By Erica Faber – Orchard Productivity Manager
The first quarter of the year is over, and this marks the official end of the 2018-2019 season. Ahead for the next quarter is flower induction and initiation and bud development.
Starch accumulation is also occurring, preparing the tree for the upcoming demands of flowering and fruit set.
The main orchard priorities for the next quarter are:
- Soil, leaf and microbial sampling
- Land prep and soil corrections for spring planting
- Phytophthora root rot control
- Fungal rot management
SOIL, LEAF AND MICROBIAL SAMPLING
Soil and leaf samples are taken so your fertiliser programmes can be tailored to ensure optimum nutrient levels and tree health going into winter. Tree deficiencies and poor reserves will lead to declining tree health in winter and poor fruit set in spring/summer.
Ensure soil and leaf samples are taken from the same trees or sites, otherwise you will not have clarity regarding the efficacy of your fertiliser programme, due to the variability from tree to tree (health, crop load etc) – you would not take a blood sample from someone else to see whether your treatment was working. Understanding the microbiological workforce in your soil also helps you understand and improve your nitrogen use efficiency, nutrient availability, Phytophthora suppression and organic matter breakdown. It is worth including this in your testing arsenal, as you can’t manage or improve what you don’t measure. Please contact John, Kyra or myself for further information on microbial testing.
PREPARING FOR SPRING PLANTINGS
If you’re doing new plantings, make sure you have taken soil samples, done your soil corrections and prepared your land well before the planting date approaches. Your new orchard is an investment that will deliver returns for more than 40 years. Getting it off to the best possible start ensures good and early returns and an orchard that will continue to perform well.
Do soil corrections prior to any planting.
PHYTOPHTHORA ROOT ROT (PRR) CONTROL
Crop load, nutrient deficiencies, environmental stresses and the massive demand on reserves for flower development and fruit maturing can make trees more susceptible to diseases and could
trigger noticeable decline in winter as the roots fight the high pressure of Phytophthora during these wet months. Control should not only be chemical, which provides transitory protection, but also cultural, which will create healthier roots that are more resistant to PRR and a soil environment where PRR is suppressed.
Increasing organic matter, with the addition of mulches and composts, will support higher numbers of fungi, bacteria and actinomycetes, as these micro-organisms use soil organic matter as a food source.
You can also drench the soil with products such as Agzyme and Super Hume or Mycorrcin, which will activate and stimulate beneficial soil microbe populations. Soils containing higher percentages of micro-organisms will enhance the biological suppression of Pc.
Composting bark also releases inhibitors as it decomposes, and allows antagonistic soil fungi such as Trichoderma spp. to build up. These fungi protect plants by killing pathogens, such as Phytophthora, and induce resistance against plant pathogens, impart abiotic stress tolerance and improve plant growth, vigour and nutrient uptake. The ability of these fungi to sense,
invade and destroy other fungi has been the major driving force behind their commercial success as biological fungicides and is a key constituent of integrated pest management. Unite
and Trichopel are examples of products containing these ‘bioagents’.
If you’re using chemical control, remember to time your application. Best results are achieved when applied after the summer flush has hardened off and autumn root flush is active. Don’t apply phosphonate during dry weather or when trees are water-stressed. Wait for good soil moisture levels or irrigate well before application to get better uptake. Treatments are always more
effective when applied during periods of active sap flow. During warm or hot weather, treatments should be applied before 10am. If any trees earmarked for phosphonate application are going to be pruned, wait three weeks after application before you start pruning to allow the leaves to draw up the chemical and translocate it down to the roots.
If you choose the injecting method, spread injection sites evenly around the tree, as the chemical only moves to the leaves directly above the injection site, then down to the roots below. Foliar spray application can be used instead of injecting if the trees have sufficient canopy to take up the spray application. Consider monitoring your root phosphonate concentrations by taking samples before and after phosphonate considered the threshold of effectiveness, aim for 40ppm for better persistence. Monitor the health of your trees by using the Ciba Geigy chart and be proactive in managing Phytophthora root rot.
Use the ciba geigy tree health chart to monitor and manage tree decline due to pythophthora root rot.
Autumn signals the start of pruning, which is vital. Pruning controls tree height, improves light penetration into the canopy for improved production and ensures more consistent return crops by balancing the productive and vegetative canopy. Open canopies also ensure better spray penetration and coverage, easier access for quicker harvesting, warmer and dryer canopies for
better pollination and less-favourable conditions for fungal pathogens to germinate, grow, sporulate, and infect fruit. That brings me to the next hot topic…
FUNGAL ROT MANAGEMENT
Fruit quality in the market continues to be an issue for the industry and control starts on your orchards. Growing competition in our export market space means that, to maintain our market share, we need to ensure we grow and supply the best-quality fruit we can. Due to fungal diseases mainly manifesting post-harvest, growers often don’t realise how severe the problem is. As with Phytophthora root rot, control is most effective by using an integrated approach of cultural, chemical/biological and nutritional management tools. Why all three you may ask? There is a valuable tool for anticipating disease emergence called the disease triangle.
Disease results from interactions between a pathogen, a susceptible host and suitable environmental conditions. Changes to any of the three components can accelerate or suppress the disease emergence. Disease management techniques therefore rely on cultural, biological and chemical methods to manage all three aspects of the triangle.
Examples of a conducive environment would be shady and moist orchard conditions resulting from canopied-out interrows, overgrown, closed-in canopies, shaded blocks etc. Here, pruning plays a vital role by ensuring good air flow and sunlight throughout the orchard and enabling canopies and the orchard floor to dry out faster. Keeping shelterbelts pruned also limits unnecessary shading in the orchard. Climatic conditions beyond our control can accelerate the disease prevalence, but ensuring good air movement and drier canopies and orchards is a step we can take.
The severity and abundance of the disease also depends on sources of inoculum of the pathogen in the orchard. To keep this to a minimum you will need to manage orchard sanitation by removing dead or amaged wood in the canopy, mulching or removing all prunings, treating rots or cankers resulting from sunburn, removing windfall fruit from the orchard floor and ensuring good sanitation practices – regularly disinfecting tools and equipment.
Chemical and biological control methods such as copper sprays and bio-fungicides are also used to suppress disease severity. The timing and coverage of these sprays are particularly important to ensure effective control.
A susceptible host is the third part of the disease triangle we need to control. This means ensuring your tree is at optimum health and and nutrition.
A host stressed by disease (Phytophthora), high insect pressure, abiotic conditions (too hot, too wet, too cold, too dry) or nutrient deficiencies is more susceptible to fungal infection.
We also know optimum calcium levels play an important part in disease resistance by strengthening cell walls and making them more resilient to the penetration and infection of the pathogen.
Poor harvest conditions and procedures will also result in higher disease infection, due to damaged lenticels or damaged fruit providing an easy pathway for infection. Ensure fruit is handled carefully during harvest and that it’s not harvested wet or too soon after heavy rain. After continued heavy rains, even though the fruit may be dry, the lenticels may still be turgid and under cellular pressure, resulting in cells that are more prone to rupturing.
Prevention is the most effective way to control fungal diseases. Managing what we can control and being proactive ensures we’re all doing our bit to improve fruit quality in the industry.