Pest detection and management is an ongoing and extremely important area of agriculture. San Diego County has a robust agricultural industry—which means we are also faced with an ongoing battle to manage agricultural pests. Everything from Asian citrus psyllid to the Diaprepes root weevil to the Mediterranean fruit fly, or Medfly, has been found in our area and could greatly damage our agriculture and backyard crops.
For example, some areas of the County are currently under Medfly quarantine. After several years of no Medfly problems, we’re experiencing the second outbreak this year. Both Spring Valley and Mira Mesa, near the Mira Mar Marine Corps base featured in “Top Gun,” are quarantined. Medflies were found in backyard trees through the ongoing fruit fly detection program conducted by the County with federal and state funding.
Neither of these areas have any commercial agricultural production, but it’s always a concern that backyard fruit, and with it the fly, will be moved. Both areas had larval properties identified, which confirms that the Medfly reproduced and shows the potential for the fly to spread.
A few methods are used to manage Medfly outbreaks. The Sterile Insect Technique, or SIT, is being used with the Mira Mesa outbreak. We’re using a newer technique that makes raising the sterile male flies used in SIT more efficient and effective. Previously, both male and female flies were raised and released. Now, temperature control is used in raising the flies. As larval maggots feed, the temperature is raised to a critical level. This strain of females is sensitive to temperature and die, which means we are only raising males from the maggot stage to adults. That means we are feeding and handling about half the number of flies. The second advantage is that there are no sterile females to distract the males from finding fertile females.
Ground treatments are also used around properties with mated females and larval stages. An insecticide developed from naturally occurring bacteria is sprayed on foliage around the property so any adult Medflies will feed on it and die. We release sterile flies for two generations and the area is quarantined for a total of three generations. Then we monitor the area as the sterile flies die out, to ensure the entire population has actually died out.
Of course, the best way to manage pest outbreaks is through prevention. San Diego recently received its first dog team. The dog, Friday, and her handler visit small parcel carriers and inspect packages for agricultural material. If any ag material is found, the handler determines if it is a legal shipment or if it is in violation of state and federal quarantine laws.
Detection methods like this give us early warning when a population threatens to become established. There will always be pests posing dangers to our agriculture, but we’re working hard to stay at least one step ahead.
Agricultural Commissioner, San Diego County