San Gabriel Valley Residents Plagued by Surge in Eye-Biting Black Flies

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Residents in the San Gabriel Valley are dealing with a dramatic increase in black flies, a small but painful pest known for biting around people's eyes and necks. The San Gabriel Valley Mosquito and Vector Control District has issued a warning about the spike in black fly activity, advising locals to take protective measures like wearing long clothing and using repellent. The district is treating breeding sites to reduce populations, but says it may take several weeks to see results.

Why it matters

Black fly infestations can be a major nuisance for communities, causing discomfort and disrupting outdoor activities. The surge in the San Gabriel Valley is likely linked to recent record-setting heat waves and increased water flow in local rivers and streams, which provide ideal breeding conditions for the flies. The district's efforts to control the population highlight the challenges of managing pests that can spread quickly and widely.

The details

The San Gabriel Valley Mosquito and Vector Control District says black fly populations are 'currently very active' in foothill communities including Altadena, Azusa, Bradbury, Duarte, Glendora, Monrovia, San Dimas and Sierra Madre. The flies develop quickly in flowing waters, where females can lay hundreds of eggs at a time. The district is treating breeding sites to reduce the population, but warns this may take several weeks to be effective.

• The district issued its warning about the black fly surge this week.
• Last year at this time, surveillance traps had single-digit black fly counts, but now they are capturing over 500 flies at a time.

What they’re saying

What’s next

The San Gabriel Valley Mosquito and Vector Control District is continuing to monitor black fly populations and treat breeding sites, but warns it may take several weeks for their efforts to significantly reduce the number of flies.