Sunday, May 20, 2018
Home and Garden

Ask Dr. Hort: What we often call inchworms do damage to bougainvillea

What we often call inchworms do damage to bougainvillea

Q: How can I control tiny green worms that make a cocoon in the green leaves on my bougainvillea? Do they just destroy the leaves and blooms? I've tried so many things and nothing seems to keep them away. Connie

A: The damage that you are talking about is caused by bougainvillea loopers: small yellow, green or brown caterpillars that bunch up their bodies and stretch back out as if they were measuring the space, which is why they are sometimes called "inchworms."

The adult is the somber carpet moth about an inch wide with brown wings. The least toxic approach in controlling these critters is to spray the bacterium Bacillus thuringiensis, sold as BT, Dipel and Thuricide which gives the caterpillar a bellyache and kills it; or Neem Oil, which acts as a repellent, birth control and kills upon contact by blocking the breathing openings (spiracles), suffocating the caterpillars. Be sure to follow the label directions for application rates and repeat applications.

Discoloration looks like rust on plants

Q: I have a few plumerias and at the end of last summer we started to get brown spots on the leaves. It almost looks like rust. I looked it up on the Internet and found it is called rust disease, but it didn't tell us how to control or get rid of it. Do you have ideas on this? It did say it comes from lots of rain and moisture which we all know we had last summer. Then the leaves turn black in the spots where the rust was. Kathy Beresford, Ruskin

A: Rust and Plumeria spp. go together like soup and sandwich. Culturally, full sun is the best exposure, keep irrigation water off of the foliage and pick off diseased leaves and discard them. Recently, I read an article on frangipani rust discussing a product from Australia that controls the problem, is labeled for rust on frangipani, available online and is called "Frangipani Rust-Rid Fungicide", a systemic product with triadimefon as the active ingredient and a caution label. There are other domestic products that contain triadimefon, but are labeled for turf.

Call in an arborist to address oak problem

Q: I have a 30-plus-year-old oak tree in the front yard, 40 feet tall, with an open cavity approximately 7 feet from the base. The circumference of the trunk at the cavity is about 7 feet with a diameter of approximately 32 inches. The cavity opening is about 10 inches by 12 inches, and extends in and downward approximately 16 to 18 inches. It appears to be a home for the squirrels, as it is partially filled with chewed items and leaves. What can be used to treat the decay and the gaping hole? Does Pinellas County still have an arborist that may share his or her opinion as to the integrity of the tree in regard to potential of a safety hazard? It is located within several feet of the house.

Also, I have St. Augustine grass, and I need to bring in some fill for low spots in the yard and along the seawall. Should I use topsoil or sand? I have received different opinions from different people, claiming to be experts. Jeff Tomes, St. Petersburg

A: You should have the tree looked at by an ISA certified arborist for a hazard evaluation. Go online, type in your city and then "ISA certified arborist." Based on your description, it is probably a laurel oak, Quercus laurifolia, which is a fast growing oak and a poor compartmentalizer. It doesn't resist decay very well and could be a hazard. On the other hand, the same wound on a live oak, Quercus virginiana, may not be a hazard at all because it is a good compartmentalizer and resists decay extremely well. Nothing should be done to the cavity. In days gone by, decay was scraped out of cavities and filled with concrete or bricks, which neither helped the disease nor did it add strength to the tree. Trees set up barrier zones to wall off disease and some trees are better at it than others.

Now for the turf. The substrate that you are dealing with is sand, so fill in low spots along your seawall and in the yard using play sand for small projects or builders sand for more extensive work which closely matches the existing soil texture and the added plus is that it is weed free. Topsoil comes from who knows where, commonly with a cornucopia of weed seed and doesn't match the texture of your underlying soil, hence water infiltration is often impeded leaving dry areas do to runoff.