Here is an elaborated discussion on integrated disease management packages for late blight of potato, citrus canker, diseases of tomato, cole crops, sugarcane, groundnut and pulses.
1. Late Blight of Potato:
The famous late blight disease of potato caused by Phytophthora infestans, which caused destruction and famine more than one and half century ago, continues to damage potato crops throughout the world. Single-gene, vertical resistance could not provide a lasting solution as the pathogen rapidly and successfully developed resistance to some of the most effective fungicides (e.g., metalaxyl) applied to control the disease.
It has been found during past decades, however, that the cost-effective control of this disease can be materialized by integrating several different control measures. The integration of host horizontal resistance with mixtures of fungicides with different modes of action (e.g., phenylamide with a dithiocarbanate) is used only when necessary according to a computer-based forecasting system can effectively control this disease.
2. Citrus Canker:
Control of citrus canker, a bacterial disease caused by Xanthomonas campestris pv. citri, is still a problem in citrus growing countries. It has been found that good crop hygiene and cultural practices integrated with host resistance, and the strategic application of chemicals can effectively control this disease. It is recommended currently, however, that such citrus cultivars be planted, which possess a degree of resistance, in farms that are disease-free, or in which eradication measures have been applied at least one year previously.
The health of nursery stock should be carefully monitored to ensure that diseased plants are not distributed. These hygiene measures must be integrated with the use of windbreaks to reduce dispersal of the pathogen, and application of copper-based bactericides to trees each year during the new flush of growth.
3. Diseases of Tomato:
There are variety of diseases of tomato, e.g., damping off by Rhizoctonia, Pithium, Fusarium, and Macrophomina (25-60% disease severity). Alternaria blight by Alternaria alternata f.sp. lycopersici and A. solani (15-80% disease severity); late blight by Phytophthora infestans (5- 80% disease severity); collar rot by Selerotium rolfsii (10-40% disease severity); Bacterial leaf spot by Xanthomonas campestris pv. vesicatoria (20-70% disease severity); leaf curl by tobacco leaf curl virus (TLCV; 25-90% disease severity); and others cause considerable damage to this crop.
A complete package of integrated disease management for tomato is recommended as follows:
a. Summer ploughing should be followed by irrigation in the first week of May and again subsequent ploughing should be done to minimize perpetuating propagules in the field.
b. Green manuring should be done in the month of June or July.
c. Neem cake should be applied in nursery bed at the rate of 100 gm/m2 area.
d. Late kharif and rabi crop of tomato should be preferred in TLCV prone area.
e. Tomato seeds should be treated with Trichoderma (1%) + imidacloprid (2.5 gm/kg of seed).
f. Seedlings should be dipped in 0.25% imidacloprid for half an hour followed by dip in 1% Trichoderma for 10 minute.
g. Seedlings should not be transplanted before second fortnight of September.
h. Soil should be drenched with Trichoderma (1%) after 15-20 days of transplanting. Soil drenching should be repeated after 15 days of the first one.
i. Mulch crop should be used to protect bacterial infection from rain splash.
j. Non-host taller border crop of maize, sorghum, and bajra should be grown to prevent the entry of white fly, the virus vector, into the field.
k. Three foliar spray of NPV at the rate of 300 litre/ha alternated with one spray of endosulfan at the rate of 1.5 ml/litre starting from flowering.
l. 0.3% copper oxychloride should be sprayed once in late kharif tomato while 0.25% mancozeb in winter tomato during fruiting stage.
m. All Alternaria infected fruits and crop debris should be collected in the month of February onwards and burnt.
4. Diseases of Cole Crops:
Important diseases occurring on Cole crop plants are leaf spot (Alternaria brassicae and A. brassicola; disease severity 10-40%), downy mildew (Peronospora parasitica; disease severity 5-25%), root rot/wire stem (Rhizoctonia solani; disease severity 5-15%), black rot (Xanthomonas campestris pv. campestris; disease severity 10-60%), etc. Pandey et al. (2002) have recommended a complete package of integrated disease management in these crops.
a. One irrigation in the first week of May should be given following summer ploughing and then further ploughing.
b. Green manuring should be done between June and July.
c. Seeds should be given hot water treatment at 50°C for half an hour or they should be soaked in streptocycline at the rate of 100 ppm to solution for half an hour.
d. Dense population of seedlings in nursery should not be allowed. Seedlings should be sprayed with 0.005% cypermethrin.
e. Seedlings should be dipped in 1% Trichoderma for 10 minutes before transplantation in main field.
f. Transplanting of cauliflower before second fortnight of September and cabbage before first fortnight of October should be avoided.
g. Trap crop (e.g., Chinese cabbage) should be transplanted.
h. Soil should be drenched with Trichoderma viride (1%) at 15 to 20 days of transplantation.
i. Lower leaves should be removed and burnt on the same day. It should be followed by one spray of 0.25% mancozeb or 0.20% chlorothalonil.
j. During flowering stage, 0.25% mancozeb spray should be followed by one spray of 0.1% carbendazim at a week interval.
k. One or two sprays of Bt (500 g ai/ha) alternating with 2-3 sprays of 4% NSKE during premordial stage.
5. Diseases of Sugarcane:
Sugarcane crop is attacked by a number of serious diseases, such as red rot, wilt, smut, mosaic, grassy shoot, ratoon stunting, sett-rot, etc. requiring the use of diverse approaches for their management.
These diverse approaches are the following:
a. The use of disease-free planting material is the single most important component of disease management, which can be obtained by heat treatment.
b. Quarantine, seed treatment with fungicides, crop rotation, field sanitation, rouging out diseased plants and growing tolerant varieties (e.g., for red rot caused by Glomerella tucumanensis, the tolerant varieties are Co 1053, Co 1214 and Co 1261, Co 1336, Co 62101, Co 62399) are some of the other measures to be taken.
c. The setts should be treated at 54°C for 4 hours, using the moist hot air treatment (MHAT) while they are treated for 2 hours at 50°C using the hot water treatment (HWT). The curative properties of HWT can be increased by the addition of a fungicide in the water tank. MHAT is more effective than HWT.
6. Diseases of Groundnut:
Early leaf spot and late leaf spot diseases of groundnut caused by Cercospora arachidicola and Cercosporidium personatum, respectively, are the most destructive diseases of groundnut. These diseases in combination with rust (Puccinia arachidis), cause severe loss. Groundnut rust (caused by Puccinia arachidis) survives through uredospores formed in self-sown plants or through plant debris.
The following measures are recommended for the management of leaf spot and rust:
a. Destruction of infected plant debris, crop residues, and volunteer plants in the field.
b. Crop rotation with soya-bean or maize.
c. Use of tolerant varieties, e.g., AK 12-24, ICG 36, MH2 and GIRNAR 1 for early and late leaf spot and SPS 38, VG 78 and AK 24-12 for rust of groundnut.
d. Use of carbendazim and mancozeb, which have been found to be effective in reducing infection.
7. Diseases of Pulses:
Wilt is a common disease of red gram or pigeon pea (Cajanus cajan), gram (Cicer arietinum) and lentil (Lens esculenta), caused by the soil-borne fungus, Fusarium sp. This fungus survives in the left-over stubbles of red gram for three years.
The following measures may help in the management of the disease:
a. Deep ploughing of soil from 15 to 18 cm.
b. Addition of organic manure in soil.
c. Solarization of soil.
d. Avoidance of post-flowering irrigation.
e. Use of tolerant varieties.
f. Mixed-cropping of gram and linseed using seeds in the ratio of 2:1.
g. Crop rotation continuously for four growing seasons.
h. Seed treatment with a mixture of Thiram and Benomyl.
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