Activation of Protic, Hydridic and Apolar E-H Bonds by a Boryl-Substituted GeII Cation.

The synthesis of a boryl-substituted germanium(II) cation, [Ge{B(NDippCH)2 }(IPrMe)]+ , (Dipp=2,6-diisopropylphenyl) featuring a supporting N-heterocyclic carbene (NHC) donor, has been explored through chloride abstraction from the corresponding (boryl)(NHC)GeCl precursor. Crystallographic studies in the solid state and UV/Vis spectra in fluorobenzene solution show that this species dimerizes under such conditions to give [(IPrMe){(HCNDipp)2 B}Ge=Ge{B(NDippCH)2 }(IPrMe)]2+ (IPrMe = 1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene), which can be viewed as an imidazolium-functionalized digermene. The dimer is cleaved in the presence of donor solvents such as [D8 ]thf or [D5 ]pyridine, to give monomeric adducts of the type [Ge{B(NDippCH)2 }(IPrMe)(L)]+ . In the case of the thf adduct, the additional donor is shown to be sufficiently labile that it can act as a convenient in situ source of the monomeric complex [Ge{B(NDippCH)2 }(IPrMe)]+ for oxidative bond-activation chemistry. Thus, [Ge{B(NDippCH)2 }(IPrMe)(thf)]+ reacts with silanes and dihydrogen, leading to the formation of GeIV products, whereas the cleavage of the N-H bond in ammonia ultimately yields products containing C-H and B-N bonds. The facile reactivity observed in E-H bond activation is in line with the very small calculated HOMO-LUMO gap (132 kJ mol-1 ).

Experimental and quantum chemical studies of anionic analogues of N-heterocyclic carbenes.

A combination of quantum chemical and synthetic/crystallographic methods have been employed to probe electronic structure in two series of anionic ligands related to the well known N-heterocyclic carbene (NHC) class of donor. Analyses of (i) the respective frontier orbital energies/compositions for the 'free' ligands and the results of ETS-NOCV studies of the bonding in model group 11 complexes; and (ii) the structural metrics for (new) linear gold(i) compounds, have been used to probe the bonding in complexes of NHC ligands which incorporate a backbone-appended weakly-coordinating anion component (WCA-NHCs) and in systems featuring the isoelectronic (formally anionic) diazaborolyl ligand family. Key findings are that WCA-NHC ligands - in which the anionic component is attached to the ligand heterocycle via a methylene (CH2) spacer - offer electronic (and steric) properties which are largely unperturbed from their 'simple' NHC counterparts, while diazaborolyl donors (in which the negative charge is formally located at the boron donor atom) offer significantly stronger σ-donation and a very high trans influence.

Wrinkles and creases in the bending, unbending and eversion of soft sectors.

We study what is clearly one of the most common modes of deformation found in nature, science and engineering, namely the large elastic bending of curved structures, as well as its inverse, unbending, which can be brought beyond complete straightening to turn into eversion. We find that the suggested mathematical solution to these problems always exists and is unique when the solid is modelled as a homogeneous, isotropic, incompressible hyperelastic material with a strain-energy satisfying the strong ellipticity condition. We also provide explicit asymptotic solutions for thin sectors. When the deformations are severe enough, the compressed side of the elastic material may buckle and wrinkles could then develop. We analyse, in detail, the onset of this instability for the Mooney-Rivlin strain energy, which covers the cases of the neo-Hookean model in exact nonlinear elasticity and of third-order elastic materials in weakly nonlinear elasticity. In particular, the associated theoretical and numerical treatment allows us to predict the number and wavelength of the wrinkles. Guided by experimental observations, we finally look at the development of creases, which we simulate through advanced finite-element computations. In some cases, the linearized analysis allows us to predict correctly the number and the wavelength of the creases, which turn out to occur only a few per cent of strain earlier than the wrinkles.

The Effects of a Modified Hot Water Treatment on Anastrepha ludens (Diptera: Tephritidae)-Infested Mango.

The Mexican fruit fly, Anastrepha ludens (Loew), is a quarantine pest in mango (Mangifera indica L.) that can be controlled by using a hot water treatment (HWT). This treatment is normally followed by a 30-min hydrocooling (HYC) process that reduces the negative effects that the treatment has on fruit quality. However, if hot water-treated fruits are immediately immersed in water at 21 °C, the survival rate of third-instar A. ludens may be increased. The current approved treatment protocol states that if HYC is used, then treated fruit should undergo an additional 10-min HWT or on platform for 30 min before HYC. We aimed to determine the efficacy of HWT without an additional 10-min treatment before being subjected to HYC, while taking into consideration that the most important conditions are the temperature of the fruit core throughout treatment and the type of infestation, either oviposition or inoculation. Two experimental tests were conducted. Our first aim was to determine the effectiveness of HWT followed by HYC using three varieties and different size classes of mangoes ('Ataulfo' 200-375 and 401-570 g; 'Tommy Atkins' 401-500 and 501-700 g; 'Kent' 401-500 g). The four treatment combinations used to test HWT and immediate HYC at 21 °C were 1) HWT, 2) HWT/HYC, 3) HWT + 10 min/HYC, and 4) HWT/30 min on platform/HYC; an independent experiment was used for each variety. The second aim was to validate the HWT/HYC combination by performing confirmatory tests in commercial packing houses. The results showed that as long as the mango core temperature reached 45 °C during the HWT, it was not necessary to add the 10-min treatment to the HWT before HYC at 21 °C was applied. To ensure that the larvae are subjected to the HWT treatment for sufficient time to be lethal, the temperature of the fruit core throughout the treatment must be recorded.

Grape Juice as a Bait for Anastrepha suspensa (Diptera: Tephritidae) and Zaprionus indianus (Diptera: Drosophilidae).

In field tests conducted in south Florida to test grape juice as a bait for the Caribbean fruit fly, Anastrepha suspensa Loew, high numbers of Zaprionus indianus Gupta were captured in traps with aqueous grape juice. These experiments included comparisons of grape juice bait with established A. suspensa protein-based baits (ammonium acetate + putrescine lures, or torula yeast) or wine, a bait found previously to be attractive to Z. indianus. Effects of different preservatives (polypropylene glycol, polyethylene glycol, proxel, or sodium tetraborate) and bait age were also tested. Traps with grape juice baits captured more A. suspensa than unbaited traps, but more were captured in traps with grape juice plus preservative baits and the highest numbers were captured in traps containing the established protein-based baits. In contrast, grape juice baits without preservative that were prepared on the day of deployment (0 d) or that were aged for 3-4 d in the laboratory captured the highest numbers of Z. indianus, while solutions that were aged in the laboratory for 6 or 9 d captured fewer. Although these studies found that aqueous grape juice is a poor bait for A. suspensa, we found that actively fermenting aqueous grape juice may be an effective bait for Z. indianus.

Univalent gallium complexes of simple and ansa-arene ligands: effects on the polymerization of isobutylene.

Using [Ga(C6 H5 F)2 ](+) [Al(OR(F))4 ](-) (1) (R(F) =C(CF3)3) as starting material, we isolated bis- and tris-η(6) -coordinated gallium(I) arene complex salts of p-xylene (1,4-Me2 C6 H4), hexamethylbenzene (C6 Me6 ), diphenylethane (PhC2 H4 Ph), and m-terphenyl (1,3-Ph2 C6 H4): [Ga(1,4-Me2 C6 H4 )2.5 ](+) (2(+)), [Ga(C6 Me6 )2 ](+) (3(+)), [Ga(PhC2 H4 Ph)](+) (4(+)) and [(C6 H5 F)Ga(µ-1,3-Ph2 C6 H4)2 Ga(C6 H5 F)](2+) (5(2+)). 4(+) is the first structurally characterized ansa-like bent sandwich chelate of univalent gallium and 5(2+) the first binuclear gallium(I) complex without a Ga-Ga bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI-BP86/SV(P) level), [Ga(PhC2 H4 Ph)](+) [Al(OR(F))4](-) (4) and [(C6 H5 F)Ga(µ-1,3-Ph2 C6 H4)2 Ga(C6 H5 F)](2+) {[Al(OR(F) )4] (-)}2 (5), featuring ansa-arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR-PIB). In comparison to the recently published 1 and the [Ga(1,3,5-Me3 C6 H3)2](+) [Al(OR(F))4](-) salt (6) (1,3,5-Me3 C6 H3 =mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR-PIB with high contents of terminal olefinic double bonds (α-contents=84-93 %), low molecular weights (Mn =1000-3000 g mol(-1)) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6, the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism.

Univalent Gallium Complexes of Simple and ansa-Arene Ligands: Effects on the Polymerization of Isobutylene.

Using [Ga(C6 H5 F)2 ]+ [Al(ORF )4 ]- (1) (RF =C(CF3 )3 ) as starting material, we isolated bis- and tris-η6 -coordinated gallium(I) arene complex salts of p-xylene (1,4-Me2 C6 H4 ), hexamethylbenzene (C6 Me6 ), diphenylethane (PhC2 H4 Ph), and m-terphenyl (1,3-Ph2 C6 H4 ): [Ga(1,4-Me2 C6 H4 )2.5 ]+ (2+ ), [Ga(C6 Me6 )2 ]+ (3+ ), [Ga(PhC2 H4 Ph)]+ (4+ ) and [(C6 H5 F)Ga(µ-1,3-Ph2 C6 H4 )2 Ga(C6 H5 F)]2+ (52+ ). 4+ is the first structurally characterized ansa-like bent sandwich chelate of univalent gallium and 52+ the first binuclear gallium(I) complex without a GaGa bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI-BP86/SV(P) level), [Ga(PhC2 H4 Ph)]+ [Al(ORF )4 ]- (4) and [(C6 H5 F)Ga(µ-1,3-Ph2 C6 H4 )2 Ga(C6 H5 F)]2+ {[Al(ORF )4 ] - }2 (5), featuring ansa-arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR-PIB). In comparison to the recently published 1 and the [Ga(1,3,5-Me3 C6 H3 )2 ]+ [Al(ORF )4 ]- salt (6) (1,3,5-Me3 C6 H3 =mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR-PIB with high contents of terminal olefinic double bonds (α-contents=84-93 %), low molecular weights (Mn =1000-3000 g mol-1 ) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6, the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism.

Comparison of torula yeast and various grape juice products as attractants for Mexican fruit fly (Diptera: Tephritidae).

Early research investigating attractants for the Mexican fruit fly, Anastrepha ludens Loew, during the 1930s indicated that fermentation products were effective attractants for Mexican fruit flies and other tropical Tephritidae, but that attraction to fruit components was only of academic interest. Tests reported here were carried out on populations of Mexican fruit flies from 2004 to 2011. Trapping experiments carried out at sites in the states Nuevo Leon and San Luis Potosi compared grape juice, reconstituted grape concentrate and powdered grape mixes, and torula yeast extract in orchards at each site. The Nuevo Leon orchard was mixed with alternate rows of pears and surrounded by alternate hosts. The San Luis Potosi site was surrounded by other orange orchards or nonhosts. Each test was run for at least 10 mo and included highest and lowest trapping periods. Results showed that grape juice captured the most total flies and had the fewest samples with zero flies. However, in the series of experiments, each product had the most captures in at least one experiment. Hydrolyzed torula was superior in one of the six experiments. In five of the tests, polyethylene glycol was tested as an additive to the grape products but never improved capture rate compared with the product without the additive. These results indicate that grape juice is superior to grape concentrate or powder and grape juice is at least equal to torula yeast hydrolysate for trapping pest populations of Mexican fruit flies in commercial citrus orchards.

Changes in free amino acids and polyamine levels in Satsuma leaves in response to Asian citrus psyllid infestation and water stress.

The effects of biotic and abiotic stresses on changes in amino acids and polyamine levels in Satsuma orange (Citrus unshiu; cultivar Owari) leaves were investigated. Asian citrus psyllids Diaphorina citri (Kuwayama) (ACP) infestation was used to induce biotic stress while a water deficit was imposed to induce abiotic stress. Potted trees were infested by placing 50 psyllids on 3 citrus leaves enclosed in nylon mesh bags for 5 d. A parallel set of plants were kept water stressed by maintaining the soil at 20% water holding capacity for 5 d. Levels of total free amino acids were higher in water stressed and ACP infested leaves. Polyamine putrescine increased in infested leaves but not in water stressed leaves. Proline was the most abundant amino acid and its levels significantly increased by both biotic and abiotic stresses. Proline levels in infested leaves were significantly higher than the water stressed leaves. Histidine, methionine, asparagine, arginine, serine, and leucine levels also increased significantly in infested leaves, but in water stressed leaves only leucine, methionine, and threonine increased. Levels of amino acids, such as tyrosine, isoleucine, phenylalanine, glutamic acid, and alanine, declined in infested leaves. Under water stress asparagine, phenylalanine, serine, and histidine also declined compared to controls. This indicates that while proteolysis occurred under both stresses, metabolic conversion of amino acids was different under the two stresses. In ACP infested leaves some amino acids may be used as feeding material and/or converted into secondary metabolites for defense.

Host status of Meyer and Eureka lemons for Anastrepha ludens.

Host status for Mexican fruit fly (Anastrepha ludens (Loew)) was examined under laboratory conditions in cage infested Eureka and Meyer lemons. Our approach was to allow females to oviposit on the two cultivars in separate laboratory cages with aluminum foil covering to restrict the areas where females had access to fruit surface. Fruit of each cultivar were placed in covered trays for incubations and at approximately weekly intervals, fruit were removed, dissected, and live and dead eggs and larvae tabulated in each tissue of the fruit. Infestation and survival were tabulated and analyzed for the effects of harvest date, fruit color and brix indices, postoviposition period, and cultivar. Infestation rate, determined by counts of total eggs and larvae was significantly higher in Meyer lemons. In both cultivars, females deposited eggs into both albedo and pulp tissue but not into flavedo. Both cultivars showed high resistance (> 90% mortality) to egg and first instars survival in albedo and pulp. Second and third instars surviving in the pulp had high survival rates (> 60%) in both cultivars in fruit dissected at weeks 2-4 after infestation. Total adults produced were slightly higher, and total second and third stage larvae were also higher for Meyer lemons. Numbers of adults and total second and third stage larvae increased in Eureka lemons in more mature fruit, but the higher numbers in Meyer lemons were not associated with fruit maturity, at time of infestation. Numbers of second and third stage larvae were significantly correlated with some fruit color indices in Eureka but not in Meyer lemons. Application of these results to quarantine risk analysis is discussed.

Host status of grapefruit and Valencia oranges for Anastrepha serpentina and Anastrepha ludens (Diptera: Tephritidae).

Anastrepha serpentina (Wiedemann) (Diptera: Tephritidae) is sporadically captured in the Rio Grande Valley of Texas. Although its preferred hosts are in the Sapotaceae family, several varieties of Citrus, including grapefruit and oranges are listed as alternate hosts. Although Mexican fruit fly, Anastrepha ludens (Loew), is known to be a major pest of Citrus, doubt exists as to the status of Citrus as a breeding host for A. serpentina. To evaluate the host status of commercial Citrus for A. serpentina we compared oviposition and development with that of A. ludens under laboratory conditions with 'Rio Red' grapefruit (Citrus paradisi MacFayden) and 'Valencia' oranges [Citrus sinensis (L.) Osbeck] in different stages of maturity. Both fly species oviposited in early season fruit in which the eggs and larvae died in the fruit albedo. Survival of either species to the adult stage occurred in later season grapefruit. In oranges, no A. serpentina larvae survived compared with 150 A. ludens surviving to adults. Survival on both Citrus species was much lower for A. serpentina, only approximately 5% of eggs eclosed into larvae in grapefruit compared with approximatley 50% for A. ludens. In oranges approximately 16% of A. serpentina eggs eclosed compared with approximately 76% for A. ludens. In grapefruit, only one fourth as many A. serpentina larvae survived to the adult stage compared with A. ludens. Additional experiments were performed in a greenhouse on small, caged trees of la coma (Sideroxylon celastrinum H.B.K.), a Texas species of Sapotaceae. The A. serpentina females readily oviposited into these berries and normal adults emerged. The present low incidence of the adults, coupled with the high mortality during development of the larvae, suggests that Texas citrus is unlikely to support a breeding population of A. serpentina.

Grapefruit as a host for the West Indian fruit fly (Diptera: Tephritidae).

The most common hosts for the West Indian fruit fly, Anastrepha obliqua (Macquart) (Diptera: Tephritidae) are fruit in the family Anacardiaceae (mango [Mangifera L.] and mombin [Spondias L.] species). However, similar to many of the tropical fruit flies of major economic importance, this species attacks several other families of crop fruit, including Annonaceae (cherimoya, Annona cherimola Mill.), Myrtaceae (guava, Psidium L.), Oxalidaceae (carambola, Averrhoa carambola L.), Passifloraceae (granadilla, Passiflora quadrangularis Mill.), and Sapotaceae [mamey sapote, Pouteria sapota (Jacq.) H. E. Moore & Steam]. In the family Rutaceae the economically important genus Citrus has been reported and until recently considered a host for this fruit fly. In this study, we reviewed the taxonomy of A. obliqua, tested specific chemicals that may inhibit oviposition, compared egg-to-adult survival of A. obliqua on preferred hosts and on grapefruit (Citrus X paradisi Macfad.), and measured fruit tissue-specific developmental rates of A. obliqua and the known citrus breeding Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), from egg to pupae. Our literature review shows much confusion concerning the taxonomy of this and related Anastrepha species, including synonymies and confusion with other species. The deterrent effect of the highest concentration of flavonoids for oviposition, although significant, was not absolute. Experiments carried out under laboratory conditions showed 15-40 times greater survival of A. ludens (whose preferred hosts include Rutaceae) on grapefruit compared with A. obliqua for both tree attached and harvested fruit. Experiments of survival of developing stages over time showed that the two species oviposit into different tissues in the fruit, and mortality is much higher for the West Indian fruit fly in the flavedo and albedo of the fruit compared with the Mexican fruit fly.

Multimodal cues drive host-plant assessment in Asian citrus psyllid (Diaphorina citri).

Asian citrus psyllid (Diaphorina citri) transmits the causal agent of Huanglongbing, a devastating disease of citrus trees. In this study we measured behavioral responses of D. citri to combinations of visual, olfactory, and gustatory stimuli in test arenas. Stimuli were presented to the psyllids in droplets or lines of an emulsified wax formulation in two different arena types in no-choice tests. First, when placed on a colored ring situated halfway between the center and perimeter of a petri dish, D. citri spent more time on yellow versus gray rings; however, this response disappeared when either gray or yellow wax droplets were applied. When the psyllids were presented with droplets scented with terpenes, the response to both scent and color was increased. The addition of a dilute (≍0.1 M) sucrose solution to the wax droplets increased the magnitude of D. citri responses. Next, groups of D. citri were placed on plastic laboratory film covering a sucrose solution, to mimic a leaf surface. Test stimuli were presented via two 'midribs' made from lines of emulsified wax formulation. Probing levels were measured as a function of color saturation and scent composition, and concentration. The test scents were based on qualitatively major volatiles emitted by Murraya paniculata (L.) Jack, Citrus aurantifolia (Christm.) Swingle, and C. sinensis (L.) Osbeck. The highest probing response was observed on the middle concentration (20-µl scent/10 ml wax formulation) of the C. aurantifolia-scented wax lines. Results indicate that there are interactive effects between the different sensory modalities in directing host-plant assessment behavior.

High hydrostatic pressure at low temperature as a quarantine treatment to improve the quality of fruits.

Application of high hydrostatic pressure has been proposed as an alternative quarantine process for the Mexican fruit fly, Anastrepha ludens Loew (Diptera: Tephritidae), one of the most important insects infesting mangoes, citrus fruits, and other fruits in Mexico and other Latin American countries. The present study was performed to determine the effect of high pressure treatments at 0 degrees C on the survivorship of eggs and larvae of this pest. The effect of time and pressure level at near-freezing temperatures on the egg hatch and survival of larvae is discussed. Eggs and larvae were pressurized at 25, 50, 75, 100, or 150 MPa for 0, 5, 10, or 20 min at 0 degrees C. Hatch was recorded for 1-, 2-, 3-, and 4-day-old pressurized eggs. For pressurized larvae (first, second, and third instars), percentage of survival was registered. Further, third instars were studied for their ability to pupate and develop to adulthood. The results showed that eggs had higher resistance than larvae to pressure. Larvae were not able to resist pressure treatments at 75 MPa for 20 min at 0 degrees C. Treatments at 150 MPa for 20 min at 0 degrees C were needed to destroy all eggs and larvae of A. ludens, indicating that this process might be useful as a quarantine method for infested fruits. However, more studies involving combination of high hydrostatic pressure at low temperature with precooling treatments are needed in order to decrease the pressure level to avoid fruit damage.

Honey bee foraging preferences, effects of sugars, and fruit fly toxic bait components.

Field tests were carried out to evaluate the repellency of the Dow AgroSciences fruit fly toxic bait GF-120 (NF Naturalyte) to domestic honey bees (Apis mellifera L.). GF-120 is an organically registered attractive bait for tephritid fruit flies composed of spinosad, hydrolyzed protein (Solulys), high-fructose corn syrup (ADM CornSweet 42 high-fructose corn syrup, referred to as invertose sugar or invertose here), vegetable oils, adjuvants, humectants, and attractants. Tests were carried out with non-Africanized honey bees in February and March 2005 and 2007 during periods of maximum hunger for these bees. In all tests, bees were first trained to forage from plates of 30% honey-water (2005) or 30% invertose (2007). In 2005 bees were offered choices between honey-water and various bait components, including the complete toxic bait. In 2007, similar tests were performed except bees were attracted with 30% invertose then offered the bait components or complete bait as no-choice tests. Initially, the 2005 tests used all the components of GF-120 except the spinosad as the test bait. After we were convinced that bees would not collect or be contaminated by the bait, we tested the complete GF-120. Behavior of the bees indicated that during initial attraction and after switching the baits, the bait components and the complete bait were repellent to honey bees, but the honey-water remained attractive. Invertose was shown to be less attractive to bees, addition of Solulys eliminated almost all bee activity, and addition of ammonium acetate completely eliminated feeding in both choice and no-choice tests. These results confirm previous tests showing that bees do not feed on GF-120 and also show that honey bees are repelled by the fruit fly attractant components of the bait in field tests.

Effects of bait age and prior protein feeding on cumulative time-dependent mortality of Anastrepha ludens (Diptera: Tephritidae) exposed to GF-120 spinosad baits.

A fruit fly bait to attract and kill adult fruit flies, GF-120, was tested in cages to determine effects of pretreatment diet and bait aging before use on cumulative mortality rates of Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae). Protein-starved and protein-fed, 9-d-old flies both experienced varying overall cumulative mortality at 4, 8, 24, and 48 h. Pretreatment diet had no significant effect on mortality. Overall mortality rates were below 10% for 4 h, 39-43% at 8 h, but mortality in all treatments increased to 89-93% by 24 h, and 99% by 48 h. In a second experiment, GF-120 baits were either freshly prepared or aged for 24 h. Subtreatments consisted of protein-fed and protein-starved flies. The 24-h-aged bait killed significantly more flies at 4 and 8 h than the freshly prepared bait. Protein-starved flies had significantly higher mortality at 4 h and marginally higher mortality at 8 h than protein-fed flies. At 24 and 48 h, there were no significant differences among treatments, and overall morality rose to 99-100% by 48 h. These results may explain differences noted in previous publications in which fruit fly mortality to GF-120 was reported as unusually low as well as reports of bait ineffectiveness for protein-fed flies. The overall impact of any initial repellency of GF-120 seems negligible as judged by overall cumulative mortality at later evaluation times.

Fruit fly (Diptera: Tephritidae) host status determination: critical conceptual, methodological, and regulatory considerations.

Although fruit fly host status determination/designation lies at the heart of strategic decisions on national and international trade of fruit and vegetables, all attempts thus far to define host plant status have been contentious and as a result long-standing disputes between commercial partners throughout the world have lingered over decades. Part of the problem is that too little effort has been devoted to understanding the underlying mechanisms involved in host plant use by fruit flies and that instead economic and political interests usually prevail. Here we review the most important evolutionary, biological, ecological, physiological, and behavioral aspects that drive host use by fruit flies, and then construct a flow diagram rooted in these fundamentals that outlines a series of steps and definitions to determine if a particular fruit or vegetable (and cultivars thereof) is a natural host, or a conditional (potential, artificial) host, or a nonhost. Along the way, we incorporate risk analysis considerations and propose that the underlying complexity determining host plant utilization by fruit flies requires a flexible systems approach capable of realistically dealing with fly/host/environment/geographic variability on a case-by-case basis.

Development of bait stations for fruit fly population suppression.

The application of insecticides is an essential component for eradication or management of fruit fly pests. Impact on nontarget organisms and public rejection of areawide pesticide applications have been major concerns in managing these programs. Bait stations have been proposed as alternative treatments in areas where broadcast insecticides are not acceptable. In this study, we defined bait stations as discrete containers of attractants and toxins, which are targeted at specific pests. Tests were carried out using the Mexican fruit fly, Anastrepha ludens (Loew), as the experimental insect. Our first bait station design was a sheet of sponge material fastened to a plastic peaked cover. Liquid bait consisting of protein hydrolyzate, sugar, adjuvants, a photoactive dye toxicant, and other additives was applied to the sponge. This station, when tested in an orchard, reduced sterile released adult populations by 70-90% in 4 d compared with check plots. Other tests in field cages showed that the bait station was approximately 22% less effective in killing adults compared with spot sprays on trees. We formulated a gelled bait by using a more refined hydrolyzed protein, supplemental attractants, feeding stimulants, and additives to protect the bait from drying. A series of experiments were carried out in field cages by using a cylindrical bait station that provided improved protection of the bait. These tests showed that there is a gradual decline in bait effectiveness with age.

Nontarget impact of spinosad GF-120 bait sprays for control of the Mexican fruit fly (Diptera: Tephritidae) in Texas citrus.

Bait sprays containing the toxicant spinosad (GF-120) were applied to citrus groves in the Rio Grande Valley of Texas where Mexican fruit flies were detected in surveillance traps. The sprays were applied as a supplement to a continuous sterile insect release program. Sterile fly captures were 47-63% lower in the treated groves compared with control groves. Eight of 10 secondary pest populations declined in the test groves subsequent to spray applications, but they also declined in the control groves, suggesting that the decline was a seasonal phenomenon rather than a result of the bait sprays. Citrus whitefly, Dialeurodes citri (Ashmead), populations increased modestly and citrus blackfly, Aleurocanthus woglumi (Ashby), populations remained unchanged compared with pretreatment levels. Thus, no outbreaks of secondary pests occurred as a result of the spinosad bait sprays in this instance, as has been reported for malathion bait sprays in citrus. The bait sprays had no detectable effect on populations of specific indicator species of parasitoids (including Aphytis spp. and Comperiella bifasciata Howard), or on numbers of beneficial insects in general, in the treated groves.

Adult diet and male-female contact effects on female reproductive potential in Mexican fruit fly (Anastrepha ludens Loew) (Diptera tephritidae).

Wild strains of fruit flies (Diptera: Tephritidae) placed into laboratory rearing conditions are subjected to selection pressures caused by the diet, cages, density of flies, and other factors. Selection that changes mating behavior of the strain may result in less effective males released in sterile insect programs. Tests were performed to examine the effects of protein in diet and adult interactions on egg production and mating during sexual maturation of the Mexican fruit fly (Anastrepha ludens Loew) in laboratory cages. Flies were offspring of wild flies collected from Chiapas or Nuevo Leon, Mexico, and reared on Valencia oranges. Experiments demonstrated effects of yeast hydrolysate protein in adult diet and pairing with males on production of mature and immature eggs, numbers of females producing eggs, and mating with females aged 15 d. Addition of protein to 4% fructose in the adult diet approximately tripled mature egg production in females maintained for the total maturation period with an equal number of males. Females that matured without males produced approximately 33% more-mature eggs when fed protein than those fed no protein. Total egg production of females matured without males and fed sugar only or sugar with protein was more than twice that of females matured with males. Tests to examine the effects of male and female diet separately on female egg production showed slightly higher egg production in females fed protein, or females paired with males fed protein, but these differences were not significant. The most definitive effects were that combining wild strain females and males in cages during maturation reduced egg production. This effect was greatest when flies were not fed protein.