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Posts Tagged ‘POTATO DISEASE’

Early blight potato disease

Monday, August 10th, 2009

Early blightEarly blight potato disease is causes by  Alternaria solani fungal pathogen. Alternaria solani is generally thought to be a weak parasite.
Early blight is often a disease of senescence, where the older leaves are infected first. The disease can progress upward; attacking newer tissue as the older leaves droop and dry up. Under severe epidemics, leaves may be killed prematurely.
The disease first becomes evident in senescent leaves, in form of dark necrotic lesions in a characteristic concentric pattern. Contamination of the tubers is manifested by dry, dark, round depressions on the peel.
If cases of severe infestation it is possible loss of yield, due to early leaf death. Dry rot develops also on the tubers during storage.
Most of the early varieties are susceptible.

Management and control of early blight potato disease


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Use seed potatoes free of the disease. Seeds infected with the disease may damp off during germination.
Minimize stress by maintaining adequate soil moisture and fertility.      Avoid watering during the hottest hours and immediately after storms.
Early blight can be prevented with some fungicides: azoxystrobin, potassium bicarbonate, hydrogen dioxide as well as the biological control agent Bacillus subtilis
Avoid harvesting non-mature tubers. Protect against insect infestations.

Preventative measures include ensuring the healthy circulation of air in garden rows and rotating crops so that solanaceous plants are only present every three years, and choosing resistant cultivars.

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Dry rot potato disease

Monday, August 10th, 2009

Dry rotSeveral species of Fusarium cause dry rot potato disease.
Young potato tubers have some resistance to dry rot which slows disease. But dry rot disease progresses noticeably during the last half of the storage season.

The first symptoms of dry rot are usually dark decay on the surface of the tuber. In cases of large lesions the skin becomes wrinkled in concentric rings as the underlying dead tissue desiccates. Internal symptoms are characterized by necrotic areas shaded from light to dark chocolate brown or black.
This necrotic tissue is usually dry and may develop at an injury such as a cut or bruise. The pathogen enters the tuber, often rotting out the center. Rotted cavities are often lined with mycelia and spores of various colors from yellow to white to pink depending on the species of the pathogen.

Management and control of dry rot potato disease

Practically the following procedures will help prevent dry rot.

  • Critical point is to purchase seed that has as little dry rot as possible. Seed should be inspected, preferably during the last months of storage.
  • To minimize injury and promote rapid growth Warm seed tubers should be warmed to at least 50° F before handling and cutting. Cold tubers are very prone to shatter bruising.
  • Clean and disinfect the seed storage before receiving seed. Knives on the cutter should be sharp to make a smooth cut for that easy healing.

Disinfect seed cutting and handling equipment often and clean up well between seed Plow Attachmentlots. Adjust the cutter and sort tubers to provide 2-ounce seed pieces that will provide substantial nutrition to the developing plant, even if some rot develops.
Get rid obviously rotted tubers before they reach the cutter.

  • Treating seed pieces with fungicide helps prevent dry rot and other diseases caused by seed pathogens.
  • Protect the seed tuber from affect of wind and sunlight during planting because dehydration greatly weakens them. Cutting pieces should be planted within 24 hours.
  • Harvest tubers after skins are set and when pulp temperature is greater than 50° F. Use antibruise practices when harvesting and piling potatoes.
  • If using a postharvest fungicide, be certain that the coverage is adequate to protect the entire surface of the tuber. Use the volume of water and fungicide rate specified on the label.
  • Allow a period for wounds to heal before dropping the temperature in storage. There should be good air circulation, high humidity (greater than 90%), and temperature around 55° F.
  • For prevention of condensation on the tubers drop the temperature slowly and store tubers as cool as possible, considering your intended market.
  • Monitor storages often for dry rot. Never place tubers with dry rot symptoms in storage because doing so spreads disease.

POTATO DISEASE : Common scab

Wednesday, August 5th, 2009

Conditions for development of potato common scab are dry soil, pH basic to neutral, and temperatures conducive to infestation (20-22°C).

Symptoms of common scab

common-scabSymptoms of potato common scab are quite variable. Usually, roughly circular, raised, tan to brown, corky lesions of varying size develop randomly across tuber surfaces.
Symptoms of common scab potato disease are superficial brownish diameter 5-8mm wounds on the tuber. The blemishes can appear on the surface, raising the peel by 1-2mm (russet scab) or causing slight depressions. Usually potato foliage has no visible symptoms.
But common scab severe damage quality of tubers.

Management and control

Cost common recommendation to prevent of common scab while growing potatoes is using of disease-free seed tubers, crop rotation, and optimal irrigation, while maintaining field capacity suitable for potato cultivation.
For growing good crop of potatoes use a 3-5 year rotation, preferably with legumes. Plant scab-free or treated seed on land free of scab. Use an acidic fertilizer, such as ammonium sulfate, for nitrogen and irrigate adequately especially during tuber initiation.
Neutralizing excessively acidic or alkaline soils may help to reduce levels of common scab.
Maintain good moisture levels in the soil while tubers are developing.
Crop rotation in which potatoes will be planted in the same area only once every 3 or 4 years. Avoid rotating with root crops; instead plant grains, grasses, or legumes.
Chemically treating seed pieces before planting with the fungicide Captan will help reduce seedborne potato common scab inoculum.

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