The Fall Whitefly Decision Every Poinsettia and Mum Grower Faces in September

Young poinsettia and mum crops are going onto benches now, and adult whiteflies are still moving in from surrounding vegetation through vents and open doors. What happens with them this month decides whether a biological program holds through the season or falls behind. Left unaddressed at this stage, populations build steadily through the crop cycle until the program can no longer keep pace on its own.

Why Whitefly Control Timing Matters for Poinsettia and Mum Crops

Silverleaf whitefly is the dominant species on poinsettia, and populations grow fastest on the young, tender growth fall crops are full of right now. Waiting until whitefly numbers are visibly high starts a biological program from behind, since parasitic wasps perform far better against low populations than ones that have already built up. Scouting with yellow sticky cards and checking leaf undersides for nymphs and honeydew from the first week plants are on the bench provides the lead time a program depends on.

Building a Whitefly Biological Program for Fall Crops

Enermix contains a combination of two parasitic wasps, Encarsia formosa and Eretmocerus eremicus, that parasitize whitefly nymphs across different temperature ranges. Encarsia performs best in stable, moderate greenhouse conditions, while Eretmocerus tolerates warmer and more variable temperatures, so together they cover a wider range of bench conditions than either species alone. Both wasps also feed directly on nymphs, adding a second source of control beyond parasitism itself.

For coverage against eggs and early nymphs, Swirski-Mite contains a predatory mite that feeds on whitefly eggs and first stage nymphs while also targeting thrips, adding protection against two pressures at once. Because Swirski-Mite works on the earliest life stages and parasitic wasps work on nymphs further along, combining them covers more of the whitefly life cycle than either product reaches alone.

What to Expect and When to Reapply

Parasitic wasps call for consistent, repeated releases rather than a single application. Adult whiteflies keep reproducing while they are alive, so new nymphs keep appearing even as earlier ones are parasitized. Weekly monitoring with sticky cards shows whether a population trend is flat or climbing, and that trend, not a single count, should guide whether release rates need to increase. A program started early in September, while poinsettia and mum populations are still young, has far more room to work than one started once whitefly numbers are already high across the bench.

Related Articles

Spring Greenhouse IPM: Setting Up Biological Control for Whitefly and Fungus Gnats Before Summer - early season program setup tips for commercial growers.
Tips and Tricks for Scouting in Integrated Pest Management - practical scouting methods for catching pressure early.
Enermix: Encarsia formosa and Eretmocerus eremicus Parasitic Wasp Cards for Whitefly Control - product level detail on the Enermix program.