The Scab of An Apple

Submitted by: Akash Singh Soares (A-2014-01-005)

IntroductionThe disease was first reported from Sweden in 1819 and occurs in all the apple growing regions. In India, the disease was first reported from Kashmir in 1935 which resulted in epidemic in the year 1975 and subsequently in 1977, it was reported from Himachal Pradesh resulting an epidemic in the year 1982-1983. The estimated yield losses were around 70%.

EtiologyThe disease is caused by Venturia inaequalis (Perfect Stage) and Spilocaea pomi (Imperfect stage).The imperfect stage is found on the living parts and perfect stage on the fallen dead leaves. The fungal hyphae in the infected fruits are located only between cuticle and epidermal cells therefore are sub-cutaneous. The fungus produces Ascocarp in stroma of fallen leaves called Pseudothecia which are dark brown to black and spherical having short beak and distinct ostiol. There are large no. of Asci which are cylindrical, fasciculate, short, stipulate and 8-spored. Ascospores are yellowish green and unequally bi-celled.

Pseudothecia

SymptomsThe symptoms of the disease appear on leaves, petiole, twigs, sepals, fruits and pedicel.ℭLeaf Lesions- On leaf, lesions are small, dull, olive

green to brown colored. As the lesions ages the margin thickens and leaf surface is deformed. When several lesions coalesce, they become curled, dwarf and distorted. The term ‘Sheet Scab’ is used to describe this phase and the leaves fall pre-maturely.

Contd…ℭ Fruit Spot- Spots are small, superficial

lesions or large patches that develop on fruit surface. Severe attack result in the formation of misshaped fruits and cracking, The scabs are rough, black and circular called as ‘Pin Point Scab’.

Contd…ℭTwig Lesions- They are small, long,

slightly raised causing bursting of bark.

ManagementŞFollow proper sanitation practices.

ŞSpray 5% urea at pre-leaf fall stage.

ŞUse resistant varieties like Red free, Mcfree, Prime etcetera.

ŞUse Biological Control Agents like Chaetonium spp.

Phenological Stage Chemical Used ConcentrationSilver Tip-Green Tip Chlorothanolil; Dodine;

Mancozeb; Captan0.4%; 0.1%; 0.25%; 0.25%

Pink Bud Stage Hexaconazol; Fenarimol; Myclobutanil

0.05%; 0.04%; 0.04%

Petal Fall Hexaconazol; Carbendazim; Thiophenatemethyl

0.05%; 0.05%; 0.05%

Fruit Stage (Pea Size) Dodine; Bitertanol; Fenarimol; Myclobutanil

0.075%; 0.05%; 0.04%; 0.04%

Fruit Stage (Walnut Size) Carbendazim+Mancozeb 0.05%+0.25%

Fruit Development (40 days before harvest)

Captan; Febarimol; Myclobutanil; Bitertanol

0.3%; 0.04%; 0.04%;0.05%

Pre-harvest Mancozeb; Captan 0.25%; 0.3%

ObrigadoSoares