Poinsettia Pests 2024: Whitefly, Mealybugs and Other Pests

Poinsettia cuttings are here again, and pest issues are already popping up! Read on to see what pests growers in Ontario are seeing, and what to do about them.

 

Bemisia Whitefly Issues

Some years we see relatively few whitefly come in on the cuttings, which generally means biocontrol will be successful all the way through till sale.  Years with heavier pest pressure means you need to be extra diligent with scouting.  If whitefly pressure passes the “tipping point” (talked about in this post), you might need to consider pesticide applications starting in late September/October.

This year I’ve been hearing reports of generally higher whitefly numbers than last year, with whitefly populations especially concentrated in some pink varieties.  So now is a good time to brush up on your whitefly monitoring skills – see here for best management practices when it comes to scouting Bemisia whtiefly in poinsettia.

An 8-inch poinsettia plant with new growth infested with whitefly pupae/nymphs (white spots on underside of leaf between the leaf veins).

Mealybug:

Although this pest used to be rather rare on poinsettia (see this post where I first talk about finding it Ontario), it now seems to be a more regular problem. Citrus mealybug have already been reported in red varieties this year.

The best option at this point in the growing season may simply be to throw out any infected plants. Mealybugs don’t spread plant-to-plant very quickly, since females don’t have a flying stage (slow meandering only for these guys!).  By culling infected plants as soon as mealybugs are detected, an infestation in a relatively short-term crop like poinsettia can often be eliminated.

Citrus mealybug adult, on top of an egg sac with crawlers emerging. Photo by S. Jandricic.

However, systemic pesticides like Beleaf (flonicamid) can effectively control mealybug, and should not interfere with a biological control program for whitefly control. Note that this chemical may cause phytotoxicity in poinsettia if applied more than 1x per crop as a drench.

Thrips parvispinus

Some of you may have seen my previous post, where a grower from Europe gave me a heads up that Parvispinus can attack poinsettia. This has now been confirmed on-farm in Ontario. However, this was a case where the grower had flowering tropical plants in the greenhouse immediately before the poinsettia crop (as opposed to the thrips coming in on cuttings). So far, the damage seems minimal and sprays have not been necessary. But, if you had a Parvi problem in your greenhouse this summer, it might be a good idea to give your poinsettias extra attention when it comes to scouting.

Damage from Thrips parvispinus on poinsettia. Damage mainly occurs on new growth and causes leaf distortion, along with leaf scarring. Photo by Anonymous.

Other issues?

If you’re seeing any other issues in your crop, let me know! You can email me at sarah.jandricic@ontario.ca or leave a comment on this post.