“What’s the difference in between powdery mildew and also downey mildew and what is used to law them?” “What is this white powdery problem infesting my tomatoes? Pls help” space questions typically asked by most first-time greenhouse farmers.

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Powdery Mildew

Powdery mildew is a fungal an illness that causes destruction of leaves, stems, and also flowers. Most common and easily known fungal disease. Affects every kinds of plants – cereals, grasses, vegetables, ornamentals, weeds, shrubs, fruit trees, woodland trees. Has quick life cycle and also produce white powdery spot on sheet surface and flower buds. Alleviate aesthetic and economic value of plants Host certain and survives broad climatic range.

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Image source: research study Gate https://www.researchgate.net/figure/Symptoms-of-tomato-powdery-mildew-O-neolycopersici-infection-on-susceptible-S_fig1_271095901

Powdery Mildew symptom

Characterized by point out or spot of white to grayish, talcum-powder-like growth.Tiny, pinhead-sized, spherical fruiting frameworks that are an initial white, later yellow-brown and finally black, may be present singly or in a group.Most typically observed ~ above the top sides of the leaves but affects the bottom side together well, young stems, buds, flowers and young fruit

Powdery Mildew Epidemiology

The severity depends on plenty of factors:

Crop factors:Variety of the host plant – some space tolerant rather not.Age and also condition that the plant – young and succulent crap much more susceptible.Environmental factors: severe in warm, dried climates. This fungus does not need the visibility of water top top the leaf surface for epidemic to occur.High loved one humidity required for spore germination. Infection boosts as relative humidity rises to 90 percent, however it walk not take place when sheet surfaces is wet (e,g., in a rain shower).Crowded crop. Negative air circulation,damp,and shaded areas.

Powdery Mildew condition cycle

All powdery mildew fungi call for living plant organization to grow.Powdery mildew survives from one season come the following as vegetative strands, called cleistothecia, top top the bark that branches and stems.Fungi grow as slim layers the mycelium ~ above the surface of the impacted plant parts.Spores, which deserve to be seen v a hand lens, are part of the white, powdery appearance and are created in chains on upper or reduced leaf surfaces.In contrast, downy mildew, produces visible powdery growth, has actually spores that prosper on branched stalks and look prefer tiny trees.Moderate temperature (15′ come 26°C) and shady conditions generally room the most favor-able because that powdery mildew developmentLeaf temperatures above 32°C, part spores might be killed.

Challenges in Powdery Mildew monitoring – grower view

Effectiveness of assets – many products but only a couple of can it is in relied on as soon as pressure is high.Fewer application approaches – all chemicals work-related through foliar applications (reduces crop working time)Certification issues with growers having direct market access reducing the selection of easily accessible productsGeneration of effective spray programmeObtaining great coverage – thick crop canopy, dilution issues

Control Challenges

Infection is v out the year however inter during dry weather.Certification bodies and their restrictionsMisuse/misapplication of an excellent products by growersCompetition for sources within farms may command to introduction of fake substandard pesticides

Chemical regulate Of Powdery Mildew

Excellent regulate when used as precautionary treatments fairly than curative treatments.Once the fungus has started come sporulate controlling added symptoms is difficultPreventive fungicides should be used when weather is appropriate for disease developmentCurative fungicides – usage at beforehand onset of visible signsSpray coverage – examine on rates, water volumes, speed of applicators and chemical agitationNozzles-select nozzles the give good coverage

Now let’s move gears and explore Downey Mildew..

Downey Mildew

Downy mildew is a fungal disease that reasons destruction that leaves, stems, and flowers. Downy mildew species are: Peronospora, Bremia, Plasmopara, and also Basidiophora. Downy mildew is a serious problem in the ornamental industry.

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Green and also yellow spots in cucurbit crops (cucumber, squash, melons) led to by Downy Mildew. Image source: university of Minnesota https://extension.umn.edu/diseases/downy-mildew-cucurbits

Downey Mildew signs and symptoms

At infection the fruiting structures of the fungus arise from the undersides the the leaves and create the greyish – colored, downy coating.The downy massive of spores are challenging to watch without a hand lens or microscope. These spores show up on the underside of sheet lesions.Purplish red come dark brown, irregular spots on leaves.Angular blotches, yellow, purple to brown, to a scorch like burn.Reddened locations on sepals and stem.Small clues or long purplish areas may type on canes and may death twigsInfection normally occurs on young plant parts yet other components are likewise affected.Defoliation may happen in too much cases.

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Downey Mildew disease cycle

The fungus to produce spores just on living plants.The fungus survives in tree debris as relaxing spores (oospores) over unfavourable periods or ~ above infected plants.Cuttings taken from infected share will bring over the disease.Take residence message is to examine plants purchases and budwood carefully for this disease.The fungus thrives in cool, humid (85% relative humidity) conditionsRoses space unaffected through downy mildew as soon as humidity Is less than 85%The optimum temperature for downy mildew is 18°CSpores type more conveniently in cool, humid conditionsOnce conditions turn warm and also dry, the an illness is preserved in checkIn the existence of water native a recent rain or heavy fog, the spores will germinate within 4 hoursBelow 11°C, the spores won’t germinate, and they are eliminated by exposure to 28°C temperatures for 24 hoursDry winds and also warm, clear days inhibit spore productionUnlike powdery mildew spores, which room spread by the wind, downy mildew is spread by splashing water
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Early symptom of Downy Mildew in Basil. Photo source: university of Minnesota https://extension.umn.edu/diseases/basil-downy-mildew

Control the Downey Mildew

Cultural control

Manage humidity – the is critical to keep relative humidity below 85% to decrease sporulation ~ above infected plants and stop germination of spores on healthy and balanced plants. Venting and also heating if excellent well deserve to reduce incidences

Hygiene

Critical in reducing microorganism sporesSanitation demands for the disease are stringentRake leaves and debris that might contain overwintering sporesDiscard debris away from production areaRoguing out infected shoots, buds and also branches that could harbor disease from season come season.

Start clean

Take cuttings from plants that have not endured a previous strike of downy mildewOnly plant clean stocks

Chemical control

Once the fungus has started to sporulate, symptoms cannot be reversedPreventive fungicides need to be applied when weather is best for disease development

Factors to think about when selecting chemicals

Stage of disease development- safeguard vs curativesEfficacy- an essential to decision making. Has actually bearing in lengthy term costs and also environmental load, resources allocation.Translocation in plant – contact or systemicPresence of other conditions e.g botrytis, powdery – alleviate spray fill by selecting large spectrum fungicidesResidues and also environmental air pollution – pick fungicides with minimal residuesResistance management-rotate chemistry according come MOA and also FRAC codes

Adapted from Floriculture brochure 2017/2018 Edition