Evaluation of the Efficacy of the Methyl Bromide Fumigation Schedule Against Mexican Fruit Fly (Diptera: Tephritidae) in Citrus Fruit

Abstract

Methyl bromide fumigation is widely used as a phytosanitary treatment. Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), is a quarantine pest of several fruit, including citrus (Citrus spp.), exported from Texas, Mexico, and Central America. Recently, live larvae have been found with supposedly correctly fumigated citrus fruit. This research investigates the efficacy of the previously approved U.S. Department of Agriculture-Animal and Plant Health Inspection Service treatment schedule: 40 g/m3 methyl bromide at 21-29.4 degrees C for 2 h. Tolerance ofA. ludens to methyl bromide in descending order when fumigated in grapefruit (Citrus X paradisi Macfad.) is third instar > second instar > first instar > egg. Two infestation techniques were compared: insertion into fruit of third instars reared in diet and oviposition by adult A. ludens into fruit and development to the third instar. Inserted larvae were statistically more likely to survive fumigation than oviposited larvae. When fruit were held at ambient temperature, 0.23 +/- 0.12% of larvae were still observed to be moving 4 d postfumigation. Temperatures between 21.9 and 27.2 degrees C were positively related to efficacy measured as larvae moving 24 h after fumigation, pupariation, and adult emergence. Coating grapefruit with Pearl Lustr 2-3 h before fumigation did not significantly affect the proportion of third instars moving 24 h after fumigation, pupariating, or emerging as adults. In conclusion, fumigation with 40 g/m3 methyl bromide for 2 h at fruit temperatures >26.7 degrees C is not found to be inefficacious for A. ludens. Although a few larvae may be found moving >24 h postfumigation, they do not pupariate.

Comparison of In Vitro Heat and Cold Tolerances of the New Invasive Species Bactrocera invadens (Diptera: Tephritidae) With Three Known Tephritids

“…Failure of pupariation may not be the measure of treatment efÞcacy ultimately used in a cold treatment for B. invadens, but it sufÞces in this comparative study as a clearly demarcated threshold, whereas direct larval mortality may be more difÞcult to determine after phytosanitary treatments. For example, Hallman and Thomas (2011) found that some A. ludens larvae that were not detected to move for several days after fumigation with methyl bromide pupariated nevertheless.…”

Synergistic effects of heat and diatomaceous earth treatment for the control of Plodia interpunctella (Lepidoptera: Pyralidae)

“…; Ross ; Fields & White ; Campbell & Arbogast ; Shim et al . ; Hallman & Thomas ). Alternative control methods advocated as replacements include heating, cooling and radiation (White ; White & Leesch ; Arthur & Phillips ).…”

Insect Thermotolerance Comparing Host Infestation Methods: <I>Anastrepha ludens</I> (Diptera: Tephritidae) Reared in Grapefruit or Diet

“…Although prevention of larval movement is normally the measure of efÞcacy used by inspectors of plant protection organizations (PPOs) for phytosanitary heat treatments (Heather and Hallman 2008), prevention of pupariation was chosen as the threshold because it is the subsequent developmental threshold and, unlike larval movement, its determination is clear and apparent independent of the moment of observation. However, some tephritid larvae subject to a treatment that left them motionless pupariated without ever having been observed to move (Hallman and Thomas 2011).…”

“…Hallman and Thomas (2010) found no difference in the efÞcacy of phytosanitary irradiation between Mexican fruit ßy third instars reared in grapefruit versus those reared on diet and inserted into grapefruit, although they cautioned that the literature on the Mediterranean fruit ßy, Ceratitis capitata (Wiedemann), indicates that there might be a difference with that species. Another study with methyl bromide fumigation of grapefruit infested with A. ludens found that larvae reared on diet and inserted into fruit were harder to kill than those reared in the fruit (Hallman and Thomas 2011).…”