Rose Slug - Rose Sawfly
Lacy leaves that eventually turn brown on roses may be a clue that rose slugs, actually a sawfly, are dining on your plants.
A close look at the underside of the leaves, especially at night, may reveal the culprit. Look for a slimy green worm-like insect that looks like, but is not a slug or caterpillar. Often the insect has finished feeding and moved on by the time we notice the damage.
Though the damage is disheartening to the gardener, it is usually not life threatening to the plant.
Natural predators, virus and disease help manage their populations.
If you discover rose sawflies early and treatment is desired, try picking them off by hand. Or knock them off and kill them with a strong blast of water to both the upper and lower leaf surfaces.
Eco-friendly products like insecticidal soap or horticulture oil will also provide control.
A bit more information: The adult, fly-like, rose sawfly doesn't feed on the plant. It just mates and lays eggs for the next generation. There may be one, two or more generations per season depending on the type of rose sawfly.
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