Rose Leaves are Turning Light Brown with a Lacy Appearance

Something is attacking my roses.   It started with small areas turning light brown and now the whole leaf is a light brown with almost a lacy appearance.

A close look at the underside of the leaves especially at night may reveal the culprit.  You are looking for a translucent green worm-like insect known as a rose sawfly and sometimes called rose slug.  The adult is a fly-like insect that doesn't feed on the plant, just mates and lays eggs for next year's generation.  The worm-like larvae (immature stage) of these insects chew away a layer of the leaf leaving the veins intact.  What's left is clear or turns brown creating the lacy appearance you described. The rose sawfly does most of its damage in the last two or three days of the worm-like stage.   If you can't find any insects, they are probably done feeding.  Though disheartening to the gardener this pest is not life threatening to the plant.  Plus the damage is usually discovered after the insect has finished feeding so no treatment is needed.  If discovered in its early stages and treatment is desired you can try handpicking or spraying the plants with a strong blast of water.  This knocks the insects off the plants and they can not crawl back up to feed.  Or try one of the more eco-friendly products like insecticidal soap, horticulture oil, spinosad or Neem.  Be sure to treat both the upper and lower leaf surfaces. 

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