A hawk or sphinx moth, a harmless insect. Photo: Pam Archer, DeRidder, LA

Sphinx Moth

Pam sent an email with an image, “What is this? It invaded my bathroom this morning while I was getting ready for work! It looks kind of like a moth, but it was buzzing like something that would bite or sting!”

AHA asked Wood Johnson, an insect specialist with the US Forest Service, for identification, and he responded, “That is a moth which belongs to the family Sphingidae (hawk moths). They are harmless.”

AHA suspects that this large moth with leaf-like wings is a walnut sphinx moth, and it is native to Louisiana and many other states east of the Rocky Mountains. According to “insectidentification.org” website, “Walnut sphinx caterpillars eat the leaves of walnut, butternut, hickory, alder, beech, hazelnut, and hophornbeam trees.” The adult moths do not eat anything because their only task is to mate. After mating, the female lays eggs.

Sooty mold on a satsuma due to excessive honeydew by an insect. Photo: Catherine Townsend, Fishville, LA.

Sooty Mold

Catherine sent several images of satsumas with two different insect problems. Here is the first complaint, “There is something on the leaves of my satsuma tree that looks like black mold or soot. The variety is Owari and it was planted about a year ago. I am wondering if this affects the 4 lovely fruits on it. I would also like to know how to treat it because it cannot possibly be healthy!”

Catherine has “sooty mold,” and earlier in 2022, Dr. Raj Singh, the AgCenter’s “Plant Doctor”, shared a publication entitled, Sooty Molds, and he writes, “Sooty molds are [harmless] fungi that grow superficially as a thin black layer on leaves, fruit, twigs and stems of various crop plants or trees. The fungi grow on the honeydew produced by insects with piercing-sucking mouthparts. The insects, including aphids, leafhoppers, mealy bugs, psyllids, scale insects and whiteflies, pierce the plant tissue with their stylets and feed on plant sap. While continuously feeding, these insects ingest a large volume of sap fluid into their bodies, and the sap fluid is not entirely digested. After extracting nutrients from the sap, these insects excrete excess water and sugars from their bodies in the form of a sticky, sugary substance called “honeydew.” Most of the time, these insects feed on young, tender new plant growth, and the honeydew drops below on all plant parts previously mentioned. Additionally, the honeydew covers understory vegetation, concrete surfaces, sidewalks, furniture, parking lots, etc. under host plants infested by sap sucking insects.

Managing sooty molds is quite simple. Keep insects, such as aphids, mealy bugs, scale insects and whiteflies, in check. Once the insect problem is solved there will be no new sooty mold occurrence. The existing sooty mold infestation dries out after some time and easily sloughs off the infested areas. Pressurized water can be used to wash off the sooty molds. Care should be taken while using pressurized water because it may damage the plant.

Insect infestations are generally controlled with insecticides, insecticidal soaps, or horticultural oils. Before applying any kind of chemical pesticide, it is especially important to identify the insect properly.”

Citrus leafminer (CLF) damaged the leaves of a Meyer lemon. Photo: Catherine Townsend, Fishville, LA.

Citrus Leafminer

Here is Catherine’s second complaint about her citrus, “I have an “Improved Meyer Lemon” that was planted about a year ago. The new growth on the tree is curly and the leaves look withered. I have watered it about twice a week during the long scorching summer, so I do not know what the problem is. Please advise.”

Catherine has an insect pest called a citrus leafminer (CLF) that feeds between the top and bottom surfaces of a citrus leaf. Robert Souvestre, retired AgCenter horticulture agent, made this recommendation for treatment of CLF, “Homeowners who have a few citrus trees in the backyard may obtain excellent control of citrus leafminers by using spinosad formulated for citrus in home gardens. Homeowners may obtain spinosad at local garden retailers under different commercial names such as Conserve, Naturalyte Insect Control, Green Light Spinosad, Success, Fertilome Borer, Bagworm, Leafminer & Tent Caterpillar Spray, etc. Citrus leafminer control is important on young, growing backyard citrus trees and mature trees that have been stressed by environmental conditions.” Always read the label of a pesticide for safe and effective treatment.

American or late boneset is a native shrub. Photo: Kevie Wright, Boyce, LA.

American Boneset

Kevie sent an email with a picture, and she asks, “[Do you] Any idea what this is?”

NC State Extension website provides this description about boneset, “Boneset is a large herbaceous, clump-forming perennial shrub with small white flowers that appear in late summer and fall. The plant grows well in average, medium to wet soils with a consistent water source. It prefers full sun or part shade and tolerates both sandy and clay soils. The soil should contain considerable organic material so that it can retain moisture. This plant can withstand flooded conditions for short periods of time, but it is not really aquatic. The root system produces rhizomes in abundance and Boneset typically forms vegetative colonies.

Historically, Boneset was commonly included in medical herb gardens and used as a folk medicine for treatment of cases of flu, fevers, colds, and a variety of other maladies. Some authorities claim the name Boneset refers to a former use of the plant to aid the healing process for broken bones; others claim that the name is in reference to the plant's use as a diaphoretic in the treatment of an 18th century influenza called break bone fever. All parts of the plant are quite toxic and bitter.