Pink Bollworm Moths Research Articles

BIO-EFFICACY OF PB-ROPE (L) AS MATING DISRUPTANT AGAINST PINK BOLLWORM, Pectinophora gossypiella (Saunders) IN COTTON

Mating disruption through sex pheromone is a very important technique in integrated pest management (IPM) of pink bollworm in cotton. Present study was carried out during 2020 and 2021 at farm area of cotton Research Station, Faisalabad, Pakistan to check the effectiveness of PB-Rope L (sex pheromone) against pink bollworm. PB-Rope L were tied to the cotton sticks @ 240/hectare at pin square stage. The block where PB-Rope were installed showed significantly lower pink bollworm moth catches as compared with control block. Mean percent reduction in moth catches was observed 68.24 and 72.52% over control during consecutive years. Minimum mean percent green boll damage was observed in block-A i.e., 4.16 and 3.98% as compared with control block-B (12.47 and 13.42%), with percent reduction 66.64 and 70.34% during both years of study. The block treated with PB-Ropes showed significantly less population (5.42 and 6.70 larvae per 50 green bolls) as compared with control block without PB-Ropes (11.69 and 13.47 larvae per 50 green bolls). The percent reduction in larval population was recorded 53.64 and 50.26% as compared to control treatment during consecutive years. Significantly low mean percent damage was recorded in left over bolls and higher yield was also recorded in PB-ropes plot as compared to control plot.

ESTIMATING THE POTENTIAL OF VARIOUS HARBORING SITES OF PINK BOLLWORM (PECTINOPHORA GOSSYPIELLA) IN RELATION TO ENVIRONMENTAL FACTORS

Pectinophora gossypiella is the most potential pest among all bollworms of cotton crop. Studies were conducted to find the Pink Bollworm (PBW) moths population in pheromone traps installed near different harboring sites. Pink Bollworm larvae overwinter in cotton seeds or in soil. From these sources moth emerges, that affect the next season crop. The sex pheromone traps charged with Gossyplure [(Z, Z) and (Z, E) 7, 11 hexadecadienyl acetate] were installed on four potential sites of PBW to catch the moths. Data regarding PBW moths catch in sex pheromone traps were recorded on weekly basis while metrological factors effecting PBW moths catch were recorded on daily basis. Relationship between the moths catch and weather factors were computed by simple correlation. The results concluded that maximum mean moths catch were recorded in those traps that were installed near cotton sticks heaps i. e 85.61 followed by cotton field 24.47. The lowest average number of moths catch was captured in traps of cotton seed store 1.22. The highest moths mean population 3.87 was trapped in the month of September from cotton field traps, however no moth was recorded during the month of December among all the sites. The moths catch in traps installed near cotton sticks heaps site has positive correlation with mean maximum and minimum temperature while has non-significant correlation with relative humidity and rainfall. Cotton sticks heaps are the major harboring sites of PBW infestation to the successive cotton crop.

ESTIMATING THE POTENTIAL OF VARIOUS HARBORING SITES OF PINK BOLLWORM (PECTINOPHORA GOSSYPIELLA) IN RELATION TO ENVIRONMENTAL FACTORS

Pectinophora gossypiella is the most potential pest among all bollworms of cotton crop. Studies were conducted to find the Pink Bollworm (PBW) moths population in pheromone traps installed near different harboring sites. Pink Bollworm larvae overwinter in cotton seeds or in soil. From these sources moth emerges, that affect the next season crop. The sex pheromone traps charged with Gossyplure [(Z, Z) and (Z, E) 7, 11 hexadecadienyl acetate] were installed on four potential sites of PBW to catch the moths. Data regarding PBW moths catch in sex pheromone traps were recorded on weekly basis while metrological factors effecting PBW moths catch were recorded on daily basis. Relationship between the moths catch and weather factors were computed by simple correlation. The results concluded that maximum mean moths catch were recorded in those traps that were installed near cotton sticks heaps i. e 85.61 followed by cotton field 24.47. The lowest average number of moths catch was captured in traps of cotton seed store 1.22. The highest moths mean population 3.87 was trapped in the month of September from cotton field traps, however no moth was recorded during the month of December among all the sites. The moths catch in traps installed near cotton sticks heaps site has positive correlation with mean maximum and minimum temperature while has non-significant correlation with relative humidity and rainfall. Cotton sticks heaps are the major harboring sites of PBW infestation to the successive cotton crop.

Effect of host plants on the oviposition preference of pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Abstract Pink bollworm (Pectinophora gossypiella (Saunders, 1843)) (Lepidoptera: Gelechiidae) is an important pest of cotton. We aimed to study the effect of different host plants on the oviposition preference of pink bollworm under laboratory conditions. Cotton (Bt and non-Bt), okra and hibiscus plants were used, which vary in morphological characteristics. Significant differences were observed in the density of trichomes and it is positively correlated with oviposition behaviour of pink bollworm. In a no-choice test, we recorded a higher number of eggs on Bt and non-Bt cotton plants. In two-, three- and four-choice experiments, pink bollworm preferred to deposit the maximum number of eggs on non-Bt cotton among other host plants. A substantially higher number of eggs were laid on Bt cotton in combinations with okra and hibiscus and a considerably lower number on non-Bt cotton. We recorded fewer numbers of eggs on hibiscus in all combinations. Overall, pink bollworm moths showed greater affinity towards non-Bt cotton plants and deposited the maximum number of eggs there. From the practical point of view, the development of cotton genotypes which are devoid or have a lesser density of trichomes may be a possible solution to reduce the pink bollworm egg load on cotton.

MANAGEMENT OF PINK BOLLWORM WITH MATING DISRUPTION TECHNIQUE IN SMALLAR PLOTS OF COTTON

Pink bollworm, Pectinophora gossypiella is the most damaging pest of cotton irrespective of Bt and non Bt. The damage of the Pink bollworm has increased in Pakistan since 2015 to till now. The main purpose to conduct this study was the evaluation of mating Disruptor’s efficiency against Pink bollworm in smaller plots of cotton. This experiment was conducted at farmer’s field at Bomb more Jalalpur pirwala district Multan on cotton season 2018. The PB-ropes were installed in 1st treatment at the rate of 150 ropes/ acre while the PB-ropes were applied in the 2nd treatment at the rate of 200 ropes/acre and the third treatment was kept as control. The gossyplure baited traps were installed in the cotton at flowering stage in 1st week of August The gossyplure baited traps were installed in the cotton field to monitor the activity of Pink bollworm moth catches in both treatments and control block. It was also observed that the mating disruption efficacy of PB-Ropes remained up to three months. The significant decrease of % damage in green bolls was observed in the plot treated with PB-Ropes @ 200 ropes/ acre (4.73±0.57b) following 150 ropes treated plot (4.73±0.57 b) as compared to control block (31.04±2.42a). The number of moth catches was reduced in the plot treated with PB-Ropes @ 200 ropes /acre(3.40±0.34b) following 150 ropes treated plot (4.64 ± 0.37b) as compared to control block(40.47 ± 1.67a) .The results were further confirmed by % infestation in leftover bolls of the plot treated with PB-Ropes @ 200 ropes / acre (14.00 ± 0.57 b) following plot treated with PBRopes @ 150 ropes / acre (20.33 ± 0.88 b) as compared to control plot (63.00 ± 2.08 a).

MANAGEMENT OF PINK BOLLWORM WITH MATING DISRUPTION TECHNIQUE IN SMALLAR PLOTS OF COTTON

Pink bollworm, Pectinophora gossypiella is the most damaging pest of cotton irrespective of Bt and non Bt. The damage of the Pink bollworm has increased in Pakistan since 2015 to till now. The main purpose to conduct this study was the evaluation of mating Disruptor’s efficiency against Pink bollworm in smaller plots of cotton. This experiment was conducted at farmer’s field at Bomb more Jalalpur pirwala district Multan on cotton season 2018. The PB-ropes were installed in 1st treatment at the rate of 150 ropes/ acre while the PB-ropes were applied in the 2nd treatment at the rate of 200 ropes/acre and the third treatment was kept as control. The gossyplure baited traps were installed in the cotton at flowering stage in 1st week of August The gossyplure baited traps were installed in the cotton field to monitor the activity of Pink bollworm moth catches in both treatments and control block. It was also observed that the mating disruption efficacy of PB-Ropes remained up to three months. The significant decrease of % damage in green bolls was observed in the plot treated with PB-Ropes @ 200 ropes/ acre (4.73±0.57b) following 150 ropes treated plot (4.73±0.57 b) as compared to control block (31.04±2.42a). The number of moth catches was reduced in the plot treated with PB-Ropes @ 200 ropes /acre(3.40±0.34b) following 150 ropes treated plot (4.64 ± 0.37b) as compared to control block(40.47 ± 1.67a) .The results were further confirmed by % infestation in leftover bolls of the plot treated with PB-Ropes @ 200 ropes / acre (14.00 ± 0.57 b) following plot treated with PBRopes @ 150 ropes / acre (20.33 ± 0.88 b) as compared to control plot (63.00 ± 2.08 a).

Males perceive honest information from female released sex pheromone in a moth

AbstractThere is accumulating evidence that male insects advertise their quality to conspecific females through pheromones. However, most studies of female released sex pheromone assume information transfer regarding merely the species of the female and her mating status. We show that more information is conveyed through the female sex pheromone, positioning it as an honest sexual trait. We demonstrate that females in bad physical conditions (small, starved, or old) lay significantly fewer eggs than females in good conditions (large, fed, or young). The ratio of components in the sex pheromone blend in gland extracts of the female pink bollworm moths provided honest information on most of the phenotypic conditions tested, whereas the pheromone amount in the glands provided an honest signal of quality for extreme phenotypes only. Moreover, males used the information conveyed by the female pheromone to choose their mates, approaching females that signaled higher reproductive potential. In addition, when simulating the female effect, using the synthetic pheromone blend that represents higher quality females (0.6:0.4 ZZ:ZE), more males were attracted to this blend than to the blend representing the population mean (0.5:0.5 ZZ:ZE). Both, female advertisement for males and the male choosiness, suggest that pheromones have evolved as sexual traits under directional, sexual selection. We suggest that the pheromone blend may serve as a multicomponent signal whereby each component adds information concerning the current condition of the female, and all are necessary to elicit a mate searching response.

Novel RNA Viruses from the Transcriptome of Pheromone Glands in the Pink Bollworm Moth, Pectinophora gossypiella.

Simple SummaryThe pink bollworm, Pectinophora gossypiella (Lepidoptera: Gelechiidae), is a major pest of cotton. In this study, we analyzed the mRNA from pheromone glands of two populations in Israel. We found several virus sequences that were the same in these populations. We identified these viruses based on high-throughput sequencing data and analysis of the assembled transcripts. Through analysis of the sequences, we identified several unique viral sequences representing possible novel viral species. Two of the viral sequences were found in relatively high abundance in pheromone glands. One of the virus sequences was also found through analysis of previous transcriptome sequencing data from the midgut of pink bollworm larvae. This is the first report of these unique viral sequences found in the pink bollworm, and these viruses could be developed to help control this pest around the world, but more research is needed to determine their utility as biological control agents.In this study, we analyzed the transcriptome obtained from the pheromone gland isolated from two Israeli populations of the pink bollworm Pectinophora gossypiella to identify viral sequences. The lab population and the field samples carried the same viral sequences. We discovered four novel viruses: two positive-sense single-stranded RNA viruses, Pectinophora gossypiella virus 1 (PecgV1, a virus of Iflaviridae) and Pectinophora gossypiella virus 4 (PecgV4, unclassified), and two negative-sense single-stranded RNA viruses, Pectinophora gossypiella virus 2 (PecgV2, a virus of Phasmaviridae) and Pectinophora gossypiella virus 3 (PecgV3, a virus of Phenuiviridae). In addition, sequences derived from two negative-sense single-stranded RNA viruses that belong to Mononegavirales were found in the data. Analysis of previous transcriptome sequencing data derived from the midgut of pink bollworm larvae of a USA population only identified PecgV1, but no other viruses. High viral sequence coverages of PecgV1 and PecgV4 were observed in both field and lab populations. This is the first report of viral sequences discovered from the pink bollworm. Results from this investigation suggest that the pink bollworm harbors multiple viruses. Further investigation of the viral pathogens may help to develop novel pest management strategies for control of the pink bollworm.

Transgenic cotton and sterile insect releases synergize eradication of pink bollworm a century after it invaded the United States

Invasive organisms pose a global threat and are exceptionally difficult to eradicate after they become abundant in their new habitats. We report a successful multitactic strategy for combating the pink bollworm (Pectinophora gossypiella), one of the world's most invasive pests. A coordinated program in the southwestern United States and northern Mexico included releases of billions of sterile pink bollworm moths from airplanes and planting of cotton engineered to produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt). An analysis of computer simulations and 21 y of field data from Arizona demonstrate that the transgenic Bt cotton and sterile insect releases interacted synergistically to reduce the pest's population size. In Arizona, the program started in 2006 and decreased the pest's estimated statewide population size from over 2 billion in 2005 to zero in 2013. Complementary regional efforts eradicated this pest throughout the cotton-growing areas of the continental United States and northern Mexico a century after it had invaded both countries. The removal of this pest saved farmers in the United States $192 million from 2014 to 2019. It also eliminated the environmental and safety hazards associated with insecticide sprays that had previously targeted the pink bollworm and facilitated an 82% reduction in insecticides used against all cotton pests in Arizona. The economic and social benefits achieved demonstrate the advantages of using agricultural biotechnology in concert with classical pest control tactics.

Pheromone gland transcriptome of the pink bollworm moth, Pectinophora gossypiella: Comparison between a laboratory and field population.

The pink bollworm, Pectinophora gossypiella, is a world-wide pest of cotton and in some parts of the cotton growing region is controlled by the mating disruption technique using synthetic sex pheromone. The sex pheromone consists of two compounds, (Z,Z)- and (Z,E)-7,11-hexadecadienyl acetates, in about a 50:50 ratio. However, recently, a population with sex pheromone compound ratios of about 62:38 were found in cotton fields that use mating disruption in Israel. To investigate how the change developed, we compared the pheromone gland transcriptomes between a reference laboratory population and a population obtained from an Israeli cotton field utilizing mating disruption. We analyzed four biological replicates from each population and found transcripts encoding 17 desaturases, 8 reductases, and 17 candidate acetyltransferases in both populations, which could be involved in sex pheromone biosynthesis. The expression abundance of some genes between the two populations was different. Some desaturases and candidate acetyltransferases were found to have mutated in one of the populations. The differentially expressed genes play potential roles in sex pheromone biosynthesis and could be involved in causing altered female sex pheromone ratios in the field population.

Detection and monitoring of pink bollworm moths and invasive insects using pheromone traps and encounter rate models

Summary The pink bollworm moth Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) is one of the most destructive pests in agriculture. An ongoing eradication program using a combination of sex pheromone monitoring and mating disruption, irradiated sterile moth releases, genetically modified Bt cotton and local insecticide applications have all but exterminated the pink bollworm from the south‐western USA and portions of northern Mexico. However, the continued threat of reinvasion from Mexico reinforces the need to improve pheromone‐based monitoring. Invasions from other parts of the world such as India, where resistance to single‐gene transgenic Bt cotton has evolved, further heightens the need for better monitoring strategies. The mean flight height and standard deviation (SD) of the vertical flight distribution of pink bollworm males were estimated from catches on transparent sticky cylinder traps baited with synthetic pheromone at several heights above‐ground. An effective attraction radius (EAR) of a standard pheromone lure was estimated from male moth catches on the pheromone‐baited sticky traps and many similar blank traps. The circular EARc was estimated from the spherical EAR and SD. The EAR of a pheromone lure for pink bollworm was 1·03 m, and the EARc was 2·61 m. The mean flight height of males was 0·82 m, and the vertical flight distribution SD was 0·26 m. A computer program simulated male moth movement and capture on various numbers of traps of EARc distributed over areas of 1–100 km2. The simulated catch results were comparable to predictions using the EARc with modified encounter rate equations of Royama and Rogers. The encounter rate equations were solved for initial populations of male moths in the regions, and Poisson statistics were used to calculate population confidence limits. Synthesis and applications. Encounter rate models and Poisson methods can be used to determine levels of pheromone trap densities that are likely to detect and estimate low population levels of resident or invasive pink bollworms and many other pest insect species.

HPLC Method for Analysis of Red Dye from MarkedPectinophora gossypiella(Lepidoptera: Gelechiidae)

Abstract We describe an HPLC analytical technique for detection of minute amounts of oil-based Red 26 dye used for marking insects. Chromatographic separation was achieved by an isocratic elution on an Inertsil 100A, 5µ silica column using hexane: isopropyl alcohol (98:2) as the mobile phase and with absorption detection at 520 nm. This newly developed technique is fast and very sensitive, with a detection threshold at 0.1 ng and quantitation down to 0.3 ng per pink bollworm adult. Using the newly developed technique we were able to correlate the titer of dye extracted from adult moths to the amount of dye included in the larval diet. This method is currently accepted by the U.S. cotton industry as a preferred technique for distinguishing artificial diet-reared sterile from wild pink bollworm moths.

Permeability Barriers to Embryo Cryopreservation of <I>Pectinophora gossypiella</I> (Lepidoptera: Gelechiidae)

The aim of this study was to develop a method to cryopreserve the embryos of the pink bollworm moth, Pectinophora gossypiella (Saunders). Previously developed dipteran cryopreservation protocols were not directly adaptable to use with the embryos of this lepidopteran species. Physiochemical and electron microscope observations revealed substantial differences in the structure of the chorion, wax layer, and vitelline membrane complex when comparing the cryopreservable embryonic stages of P. gossypiella and dipteran embryos. Thus, the initial steps dealing with dechorionation and permeabilization were ineffective and had to be altered. Exposure to the sodium hypochlorite-based chorion removal step decreased P. gossypiella embryo viability to a very low level. Survival increased and permeability was evident when an alkane wash was used as the first step in the procedure. After the alkane treatment with a surfactant yielded the maximum exchange of cryoprotectant with water as evidenced by a significant lowering of the supercooling point of the cryoprotectant-loaded embryos. The remainder of the cryopreservation and storage recovery protocol for P. gossypiella was similar to those developed for dipteran embryos. Survival of recovered, hatched embryos to adulthood was approximately 7%.

Pink bollworm moth (Lepidoptera: Gelechiidae) catches in the Imperial Valley, California from 1989 to 2003

Abstract We examined the patterns of male pink bollworm (PBW), Pectinophora gossypiella (Saunders), moth catches in gossyplure‐baited traps over a 15‐year period from 1989 to 2003 in the Imperial Valley, California, USA. Monitoring was conducted during periods when different pink bollworm areawide control strategies were being used. Numbers of male pink bollworm moths caught in gossyplure‐baited traps progressively decreased each year from 1990 to 1994 during short‐season cotton production. High numbers of male moths caught in traps from 1995 to 1997 may have been related to moth migrations from the large cotton acreages grown in the Mexicali Valley bordering the Imperial Valley. Transgenic Bollgard® (Bt) cotton was planted in 3% of the cotton area in 1996 and thereafter in 80%–94% of the cotton area from 1997 to 2003. Pink bollworm moth trap catches were significantly lower from 1998 to 2003 than catches in 1995 to 1997, except for 1999. The trapping results suggested that Bt cotton had significant input on reduction of pink bollworm populations, confirming results of other investigators and providing additional documentation on the benefits of the Bt cotton culture.

Flight Potential of Pink Bollworm,Pectinophora gossypiellaSaunders (Lepidoptera: Gelechiidae)

Abstract The potential and propensity in flight of Pectinophora gossypiella (Saunders) in the laboratory were measured using a 32-channel, computer-monitored flight-mill system. Females flew significantly farther within a 72-h flight period than did males. The mean accumulated flight distance and flight duration of 1-d-old female individuals in a tethered-flight test were 41.25 ± 7.76 km and 23.87 ± 2.55 h, respectively, whereas for male individuals, the same parameters were 23.46 ± 2.13 km and 14.12 ± 1.12 h. The flight ability of adults was significantly positively correlated with pupal weight. The flight activity of unmated pink bollworm moths increased daily from the time of eclosion, reaching a peak at 3≈5 d and reducing gradually. All the moths could fly normally at 16≈36°C; however, the optimum temperature for flight ranged from 24 to 28°C, whereas the optimum relative humidity ranged from 75 to 90%.

Synthetic examination of incorrectly proposed structures of biomolecules

Many incorrect structures of biomolecules have been proposed for natural products. Synthesis of compounds having the proposed structures often enabled us to judge the correctness of the proposals. In some cases, we were able to revise the structures by synthesizing the biomolecules themselves. In other cases, we were able to definitely disprove the proposed structures. Some examples treated in this review include: auxin-a and b; the sex pheromone of Chlamydomonas; sex pheromones of the gypsy moth, the American cockroach, and the pink bollworm moth; Persoons' periplanone-A; orobanchol; naurol A; bifurcarenone; koninginin A; alpha-acoradiene; himachalene-type pheromones of the flea beetle; differolide; blattellastanoside A and B; etc.

Mating disruption of the pink bollworm Pectinophora gossypiella (Saund.) (Lepidoptera: Gelechiidae) using gossyplure PB-rope dispensers in cotton fields

The effects of mating disruption on population densities and percentage of damage of the pink bollworm Pectinophora gossypiella (Saunders) were investigated in a cotton field in central Greece, in 1992 and 1993. A 10-ha field was divided in two parts of 5 ha each. PB-rope dispensers were installed in mid-season in one part, whereas the other was used as a control field. Catches of pink bollworm moths in pheromone-baited traps and damage caused were recorded in both the treated and control fields. Results showed that moth catches were highly reduced in the treated field and, therefore, mid-season installation of dispensers was successful. Damage (%) was significantly less in the treated compared with the control field. Consequently, the field size of 5 ha seems to be adequate for the effective implementation of mating disruption.

Calibration of an EAG system to measure airborne concentration of pheromone formulated for mating disruption of the pink bollworm moth, Pectinophora gossypiella (Saunders) (Lep., Gelechiidae)

Abstract: Electroantennogram (EAG) devices, used to measure airborne pheromone density in mating disruption experiments, so far have provided only ‘relative units’ of concentration rather than absolute concentration values. This paper describes a technique to measure the amount of pheromone delivered by calibration syringes into the Kaiserslautern EAG pheromone measurement device, thereby allowing such relative units of concentration to be converted into absolute concentrations. The synthetic pheromone used in these calibrations is of Pectinophora gossypiella (Saunders), the pink bollworm moth, and consists of a 1 : 1 mix of (Z,Z)‐ and (Z,E)‐7,11‐hexadecadienyl acetates. The syringe, driven as in field use, delivers its pheromone–air mixture into a glass capillary where it is adsorbed. The amount of pheromone trapped is measured by gas chromatography. The results show a linear relationship between the ratio of pheromone : silicone oil in a syringe and the pheromone concentration in the air puffs it generates. Efficacious mating disruption of P. gossypiella in cotton occurs with 10−6 relative EAG units, which corresponds to an aerial pheromone density of 1.7 ± 0.15 ng/m3.

Terminator: pest control by a biotech insect

A novel approach to pest control is being tested in the US. More than 3000 pink bollworm moths containing a gene that makes them fluoresce will be released under screened cages in a government-owned cotton field near Phoenix, Arizona. The pink bollworm moth is perhaps the most destructive pest of cotton crops worldwide. A native of southern Asia, this pest now infests several states in southwestern United States.If this initial trial is successful, another version of the moth, dubbed ‘Terminator’ by farmers, will be released. The Terminator moth is genetically engineered to be sterile but sexually active. The US Agriculture Department's Animal and Plant Health Inspection Services hope to contain the pest population by competition with the genetically sterilized moths. Irradiation of moths to make them sterile is currently being used in some areas. But, it takes 60 irradiated moths for every wild moth to be effective, whereas only five biotech moths should be sufficient. AP

Behaviour of pink bollworm males near high‐dose, point sources of pheromone in field wind tunnels: insights into mechanisms of mating disruption

AbstractThe mechanisms by which the application of formulated pheromone interferes with mating in the pink bollworm moth (PBW), Pectinophora gossypiella were examined in 0.4 ha cotton fields using high‐dose (78 mg A.I.) sealed polyethylene dispensers. Walk‐in, field wind tunnels 6.2 m long were placed over two rows of cotton. Treatments consisted of a control, a tunnel in a field free of disruptant formulation; a 3‐rope treatment, in which the field was free of pheromone but one of the cotton rows in the wind tunnel was treated with 3 PBW ropes; and a rope‐grid treatment, in which the field was treated with PBW ropes at the standard density of 1000 ha−1 and one of the cotton rows inside the wind tunnel was treated with 3 PBW ropes. We released marked males into the tunnels near sunset or held them in field cages for 24 h prior to assay. Two pheromone traps at the tunnel's upwind end monitored the ability of males to locate point sources of pheromone. In the 3‐rope tunnel, traps placed upwind of the cotton row treated with disruptant pheromone captured far fewer males than those placed upwind of the untreated cotton row. In the tunnel situated in the centre of the rope‐gridded field, very few males were caught in traps in both rows, indicating a camouflage of the pheromone plumes from the traps by the background of airborne disruptant drawn into the tunnel from the field. Activity of moths near the synthetic pheromone sources was video‐recorded. Males oriented to, landed on or near, and walked on or near, PBW ropes, indicating competition between pheromone sources as a mechanism of mating disruption. Most males visiting PBW ropes became quiescent or disappeared from the field of view after a few minutes, suggesting a habituation/adaptation of response. The rhythm of attraction of males held in the field for 24 h before release was comprised of a small peak of activity near 2000 h, with the majority of attraction between 2300 and 0300 h. Much of the attraction before 0100 appears to be an advancement of the male's normal diel rhythm, caused by the presence of disruptant. Together these findings indicate that mating disruption of pink bollworm using the PBW ropes is achieved by a combination of mechanisms: a camouflage of natural plumes, competition between pheromone sources, habituation, and some advancement of the male's rhythm of response.