For more than 30 years, Arbor Age magazine has been covering new and innovative products, services, technology and research vital to tree care companies, municipal arborists and utility right-of-way maintenance companies
Issue link: https://read.dmtmag.com/i/32089
PEST OF THE MONTH Leafhopper / Bacterial Leaf Scorch By Jodi Zirbel What does it look like? Leafhoppers belong to the Cicadellidae family, and, with close to 20,000 unique species, are one of the largest insect families. Although every species varies, adults range in size from 1/8 to 1/2 inch in length, and feature elongated, wedge-shaped bodies. Leafhoppers are most often recognized for their sucking mouthparts, but are also known for their maneuverability — quickly “jumping” or flying from plant to plant. Host material and range Found on every continent, leafhoppers eat plant sap and feed on a variety of plants. Species typically vary by host plants —consisting of grasses, fruit trees, flowers, vegetables, shrubs, weeds, and both decidu- ous and palm trees. Leafhopper Photo by Jack Clark, University of California —Davis, Bugwood.org Prevention tips Leafhoppers have an array of natural predators, including birds, spiders, lady beetles, wasps, moths and flies. But since leafhoppers are prevalent throughout much of the growing season, eradicating leafhoppers —and there- by preventing bacterial leaf scorch —is difficult. Ultimately, the best remedy for bac- terial leaf scorch is tree replacement; however, tips can be taken to suppress the disease and prolong the health of the tree for several years. Most leafhopper species overwinter as adults and lay eggs in late spring. Wingless nymphs emerge from eggs after approximately 10 days and quickly begin feeding on their preferred host plant. Over the next two to four weeks, leafhoppers progress through five instar stages before reach- ing winged adulthood. Current threat On their own, leafhoppers remove plant sap from their food sources and inject toxic secretions into the plant, which causes leaves to yellow or turn brown. Leaves may simply experience tip burn, but could also become permanently stunted. At times, the ongoing feed- ing activity of leafhoppers could even cause the host plant to die. However — and this is more alarming — some species of leafhoppers spread the bacterium Xylella fastidiosa, most commonly known as bacterial leaf scorch. This chronic disease causes trees to experience repeated defoliation. The initial symptoms cause the trees’ leaves to brown out. Over the next 5 to 10 years, twigs and branches die off and, eventually, the disease is fatal. Bacterial leaf scorch affects oak and sycamore trees, and has also been observed in maple, mulberry and elm trees. The disease is found throughout most of the eastern and southern United States. 8 Arbor Age / May/June 2011 Bacterial leaf scorch Photo by Purdue Plant & Diagnostic Lab Treatment tips If bacterial leaf scorch is detected, pruning is one of the easiest courses of treatments. Not only will the tree look more presentable, but if pruning takes place in spring, it may also help to reduce the number of eggs. In addition, watering and mulching can prolong the health of the tree. For a final course of treatment, symptoms have been shown to regress when trunk injections have been made with antibiotics. Although it doesn’t offer a cure, the antibi- otic oxytetracycline has been shown to cause the remission of bacterial leaf scorch symptoms. What can you do? Monitor trees, looking for signs of leaf discoloration or early fall color. Symptoms of bacterial leaf scorch often mimic other diseases, so diagnostic testing is advised to confirm its presence. If detected, prune affected areas and rely on an antibiotic to prolong the health of the tree. Jodi Zirbel is with Epic Creative, Wis. Article provided by Mauget, a leader in micro-injection and micro-infusion tree care. Contact Mauget or visit www.Mauget.com to learn more about leafhoppers and bacter- ial leaf scorch. www.arborage.com