some products can drop the pH too low (destroying the viability of the chemical) and others may not hold the chemical solution at the correct pH for long enough. Agribuff and Primabuff are examples of two products that do buffer pH in water correctly. • Water hardness (water high in Mg & Ca ions) will also reduce the efficacy. Mg 2+ or Ca 2+ will bind to two Glyphosate - ions, directly reducing the amount of active Glyphosate in the tank mix. The addition of Ammonium Nitrate to hard water will allow the NH 4+ to bind to the Glyphosate - ions (while still allowing plant uptake) leaving the NO 3- to volatilise. • Water turbidity needs to be addressed as both Glyphosate and SpraySeed will bind to soil particles in water, again reducing the active amount of chemical in the tank mix. • In order to minimise any coverage problems in either a foliar or herbicide application, a tip is to alternate the direction of travel down the row each time an operation is carried out. Instead of starting at the same point in the orchard and travelling down the row in the same direction each time, alternate the direction of travel. The feedback from participants in all the workshops was the information was practically informative and able to be easily integrated into their daily practices. It is important to remember to conduct some of your own trial work when changing from current practices. This will allow an accurate assessment of what works and what does not.
• The mode of action of herbicides and the way they react to the surrounding conditions. Glyphosate is best applied when there is good plant uptake i.e. sunny daytime weather. When Glyphosate is applied at night, the rain fast period needed is extended until the next morning and therefore subject to rain or dew affecting uptake. SpraySeed is best applied during overcast or shady conditions. The presence of direct sunlight will cause the ingredients to be activated. In overcast or dark conditions (at night) the chemical will have more time to enter the plant tissue before it’s activated, hopefully resulting in a better rate of kill. Be careful when spraying at night to avoid inversion layers that can result in off-target crop damage. • Delta T is still important when choosing when to weedicide as it’s an indication of droplet longevity. It is also important to consider the presence of inversion layers. Wind conditions may drop in the evening - early morning and the Delta T may be favourable but if it is too calm, an inversion layer may exist causing off- target crop damage. • Craig stressed the importance of getting water quality correct i.e. water hardness, high pH and high water turbidity. Since most growers are using higher rates of water/Ha, any problems with water quality will exacerbated. • Glyphosate’s effectiveness is best at a pH of 3.5, with a pH of 7 or above reducing the efficacy. Even rainwater will need to be buffered for pH. Care should also be taken when choosing which product to use for buffering pH as
The remaining two ‘Don’t Be a Drifter’ workshops were held in Griffith and Angle Vale on the 14 th and 28 th , November respectively. Once again the workshop was presented by Craig Day from Spray Safe and Save. Craig covered the same topics as the first two courses held in 2010 but also added some new and up to date information. The information presented aimed to encourage attendees to review their application methods and modify them when greater efficiencies could be achieved. A number of new key points were raised during the workshops and are summarised below: • Most herbicide labels now recommend specific water rates and nozzle selection e.g. Glyphosate labels recommend a nozzle producing coarse droplets and water rates of 80 to less than 200L/Ha. • Some herbicides are formulated with enough wetter up to a maximum water rate. Above this, extra wetter should be added e.g. PowerMAX has enough wetter up to water rates of approximately 70L/Ha and should have extra wetter added if the water rates are higher. SpraySeed has enough wetter up to water rates of 200L/Ha but beyond this, extra wetter should be added according to the label. • Care should be taken when adding wetters. Don’t add oil based wetters to most herbicides. Oil based wetters, especially when using Glyphosate and air induction nozzles, will exclude air from the chemical droplet and therefore alters the way the droplet lands on the target and its effectiveness to enter the plant. Non-ionic wetters are best to use.
Left, Below & Right: Images from the recent ‘Dont Be A Drifter Courses conducted in Griffith and the Adelaide Plains
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