Juniper Times

Latest News Magazine

Bacterial Leaf Spot and Canker – Identification, Treatment and Prevention

Bacterial Spot and Bacterial Canker are serious diseases that commonly affect nectarine, peach, plum, almond, apricot and cherry trees. Both afflictions devitalize and defoliate trees, thus reducing the yield and quality of fruit they produce.

No part of the affected trees are spared; twigs, leaves and fruit itself are attacked resulting in defoliation, blossom blight and lesions. Bacterial Spot and Bacterial Canker are prevalent concerns in regions where the annual rainfall is greater than 20 inches per year.

Signs and Symptoms

Bacterial Spot causes tiny purplish-black flecks or water-soaked spots on the surface of fruit. The disease breaks the skin of fruit and causes flesh to sink. If contracted early in the season, it makes deep lesions in the flesh of fruit. Within 30 days of harvest time it appears as circular, yellow spots on fruits’ surface.

Bacterial Leaf Spot results in angular, water-soaked spots that appear when light is shone behind affected leaves. Within one to two weeks of contracting the disease, the centres of the lesions become walled-off and drop out, resulting in shothole. Shothole is common at the distal ends of leaves and around large veins. Water film is thicker in these areas; accordingly, the leaves dry slower. Only takes two or three lesions will affect a leaf enough to make it yellow and fall a tree.

Often appear on twigs, Bacterial Cankers show up in spring and summer. Summer cankers are identified by the oddly-shaped dark, sunken lesions they leave on the present season’s twigs. Spring cankers frequently materialize near the twig tips of the past season’s growth and appear as blisters. Both types of cankers prevent buds from opening; accordingly, the affliction results in a number of dead tips on the tree.

Tomato Bacterial Spot is a unique version of the disease that results in dark, circular foliar lesions. The lesions first become angular and then may dry and fall out. Immature fruit affected by Tomato Bacterial Spot are marred by small, raised black specks with water-soaked borders. These often turn into brown, sunken scabs, but don’t usually lead to rot.

Cycle of Disease

Bacterial Leaf Spot and Bacterial Cankers infect trees in late autumn as leaves drop. Water congestion is essential for infection to occur. Bacteria then multiplies within twigs during favourable temperatures and oozes from natural openings in spring, during wet weather. The bacteria continues to exude from the cankers for 30 days and from leaves and fruit lesions throughout the remainder of the season.

Treatment and Prevention Options

Losses due to Bacterial Spot and Bacterial Cankers may be minimized by growing resistant cultivars. It is essential to monitor plants every week from shuck split until late in the season for signs of the disease. Furthermore, examine fruit for small lesions and leaves for angular, water-soaked lesions. Leaves must be held up to light in order to be checked properly.

Tomato Bacterial Spot can sometimes be prevented by using pathogen-free seeds and transplants, avoiding overhead watering and using rain shelters to reduce splash.

If disease is contracted, it is visible within 24 hours of infection and displays the heaviest at mid-vein and leaf tips. Shothole symptoms are visible within three days.

Control its spread by working in affected areas last and avoiding them entirely when the foliage is wet. It is imperative to decontaminate tools after working with infected plants.