Environ. Entomol. 8: 51-54 (1979) The minimum temperature threshold for the development of apple maggot pupae, Rhagoletis pomone//a. was 6.4°C. From 1951-75 the 1st flies emerged in cages over infested apples on the avg on June 15 near Highland, NY and on June 23 in Geneva, NY. The avg accumulated air temperature thermal units (T.U.'s) from Mar. 1 using a threshold of 6.4°C until 1st emergence were 614±53 and 641 ±48, respectively, at the 2 locations. The annual deviations between the actual first emergence and the date when the avg T. V. 's were accumulated ranged from 1-8 days with an avg of 3.5 at Geneva and from 1-14 days with an avg of 5.7 days at Highland. From 1975-77 the mean T.V. accumulation and the 99% confidence interval developed at Geneva was used to predict emergence in 5 locations in Wayne Co. The deviations between the observed emergence and dates in which the appropriate number of T.U.'s was accumulated averaged 3.5 and 0.8 days, respectively.
Thermal Unit DeterminationRecords of apple maggot fly emergence were obtained from 1951-75 in central NY State at Geneva, and in southern NY in the Hudson Valley at Poughkeepsie in ] 954-62 and High]and 1963-75 from cages described by Glass (1960) and Dean and Chapman (1973). Although multiple cages were maintained at each site, data from these were combined to give one annual record for each location. Air temperature and rainfall were recorded during this period from weather stations ca. 400 m from the emergence cages at Geneva, 1-5 m in Poughkeepsie, and 600 m (1962-72) or 30-60 m (1973-75)
The utility of the Voges-Proskauer (17) reaction in detecting bacterial metabolites responsible for specific off-flavors in frozen concentrated Florida orange juice has been denionstrated by Hill, Wenzel, and Barreto ( 7 ) and Byer ( 3 ) . This report is concernecl with the application of their niethod to California Valencia orange juice, particularly as compositional differences may affect evaluation of data from different citrus prodnciiig areas.The Voges-Proskauer reaction was selected by the original citrus workers because of its sensitivity for the oxidation-reduction compounds diacetyl and acetoin (acetyliiiethylcarbinol) . Several methods are known for the detection of diacetyl. One of these, employing hydroxylamine, yields dimethylglyoxime, which subsequently condenses with urea to give a yellow coinpound (19). The method does not appear to be sensitive below 15 p.p.m.Other workers (12, 18,11, 13) have reacted the dimethylglyoxime with a nickel salt to produce soluble tetravalent nickel dimethylglyoxime having a red color. The method, used on beer, appears to be sensitive at 0.2 p.p.m.The hydroxylamiiie reaction, although highly specific for diacetyl, is time-consuming and requires meticulous technique. Other methods based on reaction with chromotropic acid or analine extraction (15) are either not specific or sufficiently sensitive.The Voges-Proskauer reaction as modified by Barritt (1) results froin the reaction of diacetyl and peptone with u napthol to produce a red color. The test also determines 2,3 butanediol (2,3 butylene glycol). The detectable limits appear to be 0.05 p.p.m. diacetyl, 0.5 p.p.m. acetylmethylcarbinol, and 40,000 p.p.ni. 2,3 butylene glycol.The Voges-Proskauer reaction, hereinafter referred to as the V-P reaction, although highly specific for the above three named substances, can be affected by other compounds, some of which are naturally occurring or degradation products in orange juice. The Byer modificatioii ( 3 ) for citrus juices affords concentration of the significant materials to an easily detectable level and removal of same from a substrate containing a heterogeneity of interfering compounds.
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