Apple Tree Diseases: White Root Rot Pre-disposing Factors

This is in continuation to my previous post on Diseases of apple: White root rot. In today’s post we are going to discuss about the pre-disposing factors for the disease development.

Pre-disposing factors:

Soil moisture is the major key factor for the proliferation of the disease as the fungus is of polyphagous. The mycelium could grow in soils with 6-89.2 percent water content, but the fungal mats developed most vigorously at 70 percent. Soil type influences greatly the period of survival and spread of soil-borne fungi. The occurrence of white root rot disease of apple trees was closely related to soil conditions. In alluvial areas and regions with non-volcanic ash soils, the pathogen was associated with sandy soils over gravel where available water was the limiting factor. In upland regions, the disease was prevalent on shallow soils overlying stony sub-soils. Of the several factors examined in Himachal Pradesh for their possible role in the longevity and survival of the root rot pathogen, clay loam soil was reported better than clay soil for its longer survival at all temperature ranges and soil moisture regimes. Temperature has been known to play an important role in the survival and spread of the pathogen, 17^oC is an optimum temperature level. Of the two factors i.e. temperature and soil moisture, the latter plays more decisive role in increasing the longevity of the pathogen than the former.

The prevalence of white root rot in Himachal Pradesh is limited to high hill soil texture varies from loam to clay loam. The soil reaction is slightly acidic and this zone is ideally suited for apple cultivation. It receives an average of 100-140 cm rainfall per annum. The rainy season in the apple zone is during June to September, when also a higher incidence and severe symptoms of root rot are observed, indicating that the disease spread and severity are related to excessive soil moisture regimes at higher temperature. The higher elevation range was observed favourable for the spread of D. necatrix being high rainfall area and low temperature conditions prevailing for long durations. Besides soil, pH also seems to have a strong relationship with the survival of the pathogen flourishing best in 6- 6.5 pH range. Incidentally the larger area under apple cultivation in Himachal Pradesh also falls within this pH range.

Physico-environmental conditions viz., soil type (loam and clay laom), soil reaction (pH6-6.5), soil moisture (>70%) and Temperature (17^oC) play an important role in incidence and survival of Dematophora necatrix.

In coming post we shall be discussing about the management of the white root rot disease.

Apple Tree: Training Systems of Apple Trees in Intensive Orchards

The number of apple trees per acre in new orchards has gradually been increasing. Orchard intensification is motivated by the desire to produce fruit early in the life of the orchard to rapidly recover establishment costs. Intensification is possible by using dwarfing rootstocks that control tree size, induce early cropping, and produce large quantities of fruit relative to the amount of wood produced.

Apple trees grown on dwarfing rootstocks have shallow or brittle roots systems and trees grew poorly and often leaned or fell over. Therefore these plants require support systems. However, Intensive orchard systems are more profitable than traditional low-density orchards on semi-dwarfing rootstocks. However, because the establishment costs for intensive orchards are high, trees must be trained and pruned properly to induce and maintain high yields.

Motivation for orchard intensification.

The primary reasons for orchard intensification include:

1.) early fruit production, and
2.) reduced pruning and harvest costs of mature orchards.

Yield is positively related to the amount of sunlight intercepted per acre. Profit, which is influenced by yield as well as fruit size and quality, is probably at an optimum when an orchard intercepts about 70% of the available light. Traditional orchards, using vigorous rootstocks, were typically planted at a spacing of about 22 feet x 16 feet with 132 trees per acre. For the first five or six years after planting, fruiting was discouraged to promote vegetative growth so trees would fill their space as rapidly as possible. The first crop was usually harvested four or five years after planting, but high yields were not obtained until trees finally occupied their allotted space. Maximum yields did not occur until about 12 to 14 years after planting.

Intensive orchards are typically planted at narrow spacing depending upon the training system adopted but one thing is very clear that a small crop is often harvested the year after planting, because trees have so little space to fill, peak production is usually achieved during the 6th or 7th year after planting. Once trees fill their allotted space, maximum yields are similar for all types of orchard systems. Because the primary advantage of intensive orchards is early fruit production, these orchards should be planted only on excellent sites with a low probability of crop loss due to frost or hail.

Intensive orchard training systems.

The three basic types of training systems used for intensive orchards are

1. "Trellis,"
2."Slender Spindle," and
3."Vertical axis or French Axis."

There are many modifications of each system, and orchardists will need to adapt a system to suit their own particular situation. The basic systems will be discussed in coming posts

Apple Tree: High Density Plantation: Advantages of smaller trees

I discussed about Trichoderma with respect to its role in plant health management. In my previous posts I have discussed about low productivity in apple especially in our perspective. This low productivity in Himachal is because of many reasons discussed in previous posts that are to be dealt with technological back up. This requires lot of motivation of the farmers to adopt high density plantation on clonal rootstock but with this there is a great need for the technologocal backstoping. My core feeling is that what ever we are producing is not enough since if we check out the production data of our state it is hardly touching 11 T per hectare that too once or twice in the histroy of apple production but if we check out the average then it is hardly 4.5 T per hectare. Whereas countries like NewZea Land and Italy producing fruit to a tune of 40 T per hectare this makes us to review our strategies and to findout the way to increase our production. There are some farmers who are doing a very good Job in this regard they are trying to develop there own system to keep pace with the industry of apple production among these I must mention here that Mr. Vikram Singh Rawat in Karsog Valley is putting all his efforts to produce the trees on clonal rootstocks further he is putting lot of efforts in bringing the farmers under the umbrella of organic farming and high density plantation. In this series I feel that it is important to mention the name of Mr. Rajesh Thakur of Mahog, Mr. Rajender Kaushal of Chamanpur, Mr. Arun Bansal of Ruhni, Mr. Diljeet Singh Ghumman of Bakhrot, besides Mr. Dinesh Primta of Chaupal area, Mr. Neetu Dharma of Kotgarh and Rajender Chauhan of Kotkhai are the one those are working hard to make this high density apple plantation a reallity. This is a list where I know these farmers either personnaly or through my close connections. Many other farmers involved in the high density plantation this situation warrents us that we must put our steps forward to support these farmers in achieving their endeavours. That was the reason to bring out this topic ahead of disease and pest management in apple that was in planning well before persuing this blog.

In this blog I shall first cover the advantages of small trees these are as follows:

1.    Reduce pruning costs

2.    Less spray per unit fruit

3.    Better spray coverage

4.    Smaller, less expensive equipment

5.    Quicker fruiting

6.    Lower harvesting costs (no ladders)

7.    Labour prefers smaller trees

8.    Easier to mechanize

After looking on these let us see how many of farmers are getting motivation...............
In coming posts I shall be dealing with the Various rootstocks and scions that can be used in high density apple plantations