Management of Diseased Garden

The foot rot pathogen (Phytophthora capsici) can survive in soil for many months, especially in the presence of cover crops. The time lapse needed for gap filling and replanting of diseased plants have not been worked out under the West Coast condition in India. In Sarawak, Malaysia, a trial carried out to determine the time lapse period for replanting of diseased plants indicated that disease always reoccurred when the replanting was done immediately after the removal of diseased plants, inspite of fungicide treatment (Anon. 1979). The reoccurrence of foot rot was negligible when the replanting was done at least after a period of three months. But the same result may not be applicable to Indian situation because of the shade effects, cover crops and companion crops present in the field. Under such situations a gap of at least one year seems to be essential. Kueh and Sim (1992) recommend a gap of eighteen months before replanting.

Malnutrition often results in incidence of disease in pepper plants. Deficiencies of nutrients like P and K have been indicated as the reason for diseases (Harper 1974, DeWaard 1969). DeWaard stated that a fertilizer mixture having 400 kg N, 180 kg P, 480 kg K, 425 kg Ca and 112 kg Mg applied to one hectare with appropriate mulching will control the disease and yield 2.0-2.5 kg dry pepper vine-1. Slow decline of pepper was first reported by Menon (1949) in Wynad, Kerala and a crop loss of 10 per cent was recorded. Nambiar et al. (1965) worked out tentative ratios of K2O (total)/N, K2O (available)/N and CaO+K2O+MgO/N in soil, and found that slow decline of pepper occurred when these ratios were below 14.1, 0.05 and 3.8 respectively. Slow decline is attributed to fungal infection, soil moisture stress and deficiency of K and P (Nambiar and Sarma 1977) and nematode (Ramana and Mohandas 1987). Wahid and Kamalam (1982) found that K levels of the leaves of healthy vines were considerably higher than those of diseased ones and arrived at the conclusion that K deficiency as a cause for the slow decline of pepper vines.

Sadanandan and Hamza (1992) surveyed major pepper growing areas of Kerala and Karnataka states to study the relationship of nutrients with yield and slow decline of pepper. The study showed that the pepper yield was correlated with DTPA extractable Fe (r=0.55*) and Cu (r=0.41**) in healthy gardens (Table 4.1.6). The yield was also correlated with leaf iron (r=0.56**) in a healthy and also diseased gardens (r=0.62**), with leaf manganese (r=0.27*) and leaf Cu (r=0.37**) in diseased gardens. This indicated the importance of these elements in pepper nutrition. Thus, micro nutrients like Fe, Zn and Cu play a vital role in predisposing the plants to disease incidence. Wahid and Kamalam (1982) reported that foliar yellowing and necrosis of distal ends of lamina in slow wilt affected gardens were due to N and K deficiencies respectively. The adoption of integrated nutrient management together with adoption of disease and pest

Table 4.1.6 Build-up of soil nutrients due to integrated nutrient management in farmers' fields (1986-90)*.

Nutrients

Farmers'

Exp. plots

Increase over farmers'

practice

practice (%)

Organic matter (%)

1.8

2.7

50

Bray-P mg kg 1

17.0

32.0

88

Exch. K

108.0

154.0

43

Ca

454.0

691.0

52

Mg

42.0

62.0

48

DTPA extr. Fe "

16.2

18.7

15

Mn "

3.9

6.0

54

Zn "

0.9

1.4

52

Cu "

2.2

4.1

86

management brought down the incidence of Phytophthora foot rot from 6.1 to 1.9 per cent and slow decline from 6.4 to 2.2 per cent.

In Brazil the Fusarium wilt caused by Fusarium solani f. sp. piperis is the most serious disease problem and it has been hypothesized that deficiencies in minor nutrients such as Zn, Fe and Bo and the lack of equilibrium between potash and phosphorous in relation to calcium and magnesium might be predisposing the plants to infection (Durate and Albuquerque 1991).

(Note: The epidemiology of slow decline of pepper (or pepper yellows) has been thoroughly worked out and is definitely shown to be due to the infection by Radhopholus similis (burrowing nematode) along with the root damage caused by Phytophthora capsici. These organisams destroy the root system, thereby preventing the absorption of water and nutrients, eventually upsetting the nutrient balance in the plant system. See the chapter on Nematode Induced Diseases for a full discussion—Ed.).

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