Roots, Shoots, Fruits & Flowers: Small Bug, Black Aphids, Wax Scales and Elm Sawfly

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Very young juvenile of the leaf-footed bug.
Photo: Chaery Knight, Master Gardener.

Leaf-footed bug

This week, RSFF will look at different insects in our landscapes. Chaery sent a clear image of a strange life form and asked, “What is it?”

This image is a very, very immature form of the leaf-footed bug (LFB). AHA has seen the older orange LFB nymphs before, but this early stage is new to AHA. In general, both small insects and small weeds are easier to treat than the mature pests. Sevin or Malathion would be effective on this small plant insect.

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A plant stem infested with tiny, black aphids.
Photo: Walton Baggett.

Aphids

Walton asked a very basic question, “Can [you] ID?”

The tiny black insects in Walton’s image are aphids. Different species of aphids will attack numerous plants like row crops, vegetable crops and ornamental plants. They suck plant sap and excrete the surplus fluid as honeydew. The honeydew is suitable for sooty mold to grow. If a gardener has sooty mold, then aphids may be the reason. Ladybugs and tiny, parasitic wasps can attack the aphids. Another treatment for aphids includes soapy water or horticultural oils because these fluids will have a smothering effect on these tiny pests.

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An image with both wax scales(white) and sooty mold(black).
Photo: Carol Canerdy.

Both wax scales and sooty mold

Carol texted an image of another insect pest that makes honeydew and associated with sooty mold.

Carol’s image captured both wax scales and sooty mold. The scale insect moves as a juvenile “crawler” and then sets up permanent housing on a stem to suck sap and then excrete honeydew. Dan Gill shares his insights on using horticultural oil to treat scales and other insects, “Oils are also effective against aphids, whiteflies, spider mites and the crawler stage of scales, yet they are less harmful than other insecticides to beneficial predatory insects.

Oil sprays are best used when the temperature is between 45 and 85 degrees, and they should only be applied to plants that are not in stress. That is one reason that the mild weather of spring is an excellent time to use them. Light, paraffinic oil, such as Year-Round spray oil and All Seasons spray oil, however, can be used during the summer.

An added benefit of oil sprays is that they also help clean the unsightly sooty mold from the plant. The sooty mold will not quickly disappear when the scale has been controlled, but as the food supply is exhausted the sooty mold will eventually weather off. Oil sprays help speed the process.”

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A larva of an elm sawfly.
Photo: Carol Canerdy.

Juvenile sawfly

Carol also sent another image of a yellow “worm” with a black stripe and wanted to know what this insect would be when it is mature.

The elm sawfly adult feeds on elm trees and on willow trees. According to Texas Agrilife Extension website, “Adults are rarely seen and do not sting. They are called sawflies because females of most species have a saw-like structure on the tip of their abdomens used to inject eggs into plant tissue. Larvae feed of the leaves of plants and can occasionally become numerous enough to cause injury to some trees. [They are] medically harmless.”

If you want to contact Roots, Shoots, Fruits and Flowers, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 337-463-7006 or khawkins@agcenter.lsu.edu. Also, you can be on the “green thumbs” email list by emailing your request to the address above.

“This work has been supported, in part, by the USDA National Institute of Food and Agriculture, Renewable Resources Extension Act Award, Accession Number 1011417.”

5/14/2020 2:04:59 PM
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