(Update courtesty of Joseph Morse and Frank Byrne, Department of Entomology, UC Riverside)
As growers and pest control advisors plan their arthropod (insects and mites) pest management program for 2014, it is suggested they consider not only the economics and practicalities of producing a sound crop in 2014-15, but also the consequences of pesticide resistance that would make pest management problematic in the future.
The avocado industry has been using abamectin heavily since it was first made available under a Section 18 Emergency Exemption from 1999 through 2004. After 15 years of heavy use, we now occasionally hear reports of either avocado thrips or persea mite control not persisting as long as it used to after an abamectin treatment is applied (research is in progress to investigate this low level resistance). Abamectin is a unique product and losing it to pest resistance would make avocado arthropod pest control quite difficult in future years.
Once abamectin received a full registration in 2005, efficacy research shifted to focus on finding pesticides in other classes of chemistry that could be used for either avocado thrips control or persea mite management. All of the pesticides listed below are in different classes of chemistry from each other and from abamectin with the exception of Movento® and Envidor®, which are both in IRAC Class 23. Note that the UC Pest Management Guidelines have been updated to list recommendations for all of these chemicals.
Avocado thrips control
- Delegate® (2007)
- Danitol® (2010)
- Movento® (2011)
Persea mite control
- Danitol® (2010)
- Envidor® (2010)
- Zeal® (2012)
- MiteusTM (2013) (MiteusTM is the same active ingredient as Fujimite®, which is the citrus version of the chemical).
We still have more to learn about how to best use the alternatives to abamectin and what their spectrum of activity is against other pests and natural enemies on avocados. We now have data suggesting that Movento® treatments can be quite effective in controlling avocado thrips, but pest control advisors need to continue to test the best timing of treatments. Movento® is not active until after plant uptake and the in planta metabolism converts the pesticide to the active form, spirotetramat-enol, which is highly systemic (moves down to the roots and them back up to plant tissues with only very low levels going into fruit). Research in 2013 suggests that Movento® is NOT active in maintaining persea mite at low levels.
Veratran DTM recently received OMRI certification so it is a product that can be used in rotation with Entrust® for control of avocado thrips on organic avocados. Organic growers should be careful not to over use either Veratran DTM or Entrust® to avoid avocado thrips’ resistance. Unfortunately, there are limited options for control of persea mite on organic avocados – just organically-approved oils or sulfurs.
In order to reduce the potential for pesticide resistance, we suggest the following:
- Danitol® should not be used more than once every three years (pyrethroid resistance has the potential to develop quickly, in part because Danitol® is quite persistent)
- Abamectin should not be used more than once every two years (in part because it has been used so much in the past), and
- Delegate® , Movento®, Envidor®, Zeal®, and Miteus™ should not be used more than once a year.
Because Danitol® and abamectin are effective against both avocado thrips and persea mite, it is essential to avoid resistance development to either of these products. Growers may be tempted to use abamectin more than once every other year because of its low cost and known efficacy against both of these avocado pests, but we strongly advise against this. Abamectin should never be used twice in the same year (if used in the spring for avocado thrips control, do not use it in the summer to manage persea mite).
Delegate®, Movento®, and Danitol® are highly effective against avocado thrips and are good materials to rotate with abamectin in alternate years. Danitol® is an excellent choice if persea mite is also present. For summer or fall persea mite treatments, we suggest Envidor®, Zeal®, or MiteusTM be used, reserving abamectin and Danitol® treatments for avocado thrips control.
Hoddle, M.S. and J.G. Morse. 2013. The Persea Mite Invasion into California: History, Biology, Management, and Current Status. California Avocado Society 2012 Yearbook 95: 106-136.
Morse, J.G. and M.S. Hoddle. 2012. The Introduction of Avocado Thrips into California: History and Current Status. California Avocado Society 2011 Yearbook 94: 137-174.