Weevil Damage Research Articles

Impact of Insecticides and an Entomophagous Fungus on Pepper Weevil, Melon Thrips, Broad Mite, and Minute Pirate Bug in Hot Pepper, 1997

Abstract Greenhouse-raised ‘Serrano’ pepper plants were transplanted on 2 Apr at 10-inch spacing in single rows on 4 pairs of subirrigated beds, 32 inches wide and 240 ft long on 6-ft centers. Beds had been fertilized with a bottom mix of 80 lb/acre of 5-16-8 and a banded top mix of 500 lb/acre of 19-0-19 supplemented with an injection of 40 lb N/acre on 22 Apr, fumigated with methyl bromide/chloropicrin (66/33) at a rate of 2201b/acre and covered with black polyethylene film mulch. Plants were sprayed with a combination of Maneb 80 WP at 1 lb/acre plus Kocide 101 at 3 lb/acre as necessary for disease control. Each pair of beds was separated by an additional bed of Jalapefio pepper planted on 4 Mar and removed on 28 May which was inoculated with pepper weevils from an adjacent field on 27 Mar. Bed pairs were divided into 12 plots 40 ft long and assigned to 12 treatments in a RCB design with 4 replications. Treatments were applied weekly for 9 weeks beginning 7 May using a high-clearance sprayer with two vertical and one horizontal boom fitted with ceramic “yellow” Albuztm hollow-cone nozzles delivering spray at 200 psi. Initial configuration was three noz-zles, one overhead and one on each side spraying at a rate of 33 gpa. One more nozzle was added to each vertical drop 29 May for a total of five per row and an output of 55 gpa. A pre-treatment count made 6 May on 3 leaves per plant from 10 plants per replication showed a total of 1 pepper weevil, 7 green peach aphids, 8 broad mites and 17 melon thrips. An examination of the inoculum row showed similar levels of these insects except for pepper weevil which numbered more than 2 per plant. Weekly evaluations beginning 14 May were made on 8 plants per plot, searching flowers and terminals for adult pepper weevils. The youngest 3 expanding leaves on all the terminals were rated for aphids, thrips, and broad mite damage on a scale of 0-3: 0 = none, 1 up to 20% terminals damaged, 2 > 20 < 50% damage and 3 > 50% damaged. Orius insidiosus adults and nymphs were included in the count beginning 20 May. All fruit an inch or more in length was harvested, counted, and weighed on 18 Jun and 14 Jul. Incidence of weevil damage was evaluated by cut-ting open each fruit.

Control of Sunflower Insects in West Central Nebraska, 1997

Abstract Sunflowers were planted on 16 May near North Platte, NE, with a ridge till planter. Insecticides were applied with a backpack sprayer on 24 Jul, when the plants were in the 5% bloom stage. The insecticide treatments were applied with water, in a total volume of 7 gpa, at 30 psi. The treatments were replicated four times in 10 X 35 ft plots arranged in a RCB design. Sunflower moth larval damage, head clipper weevil damage, and plant lodging were evaluated 2 Oct on 20 plants from the center of each plot. Moth larval damage on the heads was rated on a 1-5 scale; 1 = no damage, 2 = 25% of the head damaged, 3 = 50% of the head damaged, 4 = 75% of the head damaged, 5 = 100% of the head damaged. Plants with missing heads were scored as damaged by head clipper weevils. Treatment means for each variable were analyzed with ANOVA. The means were separated with Fisher’s protected test of least significant difference.

Evaluation of Selected Foliar Insecticidesl for Control of Sweetpotato Weevil and Banded Cucumber Beetle on Sweetpotatoes, 1997

Abstract A test was conducted at the Burden Research Plantation, LSUAC, Baton Rouge, LA, to determine the efficacy of 15 insecticide treatments for the control of sweetpotato weevil and banded cucumber beetle. Treatments were arranged in a RCB design with four replications. The cultivar ‘Beauregard’ was planted on 18 May. Plots were 3 rows wide (4 ft/row) and 30 ft long. Insecticides were applied on an approximately weekly ba-sis starting two months after transplanting (18, 23 Jul, 1,8, 14, 22, 29 Aug). A CO2-pressurized backpack sprayer was used (30 psi) with a single-row boom (20 inches wide) containing 3 nozzles (Cone Jet sx-10) and calibrated to deliver 25 gpa. Sweetpotatoes were harvested on Sept. 6 and rated for damage. From each plot 25 roots were randomly selected. The number of banded cucumber beetle holes per root, and the presence or absence of weevil damage was noted.

Efficacy of Fipronil for Control of Boll Weevil, 1996

Abstract Cotton was planted 25 Apr in 40-inch rows (8-row X 75-ft plots) at the Texas Agriculture Experiment Station at Chillicothe. The experimental design was a RCB with 5 insecticide treatments and a check replicated 4 times. Cotton was inspected for boll weevil damage (percentage of boll weevil damaged squares per plot) and abundance of beneficial insects (25 sweeps/plot) on 3 Jul (pre-treatment), 11, 15, and 24 Jul (post-treatments). Insecticide treatments were applied on an approximate 5-day spray schedule on 5, 12, 17, and 22 Jul. The scheduled spray date of 10 Jul had to be postponed until 12 Jul because of a heavy rain on 7 Jul. Treatments were applied with a John Deere High Cycle 6000 sprayer. Spray drops were used to provide three nozzles per row, delivering 9.7 total gallons of spray solution per acre at 40 psi.

Ecological Effects of an Insect Introduced for the Biological Control of Weeds

Few data exist on the environmental risks of biological control. The weevil Rhinocyllus conicus Froeh., introduced to control exotic thistles, has exhibited an increase in host range as well as continuing geographic expansion. Between 1992 and 1996, the frequency of weevil damage to native thistles consistently increased, reaching 16 to 77 percent of flowerheads per plant. Weevils significantly reduced the seed production of native thistle flowerheads. The density of native tephritid flies was significantly lower at high weevil density. Such ecological effects need to be better addressed in future evaluation and regulation of potential biological control agents.

Control of Boll Weevil in Cotton with Selected Insecticides, 1996

Abstract Three tests were conducted to evaluate the effi cacy of selected insecticides against boll weevil in cotton planted 18 Apr. Plots consisted of 4 rows (40 inch centers) X 50 ft. in all tests. Treatments were arranged in a RCB design with 4 replications. Insecticides were applied on 28 Jun, 1,3,8, and 12 Jul in all tests. Applications were made with a high clearance sprayer calibrated to deliver 6 gpa through TX-8 hollow cone nozzles (2/row) at 42 psi. Treatments were evaluated by examining 50 cotton flowei buds (squares) per plot 2-4 DAT for evidence of boll weevil damage. No additional foliar insecticides were applied to the plots during this test. The plots received 0.51 inch rainfall on 10 Jul. Data were analyzed with ANOVA, and means were separated according to DMRT.

Evaluation of Selected Foliar Insecticides on Sweetpotato Weevil, Banded Cucumber Beetle, and White Grub on Sweetpotatoes, 1995

Abstract A test was conducted on the Burden Research Plantation, LSUAC, Baton Rouge, LA, to determine the efficacy of 9 insecticide treatments for the control of sweetpotato weevil, banded cucumber beetle, and white grub. Treatments were arranged in an RCB design with four replications. The cultivar ‘Beauregard’ was planted on 18 May. Plots were 3 rows wide (f ft./row) and 30 feet long. Insecticides were applied on an approximately weekly basis starting two months after transplanting (18, 23 Jul, 1,8, 14, 22 and 29 Aug). A CO2 pressurized back pack sprayer was used (30 psi) with a single row boom (20 inches wide) containing 3 nozzles (Cone Jet sx-10) and calibrated to deliver 25 gpa. Sweetpotatoes were harvested on 6 Sep and rated for damage. From each plot, 50 roots were randomly selected and the number of white grub feeding holes, the number of banded cucumber beetle holes, and the presence or absence of weevil damage was noted.

Predicting the extent of damage to conifer seedlings by the pine weevil (Hylobius abietis L.): a preliminary risk model by multiple logistic regression

Damage to conifer seedlings caused by the pine weevil, Hylobius abietis, was estimated within eighty-two forest sites in Northern Ireland. A wide range of environmental variables were compared with the variation in damage between study sites using multiple logistic regression. Although 45 explanatory variables were considered only four were identified as significant within the final model. The four variables were the size of the planted area, the age of the planting, whether the majority of seedlings were self-seeded or planted, and if the site had been previously planted or was a newly planted area. The identification of these four variables indicates that it is possible to build a model identifying areas at risk to weevil damage. Further, although three of the factors have been recognised as significant influences on weevil damage for some time, they still remain important variables within British Isles forestry, suggesting that there is further scope for more precise targeting of weevil control measures.

Forage Grasses Decrease Alfalfa Weevil (Coleoptera: Curculionidae) Damage and Larval Numbers in Alfalfa-Grass Intercrops

The effects of intercropping forage grasses with alfalfa, Medicago sativa (L.), on larval numbers, number of damaged tips, and intensity of feeding damage by alfalfa weevil, Hypera postica (Gyllenhal), were studied in 1990 and 1995 field experiments. The 1990 experiment consisted of treatments that included alfalfa seeded alone and in combination with 3 forage grasses: smooth bromegrass, Bromus inermis (Leyss.); orchardgrass, Dactylis glomerata (L.); and timothy, Phleum pratense (L.). There were significantly more alfalfa weevil larvae in alfalfa monocultures than in alfalfa-forage grass mixtures on 2 sampling dates in 1990. Alfalfa weevil damage also was greater in alfalfa monocultures than in 4 of 6 mixtures at harvest. The 1995 experiment consisted of treatments that included alfalfa seeded alone and in combination with smooth bromegrass, orchardgrass, timothy, and Kentucky bluegrass, Poa pratensis (L.) studied 1 and 2 yr after establishment. Number of alfalfa weevil larvae, number of damaged tips, and intensity of weevil feeding were significantly reduced in alfalfa-forage grass treatments in the 1st but not the 2nd year after establishment. Overall reductions in larval numbers of up to 80% and tip damage of up to 25% were documented in the alfalfa-forage grass intercrops. Intercropping forage grasses with alfalfa is a potential cultural control tactic to reduce alfalfa weevil populations and their damage in legume forage production systems.

The effects of overstory shading on white pine weevil damage to white spruce and its effects on spruce growth rates

A retrospective study was conducted in 1993 that quantified the effects of overstory shading on both spruce weevil (Pissodesstrobi (Peck)) and leader growth on white spruce (Piceaglauca (Moench) Voss × Piceaengelmannii Parry ex Engelm.). The study was undertaken in the interior of British Columbia, where the weevil is causing extensive damage to plantations of white spruce. Shading on the spruce trees was measured by calculating the light interception index and percent overstory cover on individual white spruce trees at the centre of a 2.52 m radius plot. Current weevil attacks decreased significantly with increasing overstory cover, and the rate of decrease was greater in heavily versus lightly attacked stands. Shading also decreased leader growth. These results indicate that the optimum level of overstory removal may be a compromise between volume loss due to overstory competition and volume gain due to decreased weevil attacks.

Evaluation of Selected Insecticides for Control of Boll Weevil, 1995

Abstract Cotton was planted on 17 May at the James Ray farm in Lonoke County. Insecticides were applied on 11, 19, 22, 26, and 29 Aug with a John Deere 6000 hi-cycle equipped with a CO2 sprayer. Total volume was 7.2 gpa at 25 psi using Teejet TX-6 hollowcone nozzles on 19 inch spacing. Plots consisted of 12 rows (38 inch centers) X 50 ft. Treatments were arranged in a RCBD with 4 replications. Ratings were made 2-3 DAT by examining 25 squares/plot for boll weevil damage. The center 2 rows of each plot were harvested on 3 Nov using a John Deere 2-row picker.

Evaluation of Selected Insecticide Combinations for Control of Bollworm/Tobacco Budworm and Beet Armyworm, 1995

Abstract Plots were replicated 4 times in a RCB design and were 4 rows wide (40-in spacing) X 65ft. ‘Stoneville LA 887’ cotton seed was planted 19 May on a Commerce silt loam soil which was sidedressed with 90 lb N/acre. Cotton seed was planted with a John Deere model 7300 series planter equipped with standard seed hoppers. All plots received 0.5 lb (AI)/acre Temik 15G and 1.0 lb (AI)/acre Terraclor 2E + 0.05 lb (AI)/acre Ridomil 2E at planting. Foliar treatments were applied with a JD600 Hi-cycle equipped with a CO2 charged spray system through two TX-12 hollow cone tips per row and calibrated to deliver 10 gpa finished spray. Foliar treatments were applied on 29 Jul, 1, 8, 12, and 24 Aug. Twenty-five squares and 25 plant terminals from the 2 center rows were examined for eggs, bollworms, tobacco budworms, beet armyworms, and boll weevil damage on 3, 11, 16, and 30 Aug. Plots were harvested on 10 Oct. The center 2 rows of the plots were mechanically harvested using a John Deere spindle type picker. Yields are converted to lb seed cotton/acre.

Evaluation of Selected Insecticide Combinations Against Boll Worm/Tobacco Budworm in Louisiana, 1995

Abstract The efficacy of selected insecticides was evaluated against BW/TBW at the Macon Ridge location of the Northeast Research Station. Cotton seed was planted 12 Jun in plots consisting of 4 rows (40 inch centers) X 50 ft. Treatments were arranged in a RCB design and replicated 4 times. Applications were made with a high clearance sprayer calibrated to deliver 6 gpa through Teejet TX-8 hollow cone nozzles (2/row) at 46 psi. Insecticides were applied on 8, 11, 14, 18 Aug and 11 Sep. Treatments were evaluated by examining 50 flower buds (squares) per plot on 11, 14, 22 Aug for evidence of BW/TBW and boll weevil damage. Data reported for boll weevil represent a mean across all sample dates. The plots were mechanically harvested on 16 Oct to determine seed cotton yields. The test area was irrigated by an overhead sprinkler “as needed” during the season, but not within 48 h of treatment applications. Rainfall did not influence the effects of these treatments. Data were analyzed with ANOVA, and means were separated according to DMRT.

Physical protection of conifer seedlings against pine weevil feeding

Protection of seedlings afforded by two types of coated barriers (CB) against pine weevil (Hylobius species) feeding was evaluated in field experiments in Sweden. The CB is an upright sheath surrounding a seedling and covered on the outside with a coating of polytetrafluoroethylene that hinders insects from crawling up. In experiments during 1992–1993 on four sites, protective treatments by CB applied after planting greatly reduced seedling mortality due to pine weevil feeding and increased survival over two growing seasons. Seedlings with correctly positioned CB were rarely attacked. In a large‐scale experiment during 1993–1994 on nine forest sites, protection by CB applied before planting reduced the risk of seedling mortality caused by pine weevil feeding by 93% in the first year and by 83% for both years. Seedling mortality due to Hylobius feeding in plots with CB protected seedlings was largely independent of the mortality in plots with unprotected seedlings. Pine weevil damage was less frequent on scarified sites than on unscarified sites. Differences in damage levels between years were partly attributed to differences in weather conditions.

Observations On Dpl Nucotn 33 And Dpl Nucotn 35, 1995

Abstract Plots were 50 feet long and 16 rows wide (40-inch spacing) and consisted of a randomized complete block design with 3 replications. Transgenic cotton seed (NuCOTN 33 and NuCOTN 35) containing a gene from Bacillus thuringiensis kurstaki that codes for a delta endotoxin (BOLLGARD) toxic to certain lepidopteran larvae and seed of standard commercial varieties from Delta and Pine Land Seed Company (DPL 5415, DPL 20, DPL 5690 were planted 16May, on a Commerce silt loam soil which was sidedress fertilized with 90 lb N/acre. A John Deere model 7100 series planter equipped with 10 inch seed cones mountedto replace the seed hoppers was used for planting. The seed rate was 4 seeds/row ft. All plots received 0.5 lbs Al/acre Temik 15G and 1.2 lbs Al/acre Terraclor Super X at planting. Control measures for the heliothine complex were applied to the appropriate treatment on an “as needed” basis. Plant terminals and squares were examined for bollworm and tobacco budworm (BW/TBW) eggs, larvae, and damage and boll weevil damage on 3, 12, 17, 20, 24, 26 July, 1, 4, 7, 14, 21 Aug. Based on those observations, the plots designated as requiring treatments for the heliothine complex received the following control measures: Karate IE, 0.33 lb Al/acre + Larvin 3.2F, 0.25 lb Al/acre (18 Jul); Karate IE, 0.028 lb Al/acre + Larvin 3.2F, 0.25 lb Al/acre (2 Aug); Karate IE, 0.033 lb Al/acre + Lannate LV 2.4, 0.24 lb Al/acre (8 Aug); Baythroid 2E, 0.04 lb Al/acre + Curacron 8E, 1.0 lb Al/acre + Larvin 3.2F, 0.4 lb AI/ acre (17 Aug); Methyl parathion 4E, 0.33 lb Al/acre + Orthene 90S, 0.33 lb Al/acre + Confirm 2F, 0.125 lb Al/acre (25 Aug); and Methyl parathion 4E, 0.33 lb Al/acre + Evasion 1.5E, 0.25 lb Al/acre + Curacron 8E, 1.0 lb Al/acre (30 Aug). Control measures for nonheliothine pests applied as oversprays to all plots and/or the border rows on an “as needed” basis, consisted of the following treatments: Provado 1.6, 0.05 lb Al/acre (23 Jun); Bidrin 4E, 0.4 lb Al/acre + Evasion 1.5E, 0.2 lb Al/acre (29 Jun); Guthion 2L, 0.25 lb Al/acre (13 Jul); Baythroid 2E, 0.033 lb Al/acr + Larvin 3.2F, 0.25 lb Al/acre (18 Jul, applied to border rows only); Methyl parathion 4E, 0.33 lb Al/acre + Larvin 3.2F, 0.25 lb Al/acre (28 Jul); Methyl parathion 4E, 0.33 lb Al/acre + Larvin 3.2F, 0.25 lb Al/acre (2 Aug); Karate IE, 0.03 lb Al/acre + Methyl parathion 4E, 0.33 lb Al/acre + Lannate LV 2.4, 0.24 lb Al/acre (10 Aug); and Methyl parathion 4E, 0.33 lb Al/acre + Orthene 90S, 0.33 lb Al/acre + Confirm 2F, 0.125 lb Al/acre (25 Aug). Percent defoliation from insect feeding and number of damaged bolls per 3 meters was determined on 30 Aug. The center four rows of the plots were harvested on 12 Oct. Plots were harvested using a John Deere spindle type picker. Yields were converted to lbs. seedcotton/acre.

Control of Foliage Feeding Pests in Cotton, 1995

Abstract Plots were replicated 4 times in a RCB design and were 4 rows wide (40-in spacing) X 65ft. ‘Stoneville LA 887’ cotton seed was planted 19 May on a Commerce silt loam soil which was sidedressed with 90 lb N/acre. Cotton seed was planted with a John Deere model 7300 series planter equipped with standard seed hoppers. All plots received 0.5 lb (AI) Temik 15G and 1.0 lb (AI) Terraclor 2E + 0.05 lb (AI)/acre Ridomil 2E at planting. Foliar treatments were applied with a JD600 Hi-cycle equipped with a CO2 charged spray system through two TX-12 hollow cone tips per row and calibrated to deliver 10 gpa finished spray. Foliar treatments were applied on 2, 8, 12, and 25 Aug. Twenty-five squares and 25 plant terminals from the 2 center rows were examined for eggs, BW/TBW larvae and damage, BAW, and boll weevil damage on 3, 11, 16, and 29 Aug. Plots were harvested on 12 Oct. The center 2 rows of the plots were mechanically harvested using a John Deere spindle type picker. Yields are converted to lb seed cotton/acre.

Weevils and Watermilfoil: Did a North American Herbivore Cause the Decline of an Exotic Plant?

The Eurasian watermilfoil (Myriophyllum spicatum) population in Brownington Pond, Vermont, declined between 1986 and 1989. Watermilfoil covered ≈10‐11 ha of the littoral zone in 1986. Less than 0.5 ha remained in 1989. An herbivorous weevil (Euhrychiopsis lecontei), which is native to North America, was found associated with this watermilfoil population and we hypothesized that this weevil played a role in the decline. We monitored watermilfoil and E. lecontei populations in Brownington Pond from 1990 through 1992 by (1) mapping the location and extent of beds in the pond, and (2) determining watermilfoil biomass along permanent transects. The abundance of weevil eggs, larvae, pupae, and adults were monitored by sampling individual watermilfoil stems. Watermilfoil cover increased to ≈ 2.5 ha by 1991 and then declined again to ≈1 ha by 1992. The reduction in watermilfoil biomass from 1991 to 1992 ranged from 4‐ to 30‐fold depending on location. Mean weevil abundance increased from 1990 (<1/stem) through early 1992 (3‐4/stem) and then began to decline. The number of weevil eggs/stem also peaked in early 1992 and then declined. These survey results are consistent with the hypothesis that the weevil played an important role in producing both observed declines. The effect of weevils on watermilfoil was evaluated in two experiments. In an aquarium experiment, we found that the viability of stem fragments damaged by weevils was reduced compared to stem fragments without weevil damage. Watermilfoil commonly spreads by producing fragments so the spread of watermilfoil beds by fragmentation may be reduced when weevil abundances are high. In a pond enclosure experiment, weevils suppressed the production of new watermilfoil biomass. The biomass of lateral stems and roots of watermilfoil plants damaged by weevils was significantly less than those of control plants. There was no significant difference in the biomass of the stems originally planted in the enclosures. Weevil damage did have a negative effect on the buoyancy of these original stems, however. These experimental results also support the hypothesis that this native weevil played an important role in the two watermilfoil declines observed at Brownington Pond.

Control of White Pine Weevil in Young Jack Pine Plantations with Permethrin and Methoxychlor

Abstract The efficacy of mistblower applications of permethrin at 70 g and 140 g active ingredient (ai)/ha and methoxychlor at 1.1 kg ai/ha was evaluated for the control of white pine weevil in young jack pine plantations. The results from 2 yr of testing indicate that 1-3% of the leaders were weevil-damaged after insecticide treatment compared to 9-13% in untreated plantations. Generally, all three insecticide treatments were similarly effective in reducing weevil damage. Additional field trials with permethrin at 70 g ai/ha showed that effective applications can be made as late as 2 wk after the first weevils have emerged in the spring from the soil. Mistblower applications of permethrin and methoxychlor can be an effective method to control the weevil in high value jack pine plantations such as seed orchards and genetic test sites where silvicultural and cultural control techniques are impractical. North. J. Appl. For. 12(1):19-22.

Evaluation of Selected Insecticides for Control of Boll Weevil, 1994

Abstract Cotton was planted on 9 May at the James Ray farm in Lonoke County. Insecticides were applied on 2, 5, 12, 19, and 22 Aug with a John Deere 6000 hi-cycle equipped with a CO2 sprayer. Total volume was 10 gal/acre at 30 psi using Teejet TX-6 hollowcone nozzles on 19 inch spacing. Plots consisted of 12 rows (38 inch centers) × 50 ft. Treatments were arranged in a RCBD with 4 replications. Boll weevil ratings were made 2-3 DAT by examining 25 squares/plot for boll weevil damage. The center 2 rows of each plot were harvested on 10 Oct using a John Deere 2-row picker.

Control of Boll Weevil and Tarnished Plant Bug in Cotton with Selected Insecticides, 1994

Abstract Three tests were conducted to evaluate the efficacy of selected insecticides against boll weevil and tarnished plant bug in irrigated cotton planted 18 Apr. Plots consisted of 4 rows (40 inch centers) × 50 ft. in all tests. Treatments were arranged in a RCB design with 4 replications. Insecticides were applied on 1, 6, 11, 18, and 21 Jul in all tests. Applications were made with a high clearance sprayer calibrated to deliver 6 gal total spray/acre through TX-8 hollow cone nozzles (2/row) at 48 psi. Treatments were evaluated 4-5 times by examining 50 cotton squares (flower buds) per plot 3-5 DAT for evidence of boll weevil damage. Treatments were evaluated for tarnished plant bug control with a standard 15 inch diam sweep net by counting the number of adults and nymphs in a 25 sweep sample/plot on 25 Jul. No additional foliar insecticides were applied to the plots during this test. The test area received 0.46 inch rainfall on 4 Jul, 0.72 inch rainfall on 9 Jul, 1.6 inches rainfall on 14 Jul, 0.51 inch rainfall on 16 Jul, and 0.46 inch rainfall on 22 Jul. Data from each test were analyzed with ANOVA, and means were separated according to DMRT.