Hopefully my bad attempt at a “Your Momma” joke will get your attention, because this is an important post.
Ongoing research by Rose Buitenhuis’ Lab at Vineland has shown that an incredible number of thrips and spider mites come in on imported mum cuttings. Here’s the scoop and what you can do about it.
To look for pest problems arriving from the U.S., the Buitenhuis team washed mum cuttings imported from Florida and California (supplied by Judy Colley, Plant Products) at 1 day post-receipt and then 7 days post-receipt, to catch any insects that needed time to hatch out.
Out of the 13 batches of mum cuttings tested, 12 of these (i.e. 92%) were infested with either spider mites or thrips (or both), with numbers as high as 76 thrips/100 cuttings (see Fig. 1, below).
What it Means:
Just think – if you import 10 thousand cuttings/week for your mum program, you might be walking almost 8000 thrips straight into your greenhouse each week.
Similarly, you could be bringing in up to 2000 spider mites/week, which can be just as difficult (or even more difficult) to control than thrips.
Can we just chalk this up to a “bad pest season” by the propagators or something? Unfortunately, no, because this is not a new finding. In 2011, student Wendy Romero found similar high numbers of thrips on imported mum cuttings as part of her graduate thesis work.
I say we need to see this as an ongoing threat to our industry, especially considering both these pests are likely arriving with a high degree of resistance to pesticides.
So what to do?
The only way to really protect yourself is to ASSUME YOUR CUTTINGS HAVE THRIPS AND SPIDER MITES – LOTS OF THEM – and that they are already resistant to all chemical control options.
Echoing last week’s post, this means starting preventative biological control programs immediately. This includes dipping cuttings as soon as they come in the door to remove thrips/spider mite larvae and adults, and releasing biological control agents right on the rooting bench to catch the “newborns” right away. Bios should be continued out into the crop until finishing, since petal damage can occur quickly.