Expert: Long Island Gardener - 5/1/2007

Question
I have five rose bushes.  Two of them (JFK especially and one other I'm not of the name, it's a beautiful red rose) well, the have gotten brown edges on the the buds before opening, they are slow to open up and the petal edges are brown.  What's happening?  I live in Southeast Texas close to Beaumont, TX.  

Answer
The Thrips are at it again.

Thrips are tiny insects that come in different colors, barely 1/25th of an inch long, in Yellow, Brown or Black.

I've never met a Thrip that could resist a juicy Rose.  Petals are completely twisted and bent oddly.  Damaged flower parts turn Brown and dry up.  Buds are especially attractive, Thrips wiggling in the closed petals and burrow down into the center, deformed and unable to open.  Because they hide so well, these are very hard to control.

Insecticidal Soap is your first weapon.  Safer makes a convenient spray bottle.  Spray and spray.  You can buy this online (http://www.saferbrand.com/index.htm) or at your local garden center.

Backup:  Yellow sticky traps.  You can buy them as Whitefly Traps, but they work equally well on any flying insect.  Hang from leaves and place near Roses.

You can also make your own.

You'll need YELLOW cardboard or index cards, a few Paper Clips, a pair of scissors, a paintbrush and something called 'TANGLEFOOT', which is used to keep pigeons off of urban roofs and windowsills.

Cut an index-card-sized piece of the Yellow Cardboard.

The cards MUST be yellow.  White, Black, Orange, Blue, Green are NOT YELLOW.

Paint the Tanglefoot on the Yellow Cardboard/Index Card.  In the middle, punch a little hole and thread it with a Clip, then hang it off a branch.

It should be hanging near the soil.

That's where newly hatched Fungus Gnats pop and jump all over the place.  There will be dozens stuck to your card in no time.

As long as you are finding Thrips on the sticky trap, keep spraying the Roses with the Safer soap.

There are natural predators for serious infestations.  This early in the season I don't think you have to worry about that.  Ladybugs are always nice to invite for dinner.  They love so many things we also love to hate.  But you can't use them if you are spraying Safer soap on the flowers.  Choose your weapon.

If things don't improve, write back and I'll tell you where to get more bugs that LOVE to eat thrips.  The Safer would have to be put in storage so you don't kill expensive beneficial insects.

Good luck.  Thanks for writing.  Keep me posted.