Vinca and geranium bloom problems - Ask Extension
The blooms on our vinca and geranium plants are not doing well, even though the plants appear to be thriving. Plants are in deck rail planters and ha...
Knowledgebase
Vinca and geranium bloom problems #653904
Asked June 21, 2020, 9:52 AM EDT
The blooms on our vinca and geranium plants are not doing well, even though the plants appear to be thriving. Plants are in deck rail planters and have morning to mid day sun. The vinca blooms have white spots and streaks on the petals and are shriveling. Sometimes there are tiny white insects on flowers. The geranium blooms are shriveling and turning brown before opening. Other plants are doing well (lantana, begonias, calibrachoa, New Guinea Impatiens). We have used Neem oil on them. Please advise on how to handle this problem. Thank you! Joan Alexander
Howard County Maryland
Expert Response
Hello Joan,
You may be experiencing damage from thrips, a type of insect that feeds on plant juices and can often be found in flowers and cause this kind of damage. If you take a piece of paper (light or dark), you can tap the flowers sharply over it and see if any thrips fall onto the paper. (Thrips can be pale yellow or black, so you can try it with two different pieces of paper if need be.) They can jump, but will fall onto the paper before trying to escape. You'll be looking for something about as skinny (and slightly shorter) than the letter "I" on a computer keyboard.
https://extension.umd.edu/hgic/topics/thrips-flowers
Neem requires good coverage of all plant surfaces to work well. Since the flowers are tightly wrapped in their buds, thrips can persist there unaffected. You can try switching to another low-impact insecticide, spinosad, which has slight systemic affects (can be absorbed into some plant tissues). Good coverage will still help, but not be as critical. You can also disbud the plants - clip off all the current open and budded flowers - to remove most of the thrips and to force any left to forage for more food, which should make them more exposed to the treatments as they wander around. The plants should regrow new flowers fairly quickly.
Miri
You may be experiencing damage from thrips, a type of insect that feeds on plant juices and can often be found in flowers and cause this kind of damage. If you take a piece of paper (light or dark), you can tap the flowers sharply over it and see if any thrips fall onto the paper. (Thrips can be pale yellow or black, so you can try it with two different pieces of paper if need be.) They can jump, but will fall onto the paper before trying to escape. You'll be looking for something about as skinny (and slightly shorter) than the letter "I" on a computer keyboard.
https://extension.umd.edu/hgic/topics/thrips-flowers
Neem requires good coverage of all plant surfaces to work well. Since the flowers are tightly wrapped in their buds, thrips can persist there unaffected. You can try switching to another low-impact insecticide, spinosad, which has slight systemic affects (can be absorbed into some plant tissues). Good coverage will still help, but not be as critical. You can also disbud the plants - clip off all the current open and budded flowers - to remove most of the thrips and to force any left to forage for more food, which should make them more exposed to the treatments as they wander around. The plants should regrow new flowers fairly quickly.
Miri
