The problem sometimes assumes so a serious proportion that unless properly controlled, almost the entire crop in a season may be lost and in severe cases, the vines may be badly damaged or even killed.
However, those that are more destructive under Indian conditions have been brought to light in the following with recommendations on effective measures that may be adopted to control them.
Insect and other animal pests
It may be stated that more than fifty species of animals act as pests to grapevines throughout the world and most of them are insects. Those that are of a more serious nature under Indian conditions may be listed as follows.
(1). Flea beetle (Scelodonta strigicolles)
This is by far, the most serious of all insect pests and even in well-managed vineyards, they are known to cause 10-30% damage. The beetle is very small (4.5 x 2.3 mm), and coppery brown in colour, and the wing covers have three black patches on the first pair of each side. It looks like an undead grain (Black gram) and hence, is also called udadya beetle. They lay eggs under the bark crevices from March to October and these hatch within a week. Larvae feed on roots but are not considered as pests. They pupate after 6-7 weeks and the adults which emerge in 7-10 days are the actual pest. The adult beetles which have a jumping habit hide under the loose bark of the trunk during day time while at night, they come out and voraciously feed on leaves, tender shoots, and swelling buds and eventually, the attacked parts dry up.
The pest may be controlled by using a broom-trap device which is very simple and does not require chemical insecticide. To employ the technique, 3 or 4 small brooms, about 15 cm long should be made from strips of dry banana leaves. These should be suitably hung in the vines and the beetles being nocturnal would hide in them during the day. In the evening, the brooms should be shaken in cloth or plastic bags where the beetles will be collected. Another way to collect the beetles may be by shaking the vines over inverted umbrellas in the morning. Scraping the loose bark of the trunk is also much helpful as the beetles hide there. Chemical control of the pest may be effectively done by spraying the vines with a number of insecticides notably, Quinalphos (0.5%) or Dichlorvos (0.05%) or a mixture of 0.01% BHC and DDT (wettable powder) or Carbaryl (0.2%) or 1 ml of Malathion (50 EC) dissolved in a litre of water. These should be sprayed within a fortnight after pruning when the leaf buds swell and turn green, i.e., just before the emergence of shoots but should be continued also after the emergence of shoots as the new growths are attacked by the beetles.
(2). Jamun or Grapevine Thrips (Rhipiphorothrips cruentatus)
This is a small, black elongated insect, and damage is caused by both nymphs and adults, especially in hot weather. Lower surfaces of the leaves are rasped with the stylets and thereby, the plant sap that oozes out is sucked by them. Leaves curl up and dry. Scab formation of the berries showing scratching marks is responsible for this insect. To control, spraying the vines with 0.03% Dimethoate or Phosphamidon or 0.1% Carbaryl or 0.05% Parathion or Monocrotophos after a month of pruning and repeating sprayings two times up to a month has been recommended. Spraying decoction made from tobacco leaves is also effective. in mild infestation.
(3). Mealy bug (Drosicha mangiferae)
greyish white, wingless, flattened, slow-moving insects lay eggs under soil clods around trunks in summer. On hatching, the nymphs climb up the vines in winter, congregate together, and suck sap from leaves, flowers, and berries which dry up. Of late, the pest has become a great problem in many vineyards in Maharastra. To control, eggs should be destroyed by digging the soil and dusting with 5% Aldrin. Tying up the trunk with a polythene (400 gauge) band (30 mm wide) near the collar in winter prevents the nymphs from climbing to the trunk. Among chemical insecticides, 0.01% Dichlorvos and 0.04% of Diazinon Monocrotophos or Parathion may be sprayed when the crawlers appear.
(4). Cockchaffer beetles (Adoratus species)
The adult beetles come out from the soil at night and voraciously feed on leaves while in the daytime, returning to the ground. Grubs cut out the roots also. Spraying the vines with 0.2 % Carbaryl or a mixture of 0.1% DDT and BHC (wettable powder) or dusting with 10% BHC at weekly intervals controls the beetles.
(5). Scale insects (Aspidiotus cydoniac)
Small, motionless insects live inside the loose bark of the trunk and suck sap from shoots that dry up. To control, 0.1% Folithion or 0.4% of Phosphamidon or Monocrotophos or Dimethoate may be sprayed 3-4 times at weekly intervals on scraping the loose bark after pruning.
(6). Leaf roller (Sylepta lunalis): These light- green coloured caterpillars are largely found in north Indian vineyards from July to December. They roll the leaves and feed from inside for which, a large number of leaves are lost. The pest is controlled by spraying 2-3 times with Carbaryl (0.1%) Malathion (0.05%) or Parathion (0.025 %) at weekly intervals.
(7). Girdling beetles (Sthenias grisator)
The pest is very common in south India from the onset of the southwest monsoon and continues till the vines are pruned in October. Adult beetles make circular cuts to form girdles in the branches and in severe attacks, the vines are killed. Hand-picking of the beetles and cutting of branches below the girdles should be done to save the vines.
(8). Horn worms (Theretra alecto and Hippotion boerhaviae)
Larvae of the insect are very large like human fingers and have horn-like projections at their tail end. They voraciously feed on leaves. Being large, they may be easily hand-picked. Spraying the vines with a mixture of 0.1 % DDT and BHC may also be done to control.
(9). Jassids (Amrasca species)
Adults and nymphs of the pest suck sap from leaves and is serious in north India during August to October. To control, the vines may be sprayed with Carbaryl (0.1%) ог Phosphamidon (0.3%) or Malathion (0.05%)
(10). Mites (Typholdromus bakeri)
Nymphs and adults of this non-insect animal pest form web-like colonies on the undersurface of leaves and suck the sap, resulting in the leaves to curl and dry. Dusting sulphur or spraying vines with 0.05%wettable sulphur is an effective control of the pest.
(11). Root-knot nematodes (Meloidogyne species)
These animal pests attack roots and the leaves become yellowish and fall. To control, the vineyards should be fumigated with DBCP before planting and in standing crop, irrigation water may be treated with this at the rate of 20-30 litres per hectare.
Diseases
Grapevines are infected by a number of diseases which are mostly fungal and the following three are most common under Indian conditions.
(1). Anthracnose (Elsinoe ampelina)
The disease, known in Maharastra as karappa is the most serious fungal disease in grapevines and particularly, in north India. Some varieties, e.g., Pusa Seedless, Perlette, Delight, Black Muscat, Fakri, Hur, Thompson Seedless etc are highly susceptible while varieties belonging to the species, Vitis labrusca are more or less resistant. Symptoms appear on all green parts as brown spots and are darker in leaves, These are usually circular and have slightly sunken areas. Border of fungus infects all parts of the vines and the berries when affected are wrinkled and dried up. The disease spreads quickly and may even kill the vines. Several sprayings with Dithane M-45 (0.3%) or 0.2% of Ridomil or Aliette or 1% Bordeaux mixture effectively control the disease.
As a preventive measure to control the disease, pruning time should be properly adjusted such that new shoots appear much before the advent of rain. After pruning, the cutout parts should not be left in the vineyard as the affected parts may be drifted elsewhere by irrigation water and contaminate the healthy vines The cut surfaces of branches should also be coated with paste made of copper fungicide. As a curative measure of control, 0.2% Bavistin or Benloate or Copper oxychloride or 0.8% Bordeaux mixture should be sprayed 2-3 times from 10 - 30 days after pruning
(2). Downy mildew (Plasmopora viticola)
Symptoms consist of greenish-yellow spots somewhat transparent against light appearing on the upper surface of leaves which later turn brown and dry up. In wet weather, white mouldy patches develop on the spots. The fungus infects all parts of the vines and the berries when affected are wrinkled and dried up. The disease spreads quickly and may even kill the vines. Several sprayings with Dithane M-45 (0.3%) or 0.2% of Ridomil or Aliette or 1% Bordeaux mixture effectively control the disease. Preventive measures as stated in anthracnose should also be adopted.
(3). Powdery mildew (Uncinula necator)
This disease spreads in dry weather, unlike other fungal diseases of grapevines for which humid weather is favourable. All parts of the vines are affected showing white powdery substances which later turn greenish brown. Berries when affected become hard. To control, vines should be dusted with sulphur (15-20 kg per hectare) or sprayed with wettable sulphur (0.3%) or Karathane (0.04 %) at weekly intervals from 75 to 105 days after pruning.
In regard to chemical insecticides, it should be kept in mind that to avoid health hazards, they should not be applied to fruit crops within at least a month of harvest. This is particularly true with grapes, the bunches of which get ready to be harvested within only a few months after the berries have set and are much earlier in the early-maturing varieties.
Dr. Bibhas Chandra Manumdar
M.SC Agri, PH.D
Prtofessor in Horticulture institute of Agriculture Sciences
Calcutta University
Kolkata, West Bengal – 700029
Mob- 09830272846
Email.- profbcmazumdar@yahoo.com
