what is my best control for whitefly while bracts are developing? I had applied Marathon, but I'm, not seeing the results.

I had the same problem with Marathon a few years ago when the whiteflies developed resistance. I have to use a rotation of chemicals: Orthene, Sanmite and Tristar along with pyrthroid and IGR total release fumigants. The Tristar seems to have the most effect on whitefly numbers.

Thanks for responding. Did you spray when the brachts were coloring?

Hi Jotto -

Now when we are so close to finish it is hard to rely solely on a chemical that is applied as a drench because it takes some time for the systemic activity to work. Chemicals that are applied as a foliar spray are usually faster working at this stage in the crop.

For late season control we have had good success with a tank mix of Talstar and Avid (could also use Tame/Orthene) followed by Tristar (could also use Safari). We haven't had any issues with damage to the bracts and spotting or residue. We also get a really good kill.

There are some documented cases of Marathon resistant whiteflies. Marathon is also not the best choice right now because it takes several days before you see results. Also as the plants near finish their growth rate slows significantly affecting how fast the chemical is moving through the plant and it is hard to get enough translocation of the chemical to the lower foliage. The clock is ticking right now and you obviously don't want to send whiteflies out the door with your plants, for this reason we like to choose a chemical that controls all stages and has contact activity.