Late production and the whitefly “tipping point” in Poinsettia

It’s that time of year again when problems early in the crop may have caught up with you. This includes root rots, Lewis mites, and Bemisia whitefly.

Now, you’ll be forced to make a choice with your poinsettia crop. Do you stay the course with a biocontrol program? Or spray for pests? And, as always, the question is, “spray with WHAT”? This post has tips on pest management decision-making when it comes to common poinsettia problems in October.

Bemisia Whitefly Issues
Some of you may be familiar with the “whitefly tipping point” I’ve referred to in several blog posts and articles (see this issue of Greenhouse Canada Magazine). Essentially, this is when growers have to decide whether or not to switch to chemicals for whitefly control so they can end up with a clean crop. Switching to pesticides later than the first two weeks of October may mean you don’t have time to get on top of your whitefly population if repeated applications are needed.

The general rule of thumb is that if MORE than 20% of your crop is infested with whitefly (using presence/absence sampling) in the first week of October, you should switch to chemicals. This is based on sampling at LEAST 100 plants, or 5% of your crop.