Interaction of the temperature with the parasite mite Acarophenax lacunatus (Cross & Krantz) (Prostigmata: Acarophenacidae) on the development of Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae)

The objective of this study was to evaluate the effect of different temperatures with the association of the mite Acarophenax lacunatus (Cross & Krantz) on the population suppression of Rhyzopertha dominica (Fabricius). The experimental units were petri dishes containing 40 g of whole wheat grains (13% moisture content) infested with 10 adults of R. dominica, under the temperatures of 20, 25, 30 and 35 masculineC, with or without A. lacunatus, in five replicates. Relative humidity of 60 +/- 5% and escotophase of 24h were used for all temperatures. Five days after the infestation, five mites were inoculated in each experimental unit. The evaluations were carried out at 20, 40, 60, 80, 100 and 120 days after R. dominica infestation. The interaction of the temperature with the parasite A. lacunatus was an important tool for the population suppression of R. dominica. In temperatures higher than 25 masculineC, however, despite the reduction of the immature stages of R. dominica, there was a high grain weight loss after 120 days. The maintenance of the temperature of the wheat grains stored at 20 masculineC can be used to complement the biological control of R. dominica with A. lacunatus.     

Interaction between organophosphate insecticides and the parasitic mite Acarophenax lacunatus (Prostigmata: Acarophenacidae) on Rhyzopertha dominica (Coleoptera: Bostrichidae)

The interaction between the organophosphate insecticides fenitrothion and pirimiphos-methyl with Acarophenax lacunatus (Cross & Krantz) (Prostigmata: Acarophenacidae), an egg parasite of the stored grain pest Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), was assessed in a range of doses for each compound. The number of physogastric females of A. lacunatus and egg parasitism (%) decreased with increasing insecticide doses and mite density for both organophosphates. Lower insecticide doses for fenitrothion and pirimiphos-methyl and lower mite densities led to higher instantaneous rates of increase of the mite population. Overall lower instantaneous rates of increase of A. lacunatus were obtained with the insecticide pirimiphos-methyl. The sustained presence of the mite species in all insecticide doses suggest that this biological control agent may be used together with insecticide applications for controlling R. dominica, but high insecticide doses, mainly of pirimiphos-methyl, compromise mite population growth. The high rates of egg parasitism obtained with the biological control agent may aid the insecticide effect on the adult pest population preventing its outbreaks in wheat grains, constituting a potential tactic for pest management of stored wheat.     

Susceptibility of Acarophenax lacunatus (Cross & Krantz) (Prostigmata: Acarophenacidae) to Sulfur

The parasitic mite Acarophenax lacunatus (Cross & Krantz) is a potentially important biocontrol agent of stored grain insect pests, but its presence in insect mass rearing is undesirable. This study was carried out to evaluate the susceptibility of A. lacunatus to sulfur. The experimental units were petri dishes containing 30 g of whole wheat grains infested with 30 adults of Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae). The treatments consisted of pulverizing the wheat grains with sulfur, at 0, 0.15, 0.3, 0.6, 0.9 and 1.2 mg a.i./g, in five replicates. Three inoculations of A. lacunatus were carried out in each petri dish at five, ten and fifteen days after infestation with R. dominica. The petri dishes were stored for 60 days at 30 +/- 1 degree Celsius, 60 +/- 5% R.H. and 24h scotophase. The parasitic mite was susceptible to all sulfur doses used in the test. The number of eggs of R. dominica parasitized by A. lacunatus showed a decreasing trend with the increase in doses of sulfur, as did the number of physogastric females of the mite. The mite showed a negative correlation of their instantaneous rate of increase with sulfur dose. No mites developed at sulfur doses higher than 0.3 mg a.i./g. The susceptibility of A. lacunatus to sulfur is an important aspect to consider in the control of this parasitic mite in colonies of R. dominica. In addition, this control method has low cost and is easy to use.     

Effect of Temperature on Development and Population Growth of Acarophenax lacunatus (Cross & Krantz) (Prostigmata: Acarophenacidae) on Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)

The parasitic mite Acarophenax lacunatus kills the eggs upon which it feeds and seems to have potential as a biological control agent of stored grain pests. The lack of biological studies on this mite species led to the present study carried out in laboratory conditions at eight different temperatures (ranging from 20 to 41°C) and 60% relative humidity using Rhyzopertha dominica as host. The higher the temperature, the faster: (1) the attachment of female mites to the host egg (varying from 1 to 5 h); (2) the increase in body size of physogastric females (about twice faster at 40°C than at 20°C); and (3) the generation time (ranging from 40 to 220 h). In addition, the higher the temperature, the shorter the maximum female longevity (ranging from about 75 to 300 h). The two estimated temperature thresholds for development of A. lacunatus on R. dominica were 18 and 40°C. The average number of female and male offspring per gravid mite were 12.8 and 1.0, respectively, with sex ratios (females/total) ranging from 0.91 to 0.94 (maximum at 30°C). The net reproductive rate and intrinsic rate of increase also presented maximum values at 30°C (12.1 and 0.04, respectively).     

Survival of the mite Acarophenax lacunatus (Cross & Krantz) (Prostigmata: Acarophenacidae) under starvation

The ability of a natural enemy to tolerate starvation increases its chances to survive in the absence of food, what is an important factor for its success in storage grain environment. The objective of the present work was to assess the survival of Acarophenax lacunatus (Cross & Krantz) in the absence of food. The experiment used individualized physogastric females of A. lacunatus placed in petri dishes (5 cm diameter) and maintained at 20, 25, 28, 30 and 32 degrees C, 50+/-5 % R.H. and 24h scotophase. The number of live mites was recorded every 6h thus assessing the progeny survival without food at different temperatures. The mites died within 60h at the temperatures 30 degrees C and 32 degrees C, while they survived for up to 108h at 20, 25 and 28 degrees C. The mean lethal time for death was 58.6h for the lowest temperatures and 39.3h for the highest temperatures. Thus, A. lacunatus subjected to starvation lived longer under lower temperatures, what is probably due to its lower metabolism. In contrast, the mites survived for about 90h at 28 degrees C, temperature commonly observed in tropical and subtropical climates, what may favor their use as control agents of stored product insects in these regions.     

Dispersion of Acarophenax lacunatus (Cross & Krantz) (Prostigmata: Acarophenacidae) in stored wheat, under artificial conditions

Ability to disperse is fundamental for a successful natural enemy in a stored grain environment. The objective of the present work was to assess whether the mite Acarophenax lacunatus (Cross & Krantz) disperses in a grain mass to locate its host Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae). The experiment was based on the release of physogastric females of A. lacunatus on the surface of glass containers containing Petri dishes with 20 adults of R. dominica at different depths (4, 8, 12, 16 and 20 cm). The Petri dishes were covered with voil to prevent insect escape. Dispersion of the progeny of these physogastric females was assessed 10, 20 and 30 days after the beginning of the experiment. The mites were able to disperse and they were observed at every depth and at every period of assessment. Nonetheless, the number of A. lacunatus decreased with the increasing depth, with highest values observed at the lowest depths after 20 and 30 days of storage. It is possible that evaluations conducted in periods longer than 30 days of the parasite release could demonstrate an increase in parasitism at higher depths. The results indicated that A. lacunatus actively disperse for up to 20 cm on its own, without the assistance of its host for phoresy.     

Biology of Acarophenax lacunatus (Cross & Krantz) (Prostigmata: Acarophenacidae) on Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) and Cryptolestes ferrugineus (Stephens) (Coleoptera: Cucujidae)

The aim of the present study was to assess the effect of six different temperatures on the development of Acarophenax lacunatus (Cross & Krantz) using eggs of Tribolium castaneum (Herbst) and Cryptolestes ferrugineus (Stephens) as hosts. The temperature affected the development of A. lacunatus. The largest values for the progeny (19 mites in T. castaneum and 15 mites in C. ferrugineus) were obtained at about 30 degrees C, as also observed for the net reproductive rate (Ro), which revealed that the A. lacunatus population increased 18 times in T. castaneum and 14 times in C. ferrugineus in a generation. The intrinsic rate of increase (r m) gradually increased with temperature, reaching the maximum value at 35 degrees C in T. castaneum (1,608) and C. ferrugineus (1,289). The generation time was negatively correlated with temperature, ranging from 1,60 to 4,85 days in T. castaneum and from 1,96 to 5,34 days in C. ferrugineus. These results suggest that the mite A. lacunatus may be used in programs of biological control of T. castaneum and C. ferrugineus in the tropics.     

象虫金小蜂中国新记录

本文首次报道了象虫金小蜂在中国的分布,并用图文简要地描述其特征.该蜂是四纹豆象、米象、谷象、玉米象、烟草甲和药材甲等重要贮藏物害虫的天敌.     

Genetics of resistance to phosphine in Rhyzopertha dominica (Coleoptera: Bostrichidae)

The inheritance of resistance to phosphine was studied in two strains of the lesser grain borer, Rhyzopertha dominica (F.), labeled 'Weak-R' and 'Strong-R'. These strains were purified versions of field-selected populations collected in Queensland, Australia. Weak-R and Strong-R were, respectively, 23.4 times (20-h exposure) and 600 times (48-h exposure) resistant to phosphine compared with a reference susceptible strain (S-strain). Each -R strain was crossed with the S-strain and the response to phosphine was measured in their respective F1, F2, and F1-backcross (F1-BC) progenies. Data from testing of reciprocal F1 progeny indicated that resistance in Weak-R was autosomal and incompletely recessive with a degree of dominance -0.96. Modified chi-square analysis and contingency analysis of the observed response to phosphine of F1-BC and F2 progenies rejected the hypothesis of single gene inheritance of resistance. Analysis of the response of the F1, F2, and F1-BC progeny from the Strong-R x S-strain cross also rejected the null hypothesis for single gene resistance. Resistance in the Strong-R strain was autosomal and incompletely recessive with a degree of dominance of -0.64. The Weak-R and Strong-R strains were then crossed. Analysis ofthe F1 and F2 progenies of this reciprocal cross revealed that the strong resistance phenotype was coded by a combination of the genes already present in the Weak-R genotype plus an extra major, incompletely recessive gene. There was also evidence of a minor dominant gene present in approximately 5% of Strong-R individuals.     

Isolation and partial characterization of three isoamylases of Rhyzopertha dominica F. (Coleoptera: Bostrichidae)

Three isoamylases of Rhyzopertha dominica (termed RdA70, RdA79, and RdA90 according to their relative mobility in gel electrophoresis) were isolated by ammonium sulfate fractionation and hydrophobic interaction chromatography. RdA70 and RdA79 showed an optimal pH of 7.0, whereas for RdA90 the optimal pH was 6.5. The three isoamylases remained stable at 50 °C for 1 h, but at 60 °C, all lost 50% of their activity in 20 min and were completely inactivated in 1 h. RdA70 and RdA79 were inhibited by albumin extracts from wheat samples varying widely in amylase inhibitory activity; however, RdA90 was highly resistant to inhibition. β-Mercaptoethanol up to 30 mM increased the activity of the three isoamylases by 2.5-fold. The action pattern of the three isoamylases was typical of endoamylases; however, differences were observed on the hydrolytic efficiency rates measured as V_max/K_m ratio on starch, amylopectin, and amylose. The hydrolyzing action of RdA90 on starch and amylopectin (V_max/K_m = 90.4 ± 2.3 and 78.9 ± 6.6, respectively) was less efficient than that on amylose (V_max/K_m = 214 ± 23.2). RdA79 efficiently hydrolyzed both amylopectin and amylose (V_max/K_m = 260.6 ± 12.9 and 326.5 ± 9.4, respectively). RdA70 hydrolyzed starch and amylose at similar rates (V_max/K_m = 202.9 ± 5.5 and 215.9 ± 6.2, respectively), but amylopectin was a poor substrate (V_max/K_m = 124.2 ± 7.4). The overall results suggest that RdA70 and RdA79 appear to belong to a group of saccharifying isoamylases that breaks down long fragments of oligosaccharide chains produced by the hydrolytic action of RdA90. The simultaneous action of the three isoamylases on starch, aside from the high resistance of RdA90 to wheat amylase inhibitors, might allow R. dominica to feed and reproduce successfully on the wheat kernel.     

Efficacy of Bacillus thuringiensis against Lesser Grain Borer, Rhyzopertha dominica (Coleoptera: Bostrichidae)

Toxins from 36 isolates, representative of all available subspecies of Bacillus thuringiensis, were tested against larvae and adults of the lesser grain borer, Rhyzopertha dominica. beta -Exotoxin was effective against both larvae and adults. Spore-crystal complexes of subspecies darmstadiensis isolates from Germany were effective against larvae. Isolates of subspecies darmstadiensis from the US and Japan were not effective. The degree of control achieved by even the best isolate was not economically satisfactory.     

The investigation of the combined effects of gamma irradiation and environmental manipulation on mortality and sterility of Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae)

With respect to the limitations use of methyl bromide and phosphine, employing ionizing radiation to control stored product pests has attracted great attention. The aim of this study is the investigation of the combined effects of gamma irradiation as viable alternatives to synthetic insecticides and environmental management on mortality and sterility of Rhyzopertha dominica (Fabricius) in a wheat cultivar (Gascogen). The effect of doses range from 30 to 2000?Gy gamma irradiation in combination with manipulation of temperature (15, 21, 27 and 32?°C) and relative humidity (20%, 50%, 65% and 85%) on 5–10?days old adults of R. dominica in Gascogen cultivar of wheat were explored. The experiments were repeated three times and conducted in The Nuclear Agriculture Research School in Karaj and laboratory of shahid steki silo in shahre-kord. Probit analysis revealed that both temperature and relative humidity had combined effects when used with gamma irradiation. The lowest doses of gamma ray required to kill 25% (14.2?Gy) and 50% (610.8?Gy) of the population (LD₂₅ and LD₅₀) were recorded at 21?°C and 85% relative humidity respectively. The low dose for 99% mortality (LD₉₉; 2386.7?Gy) was recorded for beetles maintained at 21?°C and 50% relative humidity. The effect of temperature (15, 21, 27 and 32?°C) on sterility caused by gamma irradiation was also investigated. The results showed that the F₁ generation emerged only when the beetles were treated with doses of 0–100?Gy at 32?°C and 0–70?Gy at 27?°C. These results indicate that temperature and relative humidity play an important role in the susceptibility of the lesser grain beetle to gamma irradiation. The results suggest that controlling the efficiency of gamma radiation through environmental control allows the use of low doses of gamma radiation that have a less harmful effect on human health, non-target organisms and seed agronomic features.     

Influence of growing location and cultivar on Rhyzopertha dominica （Coleoptera： Bostrichidae） and Sitophilus oryzae （Coleoptera： Curculionidae） infestation of rough rice

Long-grain rice cultivars Cocodrie, Wells, and XP 723 grown in three locations （Hazen, MO; Essex and Newport, AR, USA）, and medium-grain rice cultivars Bengal and XP 713 grown in two locations （Jonesboro and Lodge Corner, AR, USA）, were harvested and assayed for susceptibility to Rhyzopertha dominica （F.） （Coleoptera： Bostrichidae）, the lesser grain borer, and Sitophilus oryzae （L.） （Coleoptera： Curculionidae）, the rice weevil, on rice held at 27℃, 57% and 75% relative humidity （RH）. Separate samples from the same harvest lots were also analyzed for the physical characteristics of brown rice yield, percentage whole kernels and kernel thickness. Progeny production and feeding damage of R. dominica were significantly different among long-grain cultivars within two of the three locations （P 〈 0.05）, but not for location or RH （P ≥ 0.05）, while progeny production of S. oryzae was different among cultivars, location, and RH （P 〈 0.05）. On medium-grain rice, both cultivar and location were significant for progeny production of R. dominica, but not RH, while cultivar and RH were significant for progeny production of S. oryzae, but not location. On both rice types, feeding damage of R. dominica followed the same trends and was always strongly positively correlated with progeny production （P 〈 0.05）, but for S. oryzae there were several instances in which progeny production was not correlated with feeding damage （P ≥ 0.05）. Physical characteristics of both rice types were statistically significant （P 〈 0.01） but actual numerical differences were extremely small, and were generally not correlated with progeny production of either species. Results indicate that the location in which a particular rice cultivar is grown, along with its characteristics, could affect susceptibility of the rice to R. dominica and S. oryzae.     

Immediate and delayed mortality of Rhyzopertha dominica (Coleoptera: Bostrichidae) and Sitophilus oryzae (Coleoptera: Curculionidae) adults exposed to spinosad-treated commodities

A series of tests was conducted to characterize differences in the mortality of the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), and rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), exposed to three commodities treated with a liquid and dry spinosad formulation. In laboratory bioassays, adults of the two insect species were exposed to untreated wheat, Triticum aestivum L., corn, Zea mays L., and sorghum, Sorghum bicolor (L.) Moench., and to commodities treated with 1 mg (AI)/kg of liquid and dry spinosad formulations. Mortality was assessed from independent samples examined at specific time intervals to determine immediate mortality and after 24 h of recovery on untreated grain at 28 degrees C and 65% RH to determine delayed mortality. Comparison of the time required for 50% (LT50) and 95% (LT95) mortality indicated that R. dominica adults were consistently and significantly more susceptible (died quickly) than S. oryzae adults when exposed to spinosad-treated commodities. In general, the toxicity of liquid and dry spinosad formulations was similar against R. dominica or S. oryzae. The toxicity of spinosad to each species varied slightly among the three commodities, and there were no consistent trends to suggest that spinosad was more effective on one commodity versus another. LT50 values based on immediate mortality for R. dominica on all commodities ranged from 0.45 to 0.74 d; corresponding values based on delayed mortality ranged from 0.04 to 0.23 d, suggesting delayed toxic action of spinosad in R. dominica. LT50 values based on immediate and delayed mortality for S. oryzae on all three commodities treated with the two spinosad formulations were essentially similar and ranged from 2.75 to 4.56 d. LT95 values for R. dominica based on immediate mortality on spinosad-treated commodities ranged from 1.75 to 3.36 d, and those based on delayed mortality ranged from 0.49 to 1.88 d. There were no significant differences in LT95 values based on immediate and delayed mortality for S. oryzae on spinosad-treated commodities, and the LT95 values ranged from 7.62 to 18.87 d. The toxicity of spinosad was enhanced during a 24-h holding period after removal from spinosad-treated commodities only against R. dominica adults, and possible reasons for increased postexposure mortality of R. dominica adults after brief exposures to spinosad warrant further study.     

Alpha-amylase activity of Rhyzopertha dominica (Coleoptera: Bostrichidae) reared on several wheat varieties and its inhibition with kernel extracts

Total progeny of Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) reared on 10 wheat, Triticum aestivum L., varieties was evaluated. Higher amylase activities were detected in populations with few individuals, whereas the opposite was observed in higher populations. As protein ingested increased, reproductive success increased. However, consumption of wheat protein was inversely correlated with amylase activity levels (r = -0.66). Amylase activity in homogenates of R. dominica populations showed variable inhibition by wheat extracts prepared from wheat varieties on which they were reared. Insect populations with lowest amylase activities were inhibited more by wheat extracts than those with higher amylase activity (r = -0.77). An electrophoretic analysis revealed four phenotypes showing combinations of three isoamylases (Rm 0.70, 0.79, and 0.90) in different populations of R. dominica. Some of the insect progeny that emerged from resistant wheat varieties contained the three isoamylases, whereas progeny that emerged from the most susceptible varieties showed reduced activity of isoamylases 0.70 or 0.90. These results suggest that the alpha-amylase activity levels and the composition of isoamylases in R. dominica populations are modulated by diet and that the alpha-amylase inhibitory activity of the wheat kernels influences these variations.     

Characterization of midgut trypsin-like enzymes and three trypsinogen cDNAs from the lesser grain borer, Rhyzopertha dominica (Coleoptera: Bostrichidae)

Protein digestion in the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae), results from the action of a complex of serine proteinases present in the midgut. In this study we partially characterized trypsin-like enzyme activity against N-alpha-benzoyl-L-arginine p-nitroanilide (BApNA) in midgut preparations and cloned and sequenced three cDNAs for trypsinogen-like proteins. BApNAase activity in R. dominica midgut was significantly reduced by serine proteinase inhibitors and specific inhibitors of trypsin, whereas BApNAase activity was not sensitive to specific inhibitors of chymotrypsin or aspartic proteinases. However, trans-epoxysuccinyl-L-leucylamido-(4-guanidino) butane (E-64) inhibited BApNAase activity by about 30%. BApNAase was most active in a broad pH range from about pH 7 to 9.5. The gut of R. dominica is a tubular tract approximately 2.5 mm in length. BApNAase activity was primarily located in the midgut region with about 1.5-fold more BApNAase activity in the anterior region compared to that in the posterior region. Proteinases with apparent molecular masses of 23-24 kDa that were visualized on casein zymograms following electrophoresis were inhibited by TLCK. Three cDNAs for trypsinogen-like proteins were cloned and sequenced from mRNA of R. dominica midgut. The full cDNA sequences consisted of open reading frames encoding 249, 293, and 255 amino acid residues for RdoT1, RdoT2, and RdoT3, respectively. cDNAs RdoT1, RdoT2, and RdoT3 shared 77-81% sequence identity. The three encoded trypsinogens shared 54-62% identity in their amino acid sequences and had 16-18 residues of signal peptides and 12-15 residues of activation peptides. The three predicted mature trypsin-like enzymes had molecular masses of 23.1, 28, and 23.8 kDa for RdoT1, RdoT2, and RdoT3, respectively. Typical features of these trypsin-like enzymes included the conserved N-terminal residues IVGG62-65, the catalytic amino acid triad of serine proteinase active sites (His109, Asp156, Ser257), three pairs of conserved cysteine residues for disulfide bridges, and the three residues (Asp251, Gly274, Gly284) that determine specificity in trypsin-like enzymes. In addition, RdoT2 has both a PEST-like sequence at the C-terminus and a free Cys158 near the active site, suggesting instability of this enzyme and/or sensitivity to thiol reagents. The sequences have been deposited in GenBank database (accession numbers AF130840 for RdoT1, AF130841 for RdoT2, and AF130842 for RdoT3).     

Suitability of five species of stored-product insects as hosts for development and reproduction of the parasitoid Anisopteromalus calandrae (Hymenoptera: Pteromalidae)

We investigated the ability of two populations of Anisopteromalus calandrae (Hymenoptera: Pteromalidae), to parasitize and develop on late instars of five different stored-product insects that typically complete their development inside seeds of grain or legume species or other dry commodity. The host species were the cigarette beetle, Lasioderma serricorne (F.); cowpea weevil, Callosobruchus maculatus (F.); rice weevil, Sitophilus oryzae (L.); lesser grain borer, Rhyzopertha dominica (F.); and Angoumois grain moth, Sitotroga cerealella (Olivier). Experiments were conducted in the laboratory in a no-choice design by using petri dishes (15 by 100 mm) as experimental arenas with 20 host larvae. A. calandrae females from populations originating in Georgia (GA) and Oklahoma (OK) were introduced singly into experimental arenas and allowed to sting and oviposit for 24 h. Parasitism by the OK population was greater than that for the GA population across all hosts. However, no or very low parasitism was found on Angoumois grain moth for either population in this experiment. The highest number of parasitoid progeny was recorded on cowpea weevil (15.9) followed by rice weevil (11.5) and cigarette beetle (10.8) for the OK population. A similar trend was observed in the GA population. The highest proportion of female progeny was produced on cowpea weevil (73.0%) by the OK population. Conversely, a higher proportion of female progeny was produced on rice weevil (64.6%) by the GA population than produced by the OK population. Parasitoid adults were significantly larger and heavier when they developed on cowpea weevil irrespective of parasitoid population. The possible application of these results for biological control of stored-product insects is discussed.     

Morphology and chemistry of Dufour glands in four ectoparasitoids: Cephalonomia tarsalis,C. waterstoni (Hymenoptera: Bethylidae), Anisopteromalus calandrae,and Pteromalus cerealellae (Hymenoptera: Pteromalidae)

The venom apparatus of four hymenopterous parasitoids, including two bethylids, C. tarsalis (Ashmead) and C. waterstoni (Gahan), and two pteromalids, A. calandrae (Howard) and P. cerealellae (Ashmead), were removed and the associated Dufour glands characterized with respect to their external morphology and chemistry. Dufour glands in all four species have a characteristic translucent appearance that apparently results from their lipid content. The stalked Dufour glands of C. tarsalis and C. waterstoni are pear-shaped and have overall lengths of approximately 0.2 and 0.15 mm, respectively. The thin venom glands are bifurcate and insert through a fine duct into the transparent ovoid- to pear-shaped venom reservoir in these bethylids. In A. calandrae and P. cerealellae the Dufour glands are elongated, tubular structures of ca. 0.35 and 0.8 mm in length, respectively, that constrict to a short stalk that empties into the common oviduct. The venom glands in these pteromalids are simple elongated structures that insert into the sac-like venom reservoir through a fine duct. The chemistry of the volatile contents of the Dufour gland in these four species differs considerably. C. tarsalis Dufour glands contain the same hydrocarbon components as found on the cuticle of this species (Ann. Entomol. Soc. Am. 91:101-112 (1998)), and no other chemicals. The Dufour glands of C. waterstoni also contain only hydrocarbons, most of which are the same as the cuticular hydrocarbons (Ann. Entomol. Soc. Am. 85:317-325 (1992)), but in addition the Dufour gland contains ca. 3% of a mixture of 2,17- and 2,19-dimethyl C(23). A. calandrae Dufour gland chemistry is somewhat more complex than that of either of the two bethylids, but like the bethylids, only hydrocarbons are present. The carbon number range is from C(30) to C(39) and consists of a mixture of n-alkanes (C(30)-C(38)); 3-, 5-, 7-, 9-, 11-, 12-, 13-, 14-, 15- and 17-methyl alkanes; 3,7- and 3,11-dimethyl alkanes; 5,9- and 5,17-dimethyl alkanes; 7,11-, 9,13-, 13,17-, 14,18- and 15,19-dimethyl alkanes; 3,7,11- and 3, 9,15-trimethyl alkanes; and 3,7,11,15-tetramethyl alkanes. The cuticular hydrocarbons of this species have not been previously reported, but they are the same as the Dufour gland hydrocarbons. The Dufour glands of P. cerealellae contain both hydrocarbons and two long-chain aldehydes. Most of the hydrocarbons are identical to those found on the cuticle of this species (Ann. Entomol. Soc. Am. 94:152-158 (2001)), but in addition, 5,9-dimethyl C(27), 5,13-, 5,17- and 5,19-dimethyl C(35), 12- and 14-methyl C(36), 12,16- and 13,17-dimethyl C(36), 13-methyl C(37) and 13,17-dimethyl C(37) are present. The two aldehydes detected in glands from P. cerealellae are n-tetracosanal (C(23)CHO) and n-hexacosanal (C(25)CHO).     

Effect of temperature and commodity on insecticidal efficacy of spinosad dust against Sitophilus oryzae (Coleoptera: Curculionidae) and Rhyzopertha dominica (Coleoptera: Bostrychidae)

The insecticidal effect of spinosad dust, a formulation that contains 0.125% spinosad, was evaluated against adults of Sitophilus oryzae (L.) and Rhyzopertha dominica (F.) at three temperature levels (20, 25, and 30 degrees C) and four commodities (wheat, Triticum aestivum L.; barley, Hordeum vulgare L.; rice, Oryza sativa L.; and maize, Zea mays L.). For this purpose, quantities of the above-mentioned grains were treated with spinosad at two dose rates (20 and 50 ppm of the formulation, corresponding to 0.025 and 0.06 ppm AI, respectively), and mortality of the exposed adults in the treated grains was measured after 7 and 14 d, whereas progeny production was assessed 65 d later. Generally, for both species, mortality increased with dose, exposure interval, and temperature. For S. oryzae, adult survival and progeny production were lower on wheat than the other grains. After 14 d of exposure, mortality of S. oryzae adults on wheat treated with 50 ppm ranged between 61 and 98%, whereas in the other three commodities it did not exceed 42%. Mortality of R. dominica after 14 d on grains treated 50 ppm ranged between 91 and 100%. For this species, progeny production from exposed parental adults was low in all commodities regardless of temperature. Results indicate that spinosad dust can be used as an alternative to traditional grain protectants, but its effectiveness is highly determined by the target species, commodity, dose, and temperature.     

Thermal requirements of Fidiobia dominica (Hymenoptera: Platygastridae) and Haeckeliania sperata (Hymenoptera: Trichogrammatidae), two exotic egg parasitoids of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Diaprepes abbreviatus is an exotic root weevil occurring in southern US. It is a highly polyphagous species which can complete its entire life cycle on citrus and several woody ornamental plants. The lack of native egg parasitoids for this weevil in citrus orchards has triggered efforts to evaluate candidate egg parasitoids from the Caribbean Region into Florida. The egg parasitoids Fidiobia dominica and Haeckeliania sperata are two exotic natural enemies of D. abbreviatus recently introduced in the US in a classical biological control program. The thermal requirements of both parasitoids were studied in the laboratory. The upper development threshold (UDT) of F. dominica was 30.0°C, its maximal development rate (MDR) occurred at 27.6°C, its lower development threshold (LDT) was 9.6°C and its thermal constant (K) for development from egg to adult was 293.1 DD. For H. sperata, UDT was 35.0°C, MDR occurred at 31.0°C, LDT was around 15°C and K was 188.1 DD. Based on these results, both species would be able to complete 17 to 18 generations annually in southern Florida. However, host availability during critical periods could severely impair the ability of these egg parasitoids to establish and successfully control D. abbreviatus in areas where winter temperatures fluctuate around 12°C, the LDT for this pest.