necessarily by active ingredient.  For example, within the strobilurin group of fungicides, active ingredients include azoxystrobin, pyraclostrobin, trifloxystrobin, and kresoxim-methyl, all of which are quinone-outside inhibitors.  Because information on biochemical modes of action can be confusing for growers, the Fungicide Resistance Action Committee (FRAC) developed numeric codes that represent these chemical groups.  Strobilurins are classified as FRAC group 11.  These codes appear on the top right side of all pesticide labels.  Thus, growers may simply refer to the coded chemical group number on labels as opposed to depending upon complex information such as mode of action.

Considering that all fungicides within the same group have the same mode of action, it is clear that if a grower fails to properly rotate fungicide groups, fungicide resistance risk is high.  Additionally, fungicide labels indicate the maximum number of applications allowed per growing season.  A maximum of four applications of strobilurins are allowed per growing season.  The grower mentioned above used Abound and Pristine fungicides consistently over a two-year period, exceeding the maximum number of applications and failing to rotate with a different chemical group.  This rapidly induced the development of a resistant population of the downy mildew pathogen.

 

Abound fungicide is classified as a FRAC Group 11 fungicide.  The chemical group code appears on the top right corner of fungicide labels.

 

How does a grower know if a resistant population developed?

Pathogen populations do not begin as 100% resistant.  In fact, resistance develops gradually.  Thus, growers should be aware of efficacy and disease control.  If a product(s) begins to become less effective over time, he should contact his local Extension agent immediately. 

 

What next?

If resistant pathogen populations develop within a vineyard, growers should immediately stop using the fungicide in question and all others in the same FRAC group.  With the assistance with an Extension agent or specialist, growers should identify other fungicides that will effectively manage disease.  In the aforementioned case, the grower stopped using strobilurin fungicides and substituted a phosphorous acid fungicide (ProPhyt, Rampart, etc.) for management of downy mildew.  If strobilurins are used for management of other diseases, tank-mix with another product (within a different FRAC group) that provides downy mildew control.

 

More Information

Fungicide resistance can appear complicated, so growers should not hesitate to seek assistance in development of a spray program.  Contact University of Kentucky Cooperative Extension agents or specialists for assistance. 

Win the Battle Against Powdery Mildew

Powdery mildew is one of the most easily recognizable diseases of landscape and garden plants.  While most fungal pathogens are favored by wet weather, powdery mildew pathogens favor high humidity but not wet conditions.  Shady areas, areas with poor air circulation, and low areas that trap damp air are ideal environments for disease development.

Powdery fungal growth is an easily recognizable symptom of powdery mildew disease.

A wide range of plants are susceptible to powdery mildew:  annuals, perennials, shrubs, ornamental and fruit trees, small fruit, and vegetables.  While symptoms appear similar on most plants, powdery mildew fungi are usually host-specific.  For example, powdery mildew of dogwood cannot infect pumpkins or cucurbits, and powdery mildew of cantaloupe will not infect phlox or rose. 

Typical symptoms of powdery mildew include dusty fungal growth on surfaces of leaves and on young succulent plant tissue (Photo 1 & 2).  Powdery mildew may occur as isolated blotches or cover entire leaves, stems, buds, or flowers.  Early infections can lead to leaf stunting, curling, or other deformation (Photo 2).  Infected fruit may become disfigured or fall prematurely (Photo 3).  In the fall, small fruiting structures that resemble pepper flakes may be visible to the naked eye (Photo 4 & 5).  These structures contain overwintering spores that serve as inoculum for the following year.

Infection of young growth may result in stunted or deformed tissue.

Management of powdery mildew begins with prevention.  Plants should be properly spaced and thinned for improved air circulation and more rapid leaf drying.  Resistant cultivars are available for crabapple, dogwood, phlox, zinnia, cucurbits, and several other plants and are an excellent means of disease prevention.

Fruit infections ultimately lead to yield loss.

Fungicides usually are not warranted when cultural practices are implemented.  Early season infection, however, may require one or more applications of effective fungicides.  Homeowners have a wide range of fungicides available.  However, they should carefully read labels to confirm that the selected fungicide may be used legally on select plants or that the fungicide is suitable for edible plants.

Fungicides effective against powdery mildew include:

·         Chlorothalonil – broad spectrum protectant; ornamentals, some fruit and many vegetables

o   Bonide Fungonil concentrate or Fungonil RTU

o   Ortho MAX Garden Disease Control

o   Sevin Daconil

·         Myclobuanil – systemic; ornamentals, most fruit and vegetables

o   Spectracide Immunox (only Immunox Multi-purpose Fungicide Concentrate is labeled for use on fruit and vegetables)

·         Propiconazole – systemic; ornamentals, some fruit

o   Bonide Fungonil RTS (different from other Fungonil products, which contain chlorothalonil)

o   Bonide Infuse

o   Fertilome Liquid Systemic

·         Tebuconazole – systemic; ornamentals only

o   Bayer Advanced Disease Control

o   Bonide Rx Systemic

·         Triflorine – systemic; ornamentals only

o   Ortho Rose Pride Disease Control

Late in the growing season, powdery mildew fungi produce small, black overwintering structures that can serve as inoculum the following year.