Anthracnose (Colletotrichum gloeosporioides) : On tender leaves light to dark brown spots develop.
On older spots, infected tissues falls off giving shot hole appearance.
The disease results in blossom blight.Infection starts from the blossoming period
Anthracnose (Colletotrichum gloeosporioides): It is a serious disease on leaves and young shoots in rainy season and on fruits after harvest.
Symptoms: It is a serious disease on leaves and young shoots in rainy season and on fruits after harvest. The disease results in leaf spot, blossom blight, wither tip, twig blight and fruit rot symptoms. Young leaves when infected wither and dry up. At times when only the edges of the leaves are affected, their margins darken, dry up and may fall out, giving the leaf a ragged appearance. The disease causes the wither tip of young tender twigs. It also results in die-back which appears as blackening of growing tips. The affected branches ultimately dry and infection keeps on penetrating down. On fruits, infection starts from the blossoming period until the fruits are more than half grown.
The spots appear near the stem end as small brown areas that enlarge rapidly and become black. These may form streaks running down from the stem end. The affected areas are sunken and usually crack. The decay is confined to the skin of the fruit except in late stages when it penetrates the flesh in shallow areas. The unripe mature fruits carry the quiescent infection from the field that leads to rotting in the storage during ripening. Healthy fruits develop infection after coming in contact with diseased fruit.
Control:
The anthracnose could be effectively managed by four pre-harvest sprayings with Carbendazim 0.1% / Thiophanate methyl 0.1% / Prochloraz 0.1% or Chlorothalonil 0.2% at 14 days interval beginning when fruits attain pea nut size. Such pre- harvest treated fruits are to be further subjected to hot water treatment at 52°C for ten minutes immediately after harvest to provide very effective control of rot under storage.
Associated pathogens : C. gloeosporiodes, Alternaria alternata, Pestaliopsis
Mangiferae
Panicles are infected by Blossom blight, Infected panicles are shown in picture, panicles do not develop further.
Symptoms: This disease causes heavy damage to the panicles. The blossom appear blighted from the bud swelling stage and whole blossom turn into the black thick mass of the tissue. Black spots on foliage that withers, Blossom is blighted beginning from bud swelling, Panicles do not develop fully and result in heavy crop loss or total destruction.
The blossom appear blighted from the bud swelling stage and whole blossom turn into the black thick mass of the tissue. Black spots on foliage that withers, Blossom is blighted beginning from bud swelling, panicles do not develop fully.
Control :
This can be controlled by four applications of Carbendazim 0.1% or Thiophanate methyl 0.1% along with Zineb 0.2% or Chlorothalonil 0.2% or Propineb 0.2% or Mancozeb 0.2% or application of Carbendazim Iprodion 0.2% at 14 days interval beginning at fruits attaining pea nut size.
Leaf blight (Macrophomina mangiferae):
Symptoms: Yellow, pin headed spots appear on the leaves and twigs of the affected plants. Enlarges discolouring surrounding tissues. Spots becomes dark brown with slightly raised, brown purplish margins and turns into ashy colour. Infection mainly seen on leaves.
Pathogen survives more than a year on leaves. Field sanitation is important.
Control:
Spraying of Dithiocarbamate / Dithionon / Propineb (0.2%).
Powdery mildew (Oidium mangiferae) : powdery mildew symptoms on leaves.
Symptoms: Wefts of white mycelium on leaves, inflorescences and fruit lets develop. Later on the whole surface of the infected parts are covered with a powdery coating. The affected fruit lets do not grow in size and may drop before attaining pea size. Sprays of wettable sulphur 0.2 % or sulphur dusts provide reasonable control of powdery mildew, but sprays should be avoided during sunny, warm conditions as it may cause phytotoxicity to flowers and young fruits.
First appears on young leaves and inflorescence, Greatly influenced by Sunshine hours, Warm temperature with heavy morning dew and cloudy weather favour the disease development. The minimum, optimum and maximum temperature for conidia germination is 9, 22 and 30.5°C respectively, Relative humidity at 14:30 hrs influences the disease.
Control:
Sprays of wettable sulphur 0.2 % or sulphur dusts provide reasonable control of powdery mildew, but sprays should be avoided during sunny, warm conditions as it may cause phytotoxicity to flowers and young fruits. Systemic fungicides namely Tridimefon 0.1% or Dinocap 0.1% or Tridemorph 0.1% or Myclobutanil 0.1%or Fenarimol0.05% or Flusilazole 0.05% provide excellent control with the first spray at disease appearance and subsequent sprays at 15 days interval.
Die back:
Discoloration and darkening of bark some distance from the tip. This blackness advances. Young green leaves start withering – first at the base and extends outwards along the vein
Symptoms: Drying of twigs and branches followed by complete defoliation gives the tree an appearance of scorching by fire. Discoloration and darkening of the bark occurs some distance from the tip of the twigs. The dark area advances and young green leaves start withering first at the base and then extending outwards along the vein. The affected leaves turn brown and its margins roll upward. At this stage, the twig or branch dies, leaves shrivel and fall. This may be accompanied by exudation of gum. The infected twigs show internal discoloration. The association of a beetle (Xyleborusaffinis) has also known to increase the disease incidence and hence need to be controlled for disease management.
Caused by Botryodiplodia theobromae, Discoloration and darkening of bark some distance from the tip. This blackness advances, Young green leaves start withering – first at the base and extends outwards along the vein. The affected leaves turn black and roll up, Twigs/ branches die, leaves shrivel and fall, Exudation of gum is also seen, Internal discoloration is also seen on infected twigs.
Control:
Regular pruning and destruction of affected twigs or branches and application of Copper oxychloride 0.2% soon after the pruning followed by sprays of Carbendazim 0.1%or Thiophanate methyl 0.1% or Chlorothalonil 0.2% at fortnightly interval during rainy season are important for the control of the disease.