Plant protection

Plant Protection

Diseases

Foot rot disease

Foot rot (quick wilt disease) caused by Phytophthora capsici is the most destructive of all diseases and occurs mainly during the south west monsoon season. All parts of the vine are vulnerable to the disease and the expression of symptoms depend upon the site or plant part infected and the extent of damage. Symptoms are as follows:

1. One or more black spots appear on the leaves which have a characteristic fine fibre like projections at the advancing margins which rapidly enlarge and cause defoliation.
2. The tender leaves and succulent shoot tips of freshly emerging runner shoots trailing on the soil turn black when infected. The disease spreads to the entire vine, from these infected runner shoots and leaves, during intermittent showers due to rain splash.
3. If the main stem at the ground level or the collar is damaged, the entire vine wilts followed by shedding of leaves and spikes with or without black spots. The branches break up at nodes and the entire vine collapses within a month.
4. If the damage is confined to the feeder roots, the expression of symptoms is delayed till the cessation of rain and the vine starts showing declining symptoms such as yellowing, wilting, defoliation and drying up of a part of the vine. This may occur during October-November onwards. These vines may recover after the rains and survive for more than two seasons till the root infection culminates in collar rot and death of the vine.

The disease can be controlled by adopting integrated disease management strategies.

Phytosanitation

1. Removal and destruction of dead vines along with root system from the garden is essential as this reduces the build up of inoculum (fungal population).
2. Planting material must be collected from disease free gardens and the nursery preferably raised in fumigated or solarized soil.

Cultural practices

3. Adequate drainage should be provided to reduce water stagnation.
4. Injury to the root system due to cultural practices such as digging should be avoided.
5. The freshly emerging runner shoots should not be allowed to trail on the ground. They must either be tied back to the standard or pruned off.
6. The branches of support trees must be pruned at the onset of monsoon to avoid build up of humidity and for better penetration of sunlight. Reduced humidity and presence of sunlight reduces the intensity of leaf infection.

Chemical control

Any of the following chemical control measures can be adopted.

1. After the receipt of a few monsoon showers (May-June), all the vines are to be drenched at a radius of 45-50 cm with copper oxychloride 0.2 per cent @ 5-10 litres/vine. A foliar spray with Bordeaux mixture one per cent is also to be given. Drenching and spraying are to be repeated once again during August-September. A third round of drenching may be given during October if the monsoon is prolonged.
2. After the receipt of a few monsoon showers, all the vines are to be drenched with potassium phosphonate 0.3 per cent @ 5-10 litres/vine. A foliar spray with potassium phosphonate 0.3 percent is also to be given. A second drenching and spraying with potassium phosphonate 0.3 per cent is to be repeated during August-September. If the monsoon is prolonged, a third round of drenching may be given during October.
3. After the receipt of a few monsoon showers, all the vines are to be drenched with 0.125 per cent metalaxyl mancozeb @ 5-10 litres/vine. A foliar spray with metalaxyl mancozeb 0.125 per cent may also be given.
4. At the onset of monsoon (May-June), apply Trichoderma around the base of the vine @ 50 grams/vine (this quantity is recommended for a substrate containing Trichoderma @ 10¹⁰cfu). A foliar spray with potassium phosphonate 0.3 per cent or Bordeaux mixture one per cent is also to be given. A second application of Trichoderma and foliar spray of Bordeaux mixture one per cent or potassium phosphonate 0.3 per cent are to be given during August-September.

Pollu disease (Anthracnose)

This disease is caused by Colletotrichum gloeosporioides. It can be distinguished from the pollu (hollow berry) caused by the beetle by the presence of characteristic cracks on the infected berries. The disease appears towards the end of the monsoon. The affected berries show brown sunken patches during early stages and their further development is affected. In later stages, the discolouration gradually increases and the berries show the characteristic cross splitting. Finally, the berries turn black and dry. The fungus also causes angular to irregular brownish lesions with a chlorotic halo on the leaves. The disease can be controlled by spraying Bordeaux mixture one per cent.

Spike shedding

Spike shedding especially in varieties like Panniyur-1 at higher elevations like Kodagu and Idukki is one of the emerging diseases. It is seen in serious condition when the pre-monsoon showers are delayed and flowering and spiking occur during June-July. These spikes predominantly produce female flowers instead of bisexual flowers. Heavy spike shedding may occur due to lack of pollination. Irrigation of vines from second fortnight of March coupled with prophylactic spraying with Bordeaux mixture one per cent or carbendazim 0.2 per cent reduces the intensity of spike shedding.

Stunt disease

This disease which is caused by viruses is noticed in parts of Kannur, Kasaragod, Kozhikode, Wayanad and Idukki Districts of Kerala and Kodagu, Hassan and Uthara Kannada districts of Karnataka. The vines exhibit shortening of internodes to varying degrees. The leaves become small and narrow with varying degrees of deformation and appear leathery, puckered and crinkled. Chlorotic spots and streaks also appear on the leaves occasionally. The yield of the affected vines decreases gradually. Two viruses namely Cucumber mosaic virus and a Badnavirus are associated with the disease.

The major means of spread of the virus is through the use of infected stem cuttings. The disease can also be transmitted through insects like aphids and mealy bugs. The following strategies are recommended for the management of the disease.

1. Use virus free healthy planting material
2. Regular inspection and removal of infected plants; the removed plants may be burnt or buried deep in soil
3. Insects such as aphids and mealy bugs on the plant or standards should be controlled with insecticide spray such as dimethoate or monocrotophos @ 0.05 percent.

Phyllody disease

This disease which is caused by phytoplasma is noticed in parts of Waynad and Kozhikode districts of Kerala. The affected vines exhibit varying stages of malformation of spikes. Some of the floral buds are transformed into narrow leaf like structures. Such malformed spikes show leafy structures instead of floral buds, exhibiting phyllody symptoms. In advanced stages, the leaves become small and chlorotic, and the internodes are also shortened. The affected fruiting laterals give a witches broom appearance. Severely affected vines become unproductive. In severely affected vines the entire spike is converted into small branches which appear chlorotic and the vines decline rapidly. The infected vine becomes unproductive within two to three years. The infected vines are to be destroyed to prevent the further spread of the disease.

Slow decline (slow wilt)

Slow decline is a debilitating disease of black pepper. Foliar yellowing, defoliation and die-back are the aerial symptoms of this disease. The affected vines exhibit varying degrees of root degeneration due to infestation by plant parasitic nematodes. The diseased vines exhibit foliar yellowing from October onwards coinciding with depletion of soil moisture. With the onset of south west monsoon during May/June, some of the affected vines recover and put forth fresh foliage. However, the symptoms reappear in subsequent seasons after the cessation of the monsoon and the diseased vines gradually lose their vigour and productivity. The affected vines show varying degrees of feeder root loss and the expression of symptoms on the aerial parts occur after a considerable portion of the feeder roots are lost. The root system of diseased vines show varying degrees of necrosis and presence of root galls due to infestation by plant parasitic nematodes such as Radopholus similis and Meloidogyne incognita leading to rotting of feeder roots. The damage to feeder roots is caused by these nematodes and P. capsici either independently or together in combination. There is no spatial segregation of plant parasitic nematodes and P. capsici in the soil under field conditions. Hence, it is necessary to adopt a combination of fungicide and nematicide application for the management of the disease.

1. Severely affected vines which are beyond recovery should be removed from the plantation and destroyed.
2. The pits for planting should be treated with phorate 10 G @ 15 grams or carbofuran 3 G @ 50 grams at the time of planting.
3. Nematode free rooted cuttings raised in fumigated or solarized nursery mixture should be used for planting in the field.
4. Phorate 10 G @ 30 grams or carbofuran 3 G @ 100 g/vine should be applied during May/June (with the onset of south west monsoon) and September/October. Along with nematicides the basins should be drenched with either copper oxychloride 0.2 percent or potassium phosphonate 0.3 per cent or metalaxyl 0.125 per cent. In areas severely infested with root knot nematodes, cuttings of the resistant variety ‘Pournami’ may be planted. Biocontrol agents like Pochonia chlamydosporia or Trichoderma harzianum can be applied @ 50grams/vine twice a year (during April-May and September-October). The fungus load in the substrate should be 10⁸ cfu/g.

While applying nematicides, the soil should be raked in the basin of the vine lightly without causing damage to the root system and the nematicide should be spread uniformly in the basin and covered with soil immediately. Sufficient soil moisture should be ensured at the time of nematicide application. The control measures should be taken up during early stages of the disease.

Pests

Pollu beetle

The pollu beetle (Longitarsus nigripennis) is the most destructive pest of black pepper and is more serious in plains and at altitudes below 300 meters. The adult is a small black beetle measuring about 2.5 mm x 1.5 mm, the head and thorax being yellowish brown and the fore wings (elytra) black. Fully-grown grubs are creamy-white and measure about five mm in length. The adult beetles feed and damage tender leaves and spikes. The females lay eggs on tender spikes and berries. The grubs bore into and feed on the internal tissues and the infested spikes turn black and decay. The infested berries also turn black and crumble when pressed. The term pollu denotes the hollow nature of the infested berries in Malayalam. The pest infestation is more serious in shaded areas in the plantation. The pest population is higher during September-October in the field. Regulation of shade in the plantation reduces the population of the pest in the field. Spraying quinalphos (0.05 per cent) during June-July and September-October or quinalphos (0.05 per cent) during July and Neemgold (0.6 per cent) (neem-based insecticide) during August, September and October is effective for the management of the pest. The underside of leaves (where adults are generally seen) and spikes are to be sprayed thoroughly.

Top shoot borer

The top shoot borer (Cydia hemidoxa) is a serious pest in younger plantations in all black pepper areas. The adult is a tiny moth with a wing span of 10-15 mm with crimson and yellow fore wings and grey hind wings. The larvae bore into tender terminal shoots and feed on internal tissues resulting in blackening and decaying of affected shoots. Fully-grown larvae are grayish green and measure 12-15 mm in length. When successive new shoots are attacked, the growth of the vine is affected. The pest infestation is higher during July to October when numerous succulent shoots are available in the vines. Spray quinalphos (0.05 per cent) on tender terminal shoots; repeat spraying at monthly intervals (during July-October) to protect emerging new shoots.

Leaf gall thrips

Infestation by leaf gall thrips (Liothrips karnyi) is more serious at higher altitudes especially in younger vines and also in nurseries in the plains. The adults are black and measure 2.5-3.0 mm in length. The larvae and pupae are creamy white. The feeding activity of thrips on leaves causes the leaf margins to curl downwards and inwards resulting in the formation of marginal leaf galls. Later the infested leaves become crinkled and malformed. In severe cases of infestation, the growth of younger vines and cuttings in the nursery is affected. Spray dimethoate (0.05 per cent) during emergence of new flushes in young vines in the field and cuttings in the nursery.

Scale insects

Among the various scale insects recorded on black pepper, mussel scale (Lepidosaphes piperis) and coconut scale (Aspidiotus destructor) cause serious damage to black pepper vines at higher altitudes and also to older cuttings in nurseries in the plains. Females of mussel scales are elongated (about one mm length) and dark brown and that of coconut scales circular (about one mm in diameter) and yellowish brown. Scale insects are sedentary, remaining permanently fixed to plant parts and appear as encrustations on stems, leaves and berries. They feed on plant sap and cause yellowing and wilting of infested portions; in severe cases of infestation the affected portions of vines dry up. The pest infestation is more severe during the post monsoon and summer periods. Clip off and destroy severely infested branches. Spray dimethoate (0.1 per cent) on affected vines; repeat spraying after 21 days to control the infestation completely. Initiate control measures during early stages of pest infestation. In nurseries spraying neem oil 0.3 per cent or Neemgold 0.3 per cent or fish oil rosin three per cent is also effective in controlling the pest infestation.

Minor pests

Leaf feeding caterpillars, especially Synegia sp., damage leaves and spikes of younger vines and can be controlled by spraying quinalphos (0.05 per cent). Mealybugs, gall midges and aphids infest tender shoots especially in nurseries. Spraying of dimethoate (0.05 per cent) may be undertaken if infestations are severe. Mealybug infestation on roots can be controlled by drenching with chlorphyriphos (0.075 per cent) and undertaking control measures against Phytophthora and nematode infections.