Jeffrey Hahn, Asst. Extension Entomologist
Insects are out in full force in gardens and yards this spring. Are any of these pests at your home?
Aphids are small pear-shaped, soft-bodied insects. They have been reported on roses and red elderberry this spring so far, but will feed on a wide variety of herbaceous and woody plants.
They feed on plant sap with a long, needle-like mouthparts. Plants typically do not exhibit noticeable symptoms when infested by small to moderate numbers of aphids, although large numbers can cause wilting and loss of plant health. There are many natural enemies to help keep aphids under control, especially ladybird beetles. If you are dealing with larger numbers of aphids, try spraying them off with a hard stream of water. If you need a low impact insecticide, consider insecticidal soap or horticultural oil. Fourlined plant bugs have just started to hatch.
They feed on a wide variety of herbaceous plants as well as shrubs and fruit. Look for reddish nymphs now (Photo 1); eventually they mature into greenish yellow insects with four black stripes. When four-lined plant bugs feed, they produce small, round sunken lesions on the leaves. Large numbers can reduce plant health, although in many cases only smaller numbers are present which cause cosmetic damage.
When practical, crush nymphs that your find; you can also spray them with insecticidal soap. You will need a residual insecticide for the adults.
See also, http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/e121plantbugs-forulined.html
There have been several species of sawflies reported recently. European pine sawfly feeds on the old needles of pine especially mugo pine. Columbine sawfly feeds on the edge of the leaves of columbine, sometimes feeding until there is nothing left but the midrib.
Roseslug causes a different type of damage on roses. They feed on one layer of leaf tissue, feeding between the veins. At first, this damage looks kind of lacey, as if something sucked the green out of the leaves, Later these damaged areas turn brown.
Sawflies are no more than 1 inch long when fully grown (foseslugs are just 1/2 inch long), so look carefully for them on your plants.
Once your find them, you can use insecticidal soap, horticultural oil, spinosad or a residual insecticide.