Apricot Diseases A

Lecture To ToT trainees ( FFS)

By Mr. Allah Dad Khan

Provincial Coordinator IPM KPK

MINFAL Pakistan

Armillaria root rot Armillaria mellea

Symptoms

• If tree is infected after it has reached 5 years of age then typical symptoms include poor terminal growth and small leaves; around midsummer the whole tree suddenly collapses; in orchards trees usually die in a circular pattern; infected trees often have a fan-shaped white fungal mat growing between the bark and wood of the crown

Eutypa dieback Eutypa lata

Symptoms

• Cankers on branches, usually associated with a pruning wound which is several years old; discolored sapwood may extend abovwe and below canker; leaves on branches around canker may suddenly wilt as branch dies; leaves remain attached to branches; discoloured bark and inner wood; gummy amber exudate may be present

Brown rot blossom Monolinia spp.

Symptoms

• Death of young blossoms and associated twigs and leaves; small tan cankers with dark margins on twigs; gummy exudate at base of flowers; brown spore masses on flowers in humid conditions

Fungal Gummosis (fungus – Botryosphaeria dothidea): Symptoms• The fungus enters through

wounds or lenticels on lower parts of scaffold limbs and the trunk. Older infection sites typically exude gummy resin. Necrosis is associated with infection but usually is restricted to the area just under the bark. Over time the bark develops a rough texture. Trees can recover somewhat if infection is not severe. Stressed trees are damaged the most

Jacket rot Botrytis cinerea clerotinia sclerotiorumMonilinia laxa Monilinia fructicola

Symptoms

• Brown discoloration of fruit under jacket occurring while flower parts still attached to fruit

Phytophthora root and crown rot Phytophthora spp.

Symptoms

• Poor new growth; leaves chlorotic, small in size and sparse; fruit may be small, brightly colored and susceptible to sunburn; shoots may suffer from dieback and tree will often die within weeks or months of first signs of infection or decline gradually over several seasons; root crown may show signs of decay which develops into a canker; bark of infected crown tissue turns dark brown; cankers may occur on aerial parts of plant

Powdery midew Sphaerotheca pannosa Podosphaera tridactylaSymptoms

Powdery mildew symptoms on apricot fruit

• Round powdery white patches of fungal growth on fruits and leaves; rusty patches on fruits which turn brown and leathery and may crack

Ripe fruit rot  Monilinia fructicola Monilinia laxa

SymptomsSymptoms of ripe fruit rot on apricot fruits

• Dark brown circular spots on fruit; tan spore masses may be visible in center of spots; diseases fruit may not drop from tree

Shot hole disease Wilsonomyces carpophilusSymptoms Shot hole disease spots on fruit and holes in

leaves.

• Brown lesions with purple edge on fruit, twigs and buds; holes in leaves due to lesions which have dried and dropped out; brown lumps developing in the center of lesion (visible with hand lens); buds turning brown or black and exuding sap; tan lesions with brown margins which exude sap on twigs

Shot Hole Disease

Shot Hole Disease

Verticillium wilt Verticillium dahliae

Symptoms

• Withering of leaves on one or more spurs on 1 year old wood; leaves are dull and stunted; fruit small; older cherry trees do not recover from disease

Bacterial canker Pseudomonas syringae

Symptoms

• Cankers on twigs at bases of flower and leaf buds, in pruning wounds or at the base of spurs which exude amber colored gum; cankers spread upwards and form sunken areas in winter; if pathogen enters dormant buds they may be killed or open normally in Spring before collapsing in early Summer; infected buds may be symptomless

Bacterial Canker

Crown gall Agrobacterium spp

Symptoms

• Galls on root and/or crown of tree which can range in size from so small they are not visible to the naked eye up to 10 cm (4 in) in diameter; galls first become visible as white, fleshy swellings that grow rapidly and become tan to brown in color; galls typically develop at the site of a wound and new galls form adjacent to old ones the next year

Crown Gall

Rust Tranzschelia discolor

Symptoms

• Pale yellow-green spots on both upper and lower leaf surfaces which are angular in shape and turn bright yellow in color; spots on lower leaf surface develop orange-red spores

Plum pox virus Plum pox virus (PPV)

SymptomsSymptoms of plum pox virus on apricot fruits

• Pale green chlorotic spots, rings and lines on leaves which appear in early summer; pale rings, lines and spots on fruit; fruit flesh dry and flavorless; fruit may be markedly deformed

Bacterial Spot (bacterium – Xanthomonas campestris pv. pruni)Symptoms• Symptoms on leaves are observed

first as small, circular, or irregularly shaped, pale green lesions During early development, lesions almost always are concentrated near the leaf tip. In advanced stages, the inner portion of the lesion falls out, giving the leaf a “ragged” or “shot hole” appearance. Leaves heavily infected with bacterial spot turn yellow and fall. Repeated infection can occur throughout the growing season as long as the environment is favorable.

Bacterial Spot

Leucostoma Canker (fungus – Leucostoma cinata – anamorph Cytospora leucostoma):Symptoms• The fungus is a weak pathogen and is

rarely a problem in well managed orchards with rapidly growing trees. Pimple-like bumps develop on the surface of cankers. During the growing season small streams of gum are formed at each pimple. In most cases a callus layer forms around the damaged area and the canker is walled off. In a few cases the canker growth will resume in the fall after the callus growth is slowed. Leucostoma canker may become established in a limb through pruning cuts or sunburn injury. Affected trees should be pruned to remove the canker sites and fertilized to promote growth

Peach Leaf Curl (fungus – Taphrina deformans):Symptoms• The peach leaf curl fungus

infects leaves, flowers, and fruits. Infected leaves are characterized by puckering, thickening and curling. Diseased leaves become pale yellow to light green and shed after a short tim

Peach Mosaic (virus)Symptoms• This viral disease affects peach

and plum. General symptoms are delayed foliation, and small, narrow, crinkled, mottled, yellow leaves. Internodes are shortened, and lateral buds break, giving a rosette appearance. The few fruit produced are deformed resulting in bumpy, misshapen, small fruit. Spread is by grafting and the peach bud mite, Eriophyes insidiosus. Remove all virus-infected trees as soon as they are discovered.

Peach Scab (fungus – Cladosporium carpophilum):

• Peach scab, also known as “freckles,” is found wherever peaches are grown. It is most apparent on mid-late season varieties. Small spots develop on fruit and are normally concentrated around the stem or shoulder of the fruit (See Photo). Lesions formed on young twigs serve as a means of overwintering. Primary infection in the spring comes from spores produced in twig cankers formed the previous year. Fruit infection normally occurs after shuck split and 2-4 weeks following. Once infection occurs, 40 to 70 days may elapse before symptoms are visible

Peach Yellows (phytoplasma): Symptoms • The disease has been observed in Texas

but is rarely found. Fruits on diseased trees ripen from a few days to three weeks prematurely, have a bitter taste, and are reduced in size. Varieties which normally have red skin are abnormally bright. Leaves are chlorotic, fold upward, and tend to droop. Infected trees leaf out prematurely. The disease is spread by grafting and feeding by the plum leafhopperMacropsis trimaculata (Fitch). After infection, it may be 40 days to three years before disease symptoms are visible. Use only bud wood from healthy trees and destroy any trees which show typical disease symptoms.

Peach Yellow

Rhizopus Rot (fungus – Rhizopus stolonifer)Symptoms• This fungus is most active during

warm, humid weather. Fruit infection results in a “black whiskered” appearance caused by fungal strands which produce an abundance of black spores. Rhizopus attacks peaches and plums only at maturity. Disease prevention is primarily based on orchard sanitation, preharvest fungicides, and rapid refrigeration of processed fruit. Picking containers should be such that fruit receives a minimum amount of handling. Packing equipment should cause minimum injury. Pad any area where fruit will drop onto a belt or roller.

Rust (fungus – Tranzschelia discolor): 

• Reddish-brown pustules occur on the lower leaf surface marked by a yellow spot on the upper surface It causes premature defoliation which reduces tree vigor. The rust species that infects peach does not infect plum. In most parts of Texas rust is a late season disease that generally does not require treatment