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Abstract On Rose Diseases Essay, Research Paper

title = abstract on Rose diseases

Disease Control

Multi-Purpose Fungicide Daconil 2787? Plant Disease Control

This product is widely used for broad spectrum disease control on lawns,

ornamentals and listed

fruits and vegetables. Controls many foliar diseases such as: rust, black spot, leaf

spot, blights,

anthracnose and powdery mildew as listed on the label. Also controls conifer

diseases and lawn

diseases such as brown patch, red thread, rust and dollar spot. Can be mixed with

insecticides as

specified on the label to make a multi-purpose spray.

WHAT IS POWDERY MILDEW?

Powdery Mildew looks like white fuzzy powder that accumulates on leaves and stems

predominantly in spring, and again to a lesser degree in fall. It is actually a fungus that

is spread by

millions of microscopic spores. It imbeds itself into tender new growth and feeds on

the sap of the

plant. By the time the naked eye can see the white ‘powder,’ it has already invaded

the plant tissue

and is feeding and reproducing at a rapid pace. As it spreads itself on the surface, it

eventually kills

the cells of the plant leaf, leaving the leaf rippled and curled.

Mildew spores are everywhere in the garden – in the air, the soil, on debris and on

plant surfaces -

ready to sprout when the environment is just right. Warm days (50?-80?F) and cool

nights with

elevated humidity and resultant dew provide ideal conditions. Though humidity

promotes fungal

growth, it grows on DRY plant surfaces, unlike blackspot which requires immersion in

water for

about seven hours in order for infection to take place.

Tender new growth needs a chance to ‘harden’ and develop its waxy coating that

provides somewhat

of a barrier to fungal growth. Therefore, the rosarian must provide protection for new

spring growth

on a weekly basis.

CONTROLLING POWDERY MILDEW

Controlling mildew doesn’t have to mean spraying the planet into oblivion. It includes

plant genetics,

cultural practices and something as simple as WATER.

GENETICS: While rose hybridizers are chastised for breeding OUT fragrance, what

they are trying

to accomplish is breeding IN disease resistance. For scientific reasons beyond

explanation here, rose

genes don’t contain both features – it’s one or the other. Hence, you can expect either

fragrant roses

with little disease resistance, or clean plants with little fragrance. Plants with glossy or

waxy leaves

are less susceptible to mildew, as the leaf surface is harder for spores to penetrate.

Rugosas naturally

possess a high degree of disease and pest resistance. Where mildew is a constant

problem, the choice

in plantings can help prevent the need for extensive maintenance.

CULTURAL PRACTICE: Planting bushes with sufficient space between them and

away from walls

and fences will provide good air circulation which reduces the chances for mildew.

The annual pruning event plays a major role in disease prevention. Stripping leaves

from the bush at

pruning time, and cleaning up debris in the garden contribute to a cleaner

environment. Dormant

spraying will at least wipe out last year’s spores, leaving only this year’s to contend

with. Keeping the

centers of the bush open during the growing season will aid air circulation.

Avoid the use of other plant materials with high mildew susceptibility, such as

euonymus and

tuberous begonias. Apply a thick layer of mulch in early spring to cover spores in the

soil that may

have wintered over. WATER is perhaps the most misconceived element surrounding

powdery

mildew. Many gardeners still subscribe to the belief that you should NEVER get rose

foliage wet.

On the contrary, a high-pressure spray of water will remove mildew spores that

haven’t imbedded

themselves yet, and prevent them from germinating. Higher incidence of mildew

during periods of

rain is caused by the moisture in the air and soil – increasing the humidity that

promotes mildew -

not by water on the leaves. Similarly, watering early in the day will allow the soil

surface to dry out

a bit before the cool night temperatures arrive, reducing humidity from moist soil.

PREVENTION IS THE ONLY CURE

Once powdery mildew is apparent to the eye, it can’t be eradicated. It simply must be

prevented.

Prevention is achieved by coating the plant tissue with something that provides a

barrier to prevent

fungus from gaining a foothold and invading the plant tissue. Growth is so rapid in

spring that the

leaves unfolding THIS week won’t be protected by what you sprayed LAST week.

This is the reason

you find application schedules of every 7-10 days on most fungicides, and the reason

you must

follow that schedule.

The choice of what the SOMEthing is that you choose to spray is widening.

Fungicides are the most

widely used because they are chemically formulated to specifically combat fungus

diseases. Recent

reports of non- toxic, environmentally-friendly products such as baking soda and

anti-transpirants

are proving very encouraging also.

FUNGICIDES are any of a number of chemicals labeled to combat powdery mildew,

and do so by

interfering with its metabolic life process, rendering it unable to grow and spread.

Although they

must be in place on the plant before the spores arrive, they do have systemic action -

meaning they

move into the plant tissue – providing a residual effect for a short period.

Fungicides are available in many forms – liquids (mix readily with water), emulsifiable

concentrates

(a thicker, usually milky substance), wettable powders (require thorough mixing prior

to

application). Each has its own properties, all are effective. Most, however, have a

medium-to-high

degree of toxicity to humans. Extreme caution should be used to cover eyes, skin and

hair, and use a

painter’s mask or respirator during application. They are mixed at various rates,

usually 1

tablespoon per gallon of water, and require application every 7-10 days.

BAKING SODA: “New research shows that simple baking soda is a powerful weapon

against

fungus-caused rose diseases”, wrote Kristi Clark in her September 1992 American

Rose Magazine

article.

In a world that is becoming increasingly aware of environmental concerns, more

attention is being

paid to finding alternative measures to widespread chemical use. Sodium

bicarbonate

(grocery-variety baking soda) was tested originally to determine its effectiveness in

preventing

blackspot. During the experiments, it was noticed that no powdery mildew was found

on any of the

test roses.

Controlled experiments were conducted for some three years, using sodium

bicarbonate or

potassium bicarbonate in various combinations with insecticidal soap, Sunspray?

ultra-fine spray

oil, or only water. The result: both diseases were subdued by a weekly spraying of

either sodium or

potassium bicarbonate at 3 teaspoons per gallon of water, combined with Sunspray at

2 tablespoons

per gallon of water. The bicarbonates eliminated the fungi, but addition of the

Sunspray provided a

spreader-sticker action that increased its performance.

Sunspray is available commercially as Safer? Sunspray. As Clark cautioned, do not

attempt higher

concentrations of the solutions, as leaf burn may result. Rain or overhead watering

may wash the

solution off, reducing its effect.

ANTI-TRANSPIRANTS are another group of substances that hold promise as a

non-toxic method

of controlling powdery mildew (as well as pests). Anti-transpirants are emulsions and

acrylic

polymers that were developed to form an impermeable film on plant surfaces to

substantially reduce

moisture loss. Several brands are available; look for a white liquid, about the

consistancy of milk.

They are widely used on cut Christmas trees to retard drying and needle drop, and on

plants to

provide protection from drought, heat, wind and transplant shock. Since the thin film

prevents

transpiration of moisture – both in and out of the leaf – it makes sense that it would also

prevent

fungus spores from permeating the leaf surface.

Some rosarians have used antitranspirants in combination with fungicides, and feel

the combination

works better than fungicide alone. Others have used it entirely alone, and find that it

works very well

all by itself. Packaging directs us to water plants well and allow them time to take up

the water

before spraying. Since anti-transpirants are NOT yet labeled for disease protection,

there is no

accepted formula for application. They come in various concentrations that would

require more or

less dilution – anywhere from 1 tablespoon to 1/2 cup per gallon of water. Again,

frequency is not

addressed … once a week … once a month? At this stage it’s sort of experimental. If a

residue is left

on the foliage (objectionable to you as an exhibitor) then reduce the ratio.

Whether we choose the fungicide method or the non-toxic approach to controlling

powdery mildew

probably depends upon the degree of severity we encounter on a regular basis.

Regardless of the

product selected, it must be used on a regular basis in the proper dilution to prevent

fungal growth

without damaging plant tissue.

What is Blackspot?

Symptoms

Blackspot is a plant disease caused by a fungus (Diplocarpon rosae) that is generally

damaging and

usually a source of major problems. Blackspot looks like circular black spots with

irregular edges

on the top side of the leaves. The tissue around the spots or the entire leaf may turn

yellow and the

infected leaf may drop off. Plants with a severe case may lose all of their leaves if not

treated. Flower

production is often at a minimum and the quality of bloom suffers badly.

Biology

High humidity is one factor that helps the spores to germinate. The spores germinate

in 9-18 days on

a moist leaf at 70-80?F temperatures. The spores can be spread by splashing water

and by the

Rosarians themselves. The spores are wind-borne only in water drops. The spores

can be spread on

clothing, tools or even your hands, but the way it is spread most often is by infected

leaves that have

wintered over in the rose bed.

Control

Blackspot can be satisfactorily controlled by spraying with a good fungicide every

seven to ten days

(read the label and follow the directions). There are also a number of measures that

should be taken

to keep from getting and/or controlling the disease. Avoid watering in a way that

splashes water up

on the leaves and avoid watering late in the evening with a hose or sprayer. Make

sure to clean up

the beds completely of all leaves or stems to help keep the disease from wintering

over. Always have

good ventilation through the plant and good soil drainage. Apply fungicides after a

rain to keep

down spores. Put the plants on a spray schedule and spray with a fungicide that gives

good control,

such as, Manzate?, Maneb?, Daconil? and Lime-Sulfur compounds.

There are also organic methods of controlling Blackspot. Baking soda has been tried

as a cure and

as a preventative measure. It was found that using baking soda and spray oil mixed

with water as a

spray can damage roses if it is not mixed in the proper proportions. It was also found

that baking

soda gave only moderate control of Blackspot, but appeared to be effective as a

preventative. There

is a new product coming on the market that has been used by our local Rose Society

that does show



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