Welcome to the Autumn edition of Horticulture Bites. In this edition we cover the following topics:
The Importance of Effective Spray Application | Spraying Brushweeds in or Near Horticultural Properties | Spray Plans
Harvest has finished for most key permanent crops such as pipfruit, kiwifruit, winegrapes, stonefruit, etc, with reports of good yields and quality. The crop export returns for kiwifruit and pipfruit have started positively and hopefully these will continue to maintain a premium for rest of the selling season.
While the period after harvest is a great time for a well-deserved break, it is also a great period to take time to reflect on the growing season. Analysing the yields and packouts, as well as revising notes on the season, can help identify the causes of ‘profit-limiting’ issues which may have arisen e.g. pests, diseases, excessive competition from weeds, physiological disorders, etc. You can then start to identify where improvements can be made to overcome any issues for the next growing season. Reviewing the spray and nutrition programmes in relation to weather events to see if there were ‘gaps’ in these which may have impacted on the season’s performance is also worthwhile.
The Importance of Effective Spray Application
While product selection, application rates and application timing are very important in achieving effective crop protection, so is the sprayer performance. Factors affecting spray application performance include; sprayer type, mixing/agitation, nozzle selection/adjustment, pressures, water (spray) rate, travel-speed, air-assistance adjustments, weather conditions, target size and density, etc. These all play a vital part in getting the right amount of spray onto the target which is vital for effective crop protection.
Many of the sector groups have dedicated field days on effective sprayer setup and performance and I encourage all managers and spray operators to attend these. I attended a fantastic Field Day put on by NZ Apples and Pears in Hawke’s Bay where the focus was on the importance of adjusting the amount of air assistance of sprayers to ensure that air was carrying the spray onto the target. Various sprayers were demonstrated and the strengths and weaknesses of each were highlighted. The use of water sensitive papers to check spray depositions is a great way of checking spray coverage.
Air Assistance - The key takeaways are:
1. A well-adjusted airstream from air-assisted sprayers is critically important to get the spray into the canopy and onto the target. Too much air can blow much of the spray through the canopy and past the target, while not enough air (especially at the tops of the canopy) will result in the spray not reaching the target. A spray that does not hit the target at the required dose will not work!
2. Adjust the air direction and volume to allow the spray to evenly penetrate all parts of the canopy.
3. Adjust the air direction and volume during the season to account for the changing density and height of the canopy.
4. Operators must monitor for changing conditions while spraying, as a sprayer operating well in still conditions, will no longer operate efficiently if the wind picks up. Monitor and adjust the sprayer according to the conditions, or if the wind is too high, then stop spraying.
5. Higher travel speeds result in less spray coverage.
Train operators in what to look for in a high-performing sprayer. Several times I have walked into vineyards and orchards and observed issues that should have been picked up the spray operator, including blocked nozzles, poorly directed nozzles, too little or too much air assistance, too fast a travel speed, poor weather conditions, etc.
Figure 1. A demonstration of the airflow from an axial fan sprayer.
The plastic bottles are weighted with a small amount of water and placed at different positions from the sprayer fan. As the sprayer drives past, the bottles demonstrate the strength and direction of the airflow. Note that most of the bottles low down and closer to the fan have blown over, while the bottles near the top of the tree height have not.
Figure 2 & 3 – The photo on the left shows a tower sprayer (tangential fan) pushing spray out evenly on both sides. The photo on the right shows the effect of a light breeze affecting the output on the left hand side, as viewed on the photo (the right hand side of the sprayer). This highlights the importance of adjusting the air output for the wind, or if the wind gets too high, then stop spraying, as the spray is not hitting the target and if spray does not hit the target, then it cannot work!
I have mentioned the www.sprayer101.com website before in my newsletters, as it is a great resource with current articles all about sprayers, sprayer setup and spraying technique and is well worth a read.
Winterizing Sprayers
Given that the sprayers will shortly be parked up for the winter, the following article from the Sprayer 101 website on how to ‘winterize’ your sprayer is also helpful, so that it is ready to go for the new season. Incorrectly ‘winterized’ sprayers subject to frost can result in cracked pumps which is very expensive!
Spraying Brushweeds in or Near Horticultural Properties
This time of year, I get a few calls about the use of brushweed herbicides to control the likes of gorse, blackberry, broom, etc, in or close to horticultural properties. Brushweeds are typically harder to control compared to other weeds and require special brushweed herbicides such as Tordon® Brushkiller XT or Grazon®.
It should be noted that best results for spraying brushweeds are while the plants are still actively growing, so spraying should be done before it gets too cold or stressed.
Potential Off-target Damage of Brushweed herbicides.
Due to the residual nature of some brushweed herbicide active ingredients, it is important to understand how off-target damage can occur to prevent this from happening.
Off-target damage can occur via one or more of the following:
1. Physical Droplet Drift – Occurs when spray droplets move off target onto desirable plants. Information on preventing drift can be found on the following link:
Droplet drift of herbicides caused by inversions can also cause serious crop injury, so always apply these products in the ideal spraying conditions, using sprayers setup for reducing drift.
2. Volatilisation/Vapour Drift – ‘Volatile’ herbicides can form a gas after spraying and be carried for large distances (sometimes kilometres!) off-target to affect susceptible crops. There are several pasture herbicides that are considered ‘volatile’, e.g. 2,4-D Ester. The formulation can influence volatility too, for example Ester formulations are more volatile than an Amine formulation. Most brushweed herbicides are considered non or low volatile. Also, Grazon and Tordon Brushkiller XT are both EC (emulsifiable concentrate) formulations and while they are considered low-volatility, application in warm temperatures during spring could cause some volatilisation of these herbicides and appropriate care should be taken.
3. Environmental Factors – Conditions favouring the formation of an ‘inversion’ could result in off-target drift of herbicides. For more information, refer to the following links:
4. Soil Movement – Some active ingredients of brushweed herbicides are residual in the soil. These ‘actives’ can move over soils (wash off) and/or through the soils (laterally and/or downwards), especially after rainfall or irrigation. Be cautious of any potential for surface runoff or movement within the soil, especially if applying these herbicides on a slope that could runoff onto the crops below. Please contact your Corteva representative for more guidance on the use of brushweed herbicides in specific situations.
Spray Plans
Post harvest is also a great time to review your Spray Plan. Whether you do it yourself or work with a spray contractor, discussing the spray plan helps both parties understand each other's needs and expectations. Ensure details are accurate and current for timely notifications to neighbours and efficient planning and execution of spraying activities.
Update and check
· Update neighbours contact details to ensure accurate notifications.
· Review and update your Spray Plan including proposed sprays and sensitive areas.
· Check spray operators have the required certifications and training.
· Calibrate sprayers for accurate application rates.
Communicate any updates to all sprayers to ensure everyone is aware of the latest version of the Spray Plan.
Find the Spray Plan Procedure
Please get in touch if you require additional information or training.
Regards
John van der Linden
Technical Specialist – Horticulture
M: +64 27 4080 777 | E: john.vanderlinden@corteva.com | W. www.corteva.co.nz
