This document provides an in-depth profile of the sweetpotato weevil, Cylas formicarius, highlighting its significance as a major pest of sweet potatoes globally. It covers the weevil's distribution, life cycle, host plants, natural enemies, and the damage it causes. Management strategies, including sampling, insecticides, cultural practices, biological control, and other methods, are discussed to mitigate the impact of this pest. The document aims to inform both laypersons with some biological knowledge and academic audiences about the challenges and solutions related to sweetpotato weevil infestations. First published 1998.

The geographical distribution of the sweetpotato weevil, Cylas formicarius and the West Indian sweetpotato weevil, Euscepes postfasciatus were investigated on sweetpotato, Ipomoea batatas and wild host plants, I. india and I. pes-caprae on the Amami Islands except Kikai Island during 2010 to 2011. The number of C. formicarius male adults was determined using simple sticky traps with synthetic sex pheromone at 235 sites during November 2010 to February 2011. The occurrence of the two weevils were investigated at 109 sweetpotato fields and 97 creeping colonies of wild host plants, I. india and I. pes-caprae, sites during November 2010 to February 2011. Both weevil species were found in all islands of the Amami Islands. This was consistent with the result of 1997-1998, and the distribution of both weevils species have not changed on the Amami Islands. The occurrence of E. postfasciatus was on the increase from 1997. On Okinoerabu Island, the number of male adults of C. formicarius captured using pheromone traps were fewer than the other islands.

Abstract The sweetpotato weevil Cylas formicarius (F.) (Coleoptera: Brentidae) is one of the most serious insects causing damage to sweetpotatoes in the world. Small populations of these insects can cause severe damage to tubers of the crop. Without proper and effective control, weevil populations are likely to cause a huge or complete loss of sweetpotato production in sweetpotato growing areas. Consequently, there is an urgent need for development of an eco-friendly control method for this weevil. Although some control methods are effective, toxic pesticides applications are detrimental and damaging to our environment. Although pheromone traps are currently being used, no effective control of this weevil was achieved. Therefore, studies were carried out as part of the development of a trapping system for C. formicarius. Previous color-choice field tests have confirmed that C. formicarius preferred red traps over gray, green, brown, blue, white, yellow, or black; light red was more attractive than other shades of red. The current study aimed to know whether C. formicarius behavior changes in indoor conditions. Among the eight colored traps tested in the laboratory, green-colored traps were more effective in attracting C. formicarius than all other colors. It attracted nearly double the number of weevils than standard traps presently being used by growers. Based on these results, it is recommended to use green-colored traps to mass trap weevils (by attracting and killing) from sweetpotatoes grown under indoor (storage) conditions.

The West Indian sweet potato weevil, Euscepes postfasciatus Fairmaire, was distributed only on Nansei and Ogasawara (Bonin) Islands in Japan until 2008, when the weevil was found for the first time in Ibusuki City, which previously regarded as a weevil-free area. In this study, we used epidemiological approaches to determine how the weevil population in Ibusuki City was established. We conducted spatial distribution analysis and case–control studies based on survey data gathered from 270 farmers who cultivated sweet potato in 2008. Weevils were present at 46 sweet potato (Ipomoea batatas) cultivation sites and four blue morning glory (Ipomoea indica) growing sites. The weevil infestation rate was higher in sweet potato plants than in wild host plants. Weevil infestation was strongly associated with the use of tuber trench silo storage (odds ratio, 4.45). The association with silo storage suggested that the tuber storage silos provided an overwintering refuge for the weevil. The case–control study also revealed that cultivation without pesticides and for home use were associated with weevil infestation. Activities such as the transfer of tubers or leaving tubers in the field may expand the distribution of the weevil population over a wider area.

Sweetpotato weevils are the most devastating pests of sweetpotato causing yield losses ranging from 60 to 100%. Their cryptic nature, where the larvae is found within plant tissues render them difficult to manage especially using chemicals control. Development of weevil resistant sweetpotato was conducted by crossing a transgenic event CIP410008.7 as a female parent with three Ugandan cultivars as male parents. Crossing event CIP410008.7 with New Kawogo, Tanzania and NASPOT1 gave 57, 32 and 19 seeds respectively. A total of 86 F1 progenies were analysed for the presence of cry7Aa1 using polymerase chain reaction (PCR). Expected 608 bp bands were amplified in progenies that contained the cry gene. The gene was integrated at different frequencies in the F1 progenies of different families: CIP410008.7 x New Kawogo (47.2%), CIP410008.7 x Tanzania (52%) and CIP410008.7 x NASPOT1 (44.4%). Chi-square test showed that all the three families followed a 1:1 segregation cry7Aa1 gene ratio. This study shows the transfer of a transgene from genetically modified event into elite sweetpotato lines. Key words: Weevil resistance, transgenic plants, sweetpotato, cry7Aa1.

For ensuring the effectiveness of sterile insect technique (SIT) programmes, maintaining the reproductive competitiveness and dispersal ability of mass-reared sterile males is essential. Inadvertent selection is an important genetic process that frequently occurs during mass rearing to produce sterile males. We investigated the effect of mass-rearing conditions on the responsiveness to sex pheromones and spontaneous flight activity of males of the sweetpotato weevil Cylas formicarius (Coleoptera: Brentidae). There were no significant differences in the responsiveness to sex pheromones and spontaneous flight activity between wild and mass-reared strains. These results indicate that mass-reared strains of C. formicarius might not cause serious problems for implementing SIT programmes.

An improved synthesis of (Z)-dodec-3-en-1-yl (E)-2-butenoate (1), the female sex pheromone of sweet potato weevil, Cylas Formicarius, was reported. The synthesis bypassed the utilization of carcinogenic ethylene oxide, highly toxic HMPA, highly hydroscopic and unrecyclable DMPU, ethylene diamine, and liquid ammonia, for the alkylation of terminal alkyne. Instead, NaI was used to serve as a good nucleophile for alkyl bromide and a good leaving group for 1-lithiated alkyne. A safer and stereoselective palladium-catalyzed transfer semihydrogenation, using KOH/DMF as the hydrogen source, was employed for alkyne cis-hydrogenation, without using molecular hydrogen. The total yield was 62% over 5 steps, and the sex pheromone 1 obtained was verified spectroscopically. Field test results showed that the synthetic sex pheromone 1 was as effective as the commercial source or the sample provided by other research group.

Assessment of the impact of transgenic crops on non-target organisms (NTO) is a prerequisite to their release into the target environment for commercial use. Transgenic sweetpotato varieties expressing Cry proteins (Bt sweetpotato) are under development to provide effective protection against sweetpotato weevils (Coleoptera) which cause severe economic losses in sub-Saharan Africa. Like any other pest control technologies, genetically engineered crops expressing insecticidal proteins need to be evaluated to assess potential negative effects on non-target organisms that provide important services to the ecosystem. Beneficial arthropods in sweetpotato production systems can include pollinators, decomposers, and predators and parasitoids of the target insect pest(s). Non-target arthropod species commonly found in sweetpotato fields that are related taxonomically to the target pests were identified through expert consultation and literature review in Uganda where Bt sweetpotato is expected to be initially evaluated. Results indicate the presence of few relevant non-target Coleopterans that could be affected by Coleopteran Bt sweetpotato varieties: ground, rove and ladybird beetles. These insects are important predators in sweetpotato fields. Additionally, honeybee (hymenoptera) is the main pollinator of sweetpotato and used for honey production. Numerous studies have shown that honeybees are unaffected by the Cry proteins currently deployed which are homologous to those of the weevil-resistant Bt sweetpotato. However, because of their feeding behaviour, Bt sweetpotato represents an extremely low hazard due to negligible exposure. Hence, we conclude that there is good evidence from literature and expert opinion that relevant NTOs in sweetpotato fields are unlikely to be affected by the introduction of Bt sweetpotato in Uganda.

Fifty-nine sweetpotato cultivars, including 16 heirlooms, 11 near-heirlooms (developed in the 1960s and 1970s), 19 cultivars from the 1980s, and 13 modern varieties (since 1990), were evaluated for resistance to soil insects in field experiments during 2010-2011 at the U.S. Department of Agriculture-Agriculture Research Service, U.S. Vegetable Laboratory (USDA-ARS, USVL), Charleston, SC. These experiments included two insect-susceptible control cultivars ('Beauregard' and 'SC1149-19') and four insect-resistant control cultivars ('Charleston Scarlet,''Regal,' 'Ruddy,' and 'Sumor') that were developed by the USDA-ARS, USVL sweetpotato breeding program. Sweetpotato genotypes differed significantly in resistance measured by the overall percentage of injured roots, WDS (Wireworm, Diabrotica, and Systena) index, the percentage of roots damaged by the sweetpotato weevil (Cylas formicarius F.), the percentage of roots damaged by the sweetpotato flea beetle (Chaetonema confinis Crotch), and the percentage of roots damaged by white grub larvae (including Plectris aliena Chapin and Phyllophaga spp.). Twenty-three sweetpotato cultivars had a lower percentage of injured roots than the susceptible control genotype, SC1149-19, while 14 varieties had a lower percentage of injured roots than Beauregard, one of the leading commercial orange-fleshed cultivars in the United States. Over the 2-yr period, Ruddy (7.6%) had the lowest percentage of injured roots and 'Carolina Ruby' (84.6%) the highest percentage of injured roots. Carolina Ruby (1.07) also had the highest WDS index, but 15 genotypes had a significantly lower WDS index than either susceptible control, SC1149-19 (1.03) or Beauregard (0.82). Ruddy (0.07) and 'Murasaki-29' (0.09) had the lowest WDS indices. Forty-five genotypes had a significantly lower percentage infestation by flea beetles than SC1149-19 (12.3%), and the highest level of flea beetle infestation was for 'Bonita' (18.9%). The highest percent white grub infestation was for 'Caromex' (19.6%), however none of the genotypes had significantly less white grubs than the susceptible controls. The highest infestation of sweetpotato weevils was observed for SC1149-19 (17.9%), while 29 genotypes had significantly lower percentage of sweetpotato weevil infestation than SC1149-19. The moderate to high levels of resistance to soil insect pests exhibited by many of these traditional and heirloom cultivars may provide useful sources of germplasm for sweetpotato breeding programs.

Abstract Behaviour during copulation can alter the fate of sperm of the mating males. This behaviour may exert selective pressure, resulting in the evolution of diverse reproductive behaviour, morphology, and physiology. This study examined the role of female copulatory behaviour on sperm fate in the sweet potato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae). In this species, males mount the female during copulation. The female frequently walks during copulation, carrying the male on her back. Here, we describe and quantify the copulatory behaviour of mating pairs and examine the sperm fate. Insemination success, as determined by the presence of sperm in the spermatheca, was lower when females walked for longer periods during copulation. This result emphasizes the value of studying variation in female copulatory behaviour in order to understand the factors that influence sperm fate. We discuss the implications of these results on sexual selection and utility in programs applying sterile insect techniques.

El Centro para el Control Biológico en Centro América (CCBCA) fue creado en 1989 por la Escuela Agrícola Panamericana, financiado por la United States Agency for International Development (USAID) en Honduras. El CCBCA se enfocó en el control biológico clásico, el aumento y la conservación de enemigos naturales. En el 2000 cambió el nombre de Laboratorio de Control Biológico y se enfocó en el aprender haciendo de los estudiantes de la Escuela Agrícola Panamericana y la producción y comercialización de enemigos naturales de plagas agrícolas. El único parasitoide conocido que ataca al picudo de las bromelias (Metamasius quadrilineatus), fue encontrado en las investigaciones del CCBCA; resultó una especie nueva nombrada Lixadmontia franki que fue liberada en Florida en el 2007 para el control biológico del picudo mejicano de las bromelias (Metamasius callizona). Se determinaron los organismos parasíticos de las plagas Plutella xylostella, Mocis latipes, Spodoptera frugiperda, Leptophobia aripa y Liriomyza spp. Cuatro especies de avispas parasíticas exóticas, un baculovirus, un hongo y tres picudos fueron introducidos a Honduras para control biológico clásico: Cotesia plutellae (parasitoide asiático de P. xylostella); Diadromus collaris (parasitoide pupal de P. xylostella); Telenomus remus (parasitoide que ataca a los huevos de 30 especies de lepidópteros); una especie de Eretmocerus (originaria de India, para controlar Bemisia tabaci); los picudos Neochetina bruchi y Neochetina eichhorniae y el hongo Cercospora piaropi (para el control de la maleza acuática lirio de agua (Eichhornia crassipes); y el picudo Neohydronomous affinis (controlador biológico de la maleza acuática lechuga de agua (Pistia stratiotes). En el 2000, Zamorano cambió la estrategia del uso de control biológico y empezó a incursionar en la producción comercial de microrganismos para el control de plagas, debido a una demanda no satisfecha. Los controladores biológicos que ha producido son el hongo antagonista Trichoderma harzianum (Trichozam™) para combatir hongos en el suelo, Beauveria bassiana (Bazam™) para controlar lepidópteros y coleópteros, Lecanicillium lecanii (Verzam™) para el control de áfidos y mosca blanca, Metarhizium anisopliae (Metazam™) para el control de salivazo (Aeneolamia spp.) y larvas de coleópteros en caña de azúcar, y Purpureocillium lilacinum (Pazam™) para controlar nematodos. Además, ha reproducido y vendido la chinche depredadora Orius insidiosus para el control de trips, áfidos y mosca blanca, el ácaro depredador Neoseiulus longispinosus para el control de la arañita roja (Tetranychus spp.) y el nematodo entomófago Heterorhabditis bacteriophora para el control de insectos del suelo, especialmente contra Phyllophaga spp., Cosmopolitus sordidus, larvas de lepidóptera, picudo del camote (Cylas formicarius) y termitas en el suelo. Posiblemente, el mayor aporte es en la enseñanza de las técnicas y tecnologías del control biológico de plagas que se han distribuido por América Latina a través de los graduados de Zamorano que estudiaron y fueron entrenados en Zamorano.DOI: http://dx.doi.org/10.5377/ceiba.v52i1.966

The sweetpotato weevil, Cylas puncticollis Boheman, constitutes a major constraint to sweet potato production and utilization in Africa. Host plant resistance/tolerance, mulching and varying harvesting dates could provide an approach that fits well into an integrated pest management programme of this insect pest. In this study, a trial was conducted to evaluate the effect of host plant, mulching with freshly harvested, dried and chopped up aerial parts of elephant grass (Panicum maximum), and the manipulation of harvesting date, on crop damage by the sweetpotato weevil. The experiment was laid out in a randomized complete split-split plot design with three replications. Four sweet potato varieties (improved variety- kabbia, slipot 2, slipot 3 and slipot 4), four harvesting dates (90, 104, 118 and 132 days after planting (DAP)) and four mulching levels (0t/ha, 1t/ha, 3t/ha and 5t/ha) were used. Data analysis revealed significant differences in C. puncticollis tuber damage and number of tubers produced with respect to mulching. Cylas puncticollis incidence was observed to decrease with increase in mulching level. Also, significant cultivar variation with respect to C. puncticollis tuber damage and the total number of tubers produced were recorded. Slipot 3 and slipot 4 were observed to be significantly less susceptible to the sweetpotato weevil. Harvesting date was also significantly different, with respect to the number of damaged tubers. More tubers were damaged when harvesting was delayed. Hence, using slipot 3 or slipot 4, coupled with mulching at the rate of 3-5t/ha and harvesting at 104 DAP resulted in increased number of tubers and reduced sweetpotato weevil infestation in the field.

The efficacy of the pre- and post-planting application of neem seed oil (NSO) or/and diazinon and time of harvest for the control of sweetpotato weevil, Cylas puncticollis (Boh.) was evaluated during the 2009 and 2010 cropping seasons. Forty-eight plots of 3 x 4 m 2 each were demarcated and 240 sweetpotato (var. TIS2532.op.1.13) vine cuttings were dipped into 0, 30 and 50 mls NSO and 30 mls of diazinon mixed in 2 and 10 litre soapy water respectively, and kept for 30 mins before planting. Similar treatment was also basally applied post-planting at 1MAP. In 2009, results showed that treatments (NSO or diazinon or their combinations) did not significantly influence percentage plant stand at harvest in both years, but lower percentage plant stands were obtained at 6 MAP (47.72%) than at 5MAP (56.87%). Significantly higher mean total weights of 34.44 t/ha was obtained in 2009 and 8.99 t/ha in 2010 respectively. Similarly, yield ranged from as high as 53.69 t/ha at 5MAP in 2009 to as low as 5.51t/ha at 6MAP in 2010. Significantly lower C. puncticollis attributes as a pest were obtained in 2009 than in 2010. Treatments significantly suppressed total progeny from 11.07 to 7.08, scores from 3.78 to 2.52 and root damage from 68.59% (Pr0Pt0) to 44.38% (Pr3Pt3), 66.55% to 40.00% at 5 to 6MAP. Time of application was significant as 50 mls of NSO applied pre- and post-planting gave highest (35.30%) control of the pest at harvest.

サツマイモの特殊害虫アリモドキゾウムシの根絶に関する最近の研究展開

The effect of chilling and CO2 anesthesia on sweetpotato weevils was investigated to optimize the immobilization duration sufficient for topical application of insecticides. Two-minute CO2 anesthesia treatment with simultaneous chilling for the latter half of the time immobilized the weevils for about 100 seconds. This duration is sufficient to topically apply insecticides to the weevil bodies. This anesthesia method did not adversely affect the survivorship of weevils. Using this anesthesia method, we investigated the susceptibility to fenitrothion (MEP) of wild weevil populations on Kikai Island, where MEP and synthesized sex pheromone had been applied for 3 years and on Amami Oshima Island where no control measures were implemented. The LD50 values were as low (about 4.0–8.0 μg/g) for sweetpotato weevils collected from Kikai Island as for weevils collected from the control, Amami Oshima Island (about 2.5 μg/g). This result suggests that the weevil-controlling measures on Kikai Island are working satisfactorily.

The present study presents the results of farmers’ field surveys of the sweetpotato butterfly, Acraea acerata Hew., and the two African sweetpotato weevils, Cylas puncticollis Boheman and C. brunneus F. infestation and damage. The objectives of this study were to determine (i) occurrence and distribution of A. acerata and Cylas spp. as well as infestation and losses in sweetpotato (Ipomoea batatas (L.) Lam.), and (ii) the occurrence and abundance of parasitoids of A. acerata in the Lake Albert Crescent (LAC) agro-ecological zone of Uganda. Field surveys were conducted in 240 sweetpotato fields in eight subcounties in Masindi and Buliisa districts at the end of each of the two cropping seasons of 2012 (March to May and September to November). A. acerata and Cylas spp. occurred in 17% and 90% of the fields, respectively. A. acerata did not occur in two subcounties of Buliisa district. A. acerata infestation was low, with up to two and four larvae per plant in the first and second cropping season, respectively, causing minor defoliation of up to 4.1% of the sweetpotato plant. Larvae of Cylas spp. caused root yield losses of up to 56.5% and 47.5% in the first and second cropping seasons, respectively. Parasitism rates of A. acerata larvae ranged from 0.0% to 15.1% in season 1 and 0.0% to 6.3% in season 2. Out of a total of 1020 larvae collected, 8.43% were found to be parasitized. Parasitoids occurred in 56% of fields infested by its host. Charops spp. was the main parasitoid. It was evident that Cylas spp. were more prevalent than A. acerata in the LAC agro-ecological zone of Uganda. Conservation of A. acerata natural enemies may contribute to better management of this pest. Urgent attention for management of Cylas spp. is required.

The cost benefits of pre- and post (after one month) planting application of neem seed oil (NSO) on sweetpotato during late season production (August to February in 2009 and 2010) for the management of the sweetpotato weevil, Cylas puncticollis (Bohoman) was determined using the complete costing analysis. Root yield and percentage infestation was determined by ANOVA and significant means separated using SNK test at 5 % probability. The results indicated that 30 mls (4 l/ha) NSO applied pre- and post-planting (Pr2Pt2) had the highest comparative advantage as the income was 457 % (N1,130,800.50) and provided 22.70 % control of C. puncticollis infestation. However, pest control of 33.4 % was obtained when 50 ml (6 l/ha) of NSO was applied pre- and post-planting (Pr3Pt3) and it significantly suppressed root infestation from 64.22 % (Pr0Pt0)to 42.75 %. The sweetpotato pest management tactics developed in this study was discussed.

Seven low risk pesticides including 1.2% azadirachtin (Azadirachta indica), extracts from Morinda citrifolia, petroleum oil 97%, Beauveria bassiana strain GHA, mixed essential oils (rosemary oil: 0.25%, peppermint oil: 0.25%, thyme oil: 0.25%, clove oil: 0.25% and other ingredients: 99.00%), spinosad and malathion, were evaluated against adults of the sweetpotato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae) to determine potential insecticidal, repellent and feeding deterrence effects. Among the pesticides tested, A. indica and spinosad showed high insecticidal, repellent and feeding deterrence activity against C. formicarius. Spinosad, A. indica and malathion showed significantly higher insecticidal activity against C. formicarius. Similarly, these pesticides showed high repellency activity against adults, particularly 3–4 h after the treatment. The lowest food consumption was observed with the A. indica (0.8 g/adult/192 h), and the highest (9.9 g/adult/192 h) was with the petroleum oil spray. The other tested pesticides showed comparable activities. The chemicals we tested—particularly neem and spinosad—are therefore promising candidates as ecofriendly chemicals that could potentially replace broad-spectrum synthetic neurotoxins for control of C. formicarius.

Entomopathogenic nematodes (EPN) are well-known as biological control agents and are found to have associated bacteria which can produce a wide range of bioactive secondary metabolites. We report herewith isolation of six proline containing cyclic dipeptides cyclo(D-Pro-L-Leu), cyclo(L-Pro-L-Met), cyclo(D-Pro-L-Phe), cyclo(L-Pro-L-Phe), cyclo(L-Pro-L-Tyr) and cyclo(L-Pro-D-Tyr) from ethyl acetate extract of the Luria Broth (LB) cell free culture filtrate of Bacillus sp. strain N associated with a new EPN Rhabditis sp. from sweet potato weevil grubs collected from Central Tuber Crops Research Institute farm. Antimicrobial studies of these 2,5-diketopiperazines (DKPs) against both medicinally and agriculturally important bacterium and fungi showed potent inhibitory values in the range of μg/mL. Cyclic dipeptides showed significantly higher activity than the commercial fungicide bavistin against agriculturally important fungi, viz., Fusarium oxysporum, Rhizoctonia solani, and Pencillium expansum. The highest activity of 2 μg/mL by cyclo(L-Pro-L-Phe) was recorded against P. expansum, a plant pathogen responsible for causing post harvest decay of stored apples and oranges. To our knowledge, this is the first report on the isolation of these DKPs from Rhabditis EPN bacterial strain Bacillus sp.

The West Indian sweet potato weevil Euscepes postfasciatus (Fairmaire) (Coleoptera: Curculionidae) is a major pest of sweet potato Ipomoea batatas (L.) in the tropical and subtropical regions. The sterile insect technique (SIT) could be used as one of the most effective methods for suppression or eradication of the weevil. The effectiveness of SIT depends on the ability of the released sterile males to mate with and inseminate wild females. However, the effect of sterile weevils on the fitness of E. postfasciatus has not been evaluated on natural density. Here, we investigated the effect of gamma-irradiated weevil density on the number of weevil progeny. When irradiated weevils were released in numbers equal to those of non-irradiated weevils, the number of progeny was reduced by half of that in the control treatment, and it remained at this state for 2 weeks. Our results show that irradiated weevils ensure adequate and efficient suppression of wild weevils. We conclude that the SIT programs will be employed as effective eradication method for E. postfasciatus.