Why Monitor Avocados
Monitoring is a compliance requirement for export under the AvoGreen© system, which is run by New Zealand Avocado with oversight from MPI (Ministry of Primary Industries).
Q: Why should I monitor as frequently as you recommend?
Our recommendations, and the recommendations of New Zealand Avocado, have been worked out over many years, taking into consideration the cost of monitoring to the orchardist versus the loss from insect damage. Those who monitor according to recommendations are regularly achieving packout’s of 85-95% with little or no insect damage. Those who choose to try and save money and not monitor are achieving a packout of 40-60% with insect damage of 40-60%. If you add up the average cost of monitoring of $1,000 – $1,500 per year and 3-4 sprays per year (because they are timed properly), the cost is little to achieve a payout that is worth having. Lets look at some figures.
If you have an orchard with 100 trees producing 1 bin of fruit per tree that is paying $1,000 (orchard gate price), that equals $100,000 per year. Now take off the cost of monitoring which equals 1 to 1.5 bins of fruit and the cost of spraying at say 2 bins of fruit. Then take off the cost of insect damage, maybe half a bin of fruit (if sprays went on at the right time), you now have 96 bins of export quality fruit left and $96,000 in the bank.
Now if you try and save on monitoring, you will probably have to spray 1-2 extra sprays to get on top of insect infestations, at a cost of $500 plus per spray. That $500 would have paid for nearly 6 months monitoring. From the 100 bins of fruit, take off 40 bins of insect damaged fruit, less the cost of 2 extra sprays, which equals 3 bins of fruit instead of 2. Plus a saving of .5 bin of fruit from less monitoring costs. Your total payout will be for 57.5 bins of fruit – $57,500 in the bank.
In short, saving on monitoring is no saving.
Note: this is an example only and does not include other on-orchard costs.
Q: Why are the thresholds so low and what do they mean?
Pest Threshold Levels are set low to avoid as much insect damage to the fruit as possible. The ideal is to get your fruit to market with little or no insect damage.
A pest monitoring showing pest levels AT OR ABOVE threshold gives the grower justification to spray.
Some insects, particularly Greenhouse Thrip and Six spotted mite, can increase in number very rapidly. Therefore the thresholds have been deliberately set low under the AvoGreen© protocol, so sprays can be applied at the earliest opportunity.
Q: How often should we monitor for Greenhouse Thrip?
Greenhouse Thrip can create large areas of blemish in a very short time. Where Greenhouse Thrip thresholds have been exceeded and no spray has been applied, AvoGreen© best practice requires us to monitor again in 7-10 days. Once you are over the 2% threshold, it is recommended that 2 sprays are applied within 21 days, to deal with newly-hatched Thrip eggs. Thrip can be a recurring problem from mid January until the end of April and often into May.
Q: How frequently should we monitor for Leafroller?
Even where fruit are not touching, small caterpillars can be found under webbing on the stem end of fruit. A great deal of damage can occur between one monitoring round and the next. We strongly urge growers to maintain a fortnightly monitoring routine, even when a spray has been applied, as the pests multiply rapidly in warm conditions.
Q: We have been told there's no need to monitor over winter, why are you suggesting we keep monitoring?
Most insects are less active over winter, but are still there with the exception of Six spotted mite. They like conditions that are a little cooler and tend to increase through the Winter/Spring months, especially if there are low numbers of predators left following Autumn sprays for Thrip.
Six spotted mite feed on the leaves on the trees and can cause leafdrop, which affects the health of the tree for up to 3 years. Leafdrop can occur at any time of year but mostly from late Autumn till early Summer and is associated with high stress levels on the trees, such as dry weather, flowering, heavy fruit load.
It is highly recommended that you monitor 3-4 weekly through the winter months to monitor the Six spotted mite numbers, as well as Leafroller and Thrip, which can both still damage fruit over winter.