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Guava Fruit Fly
The guava fruit fly is yet another invasive pest that home gardeners need to be aware of.
You may have driven through an agricultural inspection station on your way into California, at one time or another. These inspection points, along with those at international ports, and at shipping and postal centers, all work together to prevent infestations of foreign pests. This is a lot easier and cheaper than getting rid of them after they start feeding and breeding in a new area, which may not have native predators.
Adult guava fruit fly (Ken Walker) CC BY 3.0 au
California invasion
First seen in California in 1986, guava fruit flies are a major pest in Southeast Asia. In 2015, 15 guava fruit flies were found in California; 12 in Los Angeles, and one in Orange, San Mateo, and Santa Clara counties. Since a single female can lay hundreds of eggs that hatch and grow to sexual maturity in an astoundingly short period of time, a single fly is all it takes to trigger the need for extensive eradication programs. You can help in the fight against these pests by knowing what they look like and how they live.
Guava fruit fly hosts and damage
These pests enjoy several host plants other than guava. Common California crops that are threatened by guava fruit flies include black plum, cherry, citrus, peach, and melons. Banana, cashew, coffee, dragon fruit, mango, castor bean, papaya, sandalwood, rose apples, jujubes, bael fruit, sapodilla, and various gourds may also be at risk.
Guava fruit flies damage fruit by laying eggs in it. Females have a pointed ovipositor (egg depositor) that pierces the fruit. This provides points of entry for bacterial, fungal, and viral infections. When the eggs hatch, in as little as two days, maggots tunnel through the fruit, feeding and pooping as they go. None of us wants to bite into that. Maggots shed their skins twice over a two week period, depending on temperature, before dropping to the ground to enter a pupal stage. Within 1 to 2 weeks, adults emerge. Two to five weeks later, females are sexually mature. There are several generations each year.
​Guava fruit fly identification
​While most fruit flies are quite tiny, the guava fruit fly (Bactrocera correcta) is the same size as the common house fly. There are two major families of fruit fly: Drosophila and Tephritidae. Guava fruit flies are members of the Tephritidae, or peacock fruit fly family. They get that name because of the bright colors they display. It is mostly black, with yellow stripes, with two black spots on its face that can blend into a single band. Wings are clear with a dark line along the edge most of the way around, followed by a second line that continues around to the end of the wing. They look like they have a "T" on their butt, which is actually their abdomen. Research on this pest has only recently begun, so we will have to assume that earlier developmental stages look much like their close cousins, the Oriental fruit fly. This would mean that eggs are white, very small, and tubular, while larvae (maggots) are creamy-white and legless, and pupae are held in a dark, reddish brown cylindrical puparium. [Isn't that a great word?]
The Northwest guava fruit fly (Anastrepha striata) is yet another invasive pest, but from the Americas, rather than Asia. Close cousins to the Oriental fruit fly, they can all be difficult to tell apart without looking closely.
Admittedly, capturing a fruit fly can be tricky business. After you've done it once, however, you will probably do it again. These creatures really are fascinating to look at up close. You will need to use a hand lens or a simple microscope to really see the amazing and colorful details.
​If you even remotely suspect that you have a guava fruit fly, please call the Pest Hotline at 1-800-491-1899, or bring it to your local Department of Agriculture office. If guava fruit flies were to take hold in the U.S., crop losses and pesticide use would both skyrocket.
You should always protect your own garden by quarantining new plants, to ensure that they are pest and disease free.
You can grow a surprising amount of food in your own yard. Ask me how!
​~ Kate
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