Cone flowers - Ask Extension
Hello. This is the 2nd year of my native garden and the cone flowers don't look good. They are loosing or not producing petals. I found several possib...
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Cone flowers #877699
Asked July 17, 2024, 5:39 PM EDT
Hello. This is the 2nd year of my native garden and the cone flowers don't look good. They are loosing or not producing petals. I found several possible causes on line including eriophyid mites, aster yellows, and stress. They are in full sun to around 4 pm.
I've tried putting diatomaceous earth around them at the base with no noticeable changes. They do need a lot of watering, so maybe it's being washed away. Do you have any suggestions? Thank you. MaryAnn
Montgomery County Maryland
Expert Response
Hello MaryAnn,
There are multiple culprits that could be munching on coneflower petals and causing overlapping damage, including katydids, grasshoppers, crickets, earwigs, caterpillars, slugs/snails, and several species of beetles. The insects tend to chew through the emerging petals before they expand to full size. We do not see any symptoms of Aster Yellows, which are usually very different and much more prominent than missing petals. Coneflower Rosette Mites can heavily damage the flower heads if populations become high, but the only time petals tend to go missing is when feeding injury is quite advanced, which does not appear to be the case here.
If a beetle population is high and you catch the culprits in the act of inhabiting the flowers, you can go out with a container of soapy water and try to brush or tap them into it to drown. It’s not uncommon for beetles to “play dead” and drop off of a plant when disturbed, so they will fall right into the soapy water if the container is in the right spot. (Or, they’ll just take off and fly away.) If they move too quickly, using this approach in cooler morning temperatures might make them easier to catch. Some types of beetles only feed at night, however, and some of the petal-chewers can be native species.
Generally, intervention is not needed, and the nectar- and pollen-bearing parts of the flower of value to pollinators are largely undamaged and still of use to flower visitors. We would not recommend the use of an insecticide on the plants, given their value to wildlife. Diatomaceous Earth only works for pests coming into direct contact with the powder, like insects walking over a sprinkled area or chewing coated leaves, and is ineffective when it gets wet. It does not discriminate between pest and beneficial insects.
For now, just continue monitoring the plants for watering needs given our ongoing drought. You can leave developing seed heads for birds to enjoy later, or clip spent or malformed flowers off to promote more reblooming (and remove mites, if they become abundant).
Miri
There are multiple culprits that could be munching on coneflower petals and causing overlapping damage, including katydids, grasshoppers, crickets, earwigs, caterpillars, slugs/snails, and several species of beetles. The insects tend to chew through the emerging petals before they expand to full size. We do not see any symptoms of Aster Yellows, which are usually very different and much more prominent than missing petals. Coneflower Rosette Mites can heavily damage the flower heads if populations become high, but the only time petals tend to go missing is when feeding injury is quite advanced, which does not appear to be the case here.
If a beetle population is high and you catch the culprits in the act of inhabiting the flowers, you can go out with a container of soapy water and try to brush or tap them into it to drown. It’s not uncommon for beetles to “play dead” and drop off of a plant when disturbed, so they will fall right into the soapy water if the container is in the right spot. (Or, they’ll just take off and fly away.) If they move too quickly, using this approach in cooler morning temperatures might make them easier to catch. Some types of beetles only feed at night, however, and some of the petal-chewers can be native species.
Generally, intervention is not needed, and the nectar- and pollen-bearing parts of the flower of value to pollinators are largely undamaged and still of use to flower visitors. We would not recommend the use of an insecticide on the plants, given their value to wildlife. Diatomaceous Earth only works for pests coming into direct contact with the powder, like insects walking over a sprinkled area or chewing coated leaves, and is ineffective when it gets wet. It does not discriminate between pest and beneficial insects.
For now, just continue monitoring the plants for watering needs given our ongoing drought. You can leave developing seed heads for birds to enjoy later, or clip spent or malformed flowers off to promote more reblooming (and remove mites, if they become abundant).
Miri
