The appearance of flies on jasmine (Jasminum oficinale) is most often fungus gnats (Bradysia). They thrive in moist soil and decaying potting soil matter on most houseplants, the Colorado State University Extension says. Reduce the potential for fungus gnats by letting soil completely dry between waterings.
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Lisha Smith writes for several blogs and has freelanced for six years. She has a Bachelor of Arts from UNC-Greensboro in psychology. Smith has self-published several books. Her areas of experience include gardening, cooking, home improvement, pets and mental health.