DEAR JESSICA: I just came across this insect that seems to be eating my day lilies. Can you identify it and let me know how to remove it from my flower garden?
— Linda Sturges,
DEAR LINDA: That’s a scarlet lily beetle. As you’ve experienced firsthand, its diet consists of plants in the lily family, especially Asiatic lilies and fritillaries. And the results can be devastating.
Left unchecked, the invasive insects will devour leaves, stems, buds and flowers, destroying plants entirely, leaving nothing but a mangy stem. And because leaves are necessary to store up energy for plant survival and next year’s re-emergence, the perennials may not return.
Their numbers can be great, in part due to a unique defense mechanism: their larvae coat themselves in feces, making themselves unappetizing to hungry birds. The beetles themselves don’t have any natural predators, so their population has the potential to run rampant. Cornell University is experimenting with a control method in heavily populated lily beetle areas by releasing parasitizing wasps, which lay eggs inside the larvae so that they never develop into beetles. So far, they have seen some success.
But since you don’t likely have a supply of parasitizing wasps lying around, the simplest strategy would be to pick the beetles off by hand and remove larvae from under leaves, dropping both into a bucket of soapy water as you go.
Neem (extracted from the neem tree) has shown effectiveness in killing larvae, but must be applied every five to seven days throughout summer. Another insecticide, spinosad, which is constructed from soil bacteria, is another option. Follow package directions carefully and spray only in the evenings to avoid affecting beneficial pollinators.
DEAR JESSICA: I received a beautiful peace plant in January and it thrived for six months. About three weeks ago, the leaves started turning yellow and developing brown spots. I thought it had outgrown its pot so I repotted it in a 15-inch pot with Miracle-Gro potting soil. It seems to be doing even more poorly now, although it has new growth in the middle. Any suggestions? I hate to think I killed it.
— Joanne Buckley,
DEAR JOANNE: I don’t believe your potting mix is responsible, and I don’t believe you’ve killed your peace lily (Spathiphyllum wallisii).
The yellow and browning leaves you’re seeing likely are due to a watering problem. These plants will react both to too much or too little water. They also react similarly to overexposure to minerals from tap water. White calcium deposits on the pot or under the pot around drainage holes indicates excess calcium, and it’s likely that roots are similarly coated.
But fear not: this can be fixed. Trim away any brown or yellow leaves, and flush the soil with bottled water until it pours out from the bottom of the pot. Going forward, water only with bottled water, and allow the soil to dry out between waterings.
You don’t say what size pot the plant had been growing in before you upgraded to a 15-inch container, but you should know that plants don’t typically take well to a leap in pot size. When plants become crowded, move them up only to the next size pot, which should be 2 inches larger in diameter.
DEAR JESSICA: The pachysandra in my labyrinth is dying. It outlines and defines the paths in my labyrinth. I have tried fungicides and fertilizers. They have gone from deep lush green to yellow and now brown. Right now my labyrinth is ruined.
— Lois Meyer,
DEAR LOIS: I can’t be 100 percent certain, but my guess is you’re dealing with Volutella blight, a severe fungal disease that attacks pachysandra. There’s an organic biologic product called Serenade (Bacillus subtilis, QST 713) that should be able to help. First, clean up all diseased plant parts and dispose of them in the trash, then apply according to package directions. Also, be sure to water during periods of drought.