Diaprepes Abbreviatus Research Articles

A NEW MEMBER OF THE GROWTH-PROMOTING GLYCOPROTEINS FROM DIAPREPES ROOT WEEVIL (COLEOPTERA: CURCULIONIDAE)

Abstract A new member belonging to the family of growth-promoting glycoproteins referred to as imaginal disc growth factors, IDGF, was identified from the root weevil Diaprepes abbreviatus (L.), (Coleoptera: Curculionidae). The imaginal disc growth factor full length cDNA transcript, designated as idgf-DRW, was cloned and identified from tissue of adult, teneral DRW females. Sequencing and subsequent homology comparisons of the nucleotide sequence (GenBank accession no. AY821658) indicated that the open reading frame (ORF) consisted of 1329 bases and encoded a putative protein of 442 amino acid residues with a calculated molecular weight of 49.5 kDa and a pI value of 6.68. BLASTX comparisons of the idgf-DRW cDNA sequence showed that the deduced amino acid sequence designated as IDGF-DRW (AAV68692.1) had 43% to 51% similarity with IDGF1-5 and DS47 from Drosophila melanogaster, D. simulans, and D. yakuba, 51% similarity with IDGF in Pieris rapae, and 51% similarity with an IDGF-like protein in Bombyx mori. ...

Effect of Root Feeding by <I>Diaprepes abbreviatus</I> (Coleoptera: Curculionidae) Larvae on Leaf Gas Exchange and Growth of Three Ornamental Tree Species

Diaprepes abbreviatus L. (Coleoptera: Curculionidae), feeds on a variety of ornamental plants grown in southern Florida. Studies were conducted to evaluate the effects of root feeding by D. abbreviatus larvae on leaf gas exchange and growth of three ornamental tree species commonly grown in southern Florida that are known hosts of this weevil: green buttonwood, Conocarpus erectus L.; live oak, Quercus virginiana Mill.; and pygmy date palm, Phoenix roebelenii O'Brien. These hosts were grown in containers and infested with weevil larvae. Net CO2 assimilation, transpiration, and stomatal conductance of CO, were measured monthly. Leaf, stem, and root fresh and dry weights of each species also were determined. In one of two tests, larval root feeding significantly reduced net CO2 assimilation, transpiration, and stomatal conductance of CO2 of infested green buttonwood trees. Leaf gas exchange of live oak was not affected by larval infestation. In addition to testing cumulative effects of multiple infestations of larvae, the effects of incremental infestations on leaf gas exchange and fresh and dry weights also were tested for each plant species. Net CO2 assimilation, transpiration, stomatal conductance of CO2, and dry weights of green buttonwood were reduced as a result of larval root feeding, whereas there was no effect of incremental larval infestations on leaf gas exchange of live oak or pygmy date palm within the experimental time frame. There was no effect of incremental larval infestations on dry weights of live oak, but leaf, stem, and dry root weight of pygmy date palm were lower for infested plants than for noninfested plants. Overall, green buttonwood was more susceptible to larval root feeding damage than either live oak or pygmy date palm.

Phylogenetic and Structural Relationships of the PR5 Gene Family Reveal an Ancient Multigene Family Conserved in Plants and Select Animal Taxa

Pathogenesis-related group 5 (PR5) plant proteins include thaumatin, osmotin, and related proteins, many of which have antimicrobial activity. The recent discovery of PR5-like (PR5-L) sequences in nematodes and insects raises questions about their evolutionary relationships. Using complete plant genome data and discovery of multiple insect PR5-L sequences, phylogenetic comparisons among plants and animals were performed. All PR5/PR5-L protein sequences were mined from genome data of a member of each of two main angiosperm groups-the eudicots (Arabidoposis thaliana) and the monocots (Oryza sativa)-and from the Caenorhabditis nematode (C. elegans and C. briggsase). Insect PR5-L sequences were mined from EST databases and GenBank submissions from four insect orders: Coleoptera (Diaprepes abbreviatus and Biphyllus lunatus), Orthoptera (Schistocerca gregaria), Hymenoptera (Lysiphlebus testaceipes), and Hemiptera (Toxoptera citricida). Parsimony and Bayesian phylogenetic analyses showed that the PR5 family is paraphyletic in plants, likely arising from 10 genes in a common ancestor to monocots and eudicots. After evolutionary divergence of monocots and eudicots, PR5 genes increased asymmetrically among the 10 clades. Insects and nematodes contain multiple sequences (seven PR5-Ls in nematodes and at least three in some insects) all related to the same plant clade, with nematode and insect sequences separating as two clades. Protein structural homology modeling showed strong similarity among animal and plant PR5/PR5-Ls, with divergence only in surface-exposed loops. Sequence and structural conservation among PR5/PR5-Ls suggests an important and conserved role throughout the evolutionary divergence of the diverse organisms from which they reside.

Associations of soil iron with citrus tree decline and variability of sand, soil water, pH, magnesium and Diaprepes abbreviatus root weevil: Two-site study

The hypothesis of associations of environmental soil heterogeneity with citrus tree decline and Diaprepes abbreviatus (L.) root weevil variability was tested in two flatwoods fields of ‘Hamlin’ orange trees ( Citrus sinensis (L.) Osb.). Studies were conducted on a loamy, poorly drained Mollisol in Osceola County, central Florida in 2002, and on a sandy, poorly drained Spodosol in DeSoto County, south-west Florida during 2001–2003. Adult weevils were monitored using 50 Tedders traps arranged in a 34 m × 25 m grid at the Osceola site, and using 100 identical traps in a 30 m × 15 m grid at the DeSoto site. Soil water content (SWC), texture, pH, Ca, Mg, Fe, Cu and other nutrients were measured at each trap. Soil was strongly acidic (pH 4.9 ± 0.4) at the Osceola site but near neutral (pH 6.6 ± 0.4) at the DeSoto site. The Mehlich-I extractable soil Mg and Ca were correlated to soil pH and SWC in both soils, and extractable Fe was related to pH, SWC and Mg in the Spodosol (0.30 < R 2 < 0.65, P < 0.01). The weevil density was high in areas low in soil Mg and Ca in the acidic Mollisol, but high in areas with high soil pH, and Mg and low sand content in the near neutral Spodosol ( P < 0.05). Tree decline was associated with soil Fe concentrations >40 mg kg −1 in the Mollisol ( P < 0.01). Weevil density was low at a soil pH between 5.7 and 6.2. The range of spatial dependence of weevil population, soil pH, SWC, Fe, Mg and sand varied between 60 and 100 m in the Mollisol and the Spodosol. Soil-weevil-tree simple and multivariate linear models were established to put into practices for predicting and controlling the weevil population and tree decline in the future. Differences in site characteristics suggested the need for site-specific weevil and citrus tree management.

Effect of temperature on life history of Aprostocetus vaquitarum (Hymenoptera: Eulophidae), an egg parasitoid of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Abstract The effect of temperatures ranging from 5 to 40 °C on Aprostocetus vaquitarum Wolcott (Hymenoptera: Eulophidae) oviposition and development were investigated. There were significant differences in the rate of development among the temperatures for all life stages. The egg stage lasted approximately 7 times longer at 15 than at 25 or 30 °C and the larval stage, consisting of 4 instars, took significantly less time at each increasing temperature from 15 to 30 °C. A. vaquitarum development from egg to adult took 16.3 days at 30 °C, significantly faster than the other temperatures tested. At 15 °C A. vaquitarum reached the pupal stage after a mean of 41.6 days but did not successfully complete pupation. A. vaquitarum eggs hatched on 66% of the parasitized egg masses at 35 °C but did not survive past the first instar. A. vaquitarum did not develop past the egg stage at 5 or 40 °C. Host Diaprepes abbreviatus L. (Coleoptera: Curculionidae) eggs also did not survive at temperatures of 35 and 40 °C on live plants. Upper and lower temperature thresholds for A. vaquitarum development were calculated to be 33.0 and 16.0 °C, respectively. Maximum development rate occurred at 30.9 °C and a thermal constant of 494.2 DD was calculated. Photoperiods ranging from 10L:14D to 16L:8D did not significantly affect development time from egg to adult at 25 °C. Oviposition was significantly higher at 30 °C than at the other temperatures tested; oviposition was also relatively high at 25 and 35 °C and several eggs were laid at 20 °C. Relatively cool winter temperatures in central Florida may be contributing to the limited range of A. vaquitarum in the state.

TOXICITY OF PESTICIDES USED IN CITRUS TO APROSTOCETUS VAQUITARUM (HYMENOPTERA: EULOPHIDAE), AN EGG PARASITOID OF DIAPREPES ABBREVIATUS (COLEOPTERA: CURCULIONIDAE)

Twelve pesticides used in citrus were tested for their contact toxicity to Aprostocetus vaquitarum Wolcott (Hymenoptera: Eulophidae) a parasitoid of Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae). Sevin® 80 WSP, Malathion 5 EC, and Imidan® 70 WSB resulted in the most rapid death of A. vaquitarum adults. Admire® 2F, Danitol® 2.4EC, and Surround® WP were also very detrimental. Kocide® 101 WP, Citrus Soluble Oil, Micromite® 80 WGS, Acramite® 50 WS, Micromite® 80 WGS Citrus Soluble Oil, Aliette WDG, and Agrimek® 0.15 EC Citrus Soluble Oil were slightly to non-toxic to A. vaquitarum. The relative toxicity of the pesticides was consistent up to four weeks after application. Significantly fewer adult A. vaquitarum emerged from D. abbreviatus eggs laid on foliage treated in the field with Sevin® XLR and Imidan® 70 WSB than emerged from the water treated control. Field residues of Sevin® XLR remained toxic for seven days while the effects of Imidan® 70 WSB were no longer significant after one week. The number of A. vaquitarum adults emerging from host eggs laid on treated foliage was not significantly different among Micromite® 80 WGS, Acramite® 50 WS, and the control, but significantly fewer adults emerged from foliage treated with either Micromite® 80 WGS Citrus Soluble Oil or Citrus Soluble Oil alone. There were no significant differences between oviposition or new generation adults when A. vaquitarum was exposed to Micromite® 80 WGS or a water control.

WATER STRESS AND ROOT INJURY FROM SIMULATED FLOODING AND DIAPREPES ABBREVIATUS ROOT WEEVIL LARVAL FEEDING IN CITRUS

Environmental stress from flooding can occur simultaneously with root weevil infestation to damage plant root systems. We conducted two factorial studies of flooding duration and Diaprepes abbreviatus (L.) root weevil larval feeding injury on citrus in the greenhouse in 2002 and 2003. Our objectives were to investigate the effect of soil anoxia by simulated flooding on plant water stress and the impact of prior flooding on root susceptibility to subsequent larval weevil feeding. The treatments consisted of two rootstock varieties, Swingle citrumelo [SWI; Citrus paradisi Macfad x Poncirus trifoliata (L.) Raf.] and Smooth Flat Seville (SFS; Citrus aurantium L.), flooding durations of 0, 10, 20, 30, or 40 days, and Diaprepes larval infestations of 0 and 5 neonates per seedling for 40 days. We used a Candler sand with 8 replicates in Experiment I and a Floridana loam with 15 replicates in Experiment II. Treatments were arranged in a completely ramdomized design. Plants were flooded, drained for a week, and then 1-day-old neonate larvae were introduced onto the soil surface of each seedling. Flooding significantly reduced soil redox potential (E h ), leaf stomatal conductance (g s ), and shoot growth (P < 0.05). Soil E h decreased from +220 to -100 mV within 1-3 days after flooding, and leaf g s declined from 260 to 80 mmol m -2 s -1 within 20 days of flooding. Flood-injured and larval-injured roots had little growth. With equal previous flooding durations (20 days), the larval survival was on average 25% higher in sandy soil than in loamy soil. Twenty-day prior flooded roots were more water stressed and also more susceptible to Diaprepes larval feeding injury. It is suggested that limited soil waterlogging and early root weevil larval control would be useful for plant protection.

Reduced Oviposition by Diaprepes abbreviatus (Coleoptera: Curculionidae) and Growth Enhancement of Citrus by Surround Particle Film

Reduced Oviposition by Diaprepes abbreviatus (Coleoptera: Curculionidae) and Growth Enhancement of Citrus by Surround Particle Film

Reduced Oviposition by &lt;I&gt;Diaprepes abbreviatus&lt;/I&gt; (Coleoptera: Curculionidae) and Growth Enhancement of Citrus by Surround Particle Film

Regularly applied sprays of a particle film, Surround WP, greatly enhanced the growth of citrus trees on a poorly drained Winder soil at Fort Pierce, FL. After 3 yr of applications every 3 or 4 wk, Surround-treated trees had at least 5 times the mass, 6 times the canopy volume, and approximately 4 times the cross-sectional area of the tree stems at the graft union compared with untreated trees. The larger Surround-treated trees attracted a higher number of adult weevil Diaprepes abbreviatus (L.) and to a lesser extent citrus root weevil, Pachnaeus litus (Germar), per tree, but there was an equivalent number of egg masses per tree compared with the control trees. The number of egg masses per female weevil oviposited on Surround-treated trees was significantly less than either the control trees or trees treated biannually with an entomopathogenic nematode, BioVector. The number of larvae per tree recovered from the roots of excavated trees was greater from trees treated with Surround once every 3 wk compared with control trees. The data suggest that Surround particle film greatly enhanced the growth of citrus trees grown in a poorly drained soil. The reduction in oviposition by D. abbreviatus was insufficient to significantly reduce the number of root weevil larvae per tree feeding on the roots. However, the more vigorous trees resulting from Surround applications may be more resistant or tolerant to root weevil feeding.

Transfer and fate of seminal fluid molecules in the beetle, Diaprepes abbreviatus: Implications for the reproductive biology of a pest species

Molecules transferred from males to females via seminal fluids are important to the study of insect reproduction because they affect female physiology, reproductive behavior, and longevity. These molecules (seminal fluid molecules or SFMs) interest applied entomologists because of their potential use in insect control. SFMs are also interesting because of their relatively rapid evolution and important role in post-mating sexual selection. We studied SFMs in Diaprepes abbreviatus, a major pest of numerous plant species of economic importance. Using radiolabeled-methionine ( 35S), we found that D. abbreviatus males synthesized proteins de novo in their reproductive tissues after mating. Males that were fed radiolabeled methionine transferred radioactivity to females beginning within the first 10 min of mating. Male-derived substances are absorbed from the female's reproductive tract into the hemolymph and circulated throughout the body, but are found primarily in the eggs and ovaries. As a result, SFMs may be a useful means of both horizontal (to mates) and vertical transfer (to offspring) of control agents between conspecifics.

Successes and failures in the use of parasitic nematodes for pest control

Advances in mass-production and formulation technology of entomopathogenic nematodes, the discovery of numerous isolates/ strains and the desirability of reducing pesticide usage have resulted in a surge of scientific and commercial interest in these nematodes. The lessons learned from earlier problems have encouraged scientists and leading commercial companies to increase their efforts toward improving cost efficiency and better product positioning in the market within the confines of product capabilities. The successes or failures of the nematodes against 24 arthropod pest species of agriculture and animals and against a major slug pest in agriculture are discussed in this review. Commercial successes are documented in markets such as citrus (Diaprepes root weevil), greenhouses and glasshouses (black vine weevil, fungus gnats, thrips, and certain borers), turf (white grubs, billbugs, and mole crickets), and mushrooms (sciarid flies). In addition, the successful commercialization of a nematode (Phasmarhabditis hermaphrodita) against slugs in agricultural systems is presented. Despite this progress, the reality is that nematode-based products have limited market share. Limited share is attributed to higher product cost compared to standard insecticides, low efficacy under unfavorable conditions, application timing and conditions, limited data and cost benefit in IPM programs, refrigeration requirements and limited room temperature shelf life (product quality), use of suboptimum nematode species, and lack of detail application directions. One or more of these factors affected the market

Polymorphic microsatellite loci for Diaprepes root weevil (Diaprepes abbreviatus L.)

Abstract Diaprepes abbreviatus (L.) is an insect pest of the US agriculture that originated from the Caribbean islands. Larvae are of economic importance in both nursery and commercial citrus plantings due to root feeding. Eight polymorphic microsatellite markers were developed from a (CA)n‐enriched genomic library of Diaprepes root weevil. Three to eight alleles were observed for each locus during screening of 17 to 25 individuals. Observed and expected heterozygosities ranged from 0.182 to 0.864 and 0.587 to 0.835, respectively. These markers will be useful to characterize the genetic variability and track the migration patterns of populations of D. abbreviatus (L.).

Effect of temperature on life history of Quadrastichus haitiensis (Hymenoptera: Eulophidae), an endoparasitoid of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Abstract The influence of temperature on life history traits of the egg parasitoid Quadrastichus haitiensis (Gahan) (Hymenoptera: Eulophidae) was investigated in the laboratory on eggs of the root weevil Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae). Duration of development from egg to adult decreased from 39.99 ± 0.27 days to 13.57 ± 0.07 days (mean ± SE) as temperature increased from 20 to 33 °C, respectively. No development was observed at 5–15 °C. Fecundity was highest at 25 and 30 °C (70–73 eggs per female) but was reduced at 33 °C (21.5 eggs per female). Oviposition rate was also reduced at 33 °C. Q. haitiensis accepted host eggs from 0 to 7 days old for oviposition but was most prolific when parasitizing 1- to 4-day-old eggs. Very few adult Q. haitiensis emerged from host eggs that were 5–7 days old, however, D. abbreviatus egg mortality was similar for eggs 0–7 days old. A brief description of the parasitoid egg, larva, prepupae, and pupa is provided.

INFECTIVITY OF TWO ISOLATES OF HELICOSPORIDIUM SPP. (CHLOROPHYTA: TREBOUXIOPHYCEAE) IN HETEROLOGOUS HOST INSECTS

Abstract Members of the genus Helicosporidium are the first described algal insect pathogens. They have a close affinity to the non-photosynthetic algae of the genus Prototheca, and have a wide host range, infecting many species of aquatic and terrestrial insects. In this study the infectivity of two Helicosporidium spp. isolates, originating from a black fly (SjHe) and an aquatic weevil (CsHe), was tested against a weevil Diaprepes abbreviatus (L.) and three mosquito species Anopheles quadrimaculatus Say, Culex quinquefasciatus Say, and Aedes aegypti (L.). The weevil constitutes a new experimental host record for helicosporidia. The CsHe isolate was more virulent than the SjHe isolate in D. abbreviatus. Anopheles quadrimaculatus was the most susceptible mosquito species measured by infection rate and mortality. The infectivity and virulence of SjHe and CsHe isolates did not differ in any of the mosquito species.

Chave de identificação, ocorrência e distribuição dos curculionídeos-das-raízes dos citros em São Paulo e Minas Gerais

O objetivo deste trabalho foi efetuar a diagnose de quatro espécies de curculionídeos-das-raízes que ocorrem nos citros, fornecer uma chave para identificação de 14 espécies, além de estudar sua ocorrência e distribuição na área citrícola dos estados de São Paulo e Minas Gerais. As quatro espécies são registradas pela primeira vez causando danos em citros pertencem ao gênero Naupactus Dejean (Curculionidae; Entiminae; Naupactini): N. bellus Boheman, N. cinerosus Boheman, N. decorus (Fabricius) e N. virens Boheman. Das 14 espécies listadas na chave, onze pertencem ao gênero Naupactus [N. ambiguus Boheman, N. bellus, N. cervinus Boheman, N. cinerosus; N. curtus Boheman, N. decorus, N. navicularis Boheman, N. rivulosus (Olivier), N. tarsalis Boheman, N. versatilis Hustache e N. virens; uma ao gênero Teratopactus Heller (T. nodicollis (Boheman)]; uma ao gênero Parapantomorus Emden [P. fluctuosus (Boheman)] e uma ao gênero Symmathetes (S. kollari Schoenherr). Os curculionídeos-das-raízes foram encontrados em todas as regiões citrícolas dos estados de São Paulo e Minas Gerais sendo a região centro-sul do estado de São Paulo a que apresentou maior número de espécies. N. tarsalis, N. versatilis e P. fluctuosus ocorreram em maior número de municípios.

RESPONSE OF DIAPREPES ABBREVIATUS (COLEOPTERA: CURCULIONIDAE) TO APPLICATION CONCENTRATIONS OF A PARTICLE FILM

Kaolin-based particle films were developed for horticultural applications as an environmentally benign method to deter arthropod pests and plant diseases (Glenn et al. 1999). Since the commercialization of a wettable powder formulation (Surround® WP, Engelhard Corp., Iselin, NJ), this product has been examined for applications against pests of temperate fruit trees (Puterka et al. 2000; Knight et al. 2000; Unruh et al. 2000); cotton (Showler 2002); whitefly (Liang & Liu 2002); thrips (Kerns & Wright 2000); and other pests. The value of the film includes deterrence of feeding and oviposition, and beneficial effects on carbon assimilation, leaf temperature, and fruit yield (Glenn et al. 2001). Particle film technology seems especially well suited for use in areas of low rainfall where leaf residues of the product can be maintained without frequent re-application. Use of particle films in the humid subtropical environment of Florida citrus groves may be limited by removal of residues by seasonally heavy rain (Lapointe 2000). In addition to deterring pests (Puterka et al. 2000; Unruh et al. 2000; Knight et al. 2000; Lapointe 2000), particle films have been shown to increase fruit tree productivity in semiarid and subhumid environments by reducing heat stress (Glenn et al. 2001). The humid subtropical environment experienced by citrus trees in Florida presents a different set of challenges for successful use of particle films. Periods of high rainfall are interspersed with dry periods accentuated by highly porous soils and intense solar radiation. Particle films, while effective in the laboratory (Lapointe 2000), may not adhere sufficiently to citrus leaves in the field in Florida to maintain deterrence to Diaprepes root weevils after heavy rains over the entire rainy season (May-October) when adults are active. Prior to establishment of field trials (reported elsewhere), I investigated the feeding and oviposition response of Diaprepes root weevil to varying concentrations of Surround WP. A hand-held sprayer was used to apply the product at three concentrations to bouquets of citrus leaves harvested from Citrus macrophylla Wester seedlings grown in a greenhouse. Methods were similar to those reported by Lapointe (2000). Foliage bouquets were sprayed to runoff with the manufacturer’s recommended concentration (x = 3% wt/ vol), 0.5x, or 0.1x, or with water alone. Foliage was allowed to dry and then placed in screened cages (30 × 30 × 30 cm) containing 5 male and 5 female Diaprepes root weevils. Weevils were obtained from a colony maintained at the U.S. Horticultural Laboratory, Ft. Pierce, FL (for rearing conditions, see Lapointe & Shapiro 1999). Each of the 4 treatments was replicated 3 times for a total of 12 cages and 120 weevils. Cages were randomly arranged on open shelves in a temperature-controlled greenhouse. Each cage was provided with wax paper strips as substrates for oviposition (Wolcott 1933). Bouquets and wax paper strips were removed every 2 days until 17 days and examined for egg masses. Leaf area consumed was assessed by tracing the leaf notches. Tracings were digitally scanned and the resulting files were imported into an image analysis computer program as described by Lapointe (2000). Leaf area consumed and total number of eggs oviposited were analyzed by ANOVA with the type III sum of squares for cage as the error term. Means were compared by the Tukey honestly significant differences (HSD) test (Abacus Concepts 1996). Linear regression was used to calculate the deposition of particle film required to achieve 50% reduction in leaf consumption and oviposition. The deterrent effect of Surround against feeding and oviposition fell off quickly as coverage was reduced in a greenhouse trial. Adult weevils fed untreated citrus leaves over 17 d consumed approximately 3 times as much leaf area as weevils

Successful oviposition and reproductive biology of Aprostocetus vaquitarum (Hymenoptera: Eulophidae): A predator of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Abstract Aprostocetus vaquitarum (Wolcott) causes 78–91 percent mortality to eggs of Diaprepes abbreviatus (L.), under field conditions in southern Florida. In the laboratory, A. vaquitarum was reared on D. abbreviatus eggs at 25 °C, a photoperiod of 12:12 (L:D) and with abundant hosts, A. vaquitarum adult females lived around 15 days. Oviposition was significantly affected by the age of the host egg mass. Egg masses aged 0- to 3-day-old were accepted significantly better than those aged 4–6 days. The mean number of eggs deposited per female was around 53, with extreme values of 124 and 19 eggs per female. Using these data in combination with the sex ratio observed in the field (0.16) and the duration of the preimaginal stages, r m (0.168–0142 day −1 ), T (22.39–22.89 days), and R 0 (43.03–25.81 females per female) were calculated.

EFFECTS OF HOST AGE, FEMALE PARASITOID AGE, AND HOST PLANT ON PARASITISM OF CERATOGRAMMA ETIENNEI (HYMENOPTERA: TRICHOGRAMMATIDAE)

Parasitism of Diaprepes abbreviatus (L.) eggs by Ceratogramma etiennei Delvare as influenced by host age, age of the female parasitoid, and host plant preference was evaluated under laboratory or greenhouse tests. Percent parasitism of D. abbreviatus eggs by C. etiennei decreased as eggs matured. The optimal age of C. etiennei for successful parasitism ranged from 1-2-d old. Host plant leaf thickness, leaf pubescence, and plant strata probably played a role on the parasitism by C. etiennei. This parasitoid is diurnal and spent approximately 5 min searching for eggs laid in cryptic locations, 46 min parasitizing an egg mass and 24 min resting. This biological information is relevant in evaluating the potential of C. etiennei in the classical biological control of D. abbreviatus.

Stabilization of beneficial traits in Heterorhabditis bacteriophora through creation of inbred lines

Abstract Serial culturing of organisms used for biological pest suppression often leads to detrimental genetic changes and loss of utility. We established that genetically homozygous inbred lines can deter beneficial trait decline in the entomopathogenic nematode, Heterorhabditis bacteriophora . Three inbred lines and the foundation population were serially cultured in the insect host, Galleria mellonella . Trait stability was evaluated by comparing serially cultured with non-cultured populations. Laboratory data indicated that serial culture of the foundation population (16 passages) resulted in more than a 30% loss in traits deemed beneficial for biological pest suppression i.e., virulence to an insect host ( Diaprepes abbreviatus ), reproductive capacity, heat tolerance (at 38 °C), and host-seeking ability. In contrast, the three inbred lines were impervious to decline in all beneficial traits. A greenhouse test targeting D. abbreviatus provided additional evidence that the biocontrol efficacy of the inbred lines remained stable during serial culture. Our results indicate that genetic factors played an important role in trait change, and creation of inbred lines may be a useful technique for maintaining beneficial traits.

Cuticular hydrocarbons on elytra of the Diaprepes root weevil Diaprepes abbreviatus (L.) (Coleoptera: Curculionidae)

Abstract 1 External gland openings and associated structures on the elytra of teneral and mature Diaprepes root weevils, Diaprepes abbreviatus (L.), were elucidated by scanning electron microscopy (SEM).2 There were clear differences between teneral, callow adults and fully mature adults. In the field, teneral adults remain in the pupal chamber in the soil until sclerotization of the cuticle is complete or nearly so.3 Phenotypic variation of the elytra in this species consists of varying patterns and coloration of scaled intervals between a variable number of raised ridges devoid of scales. In addition to being thinner and lighter in colour than fully mature adults, the elytra of teneral adults were devoid of waxy hydrocarbon secretions.4 External gland openings at the base of each scale were observed on teneral elytra and mature elytra washed with methylene chloride.5 SEM evidence to document the production of waxy filaments by these glands and partial characterization of these by gas chromatography and mass spectrometry are presented.