Flowers turn brown or have brown spots on them . Flowers are damaged . They may have holes in them. Flowers are smaller than normal . Not flowering .
Plant growth is slow .
Visible insects . The most common species is yellow, but they may also be brown or black. Because of their small size, you may need a magnifying glass to correctly identify them. Some advise using Malathion to treat Thrips. This may be effective on some species of Thrips, but the most common species is resistant to Malathion.