Ongoing development and testing of a new melon fruit fly lure derived from cucumbers may lead to improved monitoring and control of this costly agricultural pest. That’s the goal of U.S. Department of Agriculture scientists who developed the lure in studies at the USDA Agricultural Research Service’s Tropical Crop and Commodity Protection Research Unit in Hilo, Hawaii.
In Hawaii, the melon fly, Bactrocera cucurbitae, is one of four non-native tephritid fruit fly species that cause up to $15 million annually in direct losses to the state’s fruit and vegetable crops. B. cucurbitae is also considered a quarantine pest in the mainland United States and inflicts significant agricultural losses in other regions of the world.
The use of attractants to monitor adult fly numbers and movements plays a critical role in Hawaiian growers’ implementation of area-wide approaches to manage the 6- to 8-millimeter-long pest. These tactics include sanitation measures like destroying infested fruit and using trap crops.
Currently, two types of products are used: liquid protein baits and male-only lures. However, more accurate monitoring and better population control can be achieved if female flies can also be attracted, says entomologist Eric Jang, who leads the Hilo research unit.
In studies there, Jang and colleagues used a procedure called “gas-chromatograph electro-antennogram analysis” to measure how strongly melon flies responded to different blends of 31 volatile compounds emitted from freshly puréed cucumber, among the pest’s favorite hosts. From this analysis, they initially identified and tested a nine-compound blend that proved attractive to female flies but later focused on a seven-compound blend that worked even better when formulated as a dry bait.
During outdoor trials in Hawaiian papaya fields and in Taiwan with sponge gourd, 100 milligrams of the dried synthetic cucumber blend captured more melon fruit flies than both the protein bait and male-only lures. The blend also lasted as long as the other two products when the dosage was increased to 300 milligrams.