Botany - (ebook) - IPM Series - Stone Fruits

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Educating People To Help Themselves

Home & Garden Mimeo # HG77

IPM Series: Stone Fruits

Peaches, Plums, Apricots, Cherries, and Nectarines

Local Governments - U.S. Department of Agriculture Cooperating

The University of Maryland is equal opportunity. The University’s policies, programs, and activities are in conformance with pertinent Federal and State laws and regulations on nondiscrimination regarding

race, color, religion, age, national origin, sex, and disability. Inquiries regarding compliance with Title VI of the Civil Rights Act of 1964, as amended: Title IX of the Educational Amendments; Section 504

of the Rehabilitation Act of 1973; and the Americans With Disabilities Act of 1990; or related legal requirements should be directed to the Director of Personnel/Human Relations, Office of the Dean, College

of Agriculture and Natural Resources, Symons Hall, College Park, MD 20742.

Symptoms

FOLIAGE

Leaf yellowing/

browning

Leaf spots/blotches

White-gray powder

on leaves and buds

Possible Causes

Green peach aphid: leaves curl, yellow and

drop. Aphids excrete honeydew, which may

lead to sooty mold on foliage.

Spider mites: white flecking or stippling.

Leaves brown and die.

Cankers, Phytophthora and Verticillium

wilt, Armillaria root rot: diseases that

interrupt the vascular flow of water and

nutrients and lead to wilting and leaf death.

Bacterial spot (peaches): small, angular

spots between veins. Spots are green, then

turn purple and finally brown.

Scab (peaches and nectarines): small, olive-

green spots on leaf underside.

Cherry leaf spot: small purple spots on leaf

surfaces. Leaves develop holes and turn

yellow. Infected leaves often drop.

Plum leaf spot: similar to cherry leaf spot

but smaller.

Powdery mildew: white surface growth on

leaves that may cause leaf distortion. Most

noticeable in spring. Remains active during

dry weather. High temperatures kill fungal

colonies.

Controls/Comments

Primarily an early-season problem.

Strong water spray directed at aphids will

reduce population. Apply a dormant oil

spray at bud swell.

Apply a dormant oil spray at bud swell.

Problem more severe in hot, dry weather.

See page 4, Rapid tree decline.

FOR ALL FOLIAR DISEASES:

Promptly rake up and dispose of infected

leaves.

Bacterial spot is not common in Maryland.

Often mistaken for Captan fungicide

injury.

Follow fungicide spray guidelines found in

U of M Publication, EB 125, Home Fruit

Production Guide. First spray after petal

fall.

If defoliation was severe the previous

season, Bordeaux mixture (copper sulfate

and lime) can be applied after harvest.

Select resistant varieties. Remove

damaged shoots and prune for improved

air circulation. Spray with wettable sulfur

at bloom if powdery mildew was a problem

the previous year or check horticultural oil

labels for powdery mildew control listings.

Leaves curled and

puckered

Leaves curled, twisted

or rolled

Leaf scorching/

marginal burning

Leaves chewed

Webbed or tented

foliage

Leaves with black

sticky coating

Peach leaf curl: fungal disease on un-

folding leaves in spring. Leaves are thick-

ened, malformed and colored bright

purple, red, orange. Severe when spring

weather is cool and wet. May cause

significant defoliation.

Aphids: also feed on buds. Black sooty

mold growing on aphids honeydew excre-

tions may be observed.

Herbicide injury: new growth appears

twisted and curled.

Pesticide burn: including soaps and oils.

Stressed plants are more likely to be

burned and emulsifiable concentrates are

more likely to burn than wettable powders.

Fertilizer burn: causes marginal leaf

scorch and root dieback.

Damage from lawn herbicides: new

growth may be stunted, twisted or curled.

Drought stress: marginal scorching.

Very high temperatures

Sunburn: yellow, brown or white areas

develop on upper sides of leaves.

Various caterpillars and

Japanese beetles: Sweet and sour cherry

and Japanese plum most vulnerable to

attack. Japanese beetles skeletonize leaves

(feed between the leaf veins).

Eastern tent caterpillar: caterpillars

found within silken tents.

Sooty mold: fungus growing on sticky

honeydew which is excreted by aphids and

scales during feeding.

Apply a pre-bloom spray of liquid-lime

sulfur on all tree parts. If leaf curl was

severe the previous year, apply Bordeaux

mixture before buds swell in the spring.

Early season problem. A strong water

spray will dislodge aphids. Reduce or

eliminate nitrogen applications to reduce

succulent growth favored by aphids. Apply

labeled insecticidal soap or horticultural oil

products to control high populations.

Dont apply herbicides near fruit trees.

Leaf margins are affected first. Leaves are

particularly susceptible to burn when

temperatures exceed 80-85°F. Copper,

sulfur and Captan fungicides may cause

leaf burn.

From roots contacting excessive salts from

fertilizers. Avoid fertilizer spikes and

follow U of MD recommendations.

Symptoms from fall-applied herbicides

may not appear until spring.

Irrigate during dry periods

Damage due to excessive sunlight, heat

and insufficient water.

Hand pick pests. Where feeding is severe,

use a registered insecticide. Avoid Japanese

beetle traps which attract more beetles.

If numerous caterpillars are present, use

B.t. when the caterpillars are small. Knock

down or prune out webs on terminal

branches and destroy caterpillars.

Spray Superior oil at green tip stage of

bud development (50% of buds show some

green tissue). High pest populations can

debilitate trees.

Eastern tent caterpillar: caterpillars found

within silken tents.

Oriental fruit moth: 3/8 inch long larvae

with brown-black head. Bore several inches

into new shoots. Larvae overwinter in

debris under tree. Young, rapidly growing

trees more severely affected.

Peachtree borer: borers feed on cambium

below the bark near base of tree, preventing

food and water from flowing within the tree.

This leads to wilting symptoms.

Lesser peachtree borer (upper trunk,

scaffold limbs and branches)

Various fungal and bacterial diseases

(especially Leucostoma canker): enters

through wounds caused by insects,

lawnmowers, frost cracks and hail. Gum-

mosis may be observed (the oozing of thick,

amber colored sap).

Lecanium scale: noticeable May through

July. Crawlers feed on foliage after hatch-

ing in July.

White peach scale and white prunicola

scale: crawlers feed on foliage. High

populations can cause branch dieback.

Black knot: fungal disease of plum and

cherry.

Mechanical injury or stress: gum is clear

Peach tree borer: gum mixed with sawdust-

like frass (borer excrement). Primarily on

peach and nectarine. 1-inch long white

larva with brown head. Female adult is a

large, blue and orange, clear-wing moth.

Larvae feed in tunnels below bark and over-

winter in tree, renewing activity in early

spring. One or two borers can kill a tree.

Lesser peachtree borer (upper trunk,

scaffold limbs and branches).

If numerous caterpillars are present, use

B.t. when the caterpillars are small. Knock-

down or prune out webs on terminal

branches and destroy caterpillars.

Prune out and dispose of wilted tips, 6

inches below visible damage. Cultivate

lightly around base of tree 2 weeks before

bloom. Follow U of M guidelines for early

season sprays.

See Peachtree borer, page 3.

Prune out and dispose of infected wood

below visible damage. Prune on dry, warm

days in early spring. Do not leave stubs.

Fertilize only in late winter or early spring.

Apply white latex paint to trunk and large

branches after leaf fall to prevent frost

cracks.

Apply a dormant rate horticultural oil

spray before bud break.

Apply a dormant rate horticultural oil

spray before bud break. For light infesta-

tions, scrape away scales with a soft brush.

During dormant season, prune out and

dispose of infected wood 4 inches below

visible damage.

Borers attack stressed trees. Monitor for

borer holes. In May, scrape away gum and

dead bark from lower trunk and large roots.

Come back in one week and look for new

gum and frass deposits. Make vertical cuts

with a sharp knife through these entrance

holes. Then, insert a stiff thin wire and stab

larvae; repeat in one week and then mound

soil over damaged area (if low on the trunk).

Band lower trunk down below soil level with

corrugated cardboard to prevent egg laying

or trap larvae before they tunnel into tree.

Where holes and frass are observed and no

sap is oozing from tree, beneficial

SHOOTS,

BRANCHES,

TRUNK

Silken webs/tents in

branch crotch

Peach shoots with

wilted leaves; shoot

dies

Dark, sunken can-

kers

Small reddish-brown

and black bumps on

young wood

White encrustations

on large branches

and trunk

Black, gnarled

swellings along twigs

and branches

Gum oozes from

holes at base of trunk

or lower branch

crotches (sawdust-like

frass may be

observed)

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1EducatingPeopleToHelpThemselvesHome&GardenMimeo#HG77IPMSeries:StoneFruitsPeaches,Plums,Apricots,Cherries,andNectarinesLocalGovernments-U.S.DepartmentofAgricultureCooperatingTheUniversityofMarylandisequalopportunity.TheUniversityspolicies,programs,andactivitiesareinconformancewithpertinentFederalan...

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