Boll Infestations Research Articles

Pink bollworm (Pectinophora gossypiella) movement with respect to rosette flowers in cotton: Novel insights for integrated pest management

Aim: This preliminary study aimed to investigate the movement patterns of Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) larvae in the rosette flowers. Methodology: Field experiments conducted on the migration behavior of pink bollworm larvae with respect to rosette flowers in cotton fields. Observations included monitoring infested flowers, larval stage duration within rosette flowers, and larval movement to soil for pupation, larval mortality post-drop, and larval migration to early bolls, all conducted without insecticide application to reflect natural conditions. Results: The movement of the larvae was tracked and recorded from the start of flowering to the boll formation stage. Nearly, 44.88% of the larvae present on the infested flowers had moved to the soil for pupation, while 14.29% had moved to newly formed bolls on the same rosette flower. Additionally, 30.90% of the larvae had moved to dry leaf debris on the soil, and the remaining 9.93% either escaped or died due to environmental factors such as damp soil. Notably, the study showed that dry soils or light debris accumulation were the most favorable environments for pink bollworm larvae. Interpretation: The present study has generated useful information regarding the movement of PBWs larvae from rosette flowers to bolls that contribute to infestation. Hence, by implementing integrated pest management strategies during the early crop periods between 60 and 100 DAS, green boll infestations can be avoided and economic yields improved. Key words: Larval movement, Pest carryover, Pest management, Rosette flower

Large-Scale Evaluation of Association Between Pheromone Trap Captures and Cotton Boll Infestation for Pink Bollworm (Lepidoptera: Gelechiidae)

Although transgenic cotton producing insecticidal proteins from Bacillus thuringiensis (Bt) is a cornerstone for pink bollworm control in some countries, integrated pest management remains important for bolstering sustainability of Bt cotton and is critical for controlling pink bollworm where Bt cotton is not available or where this pest has evolved resistance to Bt cotton. Here, we used data on moth captures in gossyplure-baited pheromone traps and boll infestations for 163 Bt and 152 non-Bt cotton fields from Arizona to evaluate accuracy of chemical control decisions relying on moth trapping data and capacity of Bt cotton to suppress survival of offspring produced by moths. Assuming an economic injury level of 12% boll infestation, the accuracy of decisions based on moth captures corresponding to economic thresholds of 6%, 8%, and 10% boll infestation increased from 44.7% to 67.1%. The association between moth captures and boll infestation was positive and significant for non-Bt cotton fields but was not significant for Bt cotton fields. Although chemical control decisions based on trapping data were only moderately accurate, pheromone traps could still be valuable for determining when moth populations are high enough to trigger boll sampling to more rigorously evaluate the need for insecticide sprays.

Suppression of pink bollworm and effect on beneficial insects of a nectariless okra-leaf cotton germplasm line

AbstractInfestations of pink bollworm, Pectinophora gossypiella (Saunders), (Lepidoptera: Gelechiidae), and numbers of beneficial insects in two cottons, Gossypium hirsutum, were compared at Maricopa, Arizona, and Brawley, California, during the 1986–1988 seasons. Plots (0.8 ha) of WC-12NL (nectariless, okraleaf, and early maturing) had significantly lower boll infestations than DPL-61 (nectaried, normal leaf, and later maturing) for each location and year. The three year average (range) PBW/100 bolls for WC-12NL and DPL-61 at Maricopa were 6.8 (5.7–10.7) compared to 11.2 (6.8–15.7), respectively. At Brawley the averages were 18.9 (9.3–27.6) compared to 39.2 (15.5–52.5), respectively. With the exception of 1986 at Maricopa, the percentage of bolls with eggs was significantly greater for DPL-61 (average 8.1, range 3.4–16.0) than for WC-12NL (average 4.2, range 1.1–12.1) for each location and year. Both cottons averaged about four eggs per oviposited boll; not significantly different. The numbers of Lygus spp. and three beneficial species of insects were not different in the two cottons. Collops vittatus (Say) (Coleoptera: Melyridae) was collected in significantly greater numbers in WC-12NL (1.0 per 50 sweeps compared to 0.9 for DPL-61), while Hippodamia convergens (Guérin-Ménéville) (Coleoptera: Coccinellidae) was collected in greater numbers in DPL-61 (0.6 per 50 sweeps compared to 0.3 for WC-12NL). WC-12NL is the culmination of a 20-year breeding programme for resistance to P. gossypiella and has characteristics attractive for cotton production in areas where a shorter growing season is desirable.

Pink Boll worm (Lepidoptera: Gelechiidae): Oviposition, Larval Infestations, and Moth Emergence of a Laboratory-Reared Strain under Field Conditions

Fertile female pink boll worm, Pectinophora gossypiella (Saunders), moths released in field cages over cotton plants at Phoenix, Ariz., 20 May to 3 June did not initiate larval infestations in squares, even though viable eggs were laid; however, few squares and no bolls were available as host material. Square and boll infestations were initiated when fertile females were released in field cages periodically between 17 June and 22 July when cotton plants had 9.4 or more squares per plant and bolls were available as host material. Days to first moth emergence were significantly higher for moths from eggs laid in mid-June (31 d) than for moths from eggs laid in late June and July (23-27 d). Pink boll worm moth emergence patterns were highly variable, and moths from eggs laid 17 to 24 June, 1 to 4, 8 to 11, 15 to 18, and 22 to 25 July emerged in each case over a 26-d period following the first emergence, even though all oviposition occurred during 3 d. This resulted in significant overlap of moth emergence from each artificially-induced infestation, even though the time between initiation of the first and last infestations in cages was >30 d.

Pink Bollworm (Lepidoptera: Gelechiidae): Further Tests with (Z,Z)-Isomer of Gossyplure1

Effects of a single application of 78 g (AI)/ha of the (Z,Z)-isomer (89% pure) of gossyplure, the sex pheromone of the pink bollworm, Pectinophora gossypiella (Saunders), or applications of conventional insecticides on trap catches and boll infestations by the moth, were compared in 2-ha fields of cotton, Gossypium hirsutum L. Traps were baited with 1 mg of 9:1, 3:1, or 1:1 ratios of (Z,Z)- to (Z,E)-isomers to monitor blend preferences of native and released male moths. Additional field plot tests were conducted to determine the effects of (Z,Z)-isomer on male moths surrounding a 0.6-ha treated plot and to compare the effects of treatments of gossyplure or (Z,Z)-isomer on trap catch for 2 mo after treatment. Trap catches in the field treated with (Z,Z)-isomer were reduced 97% in June and July compared with the insecticide-treated field, and males were primarily caught in traps baited with 9:1 ratio. Boll infestations were comparable in the two fields until the third month after treatment, when the field treated with (Z,Z)-isomer became heavily infested (35.0 compared with 1.0 pink bollworms per 50 bolls in late August). Recapture of males released 90 d after treatment in the field treated with (Z,Z)-isomer was reduced 95% compared with recapture in an untreated field. Males in the field surrounding a O.6-ha block treated with (Z,Z)-isomer showed an altered response (50% of catch in traps baited with 9:1 ratio) to the maximum test distance of 214 m during a 2-wk period after treatment. Total trap catches of 18, 14, or 3,598 males per plot were obtained in other plots treated with (Z,Z)-isomer, gossyplure, or left untreated during a 2-mo period after treatment.

Development of Pink Bollworm Populations (Lepidoptera: Gelechiidae) on Nectaried and Nectariless Deltapine Cotton in Field Cages1

The development of populations of pink bollworm, Pectinophora gossypiella (Saunders), on the nectaried cultivar, ‘Deltapine 61’ (DPL-61) of cotton, Gossypium hirsutum L., and a closely related nectariless cultivar, ‘Deltapine NSL’ (’DPL-NSL’), was studied in 0.003-ha screened field cages near Maricopa, Ariz., during the 1986 season. Sixteen cages, eight containing ‘DPL-61’ and eight containing ‘DPL-NSL,’ were inoculated with a total of 25 pairs of laboratory-reared moths in three releases beginning at first Hower buds. Subsequent infestations averaged 6.9 and 12.4 infested (rosetted) blooms per cage for ‘DPL-NSL’ and ‘DPL-61,’ respectively, a nonsignificant difference. Subsequent boll infestations were significantly lower in cages of ‘DPL-NSL’ on three of nine sample dates. Linear rates of increase per day of rosetted blooms and infested bolls were not significantly different for ‘DPL-61’ and ‘DPL-NSL,’ Total catches of male moths in single Delta traps maintained in each cage for 5 wk at the end of the season were significantly lower in ‘DPL-NSL’ (390 males per cage) than in ‘DPL-61’ (525 males per cage). The overall seasonal increases, based on these trap catches, were 15.3-fold for ‘DPL-NSL’ and 21.4-fold for ‘DPL-61,’ a highly significant 29% reduction for ‘DPL-NSL.’

Pink Bollworm (Lepidoptera: Gelechiidae): Large-Scale Field Trials with a High-Rate Gossyplure Formulation1

Tests of PBW-ROPE, a hand-applied gossyplure dispenser manufactured by Shin-Etsu Chemical Co., Ltd., Tokyo, Japan, for control of the pink bollworm, Pectinophora gossypiella (Saunders), were conducted on cotton fields in the Imperial Valley, Calif., and in the Mexicali Valley, Mexico. In the Imperial Valley, 23 fields were treated with one of three systems: conventional insecticides (no pheromone), conventional pheromone dispensers (insecticides as needed), or PBW-ROPE pheromone dispensers (insecticides as needed). In the Mexicali Valley, 30 fields were divided between control with conventional insecticide and control with PBW-ROPE dispensers. PBW-ROPE dispensers were applied at the pin square stage (first flower buds) at a rate of ca. 1,000 dispensers containing 78 g (AI)/ha (release rate of 1.3 g per day per ha at application). Moth populations in all fields were monitored during the season using four Delta traps per field containing 1 mg gossyplure baits. Boll samples were taken weekly or twice weekly from first susceptible boll through September. Significant reductions in insecticide applications of 37 and 42% were obtained in fields in the Imperial Valley treated with PBW-ROPE dispensers compared with fields treated with conventional pheromone dispensers or insecticides, respectively (avg. of 11.4 applications in fields treated with conventional insecticides). Cumulative boll infestations were not significantly different in the three treatments. Trap catches in fields treated with PBW-ROPE dispensers were virtually eliminated through June and July and were reduced 97% in August compared with fields treated with conventional insecticides. The number of insecticide applications in fields in the Mexicali Valley treated with PBW-ROPE were reduced 41% compared with fields treated with conventional insecticides (avg. of 4.9 applications in fields treated with conventional insecticides). Cumulative boll infestations were significantly reduced in August and September in fields treated with PBW-ROPE. Trap catches in August in fields treated with PBW-ROPE were reduced 97% compared with fields treated with conventional insecticides.

Pink Bollworm (Lepidoptera: Gelechiidae): Field Testing a New Polyethylene Tube Dispenser for Gossyplure1

Gossyplure, a sex attractant for the pink bollworm, Pectinophora gossypiella (Saunders), was applied by hand on 5 June to 2-ha cotton, Gossypium hirsutum L., fields using a polyethylene tube dispenser. Three doses were tested: 64.4 g (AI)/ha in one application (=894 dispensers/ha), and totals of 66.9, or 31.2 g (AI)/ha divided into three applications of 22.3 or 10.4 g each, respectively, on a 31-day schedule. In addition, untreated and insecticide-treated blocks of cotton were included for comparison. Trap catches in gossyplure-treated fields averaged <1 moth per trap per night until 13 August, an average reduction in catch of 94–98% compared to untreated and insecticide-treated cotton. The field treated with three applications of 10.4 g each had a significantly greater number of larvae per ha in blooms than the other test fields during the 27 June–20 July observation period. Fields treated with 64.3 g, or three applications of 22.3 g each, had significantly lower boll infestations than the field treated with three applications of 10.4 g each or the untreated field in 6 and 13 August samples. Populations of pink bollworm were not detected in the insecticide-treated field until late August. Females in mating stations in gossypluretreated fields remained unmated through mid-August tests. Mating occurred in untreated and insecticide-treated fields on six of seven test dates. Tests of tube dispensers collected from fields during the test period indicated a half-life of ca. 58 days and a gossyplure emission rate of 1.03 mg/day and 0.35 mg/day for the first and last 10 days of that period.

Pink Bollworm: 1 Seasonal Oviposition, Egg Predation, and Square and Boll Infestations in Relation to Cotton Plant Development 2

Native pink bollworm, Pectinophora gossypiella (Saunders), female moths oviposited principally on vegetative cotton plant parts until mid-July, on vegetative cotton plant parts and bolls until mid-August, and principally on cotton bolls thereafter. Eggs on bolls were placed on the inside surface of bracts or under the calyx. Squares were not attractive oviposition sites. More eggs were laid on bolls ca. 3.2 cm in diameter than were laid on bolls ca. 1.8 cm in diameter. Predation of eggs placed on cotton terminals was highest early in the season and decreased thereafter.

Gossyplure in Laminated Plastic Formulations for Mating Disruption and Pink Bollworm Control12

Gossyplure (1:1 mixture of Z,Z- and Z,E- isomers of 7,11 hexadecadienyl acetate) in a plastic laminate formulation was applied by air to ca. 195 ha of cotton, Gossypium spp. in Arizona. In combination with TF (1-tetradecenal formate), virelure (16:1 mixture of ( Z )-11-hexadecenal and ( Z )-9-tetradecenal or ( Z )-9 TDF[( Z )-9-tetradecen-1-ol formate], gossyplure significantly reduced catches of male pink bollworm, Pectinophora gossypiella (Saunders), moths in pheromone-baited, traps, boll infestations and female mating in gossyplure-treated cotton plots as compared with these criteria in an insecticide control and an untreated check plot.

Pink Bollworm: Trap Tests with Gossyplure123

Studies related to control of the pink bollworm (PBW) by trapping were conducted on an 80-ha farm located in Phoenix, AZ. Initial laboratory studies of trap efficiency lead to the incorporation of 10% dicrotophos into Stickem® used in traps (ca. 13% increased kill compared to traps with Stickem only). During the period April 29 to Sept. 15, 1975, a trapping program on 36 ha of cotton resulted in the capture of ca. 30,000 ♂ PBW. Nine percent of the acreage attained 10% or greater boll infestations during the season compared to 45–100% for the preceding 1972–74 seasons. Early fruiting cotton (plots of 4 rows × 7.6 m) was no more attractive to PBW than surrounding, less developed cotton. Early season trap catches indicated that male moths congregated in cotton fields regardless of where they emerged.

Sex pheromones of Lepidoptera. Development of a method for pheromonal control of Pectinophora gossypiella in cotton.

Hexalure was continuously evaporated into the air of cotton fields throughout the growing season. The consequent disruption of premating pheromonal communication between males and females of the pink bollworm resulted in a reduction in larval boll infestations comparable to that provided by commercial insecticide applications.

Timing of Insecticidal Applications for Control of the Pink Bollworm1

In tests at Phoenix, Ariz., 3 insecticide-timing schedules were compared on long-staple cotton in 1967 and 2 schedules were compared on short-staple cotton in 1968 for control of Pectinophora gossypiella (Saunders). Timing treatments in 1967 consisted of 1 schedule initiated against an early-square infestation on June 21, another initiated on July 12 when 8% of the early boll-set was infested, and the last, begun Aug. 8 when 18% of the bolls were infested. Once started, the respective schedules were continued at 5 to 6 day intervals until the test was terminated on Sept. 30. Two insecticides, azinphosmethyl and carbaryl, were compared on each schedule. All 3 schedules resulted in a comparable degree of pink bollworm control and in comparable yields; all resulted in significantly lower pink bollworm infestations and increased yields when compared with the untreated check. There was no difference between the 2 insecticides in control of the pink bollworm or yields obtained. The 1968 insecticidal treatments consisted of a rigid automatic schedule which was initiated after 20% of the bolls became infested and I which was initiated at the same time but where applications were deleted as the infestation was reduced appreciably below the 20% level. Azinphosmethy] and Azodrin® (3-hydroxy- N -methyl- cis -crotonamide dimethyl phosphate), applied at the rates of 0.75 and 0.94 Ib per acre, respectively, were compared on each schedule. Both schedules significantly reduced boll infestations. However, when 3 applications Were deleted from the nonautomatic schedule a rapid increase of the pink bollworm infestation occurred. Yields from the 2 schedules were quite similar and only slightly higher than those from the untreated check. Both insecticides, regardless of schedule, were equally effective.

Observations on a Combined Boll Weevil and Pink Bollworm Infestation in Northern Mexico

A combined heavy boll weevil ( Anthonomus grandis Boh.) and pink bollworm ( Pectinophora gossypiella Saund.) infestation occurred in cotton at Tlahualilo, Durango, Mexico, in 1931. Weekly records were made on the percentage of both square and boll infestations caused by these two species. It was found that the multiplication and development of neither species was checked by that of the other.