Medfly

Orange oil is presented as a possible commercial source of (+)—a-copaene. Cost-effective studies must be made before these attractants can be established as being economical and practical. At the present time, trimedlure is still the only lure used for population monitoring of Medflies, and protein hydrolysates are used for baits in control methods. 

The economic impact of an infestation of the Medfly in California in 1981 serves as an example of how serious a problem these flies present. The costs of eradicating the Medfly in California during the 1981 infestation were large. Burk and... 

In the 1981 Medfly infestation in California, an insecticide was mixed with protein hydrolysates (1). Hedflies are attracted to protein hydrolysates and feed on this material hence, this is an efficient way to administer an insecticide. 

It is interesting to note that these compounds attract mainly the males of the respective species. Therefore, these compounds might be pheromone mimics. Protein hydrolysates, on the other hand, attract both sexes of most Tephritids and are widely used as food baits. However, volatiles from protein hydrolysates may not be simply food attractants. The cyclic imine, 3,4-dihydro-2H-pyrrole, has been identified in protein hydrolysate volatiles (12), and this compound has been identified by Baker and coworkers (11) as the sex pheromone Which attracts virgin females to the sexually mature male Medflies. Why the protein hydrolysate volatiles attract the males and other species remains unanswered. 

Table 1 shows a survey of some essential oils containing a-copaene and a-ylangene. Unfortunately the rotation is not reported in most of the articles, but we have some evidence as to which are attractive to the Medfly. The material from the synthesis by Heathcock (] ) would be racemic because the synthesis was not a... 

Phormia regina Brachycera Muscomorpha Oestroidea Calliphoridae Ceratitis capitata (medfly)... 

Christophides G. K., Mintzas A. C. and Komitopoulou K. (2000) Organization, evolution and expression of a multigene family encoding putative members of the odourant binding protein family in the medfly Ceratitis capitata. Insect Mol. Biol. 9, 185-195. 

Our search for attractants is focused on the Tephritid family of fruit flies which Includes species that are of economic importance in Europe, Asia, Australia, and the Americas. It is estimated that the olive fly, Dacus oleae. causes ten percent fruit drop in European olives. Of the Infested fruit remaining on the trees, 25 percent of the flesh is destroyed (48). A conservative estimate of the annual cost of the recent Medfly infestation in California, not including capital outlays, is 59 million for chemical controls, 38 million for quarantine and fumigation, and 260 million in crop losses (49). It is estimated that 70% of the susceptible fruit in Egypt is infested by the Medfly (50) and a 50 million control program has been started there. 

We are examining those commonly used baits, the protein hydrolysates. Initial studies have used the corn gluten hydrolysate commonly known as PIB-7 or, now, as Nu-Lure Insect Bait (NLIB). This material was used in the recent successful Medfly eradication program in California. Since the fruit flies are probably attracted to the volatile emanations from the bait, we have used equipment and techniques previously developed by members of our group for flavor research. For example, a modified Likens-Nickerson simultaneous steam distillation-extraction head was developed by Flath and Forrey (67.). Also, there is a 90 liter... 

Our first separation method involved running the simultaneous steam distillation extraction under 100 mm vacuum in order to minimize heat effects. This was followed by extraction under atmospheric pressure in order to get more complete recovery. This atmospheric extraction was run for 10 days, using a fresh hatch of solvent each day (68-69). Approximately 10 times as much material was collected each day at atmospheric pressure as was collected under vacuum. Since Schultz, et. al. (70) showed that many non-water-soluble alcohols, esters, aldehydes, and ketones can he recovered by this system in less than 3 hours, the collection of a large amount of material after 10 days is indicative of a very complex and probably dynamic system. Gas chromatograms for these extracts (68.) and some compound identifications (69.) have been reported. (Other reports on the identification of volatiles from protein hydrolysates are given In references 71-75). Prelminary results have shown that the vacuum extracts are more attractive for the Medfly than the atmospheric ones. 

Figure 4, Structural types evaluated as medfly lures...

Figure S. Dioxanes and dioxolanes tested as medfly lures. Hydrogen atoms omitted for brevity...

As a closing example of the value of asymmetric synthesis in the area of insect chemistry, we describe the synthesis of the stereoisomers of trimedlure, a material discovered by empirical screening and used to monitor for "Medfly" (Figure 9). The commercial preparation of this attractant mixture involves a non-selective addition of HC1 to a substituted cyclohexene. The several products are shown in abbreviated form (Figure 9) the t-butyl esters of this mixture of acids has been employed for many years as a bait for the medfly (19). Each component,... 

Fly blood does not normally contain substances that kill bacteria, but flies inoculated with bacteria rapidly accumulate antibacterial proteins (ABs) in their blood. Wild type Drosophila have at least three different antibacterial proteins based on isoelectric points. Genetic variants identify structural genes for these antibacterial proteins. A DNA sequence that can encode a conserved portion of moth and fleshfly antibacterial proteins has been used to synthesize a complementary oligonucleotide probe. This probe recognizes a messenger RNA that appears in the fat body of Drosophila and Medflies only after they have been inoculated with bacteria. Bacteria-sensitive lethal mutations were induced to identify genes necessary for flies to survive a bacterial infection. 

Drosophila melanogaster (Oregon R), Drosophila simulans (st pe), Drosophila mauritiana (wild type), Ceratitis capitata (Mediterranean fruit fly or Medfly), Dacus cucurbitae (melon fly), and Dacus dorsalis (Oriental fruit fly) were cultured by standard methods. 

Figure 2. Peak number plots for the Mediterranean fruit fly, or medfly, the Oriental fruit fly, and the melon fly. There is some overlap in the patterns, and many compounds with frequencies corresponding to the overlaps will attract two, or in some cases, all three species of insect.

From Figure 2, the favorable frequencies for medfly attraction and the nearest evenly-spaced frequencies are shown in Table I. 

Medfly Attractancy Pattern from the Peak Number Plot... 

It seems clear that an insect like the medfly which is attracted to about 25% of a large and diverse selection of chemicals 9), must be able to respond to a relatively small sub-pattern drawn from the total pattern of medfly-favorable frequencies. The actual size of the minimum sub-pattern is suggested by the data summarized in Table II. 

ITsecond point suggested by the Table is the fact that where there are many favorable frequencies in the pattern, a randomly selected candidate is likely to have at least one that will approximately match one element of the pattern. This is no doubt the reason why 25.3% of the 2577 compounds tested by the U.S.D.A. attracted the medfly which has a seven element pattern. This contrasts with the fact that of 2618 compounds tested as attractants for the Mexican fruit fly, only 7.8% were effective (9). For this insect the Peak Number Plot shows only three favorable frequencies which makes it less probable that any given chemical will attract. 

As with the medfly pattern, in nearly every case where the number of "musk frequencies" was zero, there is at least one and usually several which, by a shift of a few units, would be close to an evenly-spaced value. Furthermore, it must be recognized that the far infrared absorption spectra recorded with the samples dissolved in a solvent are subject to some displacement as a result of solvent effects which may vary somewhat when the solvent is changed. 

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