Number Of Adult Weevils Research Articles

The Insect Pest Management Strategies and Their Influence on The Emergence Rate of Elaeidobius kamerunicus Faust (Coleoptera: Curculionidae) From The Post-Anthesising Male Inflorescence of Oil Palm, Elaeis guineensis

Elaeidobius kamerunicus is the main pollinating insect of oil palm, Elaeis guineensis in Malaysia. Elaiedobius kamerunicus feeds and breeds on the oil palms' male inflorescences. The weevil presence is vital for the successful pollination of oil palm, thus ensuring satisfactory fruit bunch production. MPOB recently reported that the declining quality of oil palm fruit bunch, mainly due to insufficient pollination, had affected the national average oil extraction rate. In part, this scenario was caused by the declining pollinator population. As such, the factors affecting the pollinators' population need to be investigated. One of the critical criteria in estimating the population of E. kamerunicus in the field is to measure the emergence rate of the new adult E. kamerunicus from the post-anthesis male inflorescence (PAMI). The study to investigate the rate of E. kamerunicus adult emergence and their sex ratio was conducted for four months at nine oil palm estates in Malaysia by using PAMI samples that were brought to the laboratory and observed for two weeks. The results have shown that the number of adult weevils that emerged from PAMI was about 36-47 individuals, and the female-to-male ratio for the emerged progenies was 2.33-4.46: 1. Indiscriminate application of broad-spectrum pyrethroid insecticide, cypermethrin has negatively influenced the weevil emergence rate in the field. Whereas, minimal impact on the emergence rate was observed in areas applied with biopesticide. This study showed that the application of cypermethrin could threaten the future population of the pollinating weevil in the field. As such, the excessive application of such insecticides in the field is discouraged and should be replaced by biopesticides to complement other Integrated Pest Management (IPM) strategies. In addition, further investigation is needed to understand how the gender ratio of the progeny could affect the future population of E. kamerunicus.

Is the Invasive Species Listronotus bonariensis (Kuschel) (Coleoptera: Curculionidae) (Argentine Stem Weevil) a Threat to New Zealand Natural Grassland Ecosystems?

Listronotus bonariensis (Argentine stem weevil) is a stem-boring weevil that has become a major pasture pest in New Zealand, and cool climate turf grass in Australia. This species is also frequently found in native tussock grassland in New Zealand. Laboratory and field trials were established to determine the risk posed to both seedlings and established plants of three native grass species compared to what happens with a common host of this species, hybrid ryegrass (L. perenne X L. multiflorum). Adult weevil feeding damage scores were higher on Poa colensoi and Festuca novae-zelandiae than Chionochloa rigida. Oviposition was lower on P. colensoi than hybrid ryegrass, and no eggs were laid on F. novae-zelandiae. In field trials using the same four species established as spaced plants L. bonariensis laid more eggs per tiller in ryegrass in a low altitude pasture site than in ryegrass in a higher altitude site. No eggs were found on the three native grass species at the tussock sites, and only low numbers were found on other grasses at the low altitude pasture site. Despite this, numbers of adult weevils were extracted from the plants in the field trials. These may have comprised survivors of the original weevils added to the plants, together with new generation weevils that had emerged during the experiment. Irrespective, higher numbers were recovered from the tussock site plants than from those from the pasture site. It was concluded that L. bonariensis is likely to have little overall impact, but a greater impact on native grass seedling survival than on established plants.

Population Dynamics ofScyphophorus acupunctatus(Coleoptera: Curculionidae) on Blue Agave

The agave weevil, Scyphophorus acupunctatus Gyllenhal, is considered the main pest of Agave tequilana Weber var. 'Azul' (Asparagales: Asparagaceae) in Mexico. In this study, we investigated the population fluctuations of S. acupunctatus for 19 months using 2 sampling methods in blue agave fields in Ahualulco and Amatitan, Jalisco, Mexico. We recorded the direct damage caused by weevils on the sampled agave plants and evaluated the correla- tion between the number of S. acupunctatus captured by pheromone traps and the density of weevils located on plants. In Ahualulco, the highest agave weevil population density (for all developmental stages) was detected in Mar 2008, although the peak of trap captures occurred in May 2009. In Amatitan, the highest agave weevil population density was ob- served in Apr 2009, and the highest number of insects was captured in May and Sep 2009. The mean fraction of necrotic bole tissue caused by the weevils per sampled plant was 75.4 ± 2.1% and 72.6 ± 2.0% in Ahualulco and Amatitan, respectively. In Ahualulco, there was a positive correlation between the number of weevils caught in the pheromone traps and the number of adult weevils on the plants, whereas the number of weevils caught by the pheromone traps at Amatitan was positively correlated with the total number of weevils on the plants. We found that the sex ratio of weevils recovered from agave plants was approxi- mately 1:1 at both experimental sites, and this trend did not vary seasonally; conversely, the sex ratio of captured weevils in pheromone traps was female-biased year-round.

Comparison of seven methods for stored cereal losses to insects for their application in rural conditions

There are several methods for assessing harvest losses during storage with varying degrees of accuracy, reliability and practical application, however, field conditions may limit their use among subsistence farmers and traders in developing nations. We compared seven standard grain loss methods during natural and controlled infestation by Sitophilus oryzae L. in wheat and barley to select the best procedures for use in farm storage. Methods tested were: 1) visual inspection of infested lots, 2) uncorrected weight loss, 3) modified standard volume/weight ratio, 4) grain count and weight, 5) percentage of damaged grains converted to weight loss, 6) one thousand grain mass, and 7) one thousand grain mass including dust. Previously disinfested cereal lots (wheat, barley, 500 g fresh w) were exposed to 20 newly emerged adult S. oryzae for 90 d at 28 °C and 70% r.h. Naturally- infested wheat lots were also monitored under the same conditions. Before and after this period, fresh and dry weight, number, moisture content of uninfested and damaged grains, weight of 1 L of seeds and dust produced by insect activity, fresh and dry weight of 1000 kernels, and number of adult weevils was determined and applied to appropriate equations of methods (1)–(7). Grain mass loss estimations varied by wide margins (9.3 ± 1.3% to 25.8 ± 2.3% in barley, 2.2 ± 0.7% to 12.5 ± 2.5% in wheat) depending on method employed, suggesting the need for careful selection of the most appropriate procedure under field conditions and farmer/trader interests. While accurate procedures such as method 7 provided dependable results, methods 3 and 5 appear most practical for wheat and barley.

PHEROMONE BAITED TRAP FOR THE MANAGEMENT OF RED PALM WEEVIL, Rhynchophorus ferrugineus F. (Coleoptera: Curculionidae) POPULATION IN COCONUT PLANTATIONS

4-methyl-5-nonanol (ferrugineol), the major component of theaggregation pheromone of Rhynchophorus ferrugineus F. was evaluated as alure for trapping of this pest in coconut plantations in Sri Lanka. Trap design,longevity of ferrugineol in field conditions, and the effect of trapping ondamage incidence of R. ferrugineus were studied. N-pentanol, a knowncompound present in coconut stem volatiles was used in combination offerrugineol in all tested traps. Trap designs tested were; an open plasticbucket, a funnel trap, and a modified metal trap. The open plastic bucket (5 L)baited with ferrugineol-pentanol, which was hung on coconut palm stem at 1.5m, caught significantly more number of adult weevils than ferrugineolpentanolbaited funnel and metal traps. An open plastic bucket trap was sixtimes less expensive than the metal trap currently recommended by theCoconut Research Institute, Sri Lanka. Ferrugineol remained effective as abait for 12 weeks under field conditions. High capture rates of adult R.ferrugineus were obtained in ferrugineol baited open bucket traps inplantations where the initial damage incidence was high. Monthly surveys ofindividual palms during pheromone trapping revealed that a sharp reductionof the number of coconut palms damaged by R. ferrugineus in 10-hectareexperimental blocks. Continuous trapping of weevils with ferrugineol over aperiod of time significantly lowered the infestation of this pest.

Influence of release size on establishment and impact of a root weevil for the biocontrol of houndstongue (Cynoglossum officinale)

The root-boring weevil, Mogulones cruciger, was introduced into Canada to control the weed, houndstongue (Cynoglossum officinale). To optimise its use as a biocontrol agent, a 2-year study was performed in British Columbia, Canada to test if the number of M. cruciger released at sites predicted subsequent declines in weed populations. No, 100, 200, 300 or 400 weevils were released in 1999 at field sites (five replicates) corresponding to discrete populations of houndstongue separated by distances of 0.3–3 km. The sites were subsequently monitored for weevil establishment, population change, and host attack, and houndstongue population change. By 2001, M. cruciger had established at all 20 release sites and was present in low numbers in three of five control sites. The year following release, release size was positively correlated with number of adult weevils collected, their damage to host plants, and with subsequent numbers of larvae per plant. In contrast, houndstongue populations were reduced at the same rate and amount, regardless of the experimental release size, within 2 years of release. Significant release treatment×time interactions indicated that factors other than M. cruciger contributed to houndstongue reductions (e.g. drought). However, overall the addition of weevils accelerated the reductions relative to sites with no weevils added. Our study demonstrated that the lowest number within a range of release sizes typically used in weed biocontrol programmes (i.e. 100) was as effective as 200–400 weevils in achieving a consistent amount and rate of houndstongue reduction, and thus, could be implemented to optimise weevil use and achieve predictable biocontrol.

Maize Weevil Control, 1987

Abstract In Test 1, 19 treatments were applied to uninfested grain of‘Across 8363 QPM’ maize (11% moisture) in December 1986. Each treatment consisted of 1.0 kg of grain, divided into 4 replicate batches of 250 g each in pint glass jars (lids ventilated with screen apertures). They were held at 25 ± 1°C and 60-80% RH. Each replicate jar was infested with 50 ± 2 newly emerged, unsexed weevils 10 DAT, and mortality was recorded after a 7-d exposure period. The treatments with high initial mortality were reinfested with 50 ± 2 weevils/jar 3 months after treatment. Treatments giving only partial or no control were maintained with only the initial infestation. Effective treatments were again reinfested at 6 and 9 months after treatment to check on persistence of control. Between intervals, seeds were moved to Poza Rica, Mexico (a humid lowland tropical area), to simulate field conditions. Eleven months after treatment, the percentage of germination (in greenhouse flats, 4-cm soil cover) was determined to assess possible phytotoxic effects on seed and reduction in germination as a result of weevil damage to grain. In Test 2, to simulate the situation of field infested grain, weevils were allowed to feed and lay eggs on 20 kg of‘Across 8363 QPM’ maize grain (12.5% moisture) for 14 d. Then, the same 19 treatments used in Test 1 (1.0 kg grain/treatment split into 4 replicates) were made. At 40 DAT, the number of adult weevils emerged in each treatment was recorded.

Control of Thrips and the Pepper Weevil on Pepper, Spring 1987

Abstract Transplants were set 26 Feb on 2.5-ft-wide by 8-inch-high beds of EauGallie fine sand covered with black polyethylene mulch. Plots consisted of 15 plants set in a single row on 12-inch centers. Each treatment was replicated 4 times in a randomized complete block design. Treatments were applied 8, 15, 22, 29, 6, 14, 21, and 28 Apr and 3 Jun with a 2.5-gal hand-held CO2-pressured sprayer, which was operated at 40 psi and delivered 50-100 gal/acre (gallonage increased as the plants grew). On 7 May, the thrips were counted in 10 flowers from each plot. Marketable fruit were harvested and abscised fruit were collected on 18 May and 2 and 11 Jun and were examined for internal pepper weevil feeding damage. All abscised fruit were damaged internally by the pepper weevil; thus, counts of abscised fruit were combined with counts of harvested, internally damaged fruit. One, 2, 3, and 5 days after the last application, the numbers of adult weevils were counted during a 5-minute examination of flower and vegetative buds on each plot. The percentages of damaged and undamaged fruit were calculated, and analyses of variance were performed on all data

Damage byCylas formicariusFab. to sweet potato vines and tubers, and the effect of infestations on total yield in Papua New Guinea

Abstract In a series of four trials on sweet potato (Ipomoea batatas (L.) Lam.) four parameters relating to sweetpotato weevil (Cylas formicarius Fab.) population and damage levels were recorded. These were the numbers of adult weevils per m2 of foliage, the numbers of weevil life stages in 15 cm vine sections immediately above the tubers, the percentage of damaged vines and the percentage of damaged tubers. Strong positive correlations were found between the various parameters. Infestations of vines by weevils reduced the vigour of surface foliage and resulted in reduced yields. It was not possible to establish a spray threshold because reduced yields and damage to tubers occurred at low population levels. The number of rainy days between 60–90 days from planting was negatively correlated with the percentage of damaged tubers at 175 days from planting.

Efficacy of Diflubenzuron Diluted in Three Volumes of Oils on Boll Weevil Progeny12

Diflubenzuron (70g of AI/ha) was applied to cotton at 2.3, 4.7, and 9.4 liters of nonphytotoxic oil (Sun Oil 7N® or Dimoil®) per ha with ground and aerial equipment. There was a significant reduction in the number of adult weevils, Anthonomus grandis grandis Boheman, reared from puncture squares when compared with the untreated control. There was no statistical difference in emergence of adults from infested squares collected in plots treated with the three volumes of oils.

Field Selection of Sweet Potato Lines and Cultivars for Resistance to the Sweetpotato Weevil1

Resistance of 79 sweet potato lines to Cylas formicarius elegantulus (Summers) in artificially infested fields was studied. The criteria used in evaluating resistance levels were percentage of hills with infested roots, number of adult weevils emerging from roots, percentage of crowns infested, and crown index based on the severity of the infestation. Five lines were found to be resistant for all criteria at both Savannah, GA, and Yoakum, TX. An additional 26 lines were found to be resistant at Savannah, and 17 of those same lines were resistant for one or more of the criteria at Yoakum. Infestation levels were more severe in Yoakum, which may explain the apparent increase in susceptibility.

Granular Materials Used in Implanting Boll Weevil Eggs on Artificial Diet123

Granular materials were used to cover the artificial diet and the eggs of Anthonomus grandis Boheman after the eggs were sprayed on the diet surface as a substitute for the usual diet scarifyiug and drying operation, The number of adult weevils produced from the petri dishes when the diet and eggs were covered with mortar sand. Vermiculite, fine mineral granules, and corncob grit was as great as or greater than that produced from the regular egg implanting method. By use of the granular material covering, the scarifying and drying operations of the regular egg planting method can be eliminated.

Physical Factors Affecting the Fall Migration of the Egyptian Alfalfa Weevil, Hypera brunneipennis (Coleoptera: Curculionidae): A Regression Analysis 1

In an attempt to determine the primary physical factors affecting the fall migration of the Egyptian alfalfa weevil, a multiple regression analysis, based on a 2-year study in north-central California, was conducted. Physical factors monitored on a daily basis were temperature, wind, cloud cover, evaporation, and precipitation. Four aspects of daily temperature were considered: maximum, minimum, difference between maximum and minimum, and average. Total wind movement and direction was studied. The average number of adult weevils recorded per square yard of trap per sample day was used as the dependent variable and the above-mentioned physical factors as the independent (predictor) variables. We analyzed the data for both study years and obtained a total reduction of 77.6% in the residual variance the first year and 71.3% for the 2nd. Daily temperature difference was by far the single most important factor in reducing the residual variance and, hence, appears to be the most important factor influencing the fall weevil migration.

Analysis of Populations of the Boll Weevil in One Acre of Cotton at Florence, South Carolina, in 1957-5912

Input of bioclimatological factors (cumulative number of degree-days above 55°F, mean and minimum relative humidities, cumulative number of rainy days, and cumulative rainfall) in 1 acre of cotton at florence from 1957 to 1959, were linear in time during the 3 years. The deviations from the linear inputs provide an interpretive backgound for analyzing major changes in populations of Anthonomus grandis Boheman. Varying numbers of overwintering weevils in the climatic regimes of the 3 years resulted in population increases dependent upon the climatic inputs. Damage was poorly correlated with the number of adult weevils. Late-season migration was triggered by lack of oviposition sites in cotton squares.

Greenhouse Technique for Evaluating Sweetclover Weevils’ Preference for Seedling Sweetclover Plants1

A method for evaluating preference of adult sweetclover weevils ( sitona cylindricollis Fahr.) for seedling sweetclover plants is discussed. Seedling plants of a homozygous weevil-susceptible selection of Melilotus alba were subjected to the feeding of various numbers of adult weevils. Replicated tests were made with 1, 2, 4, and 6 weevils per plant. Statistical analyses run on the individual plant data showed significant differences between rows of plants. When assumed varieties were randomized so that each appeared the same number of times in each row, no significant differences were noted. Five varieties per flat replicated in two 5 × 5 Latin squares infested with two weevils per plant produced the most reliable results. The use of a homozygous susceptible standard check will provide, for flat to flat, and year to year, comparisons of materials tested.

The Local Dispersal of the Pea Weevil

Pea weevil ( Bruchus pisorum L.) infestation varies greatly in different parts of the same field; the greatest number of adult weevils and the heaviest infestations of the growing peas are usually found on the edge nearest the source of infestation, near hibernation quarters, and in the hollows and swales.