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MANAGE FORESTS & LAND
  • FOREST HEALTH: KATYDIDS

    Along State Highway 21 between Caldwell and Bastrop (near Dime Box, TX, in Lee County) several hundred acres of post oak trees were striped of leaves in July 2001. What was responsible for this defoliation? Not canker worms, drought, wind or hail storms. The cause was a severe and unusual outbreak of leaf-hungry insects known as katydids. The katydid causing the damage in Lee County was been identified as the truncated true katydid, Paracyrtophyllus robustus, by Dr. John Oswald, curator of Texas A&M University’s insect collection. This katydid is one of only four species of true katydids found in America north of Mexico. The northern true katydid, Pterophylla carnellifolia, is more commonly found in Texas and other southern and eastern states, but adults are green, rather than brown. Katydids are members of the order Orthoptera, which includes the grasshoppers, crickets and other species of katydids. Katydids are a form of long-horned grasshopper (family Tettigoniidae) that get their name from the sound made by males as they rub their wings together. The song of the male katydid, which is a form of insect communication, is a familiar sound on warm summer nights throughout the insect’s range. The females do not make sounds.

     

    The immature katydids or nymphs resemble the adults except for the absence of fully developed wings. The brown-colored adults of P. robustus resemble dead leaves, providing excellent camouflage against predators, at least when their numbers are low. The females can be easily recognized by the curved, sword-like ovipositor on the abdomen, used to lay eggs beneath the bark of trees. Near Dimebox, the adult katydids were completing their development in mid July and the females could be seen depositing eggs under the bark of cedar and elm trees in the same stands with the barren post oaks. Presumably, the bark of post oak was too dense and hard to accommodate egg laying, so the females sought other tree species nearby with softer bark.

     

    The unusual outbreak of katydids in Lee County was attributed to several years of drought, which seemed to favor an increase in many foliage-feeding insects, particularly grasshoppers. Although several insecticides are available to kill grasshoppers and katydids, numerous applications often are required to assure control and such heavy-handed treatments are seldom justified. Control of these insects with insecticides was not recommended. Time will tell if the outbreak will continue when the next generation of katydids develops. Katydid outbreaks are usually short-lived and populations subside from natural causes. The defoliated post oaks are expected to recover.

     

    On the positive side, the katydid’s natural enemies in Lee County enjoyed a real Texas buffet. Spider webs were filled with both katydids and grasshoppers while insectivorous birds gorged themselves on the abundant food supply. A selection of adult katydid specimens found a new and permanent home in the insect collection at Texas A&M University. A visit to the outbreak area at night treated the guest to nature’s version of an outdoor rock concert. So, if you ever have the privilege to witness an outbreak of katydids and someone asks you, “What ate all the leaves off those oak trees?”, you can simply and correctly answer…. Katy-did!

     

    Post oaks defoliated by katydids      

    Cedars and elms (trees with green foliage in this photo) are targets for egg-laying, but post oaks are preferred as food by nymphs and adult katydids

    Adult katydids congregating and feeding on post oak with defoliated trees in background

     Adult katydid on post oak leaf   

    Adult katydids          Female katydid laying egg in trunk of cedar elm 

    A katydid falls victim to a spider  Dead katydids on ground under post oak trees


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