A pest has decimated all Baptisia australis at Oak Hill, defoliating them to the point that I cut them down to the ground. I was told that the dusky wing and sulfur butterflies feed on them, so my natural reaction was to wait, let them move onto their chrysalis and finally fly away as pretty adults. After no end in sight to the numbers and damage from these feeding caterpillars, I did some research.
The culprit is the genista broom moth, completely new to me. A native of North America, although usually found in the southwest where its favorite food is the Texas mountain laurel or Sophora secundiflora. Feeding on members of the bean family, it will go after other garden plants including lupine, thermopsis, crape myrtle and honeysuckle.
Reports of damage to baptisia are reported as far north as Minnesota, which has never happened before. Of course the probable reason is the weather, specifically the mild winter. Since baptisia is one of my favorite plants (it is a native and thrives in stressfull times), I hate that a pest has discovered it.
If you find that your baptisia has been raveged this summer, look for the inch long caterpillar. At this point they are towards the end of their cycle and organic sprays like BT (Bacillus thuringiensis) won't help much. Hand picking is an option, ugh. Cutting them down is certainly another choice, since the plants had barely any foliage, it was my decisi0n. Sprays like Sevin will work, although do not spray it anywhere near bees or open flowers that they visit, it is deadly for them.
Many of us will be keeping an eye out next summer, hoping this southern traveler doesn't return. Another pest of mugo and deodar cedar has returned for a late summer feeding, the conifer sawfly. It's rare to see it feeding after June, so be ready to remove or spray for them. Since it's actually a wasp, BT won't work. A natural insecticide is Spinosad, chemically Sevin will work. The damage is often on the leader, so your tree's shape is dramatically altered, which can take years to correct.
Show Update:
In 9 days my featured artist show at Lorton will come down. If you have not seen it, you still have 2 weekends. For those of you that have purchased pieces... Thank-you!
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