Saturday, May 31, 2014

Cabbageworms are Camping at the Cahill's

Yep, got 'em, the little light green cabbageworms (pieris rapae) on the undersides of my broccoli plants.  These guys aren't really worms, they are the larvae of butterflies who feed on cole crops - including cabbage, broccoli, Brussels sprouts, collards, kale, mustard greens, cauliflower, radish and turnips. There are usually three generations of outbreaks each growing season. 
Cabbageworm gaping leaf damage!
Here's the cycle...the mamma butterfly, whitish with feint black spots (up to four) flits easily around the early spring garden and yard looking for a landing pad for her eggs. Many people are happy to see these early spring butterflies, not me.  I know how quick they are to lay their eggs on any host plant in the area. They deposit an egg on a leaf faster than you can swat a fly, it's a drop and go routine. The eggs are yellow and bullet-shaped and hatch in 3-5 days. They immediately start feeding on the leaf where mamma put them. Notice the small chew holes which will get bigger and bigger over time (days) to the point where you'll see a huge gaping piece of leaf missing (leaf above). Later they'll tunnel into the head of the crops and do more damage.
 
There he is munching away, leaving holes

Scout your plants often and check under the hood - the under sides of the leaves, this is where you'll find the trouble.  Squish the eggs if you're a good scout (have your hand lens with you or your readers close by). If they are already middle schoolers (green larvae stage), then pick off and squish at this size. Some gardeners dust their cole crops with while flour (under sides too) so that the larvae eat the flour while eating the leaf, then bloat too much and die with a very full stomach.  Red cabbage seems to be less susceptible than green, but both broccoli and cabbage are their favorite cole crops.

They have several natural predators including ground beetles, paper wasps, spiders and parastic wasps. They drown easily from heavy rains or overhead watering.  Use chemical controls as a last resort, try Bt (Bacillus thuringiensis) first, more http://www.ext.colostate.edu/pubs/insect/05556.html

Close Up
 





 

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