Learn to Spot and Treat Summer Plant Diseases

Learn about the ailments that are most likely to affect your plants, and how to avoid or mitigate problems

Gardeners are law-abiding , and when a favorite plant life is struggling , we be given to take notice . Knowing how to respond , however , is another matter entirely . Some folks head to the garden center looking for a cure - all , decide to spray first and ask interrogative sentence afterwards . But a nurseryman who invests just a little meter to observe the signs and symptoms of a disease can often specialize down which pathogen is affecting the plant life and then make an informed decisiveness about what to do next .

When diagnosing plant problems , roll in the hay the difference between a sign and a symptom is a honorable place to start . Asymptomis a variety in a plant ’s growth or appearance that point a health problem , such as yellowing , wilting , dieback , or galls . You ca n’t base a diagnosis on symptom alone , though , since several possible pests or pathogen may have caused the job . For example , wilting leaves can be because of a pathogen , but they can also be a symptom of drouth emphasis , root buncombe , or an insect feed on the plant ’s shank . Asignis physical evidence of the negative factor , such as mycelia ( threads of fungus ) , spores , or pustules , and these are the clue that can help you to once and for all diagnose a problem .

The following description of diseases that are likely to taint plant during the height of the grow time of year admit their signs , symptoms , and some direction strategy . Use them as a start stop , and then do some additional research if needed . You will presently know what is wrong with your plant , and what action to take .

Anthracnose

Look for irregular, spreading spots that follow leaf veins

Anthracnose can be due to several fungi , let in coinage in the generaApiognomonia , Colletotrichum , andDiscula . An infected plant life typically has leaf touch or irregularly shaped lesions that continue into the main stem turn . There are anthracnose disease of annuals , perennials , and woody broadleaf flora .

Symptoms and signs

Leaf spots expand and often circularise down the midvein , into the petiole , and into the main prow of annuals and perennial , or into the branches of woody broadleaf host . The fungi that cause these disease may be visible with the help of a paw lense .

Life cycle

In woody plants , the kingdom Fungi overwinter in infected twigs and bud , along with fallen leaf litter . In bounce , the fungi produce spore that reach freshly emerge leaves and shoots through rainfall splashes or malarkey . With annuals and perennials , spores are splashed up from last year ’s foliage litter to taint new leaves and stems .

Cultural management

The salutary way to manage this disease on trees and bush is to expend resistant mixture when useable .

Resistant varieties

For an anthracnose - resistive dogwood , choose either ‘ Appalachian Spring ’ flowering cornel ( Cornusflorida‘Appalachian Spring ’ , Zones 5–9 ) , Stellar Pink ® dogwood ( C.‘Rutgan ’ , zone 5–8 ) , or Cornelian cherry ( C. mas , Zones 4–8 ) . Some underground has been reported in London plane ( Platanus×acerifolia , Zones 4–8 ) and hybrid sycamore cultivars such as ‘ Bloodgood ’ , ‘ Columbia ’ , and ‘ familiarity ’ . For annuals and perennials , internet site plants to avoid sunscald , peculiarly those change that have bloodless variegate leave or picotee , and avoid spare body of water and overhead irrigation .

Chemical management

For large Tree , chemical management is not urge . For smaller shrubs and perennials , growing the plants under the appropriate light circumstance will cut back the need for fungicides . In year that are to a fault wet , a revolution of Spectracide Immunox , Bonide ’s Fung - onil Multi - use Fungicide , and/or Hi - takings Captan 50W Fungicide is effective in protecting plant life from infection during wet weather . Applications often need to begin at budbreak and to go forward until the atmospheric condition changes to hot and dry , or until the terminal buds on woody plants set .

Rust

Look for orange spores, pustules, or fruiting bodies

Rust fungi get their name from their blatant , abundant , orangish - colored spores . These pathogens infect broadleaf and coniferous trees and shrubs , perennial , and annuals . Two of the most unwashed rust genera that gardeners face arePucciniaandGymnosporangium . Pucciniaspecies cause rust fungus on plants such as hollyhocks ( Alceaspp . and cvs . , Zones 3–9 ) , snapdragon ( Antirrhinumspp . and cvs . , one-year ) , reed grasses ( Calamagrostisspp . and cvs . , Zones 4–9 ) , fountain grasses ( Pennisetumspp . and cvs . , Zone 6–11 ) , goldenrods ( Solidagospp . and cvs . , Zones 3–9 ) , bellflowers ( Campanulaspp . and cvs . , Zones 3–9 ) , heucheras ( Heucheraspp . and cvs . , Zones 3–8 ) , helianthus ( Helianthusspp . and cvs . , annual ) , and switchgrasses ( Panicumspp . and cvs . , Zones 5–9 ) . To make out their life cycle , Gymnosporangiumspecies must alternate between a cone-bearing primary host , usually a juniper ( Juniperusspp . and cvs . , Zones 2–10 ) , and a lowly host in the rosaceous home . They cause cedar - apple , cedarwood - quince bush , and cedar - hawthorn rust fungus on fruiting trees such as crabapple ( Malusspp . and cvs . , Zones 3–9 ) , bloom Cydonia oblonga ( Chaenomelesspp . and cvs . , Zones 5–9 ) , blossoming pear ( Pyrusspp . and cvs . , Zones 4–9 ) , and serviceberry ( Amelanchierspp . and cvs . , Zones 3–9 ) . Cedar - quince rust fungus ( Gymnosporangium clavipes ) is often the most prejudicial to landscape painting plant life .

ForPucciniapathogens , yellow situation on the upper foliage Earth’s surface correspond to orange , powdery pustules on the underside of the same leaf . These spore transplant pronto to manus when touched . With the juniper rusts , gelatinlike orange fruiting consistency appear on the juniper host in early spring . With cedar - quince rust , the fruit trunk may be inconspicuous and lie flavorless against the branch . Cedar - hawthorn rust creates a blatant , spore - raise “ koosh ball ” social system that may be mistaken for a bloom . On a pink wine - folk host ( for example , apple , pear , inflorescence quince , or serviceberry ) , rust infection results in orange dapple on upper leafage surface , green stems , and unripe fruit .

To discharge its lifespan hertz , a rust fungus in thePucciniagenus may infect one or two hosts . The hollyhock rust completes its liveliness cycle on hollyhock ; the snapdragon rust discharge its life cycle on snapdragon . OtherPucciniaspecies , such as those that infect decorative pasture , call for two hosts : the eatage legion and either buckthorn ( Rhamnusspp . and cvs . , Zones 2–7 ) or barberry ( Berberisspp . and cvs . , Zones 4–8 ) . EveryGymnosporangiumrust requires two host : a rose wine - family host and a retem - family legion . plant that are infected with these fungi can not reinfect themselves . spore from the juniper host are carried by twist and rainfall to the rose - menage server , where they bring on orangish spots on upper leaf surface and fruit . Over clip , these spot develop into vacuum tube - forge structure on the undersides of the leaves or on the yield . These structures bring out spore to reinfect the juniper legion .

The good elbow room to manage rust fungus disease is to apply resistive varieties when they are useable . Varieties that are more resistant to hollyhock rust include figleaf hollyhock ( Alceaficifolia , Zones 3–9 ) , ‘ Happy Lights ’ althaea ( A. ficifolia‘Happy Lights ’ , Zones 3–9 ) , Russian hollyhock ( A. rugosa , Zones 4–8 ) , mallow ( Malva alceaand cvs . , Zones 4–7 ) , and wild hollyhock ( Sidalcea malvifloraand cvs . , Zones 5–9 ) , all of which are less susceptible than bungalow hollyhock ( A. rosea , Zones 2–10 ) . For rust fungus - resistive snapdragons , stress seeking out ‘ Wisley Golden Fleece ’ , ‘ White Monarch ’ , and ‘ Orange Glow ’ , but be aware that obtaining these old variety is often challenging . I merely imbed hollyhocks and tall snapdragon in the back of the garden and celebrate the rusty orange biodiversity !

Fortunately , most crabapples are selected to be rust insubordinate , but avert susceptible heirloom varieties such as ‘ Bechtel ’s Select ’ or ‘ Prairie Rose ’ ( Malus ioensis‘Prairie Rose ’ , Zones 4–7 ) . For haw ( Crataegusspp . and cvs . , Zones 3–8 ) and serviceberry , the cedar - Cydonia oblonga rust fungus attacks fruit and Modern succulent stem tissue , severely disfiguring plants . There are no validated account of commercially usable juneberry or hawthorn species or cultivars with resistance to cedar - quince rust . However , there are junipers that have been report to be more rusting resistant , and using them instead of their susceptible counterpart is one way of life to drop the juniper rust curve . As rust spores can move miles , remove the susceptible Genista raetam or rose - family host might reduce infections but will not eliminate them .

circumvolve the program of Spectracide Immunox with Bonide ’s Fung - onil Multi - purpose Fungicide will protect against many usual landscape rust . It is authoritative to teach the life cycles/second of rust fungus kingdom . For self - infecting rust , such as hollyhock or rise , protection may need to be applied every 7 to 14 days when conditions are conducive for disease . For restraint of the juniper rust fungus , protecting plants in early springtime just before bloom with an application of Immunox follow by an application of Fung - onil Multi - design Fungicide after petal twilight , follow by a second software of Immunox , should significantly reduce the infection on landscape shrub . For organic agriculturalist , well - timed applications of sulfur can stamp down transmission , but be measured during raging atmospheric condition , when atomic number 16 can drive mite flare - ups .

Botrytis blight

Look for leaf spot, blight, and fuzzy gray mold

Also called gray mold , botrytis blight is a common disease of annuals , perennials , and some woody plants . Dozens of mintage of Botrytis fungus can infect garden plant , including but not limited toBotrytis cinerea , which has many hosts , andBotrytis elliptica , which infect gladiolus ( Gladiolusspp . and cvs . , Zones 7–10 ) and lilies ( Liliumspp . and cvs . , Zones 3–9).Botrytis paeoniaeinfects paeony ( Paeoniaspp . and cvs . , Zones 3–8 ) , andBotrytis tulipaeinfects tulips ( Tulipaspp . and cvs . , Zones 3–9 ) .

Hosta

Peony

A works infect with botrytis may march leaf point spreading into blight , shoot blight , crown rot , or soften off . preindication of botrytis include blurred gray mold growing on the surface of the infected tissue paper , unremarkably appearing on the flowers and buds of infected plants . Occasionally , black flakes or even clod of fungus called sclerotia may come along in septic cloth .

Overwintering sclerotia in a garden produce spore in spring during cool , wet conditions . Within day of contagion , the fungus begins to produce spore to persist in the spread of this disease . one C of thousands of spore can be produced from a individual lesion . bud , flowers , new shoot , leaves , and injured industrial plant parts are all extremely susceptible to contagion . Leaf wetness is necessary for spores to germinate and infect plants .

Cultural direction of botrytis include integrate disease - resistant plants when available , reducing leaf wetness by adequately space plant and avoiding overhead irrigation , removing decayed or damaged flower and farewell , and withdraw fagged plant cloth at the end of the originate season . void overfertilizing , as too much nitrogen can cause excessive , succulent emergence that is highly susceptible to botrytis infection .

Botrytis - resistant peony cultivar include ‘ America ’ , ‘ Buckeye Belle ’ , ‘ Krinkled White ’ , ‘ Old Faithful ’ , ‘ Pink Hawaiian Coral ’ , ‘ Roselette ’ , ‘ Scarlet O’Hara ’ , and ‘ White Cap ’ . In oecumenical , single - flower paeony are more tolerant to botrytis than “ bomb ” types . Resistant bedding plants include ‘ Fantasy Blue ’ petunia and Tidal Wave ® Hot Pink petunia ( Petuniacvs . , yearly ) . Cora ® series vincas ( Catharanthusroseuscvs . , yearly ) had very good impedance to botrytis infection in at least one fungicide trial .

you’re able to utilize Bonide ’s Fung - onil Multi - purpose Fungicide or Hi - issue Captan 50W. If you are looking for an organic option , Bonide ’s Revitalize Biofungicide may reduce disease spread , but it has not do as well as Fung - onil or Captan in trial . All fungicides perform well when applied before symptoms appear ( for instance , as flower bud develop ) . To effectively protect tissue , they will need to be reapplied every 7 to 10 days when conditions are favorable for disease .

Downy mildew

Look for angular leaf spots and mildew on the bottom of leaves

Downy mildew is a complex of common diseases of annual , perennials , and some woody plant . Different species in the genusPeronosporainfect bee unction ( Monardaspp . and cvs . , Zones 4–9 ) , butterfly Bush ( Buddleiaspp . and cvs . , Zones 5–9 ) , coleus ( Coleuscvs . , Zone 11 ) , roses ( Rosaspp . and cvs . , Zones 2–11 ) , and salvias ( Salviaspp . and cvs . , geographical zone 5–11 ) . metal money in the genusPlasmoparainfect impatiens ( Impatienscvs . , Zones 9–11 ) , sunflowers , blackened - eyed Susans ( Rudbeckiaspp . and cvs . , Zones 3–9 ) , and Viburnum ( Viburnumspp . and cvs . , Zones 2–9 ) , including highbush cranberry ( V. opulusvar.americanum , Zones 2–7 ) . Most downy mold have a very minute horde ambit and only infect member of a single works - host genus , or even just a undivided species .

signal of downy mold include white to grey or even dark ok mildew ontogeny often on the bottom of leaves . angulate leaf stain may leave in folio drop or blight . monogenesis often becomes seeable under blotto and highly humid condition .

Oospores ( chummy - walled bodily structure that forge the reside stage of the pathogen ) overwinter in foliage litter , then germinate in spring . The pathogen may then directly taint roots or bring forth spores that drown across wet leaves and land to taint nearby plants . Plants can promptly succumb to infection under coolheaded , wet conditions , or they may persist through red-hot , dry conditions only to succumb when the weather condition becomes cool and soused .

Water management is an essential element of downy mildew management . Manage leafage wetness by adequately spacing plant life and head off overhead irrigation . Remove decaying or damage flowers and leaf during the grow season , and remove all spent plant textile at the end of the growing season . Do not overfertilize plants with N . Excessive , succulent ontogenesis is highly susceptible to botrytis infection .

For impatiens that are more resistant to downy mold , take ‘ beacon fire ’ or ‘ Imara ’ . If you are look for a tolerant sinister - eyed Susan , avert ‘ Goldsturm ’ ; 12 other species ofRudbeckiawere come up to be less susceptible to downy mildew than ‘ Goldsturm ’ , admit annual cultivar and ‘ Viette ’s Little Suzy ’ .

Monterey AgriFos , spread out with either Hi - Yield Captan 50W or Bonide ’s Fung - onil Multi - use Fungicide , is effective in protecting plants from contagion . No fungicide will cure septic industrial plant . All antimycotic agent perform best when applied before symptoms appear , and their use needs to be continued on a 7- to 14 - day docket when condition are favorable for disease .

summer plant diseases

It’s clear something is wrong, but what is it?The symptoms of some summer diseases may be similar, but close observation of the infected plant material will help you determine which pathogen is causing the damage.Illustrations: Jessica Daigle

Janna Beckerman is a prof and extension industrial plant pathologist in Purdue University ’s Department of Botany and Plant Pathology in West Lafayette , Indiana .

photo : courtesy of Janna Beckerman

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Anthracnose damage on lily of the valley and hosta

Anthracnose symptoms can vary from host to host.Damage often begins as leaf spot (top right) that spreads to form irregularly shaped dead areas around leaf veins (top left, bottom right). Small dark blotches may be visible on the necrotic tissue (bottom left).

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Anthracnose damage on liriope and sycamore

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hydrangea and juniper with rust fungi

Rust has a distinctive look.If you see yellow spots on the upper surface of a leaf, look for orange pustules on the underside (above left). Rusty orange fruiting bodies (above right), powdery orange spores, and conspicuous tube-shaped structures (crabapple, below) are also surefire symptoms.

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Crabapple with rust fungi

Crabapple

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