Whitefly have been building for several weeks and are at high levels in some areas. Insecticide options for whitefly have not changed a great deal in the last year.
The cornerstone chemistries for whitefly are still the Group 4 (Venom, Assail, Actara, Sivanto and pre-mixes containing these prodcuts) and Group 28 (Coragen, Verimark, Exirel) insecticides, with some exceptions. Both of these groups appear to be providing 2 to 3 weeks of control when put in the root zone and picked up by the plants. If applied foliarly, I would expect about one week of activity. If you are using drip irrigation and the plants are small and several inches away from the tape, you can push the Group 4 products out to the plants with water. The Group 28 products do not move as readily in the soil and need to be placed in the root zone.
I have had poor results with Admire Pro for three years. Don’t know why, but resistance appears to show up with this specific product before showing up in the rest of the group. This should tell you to rotate IRAC groups. Coragen is working in my tests this year, but has become less consistent in the last few years. Again, rotate IRAC groups.
My personal opinion is that the growth regulators, Knack and Courier, are your first choice for rotation partners. These two products are not first line choices if you have allowed whiteflies to establish in a field and need to knock them back. Both perform well if used early in an infestation or as rotation partners when multiple applications are needed.
Other products that have activity on whitefly and can fit into rotation programs include Movento, Sefina, PQZ and similar products. I do not have as much experience with these products, but they can provide good activity and a different mode of action for rotation partners. I am working more with this in current studies.