On Jul 24, 2006, Joan from Belfield, ND (Zone 4a) wrote:
The crucifer flea beetle is a non-native insect pest that accidentally was introduced into North America during the 1920s. Phyllotreta cruciferae now can be found across southern Canada and the northern Great Plains states of the United States.
The adult is a small (about 1/32 to 1/8 inch), oval-shaped, bluish-black beetle with numerous dimples on the wing covers. The whitish larva is wormlike and approximatley 1/8-inch in size, with tiny legs and a brown head.
The crucifer flea beetle has one generation per year. Adult flea beetles overwinter in leaf litter of shelterbelts and grassy areas. They emerge from the overwintering sites during early spring as temperatures reach up to 57 F.
Overwintered adults feed on seedling cruciferous host plants. Summer adults feed on the pods of canola, mustard and cruciferous weeds.
Volunteer canola and wild mustard are usually the first available host plants, with the beetles moving into the new canola fields as the crop emerges. Overwintered adults are usually active in the fields until late June, feeding on the foliage and depositing their eggs in the soil. The larvae can be found in the root zone of host plants during June and July. The pupal stage occurs from early to mid-July. The new generation, or summer adults, are present from late July to early September. They can be found feeding on the pods of canola, mustard, and cruciferous weeds. The summer generation will move to overwintering sites in early fall.
On Jun 18, 2007, White_Hydrangea from Aurora, CO (Zone 5a) wrote:
I lost my brassica to them last year, and I'm losing my melons to them this year. They swarm over the plants so thickly that the plants look black. I've yet to find anything that would get rid of them.
On Jul 7, 2007, RckyMntGrdnr from Wellington, CO wrote:
What a way to find out that the precious little alsyum seeds I have been nurturing all spring were members of the mustard family!
They were just getting to the point of flowering when this little bugger, the Flea Beetle showed up. Now they are just a pitted, sagging mess.
Not finding a lot of info on how to get rid of them. They are a big problem in canola fields but it looks like all the control methods are either for big commercial farms or are preventative in nature.
On Aug 6, 2008, Wellreadfellow from Denver, CO wrote:
I had a huge problem with them last year. They destroyed the young broccoli and collard green plants before that were more than 6 inches tall. This year, they attacked the plants when they were much larger. They seem to have left the garden for the moment. But, I am sleeping with one eye open, and awaiting their return. Like others here, I have not found an effective way to eliminate them. If anyone does, please inform me. Thank You