Sunday, June 29, 2014

Apple Tree Diseases: Apple Mosaic Virus

This is in continuation to my previous post on Diseases of apple: Management of SootyBlotch and Fly Speck. In today’s post we are going to discuss about the Apple Mosaic Virus.

Apple Mosaic
Causal Organism: Apple mosaic virus (ApMV)
Description: In the spring, pale yellow to cream-coloured areas develop on expanding leaves of infected apple trees. These areas may appear as small spots, flecks, irregular blotches, vein-net patterns, line patterns, or bands along major veins. As the season advances, they turn from pale yellow or cream to a lighter chrome yellow or white and then soon become necrotic. Severely affected leaves abscise prematurely.

Economic Impact
In general, ApMV does not have much affect on fruit production and quality. However, severely infected Lord Lambourne trees often produce fruits with cream coloured blotches.  The virus results in yield reductions varying from slight to 50 per cent.  Crop losses of up to 42 per cent were recorded in infected hazelnut and average losses of 25 per cent were recorded from almonds affected by almond mosaic, a complex disease in which ApMV plays a major etiological role.

In my coming post I shall be discussing about apple cholorotic leaf virus

Saturday, June 28, 2014

Apple Tree Diseases: Sooty Blotch and Fly Speck Management

This is in continuation with my previous post on Diseases of Apple: Sooty Blotch and Fly Speck. In this post we are going to discuss about the management of the two diseases. 

These two diseases though superficial but makes a dent in the marketing of the fruit as it reduces the market value. Both the diseases can be managed easily with the scheduled spray. If a spray of Ziram @ 600g/200L water done 20 days prior to harvest the quality of the produce increases manifolds and the fruit can be sent to market with fancy grades

In coming post I shall be discussing viral and viroid diseases

Sunday, June 22, 2014

Apple Tree Diseases: Sooty Blotch and Fly Speck

This is in continuation to my previous post on Diseases of apple: Management of PrematureLeaf Fall. In today’s post we are going to discuss about the Sooty Blotch and Fly Speck.

Sooty Blotch
Causal Organism: Gloeodes pomigena
Description: Sooty blotch colonies appear as shades of olive green on mature fruit. They vary from discrete almost circular colonies to large colonies with diffuse margins, which are sooty in appearance. Large amorphous colonies that cover large portions of the fruit surface result from secondary spread on the fruit.  The fungus is found on the upper surface of fruit, which can be easily removed by rubbing leaving behind slight depression. No permanent spot is found on the fruit surface. This disease is found on late maturing varieties and under storage conditions. The fungus survives from one season to the next as mycelium and pycnidia on infected twigs of apple and numerous forest trees. The fungus is dispersed as chlamydospores or conidia during rains in the spring and early summer. Most conidia are liberated by early summer, but extensive secondary spread by chlamydospores and mycelial fragments occur throughout the seasons. The infection can also be seen on new twigs, on which it remains active. During the months of May and June, low temperature and rains are necessary for disease development. For the fungus development 18.3ÂșC is favourable. The disease is more prevalent in low and shady area of the orchard.

Fly Speck:
Causal Organism: Zygophiala jamaicensis and Mycrotheria spp.

Description: Symptoms of flyspeck on apple are approximately described by the name. Black spots are formed on fruits. Colonies are characterized by well-defined groups of 6, 8 or sometimes 50 shiny, black, superficial pseudothecia on the surface of the fruit. This disease is found abundantly during rainy days and in less windy regions. Sooty blotch and flyspeck colonies commonly occur on the same fruit, but the colonies are mutually exclusive.

Though these diseases do not cause much harm to the fruit yet it deteriorates the market quality thus affects the price of the produce.

In my coming post I shall be discussing about Management of Sooty Blotch and Fly Speck of apple.

Sunday, June 1, 2014

Apple Tree Diseases: Management of Premature Leaf Fall

This is in continuation to my previous post on Diseases of apple: Disease Monitoring System for Farmers. In today’s post we are going to discuss about the management of premature leaf fall. The holistic way of the disease management includes

1.     Phytosanitation: High and early disease incidence in shady areas is the key for the disease monitoring. The diseased leaves fallen on orchard floor must be removed from orchard floor and destroyed with the help of either by burning or decomposing in the composting pits. The cleanliness reduces the primary inoculum of the disease causing agents. This simple principle if followed the severity of the symptoms could be reduced to economic levels. Thus helps in reducing the costs.

2.     Cultural Practices: First attack of the disease takes place in shady and damp places from lower brances inner core of the tree, where the moisture remains high and air temperature is above 20oC, sun doesn’t reach. All these conditions gives an indication that the disease causing environment essentially missing the sun, so improving the reach of the sun to the different parts of the tree will help in managing the disease. Pruning is the key. Follow proper cone shape of the tree that will enhance the sunlight penetration and air circulation thus reducing the dampness from the inner core of tree and not allowing the disease causing agent to initiate the infection without enhancing the cost to a greater level.

3.     Biological Control: Introduction of biological control agents to the phylloplane is always a good idea. Trichoderma viride and Pseudomonads help the plant in fighting with plant pathogens.

4.     Chemical Control: The epidemiological studies have now established that the disease cycle begin in first week of June in most suitable and hot spot sites. The best management strategy is through preventive method. The infection sites can be cured with few systemic fungicides. Hence the assured control measures with the tank mixing of standard brand of mancozeb (0.3%) plus carbendazim (0.05%) fungicides in first week of June to 3rd week of June depending on the location of the orchards at different elevations. This first spray is preventive and can provide disease control for next 30 days. This spray combination can be repeated for second spray after 30 days to get the complete control over the disease. The farmers not adopting this method cannot control the disease later even with the above fungicides or number of sprays at short intervals. New generation chemicals like strobulins in combination with contact fungicide are also showing good results in the field.The apple blotch disease causing mid-season defoliation is a menace hence, needs appropriate selection of fungicides and spray at right stage for assured success in the management.

In my coming post I shall be discussing about sooty blotch of apple.