[From A Year of Roses
, by Stephen Scanniello, pp. 91-2:] [Thrips are] common to anyone who grows roses in a warm climate or greenhouse... Barely visible to the naked eye, these flying insects scrape the delicate surface of the rose petals with their jaws -- the injury resulting in unsightly brown streaks... [They prefer] light-colored roses... keep your garden free of fallen petals and rose leaves. Before the new larvae become full-fledged adults, they live a short period on the ground, usually in the garden litter of decaying foliage and fallen petals... there are various chemicals available to control them. Whatever you use has to get inside the bloom and soak the soil... [possible choices:] neem oil, pyrethrum-based sprays, garlic juice, diatomaceous earth, yellow sticky-tape traps, and Wilt-Pruf. [See Scanniello for more information.
[From Green Thumb Wisdom: Garden Myths Revealed!
, by Doc & Katy Abraham, p. 120:] The hotter it gets, the hotter an insect gets. When hot weather hits, insect populations explode... As temperatures increase, the time for insects to complete their life cycle decreases... Thrips
, which take 57 days to develop from egg to adult when the air temperature is 54 degrees F (12 degrees C), take only 12 days to complete the cycle when air temperature is 77 degrees F (25 degrees C)...