Apple Tree Diseases: Collar Rot Description

This is in continution to my previous post Diseases of Apple: Powdery Mildew Management. Here we are going to talk about the Collar Rot that is similar to Root Rot and Crown Rot. This disease is tedious to be managed but if understood throughly it can be managed.

Description 

The disease is caused by Phytophthora cactorum and infection starts from the collar region i.e. soil line and spread mostly to the underground parts and the above ground stem portion is also infected in highly susceptible scion cultivars. The fungus attacks the cambium thusrequires wounds to cause infection, once infected  bark at the soil level becomes coffee brown in colour, slimy and rots resulting in cankered areas. The wounds are irregular in outline but usually roughly oval which extend rapidly, often resulting in girdling of the tree. The attacked trees are recognized by sparse foliage, purple colour of the leaf veins in attcked tree, more number of spurs than normal, fruit size remain small in such trees as nutrition uptake is reduced due to rot.

In coming post we shall be talking about the Collar Rot Management.

Apple Tree: Training Systems in Intensive Apple Cultivation: Vertical Axis

This post is in continuation of the series on Training Systems in Intensive Apple Cultivation This post explains about the Vertical Axis or French Axis training system 

The vertical axis (VA) system

The vertical axis (VA) system has been touted by some growers as the next logical step from free standing central leader trees to high density supported systems. The main reason cited is the great similarities between the systems and the low emphasis on limb manipulation by tying. There are ladders used in picking, but with a flat tree wall at ladder height it is quite fast and simple to manage ladders.

Even though the VA system is one of the taller systems used in high density supported systems, there is still a critical need for lower limb development. These lower limbs will form a fruiting table yielding perhaps 60% of the crop and must be established before the trees should be allowed to grow taller. Proper development of the bottoms of the tree will allow 75% or more of the fruit to be picked from the ground. Cultivars that have a high requirement for light (e.g. McIntosh) are well suited to this system. Other cultivars like Gala, Goldrush, Golden Delicious and Empire have a growth habit highly suited to this system.

VA systems allow trees to grow taller than SS systems. The system basically consists of one or more high tensile steel wire(s) drawn tight and supported 2 - 3 m above the ground by a series of in-line posts spaced 9 to 15 m apart. The closer the spacing for the inline posts, the higher the degree of stability of the support system under strong wind or high cropload conditions. 

Individual trees in the row are supported by vertical leader supports that reach up to the top support wire. The tree consists of a conical, or "Christmas tree" shape and grown up to 3.5 - 4.0 m tall. The leader is not pruned until the tree reaches its full height. Shoots arising on the side of the axis or trunk close to and competing with the leader are removed as they arise or during the dormant pruning season. Side branches on the leader are renewed on a periodic basis.

The VA support system is somewhat more complex than the SS to install. It does require a high level of skill to build the support system and be sure it is adequate to hold the trees and crop load. A post failure in this system can result in the loss of several trees. The standard anchoring system now in use is the "auger anchor" which is screwed into place. Posts are generally pounded or watered (water gun) into the ground.

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Apple Tree: Training Systems in Intensive Apple Cultivation: Slender Spindle

This post is in continuation of the previous post on Training Systems in Intensive Apple Cultivation: Trellis. This post explains about the Slender Spindle training system further modification of spindle bush training system.

Slender Spindle:

This is the system preferred by growers who wish to work exclusively from the ground and are not confident in building wire support systems. The slender spindle (SS) consists of an individual support post at every tree.

Slender Spindle Support System:

The post should be 2.4 - 3 m in length and of pressure-treated wood, concrete or metal to ensure it lasts the life of the orchard (perhaps 12 - 18 years). A diameter of 4 - 6 cm is preferred, since risk of frost heaving increases with larger diameters. The depth of the post in the ground should be 60 - 90 cm for stability leaving 1.5 to 2.5 m above ground. A common mistake is to have insufficient post height above ground.

Slender Spindle Training Pruning:

The tree is trained to a slender bell, or pear shape with the bottom whirl of branches acting as a permanent fruiting table. The leader and top of the tree is kept quite weak to contain height. Renewal pruning of mature trees consists mainly of removing 2 - 3 of the largest diameter branches on an annual basis during the dormant season.  Tree height does not exceed 2 - 2.5 m.

In the next post I shall be discussing about the Vertical Axis or French Axis training system. This system is followed mainly in France having average productivity of about 42 Tonnes per Ha.

Apple Tree:Training Systems in Intensive Apple Cultivation: Trellis

This is in continuation to my previous blog on Training Systems of Apple Trees in Intensive Orchards where I mentioned about three basic training systems of apple trees in intensive cropping i.e. high density apple plantations. Today I am going to discuss about trellis.

Trellis:

Why trellis or any other support system based training system should be adopted for the HDP on clonal rootstocks. As you are now aware of the fact that the production can be optimized by harvesting 70 per cent of available light. Further the wood produced and fruit produced ratios are to be optimized. Why we produce wood? Wood is produced for structural strength. This is the reason for growing larger trees on strong scaffolds. If we want to grow HDP we must understand that support system is necessary to reduce wood production. This helps us in growing the trees with more fruiting wood than the structural wood. Therefore the production can be started at early stage of the plant/ orchard life. If the production can be taken as early as two to three years of planting, the breakeven point of orchard establishment can be met earlier.

The system basically consists of one or more high tensile steel wire(s) drawn tight and supported 2 - 3 m above the ground by a series of in-line posts spaced 6 to 10 m apart. The closer the spacing for the inline posts, the higher the degree of stability of the support system under strong wind or high crop load conditions.

The trellis support system is somewhat more complex than the Slender spindle and vertical axis to install. It does require a high level of skill to build the support system and be sure it is adequate to hold the trees and crop load. A post failure in this system can result in the loss of several trees. The standard anchoring system now in use is the "auger anchor" which is screwed into place. Posts are generally pounded or watered (water gun) into the ground.

The key problems of trellis systems are varieties with excessive vigorous or strong rootstocks that result in excessive pruning to contain the tree. Also, trellis systems support the total weight of the crop load and, as a result, must be exceptionally sturdy with posts for wire support located every few trees in the row.

In coming posts I shall be discussing about Slender spindle, Vertical Axis and Super Spindle training systems.

TRICHODERMA AS A BIOFERTILIZERS & PLANT GROWTH PROMOTER

This post is in continuation to Siderphore production by Trichoderma: A Magicalplant health manager

         Apart from the direct inhibition of plant pathogens, Trichoderma spp. are reported to improve crop health by promotion of plant growth (both root an shoot). It is reported to enhance growth in a number of plant species like rice, wheat, sorghum, tomato, brinjal, soybean, chickpea, pea, rajma, chilli, capsicum, apple etc. However, this growth promotary effect was not only dependent on isolate of Trichoderma but also on plant species cultivar involved.  

Plant growth promotion is one of the indirect mechanisms employed by Trichoderma spp. which plays a role in the biocontrol of various plant pathogens and in improvement of plant health. Treatment with Trichoderma generally increases root and shoot growth, reduces the activity of deleterious microorganisms in the rhizosphere of plants and improves the nutrient status of the plant.  Growth enhancement by Trichoderma spp. has been observed even in the absence of any detectable disease and in sterile soil and is not considered to be a side effect of suppression of disease or minor plant pathogens.  Secretion of hormone-like metabolites and release of nutrients from soil or organic matter, have been proposed as the mechanisms involved in plant growth promotion. Trichoderma harzianum is good solubilizer of phosphorus but different strains show wide variation in their ability to solubilize phosphorus. T. harzianum was also reported to solubilize MnO₂, metallic zinc, and rock phosphate (mostly calcium phosphate) in a liquid sucrose-yeast extract medium. Trichoderma produced chelating metabolites and used redox activity for solubilizing the minerals. Both of these mechanisms also play a role in biocontrol of plant pathogens, and they may be part of a multiple-component action exerted by Trichoderma to achieve effective biocontrol under a variety of environmental conditions. It has observed that seed treatment of corn with T. harzianum, planted in low nitrogen soil resulted in plants that were greener and larger in the early part of the growing season. An increase in the microelement content (viz. Cu, P, Fe, Zn, Mn and Na) of plants was also observed. 

Symbiotic colonization of roots by Trichoderma enhanced root growth, which may be responsible for increased tolerance of plans to biotic and abiotic stresses. Wheat plants raised from Trichoderma treated seeds tolerate drought (water stress) better under field condition.  

In coming posts I shall be discussing on Apple production with respect to future perspective in Himachal Pradesh and High Density Plantation.