Scale insects under a leaf. Photo: Silas Cecil, LSU AgCenter.

Scale Insects

Silas Cecil, Extension Agent in LaSalle Parish, sent this email on behalf of a gardener, “[I] went out to Olla Friday afternoon to look at a “gaviola” tree (in a large pot). Freddy C. called to say all the leaves were turning black. [The gaviola tree has] Sooty Mold with scale bugs moving up the tree.

What can we use to treat the scale? I was thinking ultra-fine oil but can find if there is a temperature restriction or not?”

AHA checked a label for an ultra-fine oil (UFO) insecticide, and there was no obvious instruction to avoid spraying when temperatures are hot. However, the label did not include scale in the list of insect pests controlled by UFOs.

Dan Gill, retired AgCenter horticulture specials, recommended horticultural oil for treating scale insects “when the temperature is between 45 and 85 degrees, and they should only be applied to plants that are not in stress.” However, Gill does suggest, “Light, paraffinic oil, such as Year-Round® spray oil and All Seasons® spray oil, however, can be used during the summer.” As always, read the label for safe use of any pesticide.

Purple coloring indicates a phosphorus deficiency. Photo: Kristen Fisher.

Phosphorus Deficiency

Kirsten sent a clear image and an email asking about her container tomatoes, “I purchased potting soil and tomato plants from [ a local garden center] in the spring and planted in 5-gallon buckets with holes for drainage. I only got one tomato. I used the apps I have to diagnose the problem with the plants, and it said wilt so I’m assuming it was from the soil I purchased from the store. I tried, unsuccessfully, to remove affected leaves as I saw them, but it was like fighting a losing battle. I’m attaching some photos to get confirmation. If so, I am assuming the only solution is to throw away all the plants and soil? As always, Thanks for your help.”

The purple coloring of the leaves and stem is diagnostic of a phosphorus deficiency, and phosphorus is needed for setting fruit. Keep the plant and soil and add a fertilizer with phosphorus. Also, follow the label for fertilizer rates for a container plant.

Ground moss. Photo: Kevie Wright, Boyce, LA.

Ground Moss

Ms. Kevie of Boyce, LA sent her image and email, “Can you tell me what this [is?]” and “What can you use to kill it?”

Several companies manufacture some form of moss and algae killer. These products are “ready to spray” (RTS) or “ready to use” (RTU) or dry granules. However, merely killing the moss would fail. The site conditions, that enable moss to grow, will require amending the underlying problem:

• Dense shade: Planting shade tolerant plants or apply mulch or pruning tree limbs.
• Acidic soil and/or low soil fertility: Test soil for pH and for soil nutrients, and then lime and fertilizer according to recommendations.
• Poor drainage: Trench or dig a sump or raise grade.
• Compacted soil: aerification with a lawn aerator.
• Excessive irrigation: Irrigate only one inch of water per week if needed.

Eastern lubber grasshopper. Photo: Dr. Tim Schowalter. LSU AgCenter.

Big Black Grasshopper

John, from Pollock, needs to know what to spray for big [black] grasshoppers on roses and all over his yard. His description identifies his pest as an eastern lubber grasshopper (ELG). It is also called “the graveyard grasshopper” or “the devil horse”

Dr. Tim Schowalter, an insect specialist with the LSU AgCenter, makes these insecticidal recommendations for managing these native grasshoppers:

• Carbaryl/Sevin (Drexel Carbaryl®),
• Cyfluthrin (Decathlon®, Tempo®),
• Bifenthrin (Talstar®).

Dr. Schowalter also made these comments about treating the ELG, “[Insecticides] must be applied directly on the insects. Small amounts of insecticide residue on sprayed plants may not be adequate to kill these grasshoppers.”