Effects of photoperiod on boll weevil (Coleoptera: Curculionidae) development, survival, and reproduction

Effects of photoperiod on development, survival, feeding, and oviposition of boll weevils,Anthonomus grandis grandis Boheman, were assessed under five different photophases (24, 14, 12, 10, and 0 h) at a constant 27°C temperature and 65% RH in the laboratory. Analyses of our results detected positive relationships between photoperiod and puncturing (mean numbers of oviposition and feeding punctures per day), and oviposition (oviposition punctures/oviposition+feeding punctures) activities, and the proportion of squares attacked by boll weevil females. When boll weevil females developed in light:darkness cycles, they produced a significantly higher percentage of eggs developing to adulthood than those developed in 24-h light or dark conditions. In long photoperiod (24:0 and 14:10 h), the number of female progeny was significantly higher and their development time was significantly shorter than those developed in short photoperiod (0:24 and 10:14 h). Lifetime oviposition was significantly highest at 12- and 14-h photophase, lowest at 0- and 10-h photophase, and intermediate at 24 h of light. Life table calculations indicated that boll weevil populations developed in a photoperiod of 14:10 and 12:12 (L:D) h will increase an average of two-fold each generation (Ro) compared with boll weevils developed in 24:0- and 10:14-h photoperiods and 15-fold compared with those at 0:24 h. Knowledge of the photoperiod-dependent population growth potential is critical for understanding population dynamics to better develop sampling protocols and timing insecticide applications

Effects of Burial and Soil Condition on Postharvest Mortality of Boll Weevils (Coleoptera: Curculionidae) in Fallen Cotton Fruit

Effects of soil condition and burial on boll weevil, Anthonomus grandis grandis Boheman, mortality in fallen cotton, Gossypium hirsutum L., fruit were assessed in this study. During hot weather immediately after summer harvest operations in the Lower Rio Grande Valley of Texas, burial of infested fruit in conventionally tilled field plots permitted significantly greater survival of weevils than in no-tillage plots. Burial of infested squares protected developing weevils from heat and desiccation that cause high mortality on the soil surface during and after harvest in midsummer and late summer. A laboratory assay showed that burial of infested squares resulted in significantly greater weevil mortality in wet than in dry sandy or clay soils. Significantly fewer weevils rose to the soil surface after burial of infested bolls during winter compared with bolls set on the soil surface, a likely result of wetting by winter rainfall. A combination of leaving infested fruit exposed to heat before the onset of cooler winter temperatures and burial by tillage when temperatures begin to cool might be an important tactic for reducing populations of boll weevils that overwinter in cotton fields

Reproductive Potential of Overwintering, F1, and F2 Female Boll Weevils (Coleoptera: Curculionidae) in the Lower Rio Grande Valley of Texas

The feeding and oviposition activity of overwintering boll weevils, Anthonomus grandis grandis (Boheman), and seasonal fluctuations in development, survival, and reproduction of progeny of overwintering and first- and second-generation boll weevil females were determined in the laboratory at 27°C, 65% RH, and a photoperiod of 12:12 (L:D) h. During the cotton-free period in the Lower Rio Grande Valley, female boll weevils without access to cotton resorb their unlaid eggs and enter reproductive diapause. However, when they were provided daily with greenhouse-grown cotton squares, commencement of oviposition began after 7, 15, or 20 d, depending on when they were captured. Females captured later in the winter fed longer before laying eggs than those captured in the early fall, suggesting that it may take females longer to terminate diapause the longer they have been dormant. The rate of feeding by females was significantly less during the winter months, and this may have affected the rate of diet-mediated termination of dormancy. Females of the first and second generations after the overwintering generation produced a significantly higher percentage of progeny surviving to adulthood and a higher proportion of these progeny were females. Offspring development time from overwintering female parents was significantly longer than that from first and second generations under the same laboratory conditions. The total number of lifetime eggs produced by females of the second generation during the cotton-growing season were ≈9.9-fold higher than for overwintering females and 1.5-fold higher than for first-generation females. Life table calculations indicated that the population of second-generation boll weevils increased an average of 1.5-fold higher each generation than for females of the first generation and 22.6-fold higher than for overwintering females. Our data showed variation in boll weevil survival, development, and reproductive potential among the overwintering and first- and second-generation females, suggesting inherent seasonal fluctuations in these parameters

Effects of Conventional vs. Conservation Tillage Systems on Population Dynamics of Boll Weevil (Coleoptera: Curculionidae) in Dryland Cotton

Studies were conducted during 2000-2001 to determine the effects of a conservation tillage system in dryland cotton on soil surface temperatures, soil moisture, plant canopy structure, light interception, timing of fruit set, and how these factors affect crop yield and boll weevil, Anthonomus grandis grandis Boheman, populations compared with a conventional moldboard tillage system. Soil moisture at the 10-40 cm depth was 1.6-1.9-fold higher in the conservation tillage treatment than in the conventional tillage treatment throughout the first 90 days of crop growth due to the decreased evaporation from crop residue mulch. The conventional tillage cotton treatment had a greater water stress, causing plants to shed squares and bolls. Cotton plants in the conventional tillage treatment allocated more resources into vegetative growth while the conservation tillage cotton responded by fruiting at a higher rate. At 110 days after planting the conservation tillage cotton had an average height of 42.4 cm per plant versus 63.0 cm in conventional tillage, and the number of leaves per plant was 32.4 versus 51.7, while fruit numbers were 13.0 versus 7.1, respectively. Increased plant height and number of leaves in the conventional tillage provided significantly more light interception and shading of the soil surface. In the conservation tillage cotton, 60.2% of the incoming sunlight reached the soil surface, while the conventional tillage had only 36.2%. Soil temperatures between the rows in conservation tillage cotton were 8-11º C higher than in conventional tillage and significantly influenced boll weevil mortality in infested squares shed from plants. The number of boll weevils per plant was 2.3 to 3.4-fold higher in the conventional tillage compared with the conservation tillage. Trap counts of weevil populations followed a similar trend with 1.6 to 2.8-fold more weevils in the conventional tillage compared to conservation tillage. The mortality of boll weevils in fallen, naturally infested squares, and in cohorts of laboratory-infested squares collected from the middle of the rows was 1.5-1.8-fold higher in the conservation tillage field than in the conventional. Percent punctured squares by boll weevils during the growing season averaged 2.1-fold higher in conventional than in conservation tillage fields

Pollen contamination of boll weevil traps

The boll weevil, Anthonomus grandis Boheman, has been the most devastating insect pest of cotton, Gossypium hirsutum L., in the southern United States of America (USA). Although thought to feed only on cotton, the list of non-cotton alternative food sources increases yearly. Many of these taxa are thought to be contaminates and not food sources. The purpose of this research was to examine the possibility that weevils become contaminated with pollen while sitting in the trap. Between January and April, boll weevil traps were placed near Brownsville and Weslaco (a substitute location) and in Santa Ana Wildlife Refuge, Texas. Pollen was removed from the trap’s pole, skirt, mesh cone, and lid by wiping them with an individual, sterile, 100% cellulose acetate filter. The original trap was replaced with a replacement trap that was left for three days, then wiped for pollen. Little pollen was found on the trap parts regardless of the month or the site. The mesh cone was the least contaminated. From these data, it is doubtful that weevils become contaminated with pollen while sitting in the trap. Additional research is needed to examine if pollen is transferred among trapped weevils

Effects of Burial and Soil Condition on Postharvest Mortality of Boll Weevils (Coleoptera: Curculionidae) in Fallen Cotton Fruit

Effects of soil condition and burial on boll weevil, Anthonomus grandis grandis Boheman, mortality in fallen cotton, Gossypium hirsutum L., fruit were assessed in this study. During hot weather immediately after summer harvest operations in the Lower Rio Grande Valley of Texas, burial of infested fruit in conventionally tilled field plots permitted significantly greater survival of weevils than in no-tillage plots. Burial of infested squares protected developing weevils from heat and desiccation that cause high mortality on the soil surface during and after harvest in midsummer and late summer. A laboratory assay showed that burial of infested squares resulted in significantly greater weevil mortality in wet than in dry sandy or clay soils. Significantly fewer weevils rose to the soil surface after burial of infested bolls during winter compared with bolls set on the soil surface, a likely result of wetting by winter rainfall. A combination of leaving infested fruit exposed to heat before the onset of cooler winter temperatures and burial by tillage when temperatures begin to cool might be an important tactic for reducing populations of boll weevils that overwinter in cotton fields.This article is from Journal of Economic Entomology 97 (2004): 409, doi:10.1603/0022-0493-97.2.409.</p

Effects of photoperiod on boll weevil (Coleoptera: Curculionidae) development, survival, and reproduction

Effects of photoperiod on development, survival, feeding, and oviposition of boll weevils,Anthonomus grandis grandis Boheman, were assessed under five different photophases (24, 14, 12, 10, and 0 h) at a constant 27°C temperature and 65% RH in the laboratory. Analyses of our results detected positive relationships between photoperiod and puncturing (mean numbers of oviposition and feeding punctures per day), and oviposition (oviposition punctures/oviposition+feeding punctures) activities, and the proportion of squares attacked by boll weevil females. When boll weevil females developed in light:darkness cycles, they produced a significantly higher percentage of eggs developing to adulthood than those developed in 24-h light or dark conditions. In long photoperiod (24:0 and 14:10 h), the number of female progeny was significantly higher and their development time was significantly shorter than those developed in short photoperiod (0:24 and 10:14 h). Lifetime oviposition was significantly highest at 12- and 14-h photophase, lowest at 0- and 10-h photophase, and intermediate at 24 h of light. Life table calculations indicated that boll weevil populations developed in a photoperiod of 14:10 and 12:12 (L:D) h will increase an average of two-fold each generation (Ro) compared with boll weevils developed in 24:0- and 10:14-h photoperiods and 15-fold compared with those at 0:24 h. Knowledge of the photoperiod-dependent population growth potential is critical for understanding population dynamics to better develop sampling protocols and timing insecticide applications.This article is from Environmental Entomology 37 (2008): 1396, doi:10.1603/0046-225X-37.6.1396</p

Reproductive Potential of Overwintering, F1, and F2 Female Boll Weevils (Coleoptera: Curculionidae) in the Lower Rio Grande Valley of Texas

The feeding and oviposition activity of overwintering boll weevils, Anthonomus grandis grandis (Boheman), and seasonal fluctuations in development, survival, and reproduction of progeny of overwintering and first- and second-generation boll weevil females were determined in the laboratory at 27°C, 65% RH, and a photoperiod of 12:12 (L:D) h. During the cotton-free period in the Lower Rio Grande Valley, female boll weevils without access to cotton resorb their unlaid eggs and enter reproductive diapause. However, when they were provided daily with greenhouse-grown cotton squares, commencement of oviposition began after 7, 15, or 20 d, depending on when they were captured. Females captured later in the winter fed longer before laying eggs than those captured in the early fall, suggesting that it may take females longer to terminate diapause the longer they have been dormant. The rate of feeding by females was significantly less during the winter months, and this may have affected the rate of diet-mediated termination of dormancy. Females of the first and second generations after the overwintering generation produced a significantly higher percentage of progeny surviving to adulthood and a higher proportion of these progeny were females. Offspring development time from overwintering female parents was significantly longer than that from first and second generations under the same laboratory conditions. The total number of lifetime eggs produced by females of the second generation during the cotton-growing season were ≈9.9-fold higher than for overwintering females and 1.5-fold higher than for first-generation females. Life table calculations indicated that the population of second-generation boll weevils increased an average of 1.5-fold higher each generation than for females of the first generation and 22.6-fold higher than for overwintering females. Our data showed variation in boll weevil survival, development, and reproductive potential among the overwintering and first- and second-generation females, suggesting inherent seasonal fluctuations in these parameters.This article is from Environmental Entomology 36 (2007): 256, doi:10.1603/0046-225X(2007)36[256:RPOOFA]2.0.CO;2</p

Effects of Conventional vs. Conservation Tillage Systems on Population Dynamics of Boll Weevil (Coleoptera: Curculionidae) in Dryland Cotton

Studies were conducted during 2000-2001 to determine the effects of a conservation tillage system in dryland cotton on soil surface temperatures, soil moisture, plant canopy structure, light interception, timing of fruit set, and how these factors affect crop yield and boll weevil, Anthonomus grandis grandis Boheman, populations compared with a conventional moldboard tillage system. Soil moisture at the 10-40 cm depth was 1.6-1.9-fold higher in the conservation tillage treatment than in the conventional tillage treatment throughout the first 90 days of crop growth due to the decreased evaporation from crop residue mulch. The conventional tillage cotton treatment had a greater water stress, causing plants to shed squares and bolls. Cotton plants in the conventional tillage treatment allocated more resources into vegetative growth while the conservation tillage cotton responded by fruiting at a higher rate. At 110 days after planting the conservation tillage cotton had an average height of 42.4 cm per plant versus 63.0 cm in conventional tillage, and the number of leaves per plant was 32.4 versus 51.7, while fruit numbers were 13.0 versus 7.1, respectively. Increased plant height and number of leaves in the conventional tillage provided significantly more light interception and shading of the soil surface. In the conservation tillage cotton, 60.2% of the incoming sunlight reached the soil surface, while the conventional tillage had only 36.2%. Soil temperatures between the rows in conservation tillage cotton were 8-11º C higher than in conventional tillage and significantly influenced boll weevil mortality in infested squares shed from plants. The number of boll weevils per plant was 2.3 to 3.4-fold higher in the conventional tillage compared with the conservation tillage. Trap counts of weevil populations followed a similar trend with 1.6 to 2.8-fold more weevils in the conventional tillage compared to conservation tillage. The mortality of boll weevils in fallen, naturally infested squares, and in cohorts of laboratory-infested squares collected from the middle of the rows was 1.5-1.8-fold higher in the conservation tillage field than in the conventional. Percent punctured squares by boll weevils during the growing season averaged 2.1-fold higher in conventional than in conservation tillage fields.This article is from Subtropical Plant Science 55 (2003): 32.</p