Eric B. Jang

Field captures of wild melon fly (Diptera: Tephritidae) with an improved male attractant, raspberry ketone formate.

Abstract Field-trapping evaluations of the new male attractant, formic acid 4-(3-oxobutyl) phenyl ester (raspberry ketone formate [RKF]) were conducted in Hawaii with wild populations of melon flies, Bactrocera cucurbitae Coquillett (Diptera: Tephritidae), to determine its activity in the field and to evaluate new plastic matrix formulations. All tests were compared with the standard melon fly attractant 4-(4-acetoxyphenyl)-2-butanone (cuelure [CL]), which is the attractant of choice for detection programs aimed at melon fly and other cuelure-responding Bactrocera fruit flies. Results of these tests over a range of doses on cotton wicks showed that at a 1-g dose raspberry ketone formate was 1.5–2 times more attractive compared with cuelure for up to 11 wk in the field. Lower doses applied on cotton wicks were less active, presumably due to hydrolysis of RKF to raspberry ketone. Raspberry ketone formate embedded in a plastic plug formulation also was field tested, and it was shown to be more attractive to male melon fly compared with cuelure. The use of this new attractant in control and detection programs is discussed.

Trapping and the Detection, Control, and Regulation of Tephritid Fruit Flies

The routine operations associated with tephritid fruit fly programs are divorced from the workings of the underlying science on traps and lures, which has developed more haphazardly through the work of individual researchers. Additionally, all trapping outcomes are probabilistic, rendering data interpretation problematic. Mark-release-recapture studies have proven valuable in providing estimates of minimum detectable population sizes for invasive fruit fly species. Both intraand interspecific variation in lure/trap responsiveness demand further investigation, as the notion that “one trap/bait combination fits all” is probably not maximally effective.

Response of Melon Fly (Diptera: Tephritidae) to Weathered SPLAT-Spinosad-Cue-Lure

ABSTRACT Studies were conducted in Hawaii to measure attraction of male melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), to SPLAT-Cue-Lure (C-L) and SPLAT-Melo-Lure (M-L) (raspberry ketone formate). Direct field comparisons of SPLAT-C-L and SPLAT-M-L at low (5%) and high (20%) concentrations indicated few differences in attraction over a 15-wk period. Subsequently, only SPLAT-Spinosad-C-L (5%) was compared with Min-U-Gel C-L with naled (standard used in California) in weathering studies. Treatments were weathered for 1, 2, 4, and 8 wk in Riverside, CA, and shipped to Hawaii for attraction/toxicity tests under field and semifield conditions by using released males of controlled ages, and for feeding tests in the laboratory. In terms of attraction, SPLAT-Spinosad-C-L compared favorably to, or outperformed the current standard of Min-U-Gel-C-L with naled. In terms of toxicity, the cumulative 24-h mortality did not differ between the two insecticide-containing C-L treatments in field cage studies after 8 wk. However, in feeding studies in which individual males were exposed for 5 min to the different C-L treatments after 4 wk of weathering, SPLAT-Spinosad-C-L demonstrated reduced mortality compared with the Min-U-GelC-L with naled, suggesting reduced persistence of the spinosad material. Spinosad has low contact toxicity and when mixed with SPLAT and C-L offers a reduced risk alternative for control of B. cucurbitae and related C-L—responding species, without many of the negative effects to humans and nontargets of broad-spectrum contact poisons such as naled.

An Optimized Protocol for Rearing Fopius arisanus, a Parasitoid of Tephritid Fruit Flies

Fopius arisanus (Sonan) is an important parasitoid of Tephritid fruit flies for at least two reasons. First, it is the one of only three opiine parasitoids known to infect the host during the egg stage1. Second, it has a wide range of potential fruit fly hosts. Perhaps due to its life history, F. arisanus has been a successfully used for biological control of fruit flies in multiple tropical regions2-4. One impediment to the wide use of F. arisanus for fruit fly control is that it is difficult to establish a stable laboratory colony5-9. Despite this difficulty, in the 1990s USDA researchers developed a reliable method to maintain laboratory populations of F. arisanus10-12. There is significant interest in F. arisanus biology13,14, especially regarding its ability to colonize a wide variety of Tephritid hosts14-17; interest is especially driven by the alarming spread of Bactrocera fruit fly pests to new continents in the last decade18. Further research on F. arisanus and additional deployments of this species as a biological control agent will benefit from optimizations and improvements of rearing methods. In this protocol and associated video article we describe an optimized method for rearing F. arisanus based on a previously described approach12. The method we describe here allows rearing of F. arisanus in a small scale without the use of fruit, using materials available in tropical regions around the world and with relatively low manual labor requirements.

Field Response of Mediterranean Fruit Fly (Diptera: Tephritidae) to Ceralure B1: Evaluations of enantiomeric B1 Ratios on Fly Captures

Abstract (−)-Ceralure B1 (ethyl-cis-5-iodo-trans-2-methylcyclohexane-1-carboxylate), a male attractant for the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is significantly more attractive than trimedlure (tert-butyl esters of 4(5)-chloro-2-methylcyclohexane-1-carboxylate), the current standard male attractant used in detection programs. This article reports studies that compare the effectiveness of racemic ceralure B1, mixtures of racemic ceralure B1 and pure (−)-ceralure B1, and trimedlure in field tests conducted in Hawaii, Africa, and Spain with wild Mediterranean fruit flies and in Florida with sterile released Mediterranean fruit fly. Trapping results showed that doses of (−)-ceralure B1 of 87.5 and 75% are just as effective as the 98% (−)-ceralure B1 and the racemic form to be almost as attractive. In nearly all studies, the racemic ceralure B1 was significantly better than trimedlure. These studies suggest that the racemic ceralure B1 could be a viable replacement for trimedlure in areawide detection programs for Mediterranean fruit fly. Synthesizing racemic ceralure B1 instead of a specific stereoselective enantiomer of ceralure B1 would likely be more cost-effective to produce and also might be useful in control as well as detection of this pest.

Field Response of Mediterranean Fruit Flies to Ceralure B1 Relative to Most Active Isomer and Commercial Formulation of Trimedlure

ABSTRACT In a field test to examine attractancy of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), relative to release rates, equal moles of racemic ceralure B1 and trimedlure isomer C were compared on cotton wicks. Data were collected at 2, 4, and 7 d. The substrates were analyzed for longevity and overall persistence in the field. Ceralure B1 was equally attractive as trimedlure C for the first 2 d and significantly more so at 4 and 7 d based on trap counts of captured male Mediterranean fruit flies. Residue analysis of weathered wicks showed that the trimedlure C lasted for just 2 d in our field evaluations, whereas ceralure B1 had measurable material present after 7 d. Thus, based on the amounts of chemicals released, ceralure B1 was more active even in the first 2 d. Ceralure B1 also was formulated in a plastic matrix (ceralure coin) at three different dosages and tested for attractancy in the field against a 2-g trimedlure plug. A 150-mg ceralure B1 coin was equally attractive as a commercial 2-g trimedlure plug, whereas a 300-mg coin was significantly more attractive during a 6 – 8-wk deployment. Although our results clearly show that ceralure B1 is a superior attractant to trimedlure, costs of synthesis need to be considered as part of an overall program management strategy.

Survivorship of male and femaleBactrocera dorsalisin the field and the effect of male annihilation technique

Male annihilation technique (MAT) is a key component of management of the Oriental fruit fly, Bactrocera dorsalis Hendel (Diptera: Tephritidae), because of the ‘strong’ attraction of males to the lure methyl eugenol. The optimal application density for MAT has not been investigated for this economically important pest species. We tested the effect of two levels of MAT application density compared to a no‐MAT control on the daily survivorship of male and female B. dorsalis estimated by mark‐release‐recapture (MRR) using a 1‐km2 passive sampling network. Estimated daily survivorship from two separate MRR trials under control (no MAT) conditions was 0.751 for males and 0.948 for females. Male survivorship was similar under control (no MAT) and high application density (256 spots km−2; daily survivorship 0.704). However, estimated male survivorship was significantly lower under the low application density (100 spots km−2; daily survivorship 0.211). A similar pattern was observed in estimated female survivorship, with a significant reduction in survivorship under the low rate compared with control and high application density (low‐density estimated survivorship 0.652, high density 0.881). The results suggest that a lower application density may be more effective against B. dorsalis than the high application density. A lower application density for effective MAT would benefit growers and the public with respect to management of B. dorsalis through reduced labor and material costs, limiting potential environmental impacts, and increased logistical simplicity finding application sites in urban environments.