Hackberry Aphid (Asian Woolly Hackberry Aphid) Infestations and Their Impact on Swimming Pools
Based on research by Rudy Stankowitz
Hackberry trees (Celtis spp.) are common in many yards, but they bring a hidden challenge: the Asian woolly hackberry aphid (Shivaphis celti). These insects produce honeydew, a sticky residue that drips into pools below. Once it hits the water, problems escalate quickly—chlorine demand spikes, surfaces foul, and filtration systems struggle to keep up.
Recognizing Pool Issues Linked to Hackberry Aphids
– Rapid Chlorine Loss: Pools shaded by hackberry canopies often lose chlorine at an abnormal rate, even when sanitizer levels are adequately maintained.
– Sticky Black Coating: Honeydew combined with mold growth creates a slimy, tar-like film on pool decks, patio furniture, tile lines, walls, and skimmers.
– Filter Blockage: Filters that typically last weeks between cleanings may clog in just days when aphids are active.
– Surface Debris: Pools often show fine, dust-like particulates that can be mistaken for pollen or byproducts from filtration.
National Range
First detected in Georgia in 1996. Center for Invasive Species Research+2BugGuide+2
Found in Florida by 1997; spread to many counties. Ask IFAS – Powered by EDIS
Southeastern states, including South Carolina, Georgia, Alabama, Tennessee, and Texas. Center for Invasive Species Research
Northward to at least Illinois. UC IPM
Present in California, especially in the San Joaquin Valley, wherever hackberry trees (especially Chinese/Japanese hackberry) are planted.
Evidence and Identification
To verify the cause, samples from contaminated pools were analyzed by Aquatic Facility Training & Consultants CEO, Rudy Stankowitz, and University of Florida entomologist Lyle Buss. Their work identified the culprit as the Asian woolly hackberry aphid—correcting earlier assumptions that whiteflies were responsible. This confirmation established the first direct connection between hackberry aphids and unusual chlorine demand in swimming pools.
Best Practices for Treatment and Prevention
– Immediate Pool Care: Enzyme-based clarifiers help break down honeydew in the water, while shock treatments restore chlorine residuals and burn off organics.
– Client Communication: Homeowners need to understand this isn’t a pool chemistry failure—it’s a tree problem. Unless the issue is addressed at its source, it will recur.
– Landscape Solutions: Treating the tree with horticultural oils or systemic insecticides at the root zone reduces aphid populations and limits honeydew fallout.
– Service Protocol: Always check overhead when troubleshooting unexplained sanitizer loss or sticky residues. Document nearby hackberry trees and set clear expectations—pool water can be treated, but the long-term solution lies in managing the tree.
Pictured: Tom Perugini of Natural Chemistry Products with Rudy Stankowitz at a student housing swimming pool in Gainesville, Florida, documenting water quality issues caused by hackberry aphids.
Hackberry aphids are an overlooked source of pool contamination. Their honeydew can easily be misdiagnosed as algae, filtration problems, or surface issues—costing technicians valuable time and effort. Thanks to research by Rudy Stankowitz, the link is clear: aphids overhead mean chlorine loss and sticky residue below. With proper identification, targeted pool care, homeowner education, and coordinated tree treatment, service professionals can effectively eliminate the frustration of recurring infestations and protect water quality.
