By Erica Faber – Technical Manager
Watch out for sunburn on the exposed tender green stems as well as the base of the trunk upwards. The young trees are extremely prone to sunburn resulting in poor vegetative growth, stem splitting and secondary fungal disease or even ringbarking and death. Either include sunburn products (e.g. Surround) monthly throughout summer or until the stems are protected by the new flush. Apply with your foliar sprays or paint the exposed stems with a 1:1 mixture of white water based acrylic paint and water.
Newly planted trees need regular watering. If mother nature isn’t supplying it and you don’t have irrigation, then a water tank or bucket may be required. Work on around 30-50L of water through rain or irrigation or a combination thereof, per week depending on the weather. The trees will lose more water in hot, dry and windy conditions than in warm, humid conditions and water requirements can be adjusted accordingly using either the lower or higher range.
Even though the trees are receiving adequate water they may appear wilted on really hot days. Don’t be tempted to over irrigate as this will cause overly wet soils and anaerobic conditions which can lead to root dieback or Phytophthora Root Rot. The wilting is the trees way of trying to minimize moisture loss. You can support the tree in these conditions and reduce the stress on the tree by adding an antitranspirant (eg. Vapor Gard) to your foliar spray. This reduces the rate of transpiration (moisture loss) the tree experiences and keeps them happier on those very hot days.
Insects need to be monitored and controlled. Insects will be eyeing up the new buffet you have just provided – keep an eye out for Leafroller, Passion Vine Hopper, Cicadas, Fullers RoseWeevil and Bronze Beetle.
Apply compost to your planting hole. I have been working with Revital and together we have come up with a compost planting mix. This blend includes compost, vermicast, chicken manure, lime and phosphorus and is bio certified. It has a NPK of 12.5:9.5:3 and includes Magnesium and Calcium. Apply to your planting hole at 10% (e.g. 60L of compost for a 0.6m3 hole) and mix evenly with the soil. Just Avocados growers receive a discounted price! For those that are yet to plant, refer to our planting guide.
TREE STRUCTURE MANAGEMENT
Even though the chainsaws should be packed away, the hand pruning saws can make an appearance. Doing any major structural pruning this time of year on mature trees may disrupt the fruit set causing a higher fruitlet drop than normal. This happens due to a hormonal shift in the tree with the vegetative response to structural pruning. Summer pruning also reduces late-season photosynthesis, and theoretically reduces the accumulation of reserve carbohydrates within the tree that Irrigation and monitoring soil moisture is key over summer. are used for early season growth in the following Spring. However, if this is not a concern to you for whatever reason and you want to continue pruning then ensure adequate sunburn prevention on exposed limbs during the hot summer months.
For those who are guarding their fruit set and working towards improving production then read on.If you are trying to improve the bearing capacity of your trees and have large voids off the main trunk where there is no lateral branching then this is the time of year when you can try initiate dormant (also known as latent) buds to shoot by taking advantage of the high sap flow, evidence of which can be seen by the active vegetative flush. By cincturing (a xylem and phloem interruption technique), you temporarily restrict and redirect the flow of reserves. Done in late spring or early summer you can initiate dormant vegetative buds below your cincture and done in autumn or winter can improve flowering or fruit set by increasing photosynthates to the flowers.