Do your oranges, guava, papaya, tomatoes or zucchini turn to mush before their time? Ever picked a fruit that looked fine on the outside but was rotten on the inside? Ever see small white, jumpy “worms” in a coffee cherry? Is there a pinhole less than 1 millimeter at the wound site? Does the wound ooze if you squeeze it? If so, your produce may have been damaged by a fruit fly.
There are four types of Tephritid fruit flies in Hawaii that can inflict damage on produce.
1. Melon fly (Bactrocera cucurbitae) — more than 100 known hosts — prefer cucurbits (squash, melon, etc.) and other hosts including solanaceous plants (tomato, eggplant, pepper, etc.) and papaya.
2. Mediterranean fruit fly (Ceratitis capitata) — more than 300 hosts — coffee, peach, plum, loquat, orange, guava, rose apple, solanaceous plants and the sapote family, among others.
3. Oriental fruit fly (B. dorsalis) — more than 200 wild and cultivated hosts — guava, mango, papaya, starfruit, passion fruit, citrus, fig, rose apple, tomato and many more.
4. Solanaceous fruit fly (B. latifrons) — also known as Malaysian fruit fly — prefer solanaceous (pepper, tomato and eggplant) plants and occasionally cucurbits. Their occurrence is generally in low numbers with a patchy distribution.
How can I control fruit flies?
The Hawaii Areawide Fruit Fly Pest Management Program was a collaborative project between the U.S. Department of Agriculture’s Agricultural Research Service, University of Hawaii College of Tropical Agriculture and Human Resources Cooperative Extension Service and Hawaii Department of Agriculture, that conducted many years of fruit fly research, product testing and outreach. Today, home gardeners and commercial growers in Hawaii have the ability to control fruit flies successfully as a result of this program’s development of biologically based, sustainable pest management strategies that used environmentally friendly methods to suppress fruit flies to economically manageable levels.
Identify and understand your fruit fly of concern as well as its host plants to avoid wasting your time and money with shot in the dark control tactics.
Sanitation is one of the most important control methods, which requires the physical destruction, removal, burial and containment of host plants and produce. Avoid leaving dropped and damaged fruit on the ground or unharvested produce in the field.
Monitor the levels of fruit fly damage to your crop and determine if you have economic injury. Evaluate your situation and use recommended strategies if damages warrant fruit fly control. Search “Fruit fly traps and CTAHR” to find easy to read publications on how to make traps out of recycled water or soda bottles, how to best use GF-120 and “Easy as 1-2-3” fruit fly control directions.
There are several options for fruit fly control. Methyl eugenol, cuelure and trimedlure are highly attractive lures to male oriental fruit fly, melon fly and med-fly, respectively, and are used for monitoring and male annihilation with traps.
GF-120 is a spinosad protein bait with insecticide that will attract and kill both male and female fruit flies of all four species in Hawaii. Growers who plant crops periodically may apply the protein bait before flowers appear to suppress the fruit fly populations before fruiting. For year-round gardeners and those who maintain continuous hosts throughout the year, apply the protein bait at seven- to 14-day intervals on approved crops year-round. Be sure to read and follow the label for GF-120 and all pesticides.
The steps of managing fruit flies are outlined in HAW-FLYPM educational pamphlets: fruit fly ID, monitoring populations, farm and garden sanitation, male lures, protein baits and biological control. These pamphlets can be found at fruitfly.hawaii.edu at no cost. Click on “UNI-FLY-VERSITY.”
Those interested in fruit fly management can also contact their local extension agent for fruit fly educational materials or to apply as a cooperator for the statewide fruit fly suppression program. While supplies and funding are available, including fruit fly pamphlets, free cuelure and methyl eugenol lures and GF-120 at a reduced cost, following sign-up with a UH CTAHR extension agent or with the Master Gardener program.
Commercial farmers should contact their local UH CTAHR Cooperative Extension office by visiting ctahr.hawaii.edu/site/Map.aspx.
Home gardeners can contact their local UH CTAHR Master Gardener Program at ctahr.hawaii.edu/uhmg.
Tropical gardening helpline
Diane asks: I live in Waikoloa and I grow lettuce, bush beans, snow peas, basil, sage and broccoli in an enclosed garden. Some leaves are being eaten by a small green caterpillar and a thinner brown one. I’ve tried soap, soap with red pepper and some old Sevin-5 bug killer powder, but the leaves are still being eaten. I would love some advice.
Answer: The leaf damage and the caterpillars you describe are probably the cabbage looper or the cabbage worm. These are the larvae of the cabbage looper moth and the cabbage worm butterfly.
An excellent publication about these garden pests and ways to deal with them can be found at toxicfreenc.org/organicgardening/cabbage_worms.html#.VO0MHvnF8fU. The publication has good photos for identification.
Since all of the plants you mention are edible, you should avoid using toxic pesticides. Sevin-5 is approved for vegetables and fruit but you might want to avoid using it on leaves you are going to eat or on flowers that bees might land on. It will kill the good, the bad, the beautiful and the ugly.
Another pesticide that is organically approved and is only toxic to caterpillars is BT (bacillus thuringensis). It does kill caterpillars, but that means you might get some caterpillars of desirable and beautiful butterflies as well, so again, discretion is advised. BT, often sold as Dipel, must be eaten and get into the caterpillars’ system before it affects them, so act quickly once you notice signs of their presence. It can take a few days to take them down.
The online publication mentioned also describes several prevention techniques and ways to deal with the critters before applying any products.
Email plant questions to konamg@ctahr.hawaii.edu for answers by certified master gardeners. Some questions will be chosen for inclusion in this column.
Andrea Kawabata is the assistant extension agent for coffee and orchard crops at the Kona University of Hawaii Cooperative Extension Service.