Age at sexual maturity of male and female banana weevils,Cosmopolites sordidus Germar (Coleoptera: Curculionidae)

This study was to determine the age at sexual maturity and the relationships between age and internal reproductive organs of Cosmopolites sordidus. Male banana weevils become sexually mature 18 days after emergence (DAE), that is after 2 weeks of adult eclosion, in spite of the fact that spermatogenesis is completed at emergence. A positive correlation exists between age and male internal organs, for example for mean testis diameter (r = .849, p ≤ .001), mean seminal vesicle diameter (r = .679, p ≤ .001), mean accessory gland length (r = .561, p ≤ .01) and mean accessory gland diameter (r = .498, p ≤ .05), respectively. Significant differences were recorded between sexually mature and immature weevils with respect to mean testis diameter (T = 4.471, p ≤ .001) and mean seminal vesicle diameter (T = 3.939, p ≤ .001), but not with mean accessory gland length and mean accessory gland diameter (T = 1.899 and 1.661). Male internal organs were visibly underdeveloped at emergence but became significantly enlarged and developed on attainment of sexual maturity. Female C. sordidus, on the other hand, are sexually mature at 5 DAE. There was also a strong, positive correlation between age of females and mean ovariole length (r = .656, p ≤ .001), and significant differences existed between mean ovariole lengths of sexually mature and immature females (T = 4.306, p ≤ .001). Increasing age of females witnessed progressive increases in ovariole lengths and developmental changes within female ovarioles and calyces. The findings made here may be helpful in Musa germplasm screening works, as weevils bred on susceptible cultivars may reveal similar results, while those bred on resistant ones may experience possible delays in their reproductive developments.     

The challenge of biological control of Cosmopolites sordidus Germar (Col. Curculionidae): A review

The banana weevil (also known as banana root borer) Cosmopolites sordidus Germar (Coleoptera Curculionidae) is the major pest of banana and plantain. Because banana ranks 2nd in fruit production worldwide, this pest has substantial social and economic importance. The biological control of the C. sordidus remains challenging because of its behaviour and resistance to parasitism and predation. The last review concerning the biological control of C. sordidus was published two decades ago, and relevant knowledge and methods have developed in the interim. The present paper provides an update of that knowledge and summarizes past and current challenges as well as providing perspectives on achieving sustainable control of C. sordidus. We first discuss studies on the classical biological control of C. sordidus, underlining the limits of classical biological control methods such as the importation of predators, parasitoids or pathogens. Next, we consider conservation biological control of C. sordidus, with a focus on ants. We also highlight an ‘arthropod bias’ that has led to a lack of information on the role of vertebrates in the regulation of C. sordidus.     

Visual cues are relevant in behavioral control measures for Cosmopolites sordidus (Coleoptera: Curculionidae)

Trap designs for banana root borer, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae), have been done essentially on the understanding that C. sordidus rely primarily on chemical cues. Our present results indicate that these borers also rely on visual cues. Previous studies have demonstrated that among the eight differently colored traps tested in the field, brown traps were the most effective compared with the performances of yellow, red, gray, blue, black, white, and green traps; mahogany-brown was more effective than other shades of brown.In the current study, efficiency of ground traps with different colors was evaluated in the laboratory for the capture of C. sordidius. Response of C. sordidus to pheromone-baited ground traps of several different colors (used either individually or as 1:1 mixtures of two different colors) were compared with the standardized mahogany-brown traps. Traps with mahogany-brown mixed with different colors had no significant effect. In contrast, a laboratory color-choice tests indicated C. sordidus preferred black traps over other color traps, with no specific preferences for different shades of black. Here again, traps with black mixed with other colors (1:1) had no influence on the catches. Therefore, any other color that mixes with mahogany-brown or black does not cause color-specific dilution of attractiveness. By exploiting these results, it may be possible to produce efficacious trapping systems that could be used in a behavioral approach to banana root borer control.     

Effects of neem seed derivatives on behavioral and physiological responses of the Cosmopolites sordidus (Coleoptera: Curculionidae)

Both in a choice and multi-choice laboratory tests, fewer adults of the banana root borer, Cosmopolites sordidus (Germar), settled under the corms of the susceptible banana "Nakyetengu" treated with 5% aqueous extract of neem seed powder or cake or 2.5 and 5% emulsified neem oil than on water-treated corms. Feeding damage by larvae on banana pseudostem discs treated with 5% extract of powdered neem seed, kernel, or cake, or 5% emulsified neem oil was significantly less than on untreated discs. The larvae took much longer to locate feeding sites, initiate feeding and bore into pseudostem discs treated with extract of powdered neem seed or kernel. Few larvae survived when confined for 14 d on neem-treated banana pseudostems; the survivors weighed two to four times less than the larvae developing on untreated pseudostems. Females deposited up to 75% fewer eggs on neem-treated corms. In addition, egg hatching was reduced on neem-treated corms. The higher the concentration of neem materials the more severe the effect.     

香蕉球茎象甲成虫田间活动规律

【目的】明确香蕉球茎象甲Cosmopolites sordidus(Germar)成虫在田间的活动规律,为香蕉球茎象甲成虫的防治提供科学依据。【方法】利用诱捕器诱捕研究了海南省澄迈县香蕉园香蕉球茎象甲成虫的田间活动规律。【结果】香蕉球茎象甲成虫主要在香蕉叶鞘及叶柄附近飞行,距地面160 cm的单个诱捕器的香蕉球茎象甲诱捕量为26.5头,显著多于距地面250 cm的单个诱捕器的香蕉球茎象甲诱捕量14.3头和距地面0 cm的单个诱捕器的香蕉球茎象甲诱捕量14.2头。在田间飞行时,香蕉球茎象甲在东西南北各方位上的成虫诱捕量没有显著差异(P>0.05),说明成虫没有明确的偏好方向。在昼夜节律上,香蕉球茎象甲成虫集中在傍晚至凌晨时分活动,其中16:00至翌日4:00之间雌、雄成虫的诱捕量分别占全天的100%和92%。【结论】香蕉球茎象甲成虫在田间的昼夜活动和飞行高度上呈现明显规律性,为引诱剂、性诱剂的使用等成虫防治关键技术的研发与应用提供了科学依据。     

Evaluation of pseudostem trapping as a control measure against banana weevil,Cosmopolites sordidus (Coleoptera: Curculionidae) in Uganda

Controlled studies to determine the efficacy of pseudostem trapping in reducing adult populations of the banana weevil, Cosmopolites sordidus (Germar), were conducted under farmer conditions in Ntungamo district, Uganda. Twenty-seven farms were stratified on the basis of C. sordidus population density (estimated by mark and recapture methods) and divided among three treatments: (i) researcher-managed trapping (one trap per mat per month): (ii) farmer-managed trapping (trap intensity at discretion of farmer); and (iii) controls (no trapping). Intensive trapping (managed by researchers) resulted in significantly lower C. sordidus damage after one year. Over the same period, C. sordidus numbers declined by 61% on farms where trapping was managed by researchers, 53% where farmers managed trapping and 38% on farms without trapping; however, results varied greatly among farms and, overall, there was no significant effect of trapping on C. sordidus numbers. Moreover, there was only a weak relationship between the number of C. sordidus removed and the change in population density. Trapping success appeared to be affected by management levels and immigration from neighbouring farms. Although farmers were convinced that trapping was beneficial, adoption has been low due to resource requirements.     

Evaluation of entomopathogenic nematodes for control of Cosmopolites sordidus Germar (Coleoptera: Curcilionidae), a pest of bananas in Australia

Applications of Steinemema carpocapsae All strain in water thickener into cuts or holes made in residual rhizomes of bananas gave significant mortality of Cosmopolites sordidus larvae in the rhizomes. The methods proved suitable for field application and two large scale field trials using S. carpocapsae All and S. carpocapsae NC513 gave acceptable levels of control as measured by Vilardebo's (1973) Co-efficient of Infestation. Mortality of adult C. sordidus attracted to the application sites on treated rhizomes was observed during these field trials.     

On the Taxonomy and Distribution of the Weevil Genus Anthonomus Germar (Coleoptera,Curculionidae) in the Russian Far East

Entomological Review - Anthonomus (s. str.) alni Kojima et Morimoto, 1994 and A. (s. str.) takahashii Kojima et Morimoto, 1994 are recorded for the first time for Russia. Anthonomus (Anthomorphus)...     

Field Evaluation of Selected Formulations of Beauveria bassiana for the Management of the Banana Weevil ( Cosmopolites sordidus ) on Plantain ( Musa spp., AAB Group)

Field experiments were undertaken to determine the efficacy of two formulations of Beauveria bassiana isolate IMI331094 against the banana weevil, Cosmopolites sordidus . Oil palm kernel cake-based formulation of conidia (OPKC-C) and conidial powder (CP) were applied to the planting holes and suckers. After artificial weevil release, OPKC-C and CP gave the same high level of weevil mortality (75%) compared with only 1% in the untreated control. Under natural levels of weevil infestation, 42% of weevils collected from suckers treated with OPKC-C died compared with 6% and 3% weevil mortality for CP and the untreated control, respectively. None of the suckers treated with OPKC-C died during the study period (60 days) while 17% and 19% of suckers from the CP treatment and the untreated control respectively, were killed. A study on the spread of fungal conidia using artificially infected and non-infected adult weevils showed a possible dissemination of B. bassiana conidia from infected weevils up to 18 m from the release point. On the basis of these results, the isolate IMI330194 of B. bassiana could clearly play a key role in the management of C. sordidus adults on plantain.     

Diversity of indigenous Beauveria and Metarhizium spp. in a commercial banana field and their virulence toward Cosmopolites sordidus (Coleoptera: Curculionidae)

Metarhizium anisopliae and Beauveria bassiana sensu lato were isolated, from 7 and 41 % of soil samples from a commercial banana field, with average fungal density of 4.3 × 10³ and 8.2 × 10³ CFU g^?1 soil, respectively. Twenty-one morphologically distinct B. bassiana and four M. anisopliae sensu lato isolates from different plots within the field were further characterized. ISSR fingerprinting revealed six different clusters for B. bassiana, whereas gene sequencing revealed three M. anisopliae sensu stricto and one unclassified Metarhizium sp. Bioassays with one or more representative isolates from each Metarhizium species and B. bassiana cluster showed that all indigenous isolates had lower virulence and significantly greater ST₅₀s than reference (exotic) isolates. The data suggest that the low virulence of most indigenous isolates toward Cosmopolites sordidus adults and their relatively low density in soil samples, may help explain the low occurrence of epizootics caused by entomopathogenic fungi in populations of this pest, also known to burrow under the soil surface in banana plantations.     

Efficacy of cultural control measures against the banana weevil, Cosmopolites sordidus (Germar), in South Africa

The banana weevil, Cosmopolites sordidus, is the most important insect pest of banana and plantain in the world. Cultural control methods were investigated over 2 years in southern KwaZulu‐Natal, South Africa. Harvesting at ground level and dissection of remnants (treatment 1), and covering the base of the mat (entire plant consisting of several meristems) with soil and moving debris to the inter‐row (treatment 2), were compared to a positive control that involved treatment of plants with a registered pesticide (treatment 3), and a negative control that involved harvesting at 150 cm from the collar with no soil or sanitation amendments (treatment 4). Yield, weevil damage and pseudostem girth of plants were measured from August to November annually, while adult beetle densities were assessed over 4 weeks in October/November and April. Nematode samples were taken and analysed in October/November every year. Damage parameters included the coefficient of infestation, the percentage coefficient of infestation (PCI) at two intervals, the summed PCI value, the percentage cross‐sectional damage of the central cylinder and cortex, and the mean cross‐sectional damage percentage. A randomized block design with three replicates was used in the trial. The parameters were similar before the onset of the trial. Fruit yield and plant girth, corrected by nematode densities, were not significantly different in any treatment, nor were the nematodes controlled. Soil cover and recession of remnants was the only effective treatment, significantly reducing the CI, but not the adult density or the other damage parameters. Soil cover showed promise as a cultural control method because it only needs to be applied seasonally and reduced the percentage cross‐sectional damage of the central cylinder, the damage parameter most closely related to yield, by 14%.     

Selection of assessment methods for evaluating banana weevil Cosmopolites sordidus (Coleoptera: Curculionidae) damage on highland cooking banana (Musa spp., genome group AAA-EA)

Cosmopolites sordidus (Germar) is an important pest on bananas and plantains. Population build-up is slow and damage becomes increasingly important in successive crop cycles (ratoons). Yield loss results from plant loss, mat disappearance and reduced bunch size. Damage assessment requires destructive sampling and is most often done on corms of recently harvested plants. A wide range of damage assessment methods exist and there are no agreed protocols. It is critical to know what types of damage best reflect C. sordidus pest status through their relationships with yield loss. Multiple damage assessment parameters (i.e. for the corm periphery, cortex and central cylinder) were employed in two yield loss trials and a cultivar-screening trial in Uganda. Damage to the central cylinder had a greater effect on plant size and yield loss than damage to the cortex or corm periphery. In some cases, a combined assessment of damage to the central cylinder and cortex showed a better relationship with yield loss than an assessment of the central cylinder alone. Correlation, logistic and linear regression analyses showed weak to modest correlations between damage to the corm periphery and damage to the central cylinder. Thus, damage to the corm periphery is not a strong predictor of the more important damage to the central cylinder. Therefore, C. sordidus damage assessment should target the central cylinder and cortex.     

The influence of crop management on banana weevil,Cosmopolites sordidus (Coleoptera: Curculionidae) populations and yield of highland cooking banana (cv. Atwalira) in Uganda

A field study was undertaken in Uganda using highland cooking banana (cv. Atwalira) to test the hypothesis that bananas grown under stressed conditions are more susceptible to attack by Cosmopolites sordidus (Germar). Four banana treatments were employed to create different levels of host-plant vitality: (1) high stress: intercrop with finger millet; (2) moderate stress: monoculture without soil amendments; (3) low stress: monoculture with manure; (4) high vigour: monoculture with continuous mulch and manure. Adult C. sordidus were released at the base of banana mats 11 months after planting and populations were monitored for three years using mark and recapture methods. Cosmopolites sordidus density was greatest in the mulched plots which may have reflected increased longevity and/or longer tenure time in moist soils. Lowest C. sordidus numbers were found in intercropped banana. Damage, estimated as percentage corm tissue consumed by larvae, was similar among treatments. However, the total amount of tissue consumed was greater in mulched banana than in other systems. Plants supporting the heaviest levels of C. sordidus damage displayed bunch size reductions of 40-55%. Banana yield losses ranged from 14-20% per plot with similar levels in the intercropped and mulched systems. Yield reductions, reported as t ha-1, were twice as high in the mulched system as in the intercrop. The results from this study indicate that C. sordidus problems are not confined to stressed banana systems or those with low levels of management, but that the weevil can also attain pest status in well-managed and productive banana stands.     

Cosmopolites sordidus (Germar) susceptibility to indigenous Cameroonian Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae (Metsch.) isolates

Management of the banana root borer (BRB), Cosmopolites sordidus (Germar; Coleoptera: Curculionidae), remains a challenge in banana and plantain production worldwide. Synthetic pesticides remain the most widely used solution while mycoinsecticides are increasingly being recommended. In this study, we selected indigenous isolates of Beauveria bassiana and Metarhizium anisopliae collected from plantain fields in Cameroon, and tested them in the laboratory for their viability, pathogenicity and virulence against all C. sordidus life stages. Of 13 isolates initially screened for spore germination and pathogenicity to adult weevils in conidial suspension of 3.2 × 10⁸ conidia/ml, eight isolates with high to moderate germination and highest weevil mortality were selected for dose–response bioassays with four concentrations per isolate: 3.2 × 10², 3.2 × 10⁴, 3.2 × 10⁶ and 3.2 × 10⁸ conidia/ml. The virulent isolates from adult bioassays were tested with eggs, larva and pupae in conidial suspension of 3.2 × 10⁸ conidia/ml. Isolates performance depended on insect life stage with significantly high pathogenicity and virulence against larval, pupa and adult stages. The Beauveria isolate BIITAC6.2.2 caused the highest mortality rates followed by MIITAC1.1.5. Lethal times and lethal concentrations were relatively low for the three M. anisopliae isolates and three B. bassiana isolates which were the best isolates in almost all insect life stages. Apart from being effective in multiple life stages, these isolates were transmitted horizontally from one stage to another when eggs and pupae were treated. The implication of these findings for integrated management of the BRB, and potential biopesticides development and commercialization are discussed.     

Species of the Weevil Genus Anthonomus Germar (Coleoptera,Curculionidae) Associated with Herbaceous Rosaceae in the Northern and Southern Foothills of the West Sayan Mountains

Entomological Review - Two species of the Anthonomus Germar subgenus Anthonomidius Reitter were found on different species of Potentilla L. in southwestern East Siberia: Anthonomus dauricus Fst. in...     

A new species of Polydrusus (Polydrusus) Germar (Coleoptera:Curculionidae) from the Kurdistan region of Iraq

Polydrusus (s. str.) akreanus sp. n. is a new record of Curculionidae found in Iraqi Kurdistan. The new species is described, illustrated and compared with Polydrusus (s. str.) kadleci Borovec & Germann, 2013 known from Turkey and Iran, which is morphologically similar to the new species.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:9FDC3C5B-6854-4DEF-BDF6-EE6809F82DEE     

Resistance of Maize Landraces to the Maize Weevil Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

The maize weevil Sitophilus zeamais Motsch. is an important pest of maize that attacks the grain both in the field and during storage. The damage caused by the maize weevil S. zeamais on maize landraces, Amarelo Antigo, Asteca, Caiano, Carioca, and Ferrinho, was evaluated by no-choice tests under laboratory conditions. The commercial varieties Sol da Manh?, BR 106, BR 451, and the synthetics PC 0203 and PC 9903 were evaluated for comparisons with the maize landraces. The parameters evaluated were susceptibility index, number of weevil progeny, development time, weevil progeny dry weight, and grain dry weight loss. The landraces were more susceptible to the maize weevil as compared to the commercial varieties. Based on the cluster analysis, two groups of susceptibility to the maize weevil were observed: one of more susceptible populations formed by local landraces and BR 451, and another less susceptible, with commercial varieties, synthetics, and the landrace Amarelo.     

Trail Marking and Processionary Behavior of the Larvae of the Weevil Phelypera distigma (Coleoptera: Curculionidae)

We present here the results of an investigation of the behavioral bases of the first documented instance of trail marking and processionary behavior in a beetle. The larvae of Phelypera distigma (Coleoptera: Curculionidae) forage communally, moving over the host plant in head-to-tail processions. Our study shows that the larvae secrete a pheromone from the ventral surface of the posterior abdomen that both elicits and guides the collective locomotion of the cohort. The pheromone is soluble in acetone and other nonpolar solvents and is relatively short-lived, eliciting trail following for less than 4 h after its deposition. When in processionary formations, larvae stimulate locomotion in others by rapidly bobbing their heads against sets of setae that occur on the lateral flanks of the posterior tips of the abdomens of precedent individuals. Larvae are also strongly attracted to tactile or chemotactile stimuli found at the tip of the abdomen of other larvae and their response to lures made of eviscerated abdomens show that such stimuli take precedence over the trail pheromone in eliciting and orienting locomotion. The cycloalexic formations adopted by resting larvae maximize the amount of body contact possible in a two-dimensional aggregate and allow tactile signals to rapidly radiate through the groups, alerting all members of a cohort to the onset of bouts of activity.     

Social Behavior of Larvae of the Neotropical Processionary Weevil Phelypera distigma (Boheman) (Coleoptera: Curculionidae: Hyperinae)

Socially gregarious behavior among free‐living leaf‐eating insect larvae occurs mostly among Lepidoptera, Symphyta, and a few Chyrsomelidae (Coleoptera). However, the Neotropical hyperine curculionid Phelypera distigma has also evolved this lifestyle, exhibiting a suite of social behaviors unique among beetles. The larvae are nomadic processionary foragers that punctuate foraging bouts with rosette‐shaped resting formations (cycloalexy). Larvae also vibrate or bob their heads rapidly when moving, especially when in contact with conspecifics, and this suggests acoustic or vibrational communication. In this study we used observational and experimental approaches to investigate the basis of processionary, cycloalexic,and head‐vibration behavior of this species. Larvae used both trail pheromones and thigmotactic signals to organize themselves into head‐to‐tail processionary columns. The trail pheromone, produced from the center of the abdomen, remains active for up to 4 h. Processions are not consistently led by particular individuals, but dynamically change over time and often temporarily break into two or more subprocessions. Subprocessions reunite through use of the trail pheromone. We found no evidence that head‐bobbing generates attraction through substrate‐borne or acoustic signals, but this behavior functions in direct contact to excite group activity. Time‐lapse videography used to analyze cycloalexic group formation showed that larvae transition from feeding in a line along the leaf margin to cycloalexic formations on the upper leaf surface via a coordinated back‐up movement that brings the posterior tip of their abdomens into contact. We identify three phases of cycloalexic formation: line‐up, back‐up, and an adjustment phase. Complete assembly can be achieved in as little as 5 s, but often the two phases establishing the basic rosette lasts 5–10 min, while the adjustment phase slowly tightens the group over a period of up to an hour. Collectively these studies present the first documented case of chemical trail marking in a beetle, and provide insight into a remarkable social‐behavioral repertoire convergent in key respects with the better‐studied social caterpillars and sawflies.