Cylas Formicarius Research Articles

Empirical evidence of a trade–off between reproductive effort and expectation of future reproduction in female three-spined sticklebacks

Optimal life-history models generally predict that the reproductive effort of iteroparous organisms may increase with age, as their expectation of future reproduction decreases. The population of three–spined sticklebacks ( Gasterosteus aculeatus ) in the Camargue (Rhone River Delta, France) is annual, all adults dying after their first breeding season. As the three–spined stickleback is a multiple spawner, we tested the hypothesis that reproductive effort may increase during the breeding season on field data. From 1987 to 1998, 653 female sticklebacks were collected in the field during the breeding seasons. The body size, body weight and weights of the liver, gonads and carcass were measured for these individuals. Only gravid females with mature eggs (176 fish) were included in the analysis. Considering the female three–spined stickleback as a capital breeder, the energetic resources available for allocation between soma and gonads were estimated by its body weight. Somatic condition decreased during the breeding season and reproductive effort (gonad weight relative to body weight) increased. These patterns did not vary significantly between years. These observed variations in reproductive effort during the breeding season can be interpreted as empirical evidence of a trade–off between reproductive effort and expectation of future reproduction.

Insect Resistance in Sweetpotato Plant Introductions

One hundred U.S. sweetpotato [Ipomoea batatus (L.) Lam.] plant introductions (PIs) and four control cultivars were screened for insect injury in 1993. Of the least injured by insects, 56 and 31 were tested again in 1994 and 1995, respectively. Among control cultivars, the most highly resistant was `Regal' (moderately resistant), followed by `Beauregard' (susceptible), `Centennial' (susceptible), and `Jewel' (susceptible). Stem and root injury by the sweetpotato weevil (SPW) [Cylas formicarius elegantulus (Summers)] and root injury by the wireworm (Conoderus sp.)–Diabrotica sp. (cucumber beetle)– Systena sp. (flea beetle) (WDS) complex were measured. SPW stem injury was less severe (P ≤ 0.05) in 1994 and 1995 in PIs 508523, 531116, and 564107 than in control cultivars. PIs 508523 and 531116 also suffered less SPW root injury than did `Regal'. In the six PIs with least SPW root injury, PIs 538354, 564149, 508523, 538286, 531116, and 564103, 70% to 85% of the roots were not injured compared with 36% in `Regal' and 6% in `Jewel'. SPW root injury scores (0 = no injury; 5 = severe injury) in those PIs averaged 0.5 vs. 2.3 for `Regal'. Only in PI 538286 was WDS injury to roots less than in `Regal' over 2 years. However, eight additional accessions suffered less WDS injury than `Regal' in 1995 and four of those were among the six with least SPW injury. The lower levels of combined insect injury found in these four PIs (compared to `Regal') show that PIs have potential use for increasing insect resistance in sweetpotato improvement programs.

Sweet Potato Pest Management. A Global Perspective

Drawing on the work of researchers from around the world, this book is a state-of-the-art summary of work in sweet potato pest management. The contributors address issues of crop protection and management of pests such as the sweet potato weevil, wireworms, chrysomelid and flea beetles, vine borers, plant-parasitic nematodes, and aphid and whitefly virus vectors and their associated viruses. They also present data on biological control of pests and the breeding of resistant cultivars. Most importantly, however, the researchers look beyond the fields to address regulatory issues and the socioeconomic problems of management.

Evaluation of the impact of sweetpotato weevil (Cylas formicarius) and of the effectiveness of Cylas sex pheromone traps at the farm level in Indonesia

We evaluated the impact of sweetpotato weevil ( Cylas formicarius (Fabricius); Coleoptera: Apionidae) and of other direct pests and diseases (rats, Ceratocystis fimbriata, white grubs, rootrots and root cracks), and the effectiveness of C. formicarius sex pheromone traps at the farm level in four villages in East and Central Java, Indonesia during 1994 - 1996. Marketable yields of sweetpotato and damage from weevils and from other pests and diseases were higher during the dry season, when damage from weevils reached 8.2% and the impact of other pests and diseases was 16.3%, reducing marketable yield from 3.32 to 2.50 kg/m2. During the wet season damage from sweetpotato weevil and from other pests and diseases dropped to 2.1 and 12.7% respectively. Varietal differences in damage from weevil and from other pests and diseases were not significant. In field trials with sex pheromone, lure loadings of 10, 50 and 100 mug placed at trap densities of 9, 25 and 100 traps/ha the average yield was 2.41 kg/m2 with sweetpotato weevil and other direct pests and diseases accounting for losses of 2.7% and 4.7% respectively. However, there were significant location-specific differences in weekly trap catch averages and in seasonal trap catch patterns. Trap catches ranged from averages of 475 and 584 weevils/week in the villages of Bendunganjati and Turi to 254 and 46 weevils/week in Ngargoyoso and Kradenan. The highest trap catches occurred at the highest sex pheromone loadings in all four locations. The effect of trap density on average weekly trap catch depended on location, with no significant effect of trap density on trap catch when the data from all locations were pooled. There was no statistically significant impact of sex pheromone traps on losses from sweetpotato weevil, although fields with blank lures had consistently higher levels of sweetpotato weevil damage. The highest trap catches occurred in Turi, which also had the highest levels of weevil damage. The use of sex pheromone traps led to damage reduction, even when weevil pressure and damage levels were low, as in the village of Kradenan. This suggests that there is potential for traps to play a role in reducing weevil damage in situations of higher weevil pressure.

さなぎ期にγ線を５０Ｇｙ照射されたアリモドキゾウムシの性的競争力

さなぎ期にγ線を５０Ｇｙ照射されたアリモドキゾウムシの性的競争力

Marking of the West Indian sweet potato weevil, Euscepes postfasciatus (Fairmaire) (Coleoptera : Curculionidae) with Calco Oil Red dye I. Effect of dye added to the artificial larval diet on development of the weevils, yield of adults and long lasting internal coloration in the adult

Adults of the West Indian sweet potato weevil, Euscepes postfasciatus were effectively marked with Calco Oil Red N-1700〔○!R〕 dye contained in the larval artificial diet. Addition of the dye to the diet had no significant effects on developmental period from egg hatch to adult eclosion, yield of adults, or the percent hatchability of eggs oviposited by marked adults. The color of the dye in the adult metathorax was still visible externally even 6 weeks after eclosion. These results indicate that the dye is useful as an internal marker of E. postfasciatus in the sterile insect technique.

Specificity of Response to Sex Pheromones Among Sweetpotato Weevils, Cylas puncticollis and C. brunneus

Trapping experiments were carried out in Uganda and Indonesia with decyl (E)-2-butenoate and dodecyl (E)-2-butenoate, previously identified as components of the female sex pheromones of the African species of sweetpotato weevil, Cylas puncticollis and C. brunneus, respectively. In Uganda, decyl (E)-2-butenoate attracted only C. puncticollis males, but dodecyl (E)-2-butenoate attracted males of both C. brunneus and C. puncticollis. Catches of C. puncticollis with both compounds were higher when they were dispensed from polyethylene vials rather than rubber septa, while dodecyl (E)-2-butenoate dispensed from rubber septa gave higher catches of C. brunneus and was more selective for this species. Release rates of the two compounds from the two types of dispenser were measured in the laboratory and possible explanations for differences in dispenser performance considered. Lures containing decyl (E)-2-butenoate were as attactive to male C. puncticollis as 10 live virgin female C. puncticollis weevils, but lures containing dodecyl (E)-2-butenoate were not always as attractive to male C. brunneus as the conspecific virgin female weevils. Dose–response relationships with the synthetic pheromones varied between repeat experiments and with the type of dispenser. Addition of dodecyl (E)-2-butenoate to decyl (E)-2-butenoate either did not affect or increased catches of C. puncticollis males, but adding 1% or more of decyl (E)-2-butenoate to dodecyl (E)-2-butenoate significantly reduced attractiveness to C. brunneus. Traps baited with synthetic lures captured male C. brunneus weevils mostly early in the evening while the majority of male C. puncticollis were trapped between 01:00 hr and 03:00 hr. This clear temporal separation of activity of males of the two species helps to ensure species specificity of mating in these sympatric species. In Indonesia, dodecyl (E)-2-butenoate but not decyl (E)-2-butenoate attracted C. formicarius males, but this attractiveness was less than 0.4% that of the pheromone of C. formicarius, (Z)-3-dodecenyl (E)-2-butenoate.

Transgenic sweet potato plants carrying the delta-endotoxin gene from Bacillus thuringiensis var. tenebrionis.

Some clones of sweet potato (Ipomoea batatas L.), transgenic plants of the cultivar ‘Jewel’, carrying the cryIIIA gene from Bacillus thuringiensis subsp. tenebrionis (B.t.t), were obtained. Molecular tests and biological activity experiments against sweet potato weevil (Cylas formicarius), were performed. The cryIIIA delta-endotoxin gene was cloned under the regulation of the 35S CaMV promoter and the TMV Omega fragment. The neomycin phosphotransferase (nptII) gene for kanamycin resistance was used as selection marker. An efficient protocol for in vitro plant regeneration, which combines naphtalenacetic acid (NAA) and 6-benzilaminopurin (BAP), was established. An Agrobacterium tumefaciens-mediated transformation protocol for sweet potato was implemented. An increase of the transformation frequency of sweet potato, compared to that previously reported, was obtained. Biological activity experiments to evaluate the insecticidal capacity of transgenic plants were performed against sweet potato weevil under both controlled, and field conditions. Plants from the two best resulting clones were tested by molecular methods such as RNA. dot blot and Western blot.

Insecticidal properties of benzofuran-2-carboxylic acid derivatives

A series of amides and esters of substituted benzo[b]furan-2-carboxylic acids have been synthesised, and their activity against adult sweet potato weevils, Cylas formicarius elegantulus (Summer) studied. The topical insecticidal potency of these compounds was compared in acetone solution and in a mixture of piperonyl butoxide (PB) and acetone (0·05+99·95 by volume). The compounds were much more active when administered in the acetone/PB mixture, and exhibited 48-h LD50 values ranging from 1·7 to 26·6 μg per insect. The most active compound, 2-(3,5-dimethylpyrazol-1-ylcarbonyl)-6-methoxy-3-methylbenzofuran, was equiactive with technical grade dimethoate (in acetone/PB) on a weight basis. © 1998 SCI

Biology of the African sweetpotato weevil species Cylas puncticollis (Boheman) and C. brunneus (Fabricius) (Coleoptera: Apionidae)

The biology of two African sweetpotato weevil species, Cylas puncticollis and C. brunneus (Fabricius) (Coleoptera: Apionidae), was studied in laboratory experiments carried out at 27 ± 1°C, 45 ± 5% RH, and a 12 h photophase. Cylas puncticollis females lived longer than C. brunneus (141 ± 10 and 92±12 days respectively), developed faster (egg to adult 20–28 days, and 32–41 days respectively) and had a lower oviposition rate (1.10 ± 0.04 and 1.53 ± 0.06 eggs per female per day respectively). The total egg production per female (average 101), sex ratio (1:1) and proportion of eggs surviving to adulthood (average 89%) were similar for both species. The intrinsic rate of increase was higher for C. puncticollis (0.553 per 10-day period compared to 0.521 for C. brunneus). Under field conditions C. brunneus will benefit from its higher oviposition rate during periods of favourable conditions for sweet potato weevils, like dry spells which expose tubers for egg laying. Cylas puncticollis will benefit from its longer longevity during less favourable conditions, as females can survive extended periods when no oviposition sites are available and then resume egg laying when conditions improve.

Flight and Locomotion Activity of the Sweet potato Weevil (Coleoptera: Brentidae) in Relation to Adult Age, Mating Status, and Starvation

The flight and walking performance of Cylas formicarius (F.) adults were evaluated with respect to their age, mating status, and the degree of starvation by using a flight mill and an actograph system. Males showed a much higher Bight ability than females in all ages tested between 0 and 42 d old after spontaneous exiting from the sweet potato root. Locomotion activity of the male was also higher than that of the female for 0- to 28-d-old adults, but the difference was not as large as that of flight activity. Except for the effects of a 3-d starvation period on locomotion, mating status and starvation with only water for 1-3 d had little affect on flight or locomotion ability. No distinct signs of migratory behavior of adults were detected. Females seemed to disperse mainly by walking because of their extremely low flight ability.

Evaluation of Selected Soil Insecticides and Foliar Insecticides for Control of Banded Cucumber Beetle, Whitefringed Beetle, White Grub, and Sweetpotato Weevil, 1997

Abstract A test was conducted in Avoyelles Parish, LA to determine the efficacy of two soil insecticides and four foliar treatments for control of above-listed insects. Treatments were arranged in a CRB design with four replications. Plots were 4 rows wide (3.5/row) and 50 ft long. Soil insecticides were applied on June 14 approximately one week before trans-planting. The cultivar ‘Beauregard’ was transplanted 19 Jun. Foliar insecticide applications were made at approximately weekly intervals starting three weeks after transplanting. A CO2-pressurized backpack sprayer was used (36 psi) with a two-row boom containing four nozzles (Cone Jet TX-lO) and calibrated to deliver 15 gallons per acre. A single sweetpotato weevil pheromone trap was used to monitor the weevil population throughout the season. Sweet-potatoes were harvested on 6 Oct and field graded into U.S. number 1, 2, or 3. From each plot, in each of the 3 grades, 25 potatoes were randomly selected and evaluated for insect damage. The number of potatoes damaged by whitefringed beetle, sweetpotato weevil, white grubs, as well as the number of holes present caused by banded cucumber beetles were counted.

Evaluation of Selected Foliar Insecticidesl for Control of Sweetpotato Weevil and Banded Cucumber Beetle on Sweetpotatoes, 1997

Abstract A test was conducted at the Burden Research Plantation, LSUAC, Baton Rouge, LA, to determine the efficacy of 15 insecticide treatments for the control of sweetpotato weevil and banded cucumber beetle. Treatments were arranged in a RCB design with four replications. The cultivar ‘Beauregard’ was planted on 18 May. Plots were 3 rows wide (4 ft/row) and 30 ft long. Insecticides were applied on an approximately weekly ba-sis starting two months after transplanting (18, 23 Jul, 1,8, 14, 22, 29 Aug). A CO2-pressurized backpack sprayer was used (30 psi) with a single-row boom (20 inches wide) containing 3 nozzles (Cone Jet sx-10) and calibrated to deliver 25 gpa. Sweetpotatoes were harvested on Sept. 6 and rated for damage. From each plot 25 roots were randomly selected. The number of banded cucumber beetle holes per root, and the presence or absence of weevil damage was noted.

Development of pheromone traps for control and monitoring of sweetpotato weevils, Cylas puncticollis and C. brunneus, in Uganda

AbstractExperiments were carried out in Uganda to optimise pheromone traps for the African sweetpotato weevil species, Cylas puncticollis Bohe. and C. brunneus F. (Coleoptera: Apionidae). Various designs of funnel, water and sticky traps were compared and a 5‐l plastic jerry can trap was the most appropriate design for effectiveness and practicability. A solution of Omo detergent in water was found to be the most effective trapping agent. Fewer weevils were caught in red traps than in yellow, white, green or blue traps. Catches of C. puncticollis increased when the trap was raised above crop height, but catches of C. brunneus were unaffected. When marked weevils were dropped onto the trap, 36% of C. puncticollis and 23% of C. brunneus were captured, and, of weevils placed in the trap, 88% and 92%, respectively, of the two species remained overnight. Lures for the two species showed no significant loss in attractiveness after 8 weeks in the field, and chemical analysis showed 19% of the C. puncticollis pheromone and 72% of the C. brunneus pheromone remaining after this time. Summarizing, the following trap is presently recommended for monitoring/controlling African Cylas species: a 5‐l plastic jerry can trap of any colour with rectangular openings of 11×5 and 6×5 cm positioned 15 cm above the crop canopy, filled with 0.5 l Omo solution (1 g/1 l water), with 0.1 mg lures to be replaced every 8 weeks.

Números cromosómicos de algunos escarabajos de las familias Brentidae y Curculionidae de Puerto Rico y las Islas Vírgenes de Estados Unidos

Se preparó una lista de ios cromosomas de 24 especies de Curculionoidea de la Gran Región de Puerto Rico y de las Islas Vírgenes de U.S.A. Siete especies son endémicas y ocho son plagas notables en la agricultura. La meiofórmula del macho de los picudos de nariz ancha (Brachyderinae, Otiorhynchinae) así como del bréntid Cylas formicarius elengantulus es la esperada 10 + Xyp, excepto en Lachnopus kofresi de la Isla de Mona (16 + Xyp). Representantes de otras subfamilias de Curculionidae tienen números auiosomales más altos y combinados con el bivalente sexual primitivo Xyp. Anthonomus eugenii, con su trivalente sexual (X1X2Y) en el macho, es una excepción. Por razones morfológicas y citológicas los taxones L. coffeae montanus Marshall, L. seini Wolcott y L. yaucona Wolcott fueron sinonimizados con Lachnopus coffeae Marshall (SINONIMIAS NUEVAS). Una especie de Ischionoplus (Brachyderinae) es nueva para la ciencia y es endémica para la Isla de Mona.

The effect of the indigenous cultural practices of in-ground storage and piecemeal harvesting of sweetpotato on yield and quality losses caused by sweetpotato weevil in Uganda

Traditionally, in Uganda most farmers growing sweetpotato practise in-ground storage combined with piecemeal harvesting. Several times during the growing period, between 3 and 7–12 months after planting, large roots are removed from individual plants and small roots are allowed to remain in the ground to enlarge further. The overall aim of the practice is to maintain a supply of roots in the ground for the longest possible period. In a series of four trials, once-over harvests at different intervals after planting and a simulated piecemeal harvesting treatment are compared for yield and quality losses caused by sweetpotato weevils ( Cylas puncticollis and C. brunneus). For the once-over harvests, the percentage of damaged roots increased linearly the longer the harvest was delayed. Losses ranged between 3% at a harvest 3.5 months after planting (MAP) and 73% at 9.5 MAP. The total yield and undamaged yield for the piecemeal harvesting treatments were comparable to the yields at the optimum harvest times for once-over harvesting at 6–7.5 MAP. The results indicate that piecemeal harvesting is a practice with a controlling effect on sweetpotato weevil infestation.

An Insecticidal and Acaricidal Polysulfide Metabolite from the Roots of Petiveria alliacea

The present study reports on the insecticidal and acaricidal potentials of dibenzyltrisulfide (DBTS) isolated from the roots of Petiveria alliacea L. using thin layer and high performance liquid chromatography. The 96-h LD50 value (μg per tick) obtained for adult Boophilus microplus (Canestrini) topically treated with DBTS was 0·920. The LD50 values obtained for three commercial acaricides dimethoate, lindane and carbaryl were 4·6, 9·3 and 6·9 μg per tick respectively. The IOD50 and IHD50 (concentrations inhibiting egg laying and hatching by 50% respectively) in μg per tick doses for DBTS were 0·22 and 0·24 respectively. The 24-h LD50 dose (μg per insect) obtained for DBTS on adult Cylas formicarius elegantulus (Summer) was 0·193 μg per insect. The vapour from a stock solution of 5 g litre-1 of DBTS was highly toxic to adult Hypothenemus hampei Ferr. inside coffee berries, inflicting 89% mortality within 24 h. © 1997 SCI.

An Insecticidal and Acaricidal Polysulfide Metabolite from the Roots ofPetiveria alliacea

The present study reports on the insecticidal and acaricidal potentials of dibenzyltrisulfide (DBTS) isolated from the roots of Petiveria alliacea L. using thin layer and high performance liquid chromatography. The 96-h LD50 value (μg per tick) obtained for adult Boophilus microplus (Canestrini) topically treated with DBTS was 0·920. The LD50 values obtained for three commercial acaricides dimethoate, lindane and carbaryl were 4·6, 9·3 and 6·9 μg per tick respectively. The IOD50 and IHD50 (concentrations inhibiting egg laying and hatching by 50% respectively) in μg per tick doses for DBTS were 0·22 and 0·24 respectively. The 24-h LD50 dose (μg per insect) obtained for DBTS on adult Cylas formicarius elegantulus (Summer) was 0·193 μg per insect. The vapour from a stock solution of 5 g litre-1 of DBTS was highly toxic to adult Hypothenemus hampei Ferr. inside coffee berries, inflicting 89% mortality within 24 h. © 1997 SCI.

Progress in Breeding for Sweetpotato Weevil Resistance

A breeding program to develop improved sweetpotato genotypes with increased sweetpotato weevil resistance was started in 1990. Germplasm, including plant introductions, cultivars, and breeding lines with reported insect resistance, was field tested for injury levels by applying low numbers of weevils. Low levels of resistance were found and `Regal' was among the highest. Top performing lines were selected and intermated. After 2 selection cycles the most highly resistant selection produced 89% uninjured roots compared to 28% in `Regal'. Severity of injury score was 16 times lower in the most resistant selection (0.15) compared to `Regal' (2.40).

Induction of Adult Female Sweetpotato Weevil (Cylas fromicarius elegantulus Summers) Volatile Attractant Triggered by Root Periderm Feeding

The sweetpotato weevil is the single most critical insect pest of the sweetpotato worldwide. While male weevils can be lured to traps using a synthetic female pheromone, crop losses are not adequately reduced since damage is caused by the larvae arrising from eggs laid by female weevils in the storage roots. Identification of a female attractant could greatly enhance the control of the insect. The leaves and storage roots are known to emit volatiles that attract the female and in the following tests, we demonstrate that feeding by female weevils stimulates the synthesis of a volatile attractant which attracts additional females to the root. Undamaged, artificially damaged, and female weevil feeding damaged periderm were tested in dual-choice and no-choice olfactometers. Volatiles from feeding damaged roots were significantly more attractive than undamaged and artificially damaged roots. To test whether the volatile attractant was of weevil or root origin, volatiles were collected in MeCl2 after removal of the weevils and fractionated on a megabore DB-1 capillary column using a GC fitted with a TC detector. Fractions were collected from the exit port and their activity index (AI) determined using dual choice and no choice olfactometry. The active fraction was ascertained and active components identified via GC-MS.