If you’re a football fan, you understand that no coach heads into the fourth quarter without a plan. Late-season whitefly control in poinsettias requires the same type of proactive planning: Be ready to deploy your best players in a manner that will provide the greatest benefit. Factors affecting player choice for late-season whitefly control include bract safety, pest pressure, and previous product use. Rotation is critical to avoid development of resistance.
Hopefully, a successful whitefly control plan was implemented early in the crop, whether it’s chemical-based or a plan based on biological controls (BCAs). Either way, if whiteflies were well-controlled early, late-season outbreaks are greatly reduced and much easier to manage. Ensuring this success requires diligent scouting and a quick response to increasing pest pressure.
Growers using BCAs should continue to release wasps through shipping to maintain control. Eretmocerus eremicus provides more aggressive and complete control of whitefly species than does Encarsia formosa, but Encarsia can work well if the only whitefly species present is correctly identified as Trialeurodes, the greenhouse whitefly.
For growers relying on chemical control of late-season whiteflies, the first step in planning is to consider bract safety. When applied properly, the following products will not harm bracts: Flagship, Judo, Kontos, Rycar, Safari, Sanmite, and TriStar.
Know Your Pest
Next, consider the pest. Bemesia whitefly occurs as two biotypes, B and Q, which are indistinguishable by physical appearance. The Q-biotype is known to be resistant to some important whitefly products. If you experienced failures in control earlier in the season when using Distance, Fulcrum, Talus, or Sanmite, you have higher odds of having Q-biotype whiteflies present late. If this is the case, avoid the use of Sanmite for late-season control.
Rotate Your Chemicals
Finally, plan your application to provide rotation across modes of action (MOAs). Remember that a spray application following an early- or late-season drench must provide a rotation away from the drench MOA to ensure control. Chart 1 outlines outlines sound rotational choices. As you progress to the right in the chart, choose from one product in a subgroup if more than one option is listed.
One last thought about late-season control of whiteflies in poinsettias: The tight canopy makes control difficult. If possible, plan a drench of an upwardly systemic product to cover the later part of the season. Also, consider applying chemicals via a fogger for better contact, and look to translaminar products to help improve pest exposure.