There are three pesticides registered for use against the avocado thrips, Veratran-D, Success, and Agri-Mek. Each of these three has different properties which make them advantageous to use at different times in the crop cycle.
Veratran-D is the weakest of the three materials with respect to controlling avocado thrips. It is the only one that is not highly toxic to bees, however, which makes it the easiest to use when the avocado trees are in bloom. It is mixed with sugar and/or molasses which attracts the thrips to the spray droplet. When the thrips feeds on this bait it also takes up the insecticide. This is probably also the least toxic to beneficial insects.
Success was newly registered last year, so we have the least experience with it. So far in groves were we've applied it it has reduce pest numbers to less than 1 thrips per leaf and has held them down for over 5 weeks. This is very good control and should result in very little fruit scarring. We mixed the Success with 2% 415 oil which seems to have improved its efficacy over using Success alone. Success may be a little harder on the beneficial insects than Agri-Mek, but so far it hasn't caused any problems in that area. The caveat with Success is that it seems take about 3 weeks to show the full amount of control it will provide, so it must be sprayed earlier in the season to prevent damage.
Agri-Mek can be applied only under a Section 18 permit (see Pest Control Resources for the Ag Commissioner's number for questions about permit requirements). Agri-Mek has done an excellent job of reducing pest numbers without doing much harm to the beneficial insects. In our opinion it is the best material, but it is also the most expensive.