Apple and diseases and pear Scab(black spot) Pathogen: Venturia inaequalis Apple Venturia pirina Pear The apple scab survive winter in fallen leaves. primary infection by ascospores in the spring secondary infections by conidia Ascospore Pseudothecia

Pseudothecia Symptoms On leaves: 1-Patches of olive-green spots or blotches appear, which are initially smooth and soft as they release airborne spores, and then darkening. 1- Affected leaves often fall prematurely On young shoots. Infections cause blistering and cracking that can then provide entry for the apple canker pathogen.

Scab of apple Scab of pear On fruit: Black scab by blotches develop and, as the fruit matures, these restrict expansion of the skin, leading to distortion and cracking

Scab of apple Scab of pear Powdery mildew Powdery mildew of apple Pathogen: leucotricha Overwintered; mycelium , conidia

Conidia Cleistothecia Symptoms 1- Dormant shoots that were heavily infected in the previous growing season are covered with dense white mycelium. have a terminal bud that is pinched and shrivelled. 2- Other shoots might look normal but the fungal mycelium can overwinter in otherwise healthy looking fruit or leaf buds. Dormant shoots infected with powdery mildew. 2-These buds may be killed, or they may grow abnormally; 3- leaves become narrow, brittle, curled and covered with a white powdery layer, 4-while flowers may be stunted and fail to develop.

Primary mildew of apple blossom and leaves resulting from bud infection in the previous season.

5- Early fruit infection causes a web-like russet on the skin.

6- fruit may be distorted and partly covered with a white powdery coating of spores

Fruit infected with powdery mildew showing the white powdery coating of spores Symptom of fruit and leaves Pear Powdery Mildew

Causal agent: Podosphaera leucotricha Symptoms 1-White powdery fungus growth on terminal shoots of is less evident than in . 2- appears as black marks and russeting(reddish-brown or yellowish- brown color) on young fruit. 3-Powdery mildew does not overwinter in pear buds, as it does on apple. 4-Primary inoculum affecting pears originates from nearby apple orchards

Grown Galls

Crown gall is a disease caused by the bacterium Agrobacterium tumefaciens, Symptoms 1- rounded galls or swellings that occur at or just below the soil surface on stems or roots. 2- Occasionally, the galls can be seen above ground on trunks or branches. 3- Young galls are light green or nearly white in color. As they age, the galls become darkened and woody.

4- Galls range from pea-size to larger than 1 foot in diameter.

5- The galls disrupt the flow of water and nutrients traveling up from the roots and stems, thus weakening and stunting the top of the plant.