The pruning window is closed and chainsaws should be cleaned and packed away until March. Not only can pruning in summer cause considerable sunburn damage but the regrowth is also very vigorous, often resulting in quickly closed up canopies. Sometimes the regrowth supersedes what was pruned back in the first place. The most important reason, however, is that it swings the hormonal balance in the trees and can cause excessive fruitlet drop. Ensure you don’t leave managing the pruning regrowth too late as it will harden off and become more labour intensive to thin out and remove. If you haven’t applied a whitewash for sunburn protection yet, now is also the time to do so.
Manage pruning regrowth
For those that have a problem letting go of the chainsaw … grab the secateurs and get to work on your young non-bearing trees. On these trees we want to grow the canopy quickly so vigorous growth is not a problem and nor do we need to worry about causing fruitlet drop. In this case we want to do tipping and thinning pruning and also prune out any intrusions, weak or damaged branches and start to develop a framework that will optimise production and light penetration into the young canopy.
A lot of new plantings, replants or interplants have gone in the ground or will soon be planted. A few precautions to take note of are planting depth, overwatering and sunburn. When planting, ensure you firm the soil down gently as you plant so that the tree does not collapse in after rain or irrigation as this can cause collar rot and death especially on clonals. If you are not following my pre-planting and planting programme, your trees may display a wilted appearance for a period after planting. This is sometimes misdiagnosed as water stress and treated with additional irrigation eventually to the point of overwatering – the symptoms of which are also a wilted leaf appearance. The cycle continues until the soil becomes waterlogged and anaerobic, resulting in tree mortality.
Newly planted trees are also prone to sunburn as the sensitive, green cambium has little leaf cover and can quickly get sunburnt if precautions have not been taken. Sunburn damage in severe cases can cause ringbarking and also eventual tree mortality.
Remove any flowers or fruitlets on newly planted trees as you want all the energy and resources to go into vegetative growth. Any flowers or setting fruit will hold back canopy growth. Remember that any orchard development or new plantings are an investment and one that will yield returns for up to 40+ years. In light of orchard longevity, do not take any shortcuts and ensure you put in the time, resources and effort and it will definitely pay off.
On our Woodlands Road Orchard, to ensure the best possible establishment and growth, we have also done pre-plant drenches, drenches at planting and two post-planting drenches with two products called Trichopel & Unite. This will be especially beneficial in plantings within existing orchards, marginal areas and when replacing sick trees with new ones in the same hole or vicinity. You will find further information on these products, if you are interested in using them, at the end of this article. We have also done various spacings and planting densities which we will visit at future Field Days or Discussion Groups. Planting densities are always of interest and now our growers will be able to see first-hand various options that can be implemented.
Fruit set is looking good this year. Now the challenge is to keep it on the trees. It is normal for a large portion of fruitlets to abort and fall, up to the end of February, even under optimum conditions. But we can ensure optimum fruit set by not pushing vegetative flush too strongly. Vegetative growth that is too strong during the period critical to fruitlet retention will result in too much competition with the fruitlets and increased fruitlet drop and reduced yields. Remember that balanced nutrition is crucial.
Remember to time your soil fertiliser application to weather events. If the forecast is for heavy rain and your soils are already very wet or at field capacity, then hold off as most of the fertiliser will be leached down beyond the root zone. On the other hand, if the long-term forecast is looking hot and dry for the next month’s application, then bring your application forward as you will not get much uptake of fertiliser if the soil is too dry. If you have irrigation, then you will be patting yourself on the back during those dry periods and timing your fertiliser according to your fertiliser application windows and with good root flush.
USING BENEFICIAL MICROBES TO SUPPORT NEW PLANTINGS
Trichoderma spp. are utilised in many of the most successful bio-fungicides used in horticulture today. Their many beneficial properties are harnessed in bio-control agents used to grow strong healthy plants in all conditions.
Trichoderma has multiple modes of action and can be readily cultured and formulated into cost effective bio-control products.
Trichoderma has two major plant benefits
- Stimulating root and shoot growth
- Reduction of soil borne diseases such as Phyophthora Root Rot.
Trichoderma is a family of fast-growing saprophytic fungi – they establish predominantly in the rhizosphere but are also capable of surface penetration and colonising plant roots.
Trichoderma have a symbiotic relationship to the plant, feeding off sugary root exudates from the plant, in turn releasing secondary metabolites that help to stimulate both root and shoot growth.
Trichoderma improves the plant’s ability to take up nutrients and also to buffer the pH in the root zone which increases nutrient availability.
Trichoderma is effective at colonising the rhizosphere to the exclusion of other pathogenic fungi. They outcompete other fungi for nutrients and reduce the presence of the pathogens. Trichoderma can even actively consume pathogens as they multiply.
The Agrimm company grow selected strains of Trichoderma and formulate a range of granules and powders designed to support growing plants. In new orchard plantings or replants, Trichopel and Unite WP (a protectant bio-fungicide) is used both before and after planting.
Recommendations for plantings are:
- Prior to planting, drench Unite at 1g/tree into the plant bag (ideally 1 week prior to planting)
- Apply 20g of Trichopel into the planting hole
- After planting, mix Unite at 1g/L and apply 2-3L per tree drenched into the root zone.
Unite is registered for a range of root diseases including Phytophthora. Agrimm recommends a programme of drenches annually through the growing season at periods of root flushes. The rate is 3g/tree.
For further information you can call Alistair Pullin at Agrimm on 021 590 329 or (03) 325 3311 or go to their website for further information: www.agrimm.co.nz
-Erica Faber, Orchard Productivity Manager