Sunday, June 24, 2018
Home and Garden

Ask Dr. Hort: Can coffee grounds help with scale control?

Grounds for fighting cycad scale?

Q: I read on that spreading used coffee grounds around the trunk of a sago will control scale, and that putting the grounds in a hand spray bottle along with water to spray the fronds helps control it. Is there any truth in this, and do I use fresh grounds or used ones in the spray bottle? We have three sagos we try to keep under control, if not scale free. Thank you for your advice. Tricia Pettys

A: I haven't read any research-based studies on controlling Asian cycad scale with coffee grounds mixtures as far as application rates, concentrations or application methods, but you never know, there is some information out there. Tom Broome, owner of the Cycad Jungle in Polk County, thinks that he is on to something using the spent coffee grounds scattered at the base of king sago, Cycas revoluta, and queen sago, Cycas circinalis, the two primary cycads grown as ornamentals. The mixture seems to control the scale systemically. He also makes a sun tea from the grounds. When sprayed directly on the scale insects, it seems to control the varmints. Hey, look at how many insecticidal and fungicidal properties are now found in neem oil, including insect birth control. Caffeine and other alkaloids found in the coffee bean could be the new real deal in controlling small sucking insects such as scale, aphids, mealybugs, leaf hoppers and others. Okay, university researchers, let's see some data, and readers, give me some feedback.

Candle bush may not survive transplant

Q: Can you tell me the name of this plant and a little bit about it? Also, do you think we could transplant it? Nancy, New Port Richey

A: The yellow flowering plant that you have pictured is, get ready, candle bush, empress candle plant, candle tree, candelabra bush, ringworm tree, candlestick cassia or Senna alata (Cassia alata). It grows very fast, resulting in brittle wood, up to 30 feet, if not killed by winter temperatures near freezing. The eye-catching, footlong clusters of bright yellow flowers seen from midsummer to fall attract bees and butterflies. They are followed by interesting-looking fruits that are 4 to 8 inches long and fluted. They start out green then turn brown when ripe, housing many seeds birds find tasty. If you don't want volunteers popping up, clip off pods when green.

It probably wouldn't handle transplanting because the very large compound leaves could lose too much water through transpiration (water movement into the root, up the plant and out through the leaves), dehydrating your transplant before the roots could catch up. However, start a few seeds, plant outside in early spring, protecting from cold temperatures, and you'll have a replacement in no time.

Bringing blooms, beauty back to azaleas

Q: We have some azaleas that are 5 feet high and 5 feet wide, approximately 40 years old, and have started to die. Until the past year they were full of blooms, and now they're starting to die off. How can we save them? Victor

A: Wow, azaleas, Rhododendron simsii, at 40 have probably served their useful life. But what is causing their decline?

There is a new insect in town called "chilli thrips," which are attacking darn near everything in the landscape. If the new growth is becoming distorted and turning a brown rusty color, like somebody hit it with a blowtorch, it is chilli thrips. If most of the leaves look a silvery-green, stippled in appearance with some leaf drop, and there are small dark varnishlike dots on the undersides of the leaves, it is lace bugs.

Either way, spray your azaleas completely with a product containing "spinosad," such as Conserve, a great biorational insecticide. Follow label directions and repeat spray as new growth reappears. If the plants lose their leaves and you snap back the twigs and they are dead well into larger branches, a root-rotting fungus is the culprit. Drench with a systemic fungicide such as Spectracide Immunox following label directions as a preventative on the bushes still alive.