The California Department of Food and Agriculture (CDFA) has initiated a 4.5-mile quarantine buffer zone in Kern County, Calif., around an area where five melon fruit flies (MFF) Bactrocera cucurbitae were discovered on Aug. 9., southeast of Bakersfield.
The finds in an agricultural production area called Meridian south of Lamont indicate an incipient infestation of this serious agricultural pest, according to CDFA.
A MFF informational meeting is scheduled for 6-8 p.m. Wednesday (Aug. 18) at the University of California Cooperative Extension farm and home advisors office, 1031 S. Mt. Vernon Ave., Bakersfield.
MFF feeds on more than 100 different host plant species. Kern County growers produce several of the fly’s favorite hosts, including apple, peach, cantaloupe, citrus, pepper, tomato, and watermelon.
CDFA will restrict the movement out of the quarantine area fruits and vegetables known to be fruit fly hosts. Growers inside this area will be required to enter into compliance agreements with CDFA that specify how their commodities are to be treated with insecticides, harvested and shipped.
To eradicate the flies already in the area, the Kern County Agriculture Department and CDFA are implementing a "male attractant" technique within the quarantine area and have increased trapping densities to 1,000 traps per square mile within a nine-mile grid. Mated female MFF flies pierce the skins of different fruits and vegetables and deposit eggs. After maggots hatch from the eggs, they feed on the flesh of the fruits and vegetables, rendering them unfit for consumption. Not native to California and not established in the state, the MFF originates from Asia. The MFF occurs in Africa, Sri Lanka, China, Guam, India, New Guinea, Taiwan, Rota, the Ryukyu Islands, Thailand and much of Southeast Asia. In the United States, its distribution is limited to the Hawaiian Islands.
"While we have highly trained biologists working diligently to prevent exotic insect pests from coming into Kern County, we still need the public’s help in preventing the introduction of pests," said Ruben Arroyo, Kern County agricultural commissioner.
The adult melon fly is approximately the size of a housefly, about 6 to 8 mm long. The body is orange-brown in appearance with brown spots along veins of otherwise clear wings. The female has a slender pointed ovipositor to deposit eggs under the skin of the host fruit. The maggots (larvae) are creamy-white, legless and attain a length of 10 mm inside the host fruit.
Females lay eggs an average of about 15 eggs per day. A female may lay up to 1,000 eggs in her lifetime. The eggs take 19 to 28 hours to hatch, depending on temperature. The developing larvae go through three instars which may take from four to 17 days. At maturity, the larvae drop from the fruit and burrow beneath the soil to pupate. In nine to 18 days, the adults emerge from these puparia. The newly emerged adults normally require 11 to 12 days to become sexually mature depending on their diet. Breeding is continuous, with several annual generations. Adults live from one to five months and feed on a diverse array of food sources including honeydew, plant exudates, fermenting fruit and animal feces. Completion of the life cycle normally requires one to two months, but may be completed in 15 days under optimal conditions.
The melon fly also oviposits in tender plant tissues such as terminals, unopened flowers, young stems, roots, and seedling. This may result in the death of the plant.