A visit to the West Washington Park community garden reminded me of several things. The first was how much the heat island effect of city centers has on advancing the season. Their gardens are about a week ahead of gardens in the outer parts of Denver due to the warmer temperature.
Second, early season insect pests are becoming active, foremost among them flea beetle. Germinated beans were already showing holes (photo above left) and upon closer examination, the shiny hopping beetles were present (palestriped flea beetle photo below).
Not only beans but tomato family and cabbage family plants are attacked among other vegetables. Watch young seedlings closely and take action before damage becomes too extensive. While mature plants can withstand some 10 to 20 percent loss of leaf tissue with no adverse affect, seedlings are another matter.
Trap crops such as radish are one good idea. Diatomaceous earth is an effective repellent, and several insecticides including the bio-derived spinosad are effective. Weekly reapplications are often necessary as new plant growth will be unprotected and insects are very mobile. For more photos and control recommendations, see the Colorado State University Extension Flea Beetles fact sheet.
The third reminder I received from my visit is to involve children in your vegetable gardening efforts. Now that school is out, choose age-appropriate garden activities for children and youth, whether they are yours or your neighbors. They will be the richer for early involvement in the garden and receiving the benefit of your presence in their lives.
Flea beetle damage on bean seedlings, Carl Wilson
Palestriped flea beetle close up, Frank Peairs, Colorado State University, Bugwood.org
Children’s toys among beet seedlings, Carl Wilson