Teague: Yellow fever mosquitoes are dangerous

October 25, 2013 

The recent discovery in our area of the species of mosquito that can carry and transmit yellow fever, dengue fever and other diseases is of serious concern. The mosquitoes are brown with white markings and they aggressively seek out and bite humans during the day, rather than at dusk. Homeowners should carefully examine their properties for any standing water, no matter how small the amount. The yellow fever mosquito will lay eggs in just a teaspoon of standing water. Plant saucers, broken pots, half-empty plastic swimming pools, roof gutters, puddles on the patio that never dry out, dog water bowls that aren't refilled daily all must be drained and kept dry. Report mosquito sightings, bites and standing water in abandoned pools, streets, gutters, etc. to local mosquito abatement agencies.

Bacillus thuringiensis israeliensis or Bti kills mosquito larvae breeding in ponds, fountains and other water sources. It is available in granular or dunk form at most garden centers and nurseries. Because Bti degrades fairly quickly in sunlight, plan on replacing it every 7 to 10 days or according to label directions. Bti is non-toxic to wildlife, pollinators and vertebrate animals (humans, birds, horses, etc.).

Invasive fruit flies (including the Medfly, the Mexican, olive, oriental, melon, peach and guava flies) have now found permanent homes in California. They're no longer imported, temporary visitors; they are resident populations that can reproduce up to 10 times a year. The invasive fruit flies pose a serious potential threat to commercial agriculture as well as home gardeners. Unlike other fruit flies that lay their eggs in rotting fruit, the invasive fruit flies burrow into ripening fruit to lay their eggs and the maggots that eat the fruit from the inside make it inedible and unsellable.

The extended warm growing season in the central Valley has fostered the spread of the invasive fruit flies. Good garden sanitation is essential in helping to reduce the fruit fly populations. Home gardeners should monitor their crops, on the vines or trees or fallen on the ground, for maggot infestations and remove ripening crops if necessary and clean up all fallen fruit and debris. Infested fruit should be double bagged in plastic and disposed of in the trash, not the compost or the green waste bin.

Researchers from government agencies and university research departments are trapping, tracking and monitoring invasive fruit fly populations and are investigating possible IPM controls as wells as pesticide types and application methods that will cause the least harm possible to pollinators and beneficial insects.


Elinor Teague is a Fresno County Master Gardener. Send her plant questions at etgrow@comcast.net or features@fresnobee.com ("plants" in the subject line).

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