Diseases and Pests of Tropical Tasar Food Plants

MAJOR FOLIAR DISEASES OF TROPICAL TASAR FOOD PLANTS (TERMINALIA.ARJUNA AND T.TOMENTOSA)

1. Leaf spot (Pestalotiopsis palmarum):

The disease appears on any part of the blade as circular to irregular patches, sometimes delimited by veins. The infected leaves show characteristic copper brown spots, just above the fungal growth, on the upper surface. Usually these are 2-8 mm in diameter but sometimes more extensive.  Affected leaves become brittle. The necrotic area becomes dry, shrunken and severed partly or entirely from the leaf as a hole. Severely infected leaves from which much of the dead tissue has fallen away present an extremely ragged or insect eaten appearance. Leaf yield loss due to leaf spot disease has been reported to be 8-12%.

Leaf spot occurs during July to November all over India when high humidity and high temperature prevail in the atmosphere. At CTRTI, Ranchi disease incidence in both T.arjuna and T.tomentosa was first observed during the month of June which increased steadily in the subsequent months and reached at its peak during the month of October. The disease shows positive correlation with relative humidity and rainfall. At R.T.R.S., Dumka, Baripada and Warangal r-value for RH was 0.888, 0.468 and 0.551, respectively. The r-value for rainfall was 0.455 at Dumka and 0.789 at Warangal.

Management:

• Proper cultural operations and field sanitation.
• Plucking and burning of diseased leaves.
• Spray of Carbendazim @ 0.1% or 0.5% Biltox or 0.5% Diathane M-45.

2. Black nodal girdling (Uredo spp):

Disease symptoms begin from nectar gland and gradually spread to lower petiole region, in due course of time petiole and internodal regions get covered with black sooty spores along with mycelia, forming girdle like appearance. Thus, the entire leaf becomes unsuitable for silkworm rearing. In both Arjun and Asan plants, about 7-10% crop loss is reported.

The disease occurs during rainy and winter seasons. This disease also appears during July at most of the places, increases up to January and then declines. At CTRTI, Ranchi disease started appearing in the month of August and found maximum during the month of October. Minimum temperature, rainfall and RH are found positively correlated. wherwas maximum temperature is negatively correlated.

Management:

• Proper cultural operations and field sanitation.
• Plucking and burning of infected leaves.
• Spraying of Carbendazim @ 0.1% (a systemic fungicide).   

3. Powdery mildew (Phyllactinia terminaliae):

As the name indicates white powder like patches appear on the ventral surface of leaves, afterwards appearance of distinct dot like structures is noticed on the powdery patches. Under advanced stage, the disease shows chlorotic symptoms on dorsal surface of leaves with curved lamina. Affected leaves become yellow and fall down prematurely. The crop loss has been reported to be 25-30% in Arjun and 8-10% in Asan, though qualitative loss may be much more.

Powdery mildew is prevalent during October to December at most of the places. Maximum severity of powdery mildew at CTRTI, Ranchi in T. arjuna was observed during November. The disease occurs during October to March at all the places mainly due to change in minimum and maximum temperature. The disease is negatively correlated with temperature i. e., when the temperature is low, disease is more and vice versa. Rainfall is also negatively correlated.

Management:

• Proper cultural operations and field sanitation.
• Plucking and burning of diseases leaves as and when they appear.
• Spraying of Carbendazim @ 0.1% or 0.2% Dinocap or 0.2% Sulfex.

4. Leaf Curl (Copper deficiency):

This disease is believed to be caused by deficiency of copper. Withering of leaves is observed in young and tender leaves, which show crinkling soon after expansion from the buds. Leaves exhibit boat shaped form due to folding of the leaflet along the midrib. Venation pattern shows tendency of conversing towards the apex of lamina and shows deep serration. Chlorosis of leaf starts from the margin as a result the tip and margin start drying and withering.

Leaf curl disease is prevalent during June/July to November/December at most of the places. It is positively and significantly associated with relative humidity (RTRS Bhandara: r= 0.640; Jagdalpur: r=0.564 and Warangal: r=0.744).

Management:

• Proper cultural operations and application of fertilizers.
• Spray of 175 ppm Copper Sulphate or 0.5%.Biltox.

A calendar of occurrence of foliar diseases and different activities in Tropical Tasar culture areas is annexed as ready reckoner for management.

Leaf spot disease

Causal organism-Pestalotiopsis palmarum

Class-Ascomycetes

Black nodal girdling disease

Causal organism- Uredo spp.

Class- Basidiomycetes

Powdery mildew disease

Causal organism – Phyllactinia terminaliae

Class-Ascomycetes

Leaf curl disease

MAJOR PESTS OF TROPICAL TASAR FOOD PLANTS

• Weevil (Myllocerus viridanus Fab.):   Prevalence of weevil was observed throughout the year.  High incidence of weevil was recorded from November to January.  However, the peak period of its incidence was recorded in the month of August

• Red Beetle (Tricliona picea Jacoby): The red beetle infestation was recorded from May to August where the peak period being in the month of August.
• May-June Beetle (Anomala blanchardi):  The incidence of May-June beetle was higher during April to August. While its peak infestation was recorded in the month of June and August.
• Vapourer tussock moth (Notolophus antiqua Linn.): The higher prevalence of vapourer tussock moth was observed throughout the year except April, May, October and November months where the infestation is low.
• Gall fly (Trioza fletcheri Monior):Gall infestation was also observed throughout the year and the peak infestation was recorded in the month of August. However, its infestation was very low or negligible in April, September and October months.
• Stem borer (Aelosthes holosericea): The infestation of stem borer was observed throughout the year. 

CONTROL MEASURES FOR PESTS OF TASAR HOST PLANTS

IPM  package for the control of gall insect, Trioza fletcheri

Cultural: Pruning of tasar food plants at 4 to 6 feet height is to be postponed up to 30th April to minimize gall insect infestation.

Mechanical:  Clipping the gall infested leaves of tasar food plants, collecting them into polythene / gunny bags and burning the same to avoid further spread of gall insect infestation; plucking and burning of gall infested tender leaves having eggs and matured gall  infested leaves; collection and burning of old leaves having diapausing nymphs during winter (Dec- Feb.) and off rearing seasons.

Chemical:  Soil application of Neem cake (dried and fine meshed @ 60 kg per acre) in the month of May before the onset of monsoon; foliar application of 15 ppm of Azadirachtin  (10 ml per litre of water) three times from May to June at an  interval of 15 days after sprouting (quantity of insecticides required-

Control of stem borer,  Aelosthes holosericea

Mechanical:  Collection and destruction of adults of stem borer insects; Collection and destruction of egg and grub with the help of sharp knife manually from bark and woody part of stem.

Chemical: Cotton soaked with 36% EC of Monocrotophos 0.07 % should be inserted in the holes made by the borer followed by mud plastering (quantity of insecticides required-1.94 ml per litre of water); plugging of holes with cotton soaked with 0.07% Monocrotophos (36% EC) followed by mud plastering (quantity of insecticide required-1.94 ml per litre of water).

Integrated package for the control of major defoliating pests

Cultural: Two times deep ploughing after silkworm rearing: Nov.-Dec. and March-April is to be done.

Mechanical:   Collection and destruction of different developmental stages of insect such as eggs, grubs/larvae, pupae and adults of coleopteran and lepidopteran pests during morning and evening hours  twice a week from the month of May to July.

Bio-pesticide:

• Soil application of neem cake: Soil application of neem cake (dried and fine meshed @ 60 kg per acre in two split doses at 15 days interval before the onset of monsoon (1st dose – 15th May, 2nd dose-30th May).
• Foliar application of Azadirachtin: Foliar application of 15 ppm Azadirachtin (10 ml per litre of water)once after 15 days of soil application of neem cake (15th June).

Source:

Central Tasar Research & Training Institute, Central Silk Board, Ranchi

CALENDAR OF OCCURRENCE OF FOLIAR DISEASES AND DIFFERENT ACTIVITIES IN TROPICAL TASAR CULTURE AREAS

Source:

Central Tasar Research & Training Institute, Central Silk Board, Ranchi