POPULATION DENSITY AND SEX RATIO DYNAMICS OF OVERWINTERING MAIZE WEEVILS (COLEOPTERA: CURCULIONIDAE) INFESTING FIELD CORN

Natural infestations of the maize weevil, Sitophilus zeamais (Motschulsky) were monitored in selected corn fields located in each of five major climatic or edaphic environments of Georgia. The population density and sex ratio of each population was recorded on a monthly basis during the fall and winters of 1982–83–84. Females suffered higher winter mortality than males, resulting in increasingly male-skewed sex ratios (from 0.8/1.0 to 1.6/1.0) as winter progressed. The degree of male-skewedness was positively correlated with the amount of subzero weather experienced by each population. Surviving weevil populations decreased in size as winter progressed, with the greatest reductions at the higher latitudes. No weevils survived through spring north of 33° 57′N where winter weather extremes of −15°C occurred. No true diapausing stage was found; however, cold tolerance tests indicated that winter-collected weevils were significantly more cold hardy than laboratory-reared weevils.

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Effect of Planting Date, Variety and Degree of Ear Maturation on the Colonization of Field Corn by Maize Weevils (Coleoptera: Curculionidae)

Journal of Entomological Science ◽

10.18474/0749-8004-37.2.137 ◽

2002 ◽

Vol 37 (2) ◽

pp. 137-142 ◽

Cited By ~ 5

Author(s):

Steve L. Brown ◽

R. Dewey Lee

Keyword(s):

Adult Emergence ◽

Planting Date ◽

Sitophilus Zeamais ◽

Maize Weevil ◽

Field Corn ◽

Second Period

A 3-yr study evaluated the effect of planting date, variety and degree of ear maturation on maize weevil, Sitophilus zeamais (Motchulsky), colonization of corn in the field. Within each plot, paper bags were used to prevent oviposition during one of three consecutive 2-wk periods beginning at the 3/4-milk-line stage. Adult emergence from bagged ears was compared to that from unbagged ears. Maize weevil adults emerged from 15.6% of all ears tested. Numbers of adults emerging from infested ears ranged from 1 to 135 with a mean (±SE) of 11.9 ± 18.5. A greater percentage of Mycogen 7559 ears were infested than those of Pioneer 3167 or Pioneer 3146, and the infested Mycogen 7559 ears also supported the emergence of a greater number of adults. A significant planting date effect was found each year of the study, but the nature of that effect was not consistent. A significant planting date-by-year interaction may have been due to weather affecting the date maize weevils were available for colonization, or more likely, to interference from earlier planted corn near our plots that attracted the first overwintering weevils. Oviposition resulting in successful emergence was found to occur during all 3 of the 2 wk exclusion periods with the last period having the greatest impact on the percentage of infested ears and the second period having the greatest impact on the number of emerging weevils per 500 g of kernels.

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Invasion Patterns and Sex-ratio Dynamics of the Maize Weevil (Coleoptera: Curculionidae) Infesting Field Corn

Journal of Economic Entomology ◽

10.1093/jee/78.5.1072 ◽

1985 ◽

Vol 78 (5) ◽

pp. 1072-1075 ◽

Cited By ~ 3

Author(s):

D. E. Dix ◽

J. N. All

Keyword(s):

Sex Ratio ◽

Maize Weevil ◽

Field Corn ◽

Invasion Patterns

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Efficacy evaluation of common botanicals to manage maize weevil (Sitophilus zeamais M) in laboratory condition

Farming and Management ◽

10.31830/2456-8724.2018.0002.20 ◽

2018 ◽

Vol 3 (2) ◽

Keyword(s):

Laboratory Condition ◽

Sitophilus Zeamais ◽

Efficacy Evaluation ◽

Maize Weevil

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Biopesticidal Extractives and Compounds from Warburgia ugandensis against Maize Weevil (Sitophilus zeamais)

The Natural Products Journal ◽

10.2174/2210315505666150916000539 ◽

2015 ◽

Vol 5 (4) ◽

pp. 236-243

Author(s):

Sylvia A. Opiyo ◽

Lawrence O. A. Manguro ◽

Dorothy A. Okoth ◽

Anjeline A. Ochung ◽

Charles O. Ochieng

Keyword(s):

Sitophilus Zeamais ◽

Maize Weevil

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Effects of Essential Oils from 24 Plant Species on Sitophilus zeamais Motsch (Coleoptera, Curculionidae)

Insects ◽

10.3390/insects12060532 ◽

2021 ◽

Vol 12 (6) ◽

pp. 532

Author(s):

William R. Patiño-Bayona ◽

Leidy J. Nagles Galeano ◽

Jenifer J. Bustos Cortes ◽

Wilman A. Delgado Ávila ◽

Eddy Herrera Daza ◽

...

Keyword(s):

Essential Oils ◽

Chemical Control ◽

Sitophilus Zeamais ◽

Contact Toxicity ◽

Stored Products ◽

Collateral Damage ◽

Maize Weevil ◽

Active Constituents ◽

Insect Mortality ◽

Sitophilus Zeamais Motsch

Chemical control of the maize weevil (Sitophilus zeamais) has been ineffective and presents serious collateral damage. Among plant-derived insecticides, essential oils (EOs) are suitable candidates to control this stored products pest. In this work, the insecticidal activities of 45 natural EOs against S. zeamais adults were screened, and the most promising ones (24 EOs) were characterized by GC–MS. The repellent and toxic effects (contact and fumigant) of these 24 EOs were determined, and by a cluster analysis they were classified into two groups considering its fumigant activity and contact toxicity. For the EOs with the highest fumigant potential (14 oils) and their main active constituents (17 compounds), lethal concentrations were determined. The most active EOs were those obtained from L. stoechas and L. alba, with LC50 values of 303.4 and 254.1 µL/L air and characterized by a high content of monoterpenes. Regarding the major compounds, the oxygenated monoterpenes R-(+)-pulegone (LC50 = 0.580 mg/L air), S-(-)-pulegone (LC50 = 0.971 mg/L air) and R-(-)-carvone (LC50 = 1.423 mg/L air) were the most active, as few variations in their concentrations significantly increased insect mortality.

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Natural variation in social conditions affects male mate choosiness in the amphipod Gammarus roeselii

Current Zoology ◽

10.1093/cz/zoab016 ◽

2021 ◽

Author(s):

Konrad Lipkowski ◽

Sophie Steigerwald ◽

Lisa M Schulte ◽

Carolin Sommer-Trembo ◽

Jonas Jourdan

Keyword(s):

Population Density ◽

Sex Ratio ◽

Natural Variation ◽

Natural Populations ◽

Social Background ◽

Social Conditions ◽

Background Information ◽

Male Mating ◽

Natural Environments ◽

Male Mate

Abstract The extent of male mate choosiness is driven by a trade-off between various environmental factors associated with the costs of mate acquisition, quality assessment and opportunity costs. Our knowledge about natural variation in male mate choosiness across different populations of the same species, however, remains limited. In this study, we compared male mate choosiness across 10 natural populations of the freshwater amphipod Gammarus roeselii (Gervais 1835), a species with overall high male mating investments, and evaluated the relative influence of population density and sex ratio (both affecting mate availability) on male mate choosiness. We investigated amplexus establishment after separating mating pairs and presenting focal males with a novel, size-matched female from the same population. Our analysis revealed considerable effects of sex ratio and (to a lesser extent) population density on time until amplexus establishment (choosiness). Male amphipods are able to perceive variable social conditions (e.g., sex ratio) and modify their mating strategy accordingly: We found choosiness to be reduced in increasingly male-biased populations, whereas selectivity increases when sex ratio becomes female biased. With this, our study expands our limited knowledge on natural variations in male mate choosiness and illustrates the importance of sex ratio (i.e., level of competition) for male mating decisions in natural environments. Accounting for variation in sex ratios, therefore, allows envisioning a distinctive variation of choosiness in natural populations and highlights the importance of considering social background information in future behavioral studies.

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Effects of phytoseiid predators on the sex ratio of the spider mite Panonychus ulmi

Canadian Journal of Zoology ◽

10.1139/z91-031 ◽

1991 ◽

Vol 69 (1) ◽

pp. 208-212 ◽

Cited By ~ 3

Author(s):

Dan L. Johnson ◽

Heather C. Proctor

Keyword(s):

Population Density ◽

Sex Ratio ◽

Spider Mite ◽

Total Population ◽

Panonychus Ulmi ◽

Encounter Rate ◽

Male Mortality ◽

Adult Sex Ratio ◽

Biased Sex Ratio ◽

Male Activity

The effect of predator presence on the adult sex ratio of a spider mite (Panonychus ulmi) was examined in a field experiment. Phytoseiid predators (chiefly Typhlodromus occidentalis) were removed from 32 trees harboring P. ulmi populations, and allowed to remain at natural levels on 32 other trees. Both total population density and proportion of males in the prey population were significantly higher in predator-free trees. Mechanisms that could explain the increase in the proportion of males are examined. The most probable is that greater male activity results in a higher encounter rate between predator and prey, and that subsequent higher male mortality when predators are present exaggerates the female-biased sex ratio. The theoretical effects of sex-biased predation on diplo-diploid and haplo-diploid organisms are discussed.

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Effect of X-ray irradiation on the F1 generation of Sitophilus zeamais Motschulsky and the germination rate of maize grain

The Journal of Basic and Applied Zoology ◽

10.1186/s41936-021-00225-y ◽

2021 ◽

Vol 82 (1) ◽

Author(s):

Sobifagha Princess Bell-Gam ◽

Luke Chinaru Nwosu ◽

Kayode David Ileke ◽

Uwaoma Otuodichinma Aguwa

Keyword(s):

Germination Rate ◽

Seed Viability ◽

Control Process ◽

Progressive Increase ◽

Sitophilus Zeamais ◽

Maize Weevil ◽

Maize Production ◽

X Ray ◽

Significant Difference ◽

Flour Production

Abstract Background The use of X-ray irradiation in the control of the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) infesting stored maize was tested at 60, 70 and 80 KeV as part of the international concerted efforts to save maize production and enhance food security. Investigations were done in the laboratory at mean temperature and relative humidity of 29.2 °C and 75.7%, respectively using three varieties of maize. The possibility that X-ray irradiation can affect the viability of maize grains when planted after weevil control process was also evaluated in the laboratory. Standard methods were used to achieve the specific objectives, and X-ray machine snap constituted the exposure time for each dose. Results The results revealed 10% mortality of adult weevils after 24 h and 40% mortality after a period of 7 days. The result indicates moderate effect on mortality. Progressive increase in mortality was recorded as dose increased from 60 to 80 KeV. X-ray irradiation at the doses tested did not significantly (P > 0.05) restrict S. zeamais emergence from maize grains and did not also significantly protect grains against damage and flour production. There was no difference in the pattern of daily emergence of new progenies and pattern of accumulated emergence. The relationship between X-ray irradiation doses and weight of emerging progenies require more specific analysis. Absence of significant difference between the viability of irradiated grains and un-irradiated grains strongly suggests that X-ray irradiation did not adversely affect seed viability, and this gives irradiation technique an opportunity of higher acceptability in agriculture. Conclusions We recommend > 80 KeV of X-ray irradiation or its incorporation into integrated pest management system in order to achieve effective post-harvest control of the pest.

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Convolutional Neural Networks Using Enhanced Radiographs for Real-Time Detection of Sitophilus zeamais in Maize Grain

Foods ◽

10.3390/foods10040879 ◽

2021 ◽

Vol 10 (4) ◽

pp. 879

Author(s):

Clíssia Barboza da Silva ◽

Alysson Alexander Naves Silva ◽

Geovanny Barroso ◽

Pedro Takao Yamamoto ◽

Valter Arthur ◽

...

Keyword(s):

Neural Networks ◽

Convolutional Neural Networks ◽

Prediction Models ◽

Sitophilus Zeamais ◽

Human Consumption ◽

Storage Pests ◽

Maize Weevil ◽

X Ray ◽

Precise Control ◽

X Ray Imaging

The application of artificial intelligence (AI) such as deep learning in the quality control of grains has the potential to assist analysts in decision making and improving procedures. Advanced technologies based on X-ray imaging provide markedly easier ways to control insect infestation of stored products, regardless of whether the quality features are visible on the surface of the grains. Here, we applied contrast enhancement algorithms based on peripheral equalization and calcification emphasis on X-ray images to improve the detection of Sitophilus zeamais in maize grains. In addition, we proposed an approach based on convolutional neural networks (CNNs) to identity non-infested and infested classes using three different architectures; (i) Inception-ResNet-v2, (ii) Xception and (iii) MobileNetV2. In general, the prediction models developed based on the MobileNetV2 and Xception architectures achieved higher accuracy (≥0.88) in identifying non-infested grains and grains infested by maize weevil, with a correct classification from 0.78 to 1.00 for validation and test sets. Hence, the proposed approach using enhanced radiographs has the potential to provide precise control of Sitophilus zeamais for safe human consumption of maize grains. The proposed method can automatically recognize food contaminated with hidden storage pests without manual features, which makes it more reliable for grain inspection.

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