Plant Q & A Texas A&M

Cactus insects identified


Q. What is the white, fluffy material on our prickly pear cactus? We squashed some, and it is purple inside. It looks gross on the cactus. Is it a fungus? How can we remove it?

A. The white material is the coating on cochineal. Cochineal is a scale-like insect that makes its living by sucking the juices from the cactus pods. It is most famous as the raw material for royal purple dyes that have been valuable through history. The dyes were sometimes limited to use by royalty.

The insect is not thought to be a threat to the cactus, but you can probably kill the insects with a spray of horticulture oil and acephate, if necessary. Both products are available at area nurseries.

Q. You have written about planting Mexican milkweed and other Asclepias for Monarch butterflies. What are some of the other top food sources for butterflies?

A. Blue mistflower is hard to beat. The blue mistflowers at Mitchell Lake Audubon Center are covered by butterflies. Other good nectar sources are zinnias, lantanas, coral vine, rock rose, lantanas and blue plumbago. Sunflowers, passion vine and dill are favorite egg laying sites.

Q. Is it time to prune roses for the fall flush of blooms?

A. Yes, but don’t overdo it. Remove dead and broken stems and stems that are overgrown and blocking the sidewalk. Fertilize with slow release lawn fertilizer, and resume your spray program for fungus and insects.

Q. My tomatoes look good but have not started to set fruit. Should I be worried?

A: Once temperatures drop to near or below 70°F at night and near 90°F during the day, they should start setting fruit. Heat setters like BHN 968, Surefire, Heatwave, Tycoon and Solar Fire may start setting quicker than other varieties.

Q. I have dry spots in the lawn. When I examine them, I see pin head-sized beetles running around at the base of the plants. Could they be a problem?

A. Yes. It sounds like you have chinch bugs rather than drought damage— though it may be both! Control the chinch bugs with a soil insecticide for the lawn. Look for a product with chinch bugs named on the label.

CALVIN R. Finch, Ph.D. is a Horticulturist and Director of Texas A&M Water Conservation and Technology Center. Do you have a question for him? Write to him at calvin. finch@tamu.edu.



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