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IF you see brown edges on your rose blossoms, and the buds only partially open or don't open at all, suspect thrips. These insects attack buds in their early stages, working among unfurled petals. The buds become deformed and fail to open properly, and the damaged petals turn brown and dry. New growth also can be damaged, in the same way.
Roses are vulnerable to flower thrips (Frankliniella tritici) and tobacco thrips (F. fusca). The adults are tiny, slender insects, i/15 inche long, and may be pale yellow, black or brown. They have four narrow wings fringed with long hairs, and their legs are very short.
Since thrips burrow deeply between the petals, early identification and control is important. Set out yellow sticky traps about 4 weeks after the last frost. as soon as you spot thrips on the traps, spray your roses with insecticidal soap every three days fro 2 weeks. Commercially available predatory mites, lacewings, ladybugs are effective backup to the soap sprays. Thrips prefer a dry environment, so make sure plants are adequately watered.
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