Pink Bollworm Moths Research Articles

Field-Based, Degree-Day Model for Pink Bollworm (Lepidoptera: Gelechiidae) Development

Lower and upper developmental temperature thresholds of 13.9 and 32.8 degrees C were determined for the pink bollworm, Pectinophora gossypiella (Saunders), using 21 occurrences documenting overwintering larvae to adult moth development in the field. The events were induced by irrigation of pink bollworm infested cotton bolls held in emergence cages in experiments conducted from 1987 through 1991 in the Palo Verde Valley, CA. The whole day, sine wave method with a horizontal upper cutoff was found to be the best of several methods for calculating daily degree-days. Dates of beginning and peak spring moth emergence from overwintering diapaused larvae were determined from plots of male moth captures in 48 pheromone-baited survey traps situated along roadsides throughout the cotton producing area. Using the same method, degree-days from 1 February (determined to be the best starting date for heat accumulation) to the peak of spring moth emergence were calculated to be 510 DD (centigrade). Two weeks before peak infested cotton flowers was used as the date for initial in-field infestation. Numbers of male pink bollworm moths captured in field-situated pheromone traps were used to establish subsequent peak activity points for the 1st and 2nd generations. Using 12 of these generation events and the 13.9/32.8 degrees C thresholds, horizontal cutoff, and whole day sine wave method, the degree-days for 1 generation, adult to adult, were determined to be 492 DD. These field-derived thresholds corresponded well with thresholds obtained by some researchers using constant temperature laboratory trials

Reduction of Pink Bollworm (Lepidoptera: Gelechüdae) Populations in the Imperial Valley, California, Following Mandatory Short-Season Cotton Management Systems

A cotton management program in the Imperial Valley, California, was specifically designed to reduce pink boll worm, Pectinophora gossypiella (Saunders), populations in the area by optimizing the host-free period. The program established 1 March as the earliest planting date, 1 September for defoliant or plant growth regulator application and 1 November for cotton stalk destruction and plowdown. In-season gossyplure-baited pink boll worm male moth activity monitoring and immature green cotton boll inspections for larval infestation were encouraged as decision making aids to determine the need for additional control action. Male pink boll worm moth catches in gossyplure-baited Lingren and delta sticky traps were substantially reduced each year from 1990 to 1994 following the initiation of the management program in 1989. Fewer larvae per cotton boll occurred in the years from 1990 to 1992. Fiber quality of commercial cotton sampled was also improved from 1989 to 1994, as compared with the 1984 to 1988 average. Male moth trap catches in gossyplure-baited traps placed around the perimeter of the Imperial Valley suggest that pink boll worm moth migration into the valley occurred from surrounding cotton growing areas during the growing season. Highest numbers of moths were caught in perimeter traps directionally placed toward cotton growing areas in the Mexicali, Baja California, Mexico, and Bard-Winterhaven and Palo Verde, CA. Cotton production, in general, was reduced during 1989-1994 in these areas and may have contributed partially to reduced populations in Imperial Valley.

Twin Screw Extrusion Processing of Diet for Mass Rearing the Pink Bollworm

The use of a long barreled twin screw extruder (L/D = 39.7) for continuous processing of diet (63% moisture, w.b.) for mass rearing of the pink bollworm moth (Pectinora gossypiella) was studied. Heating to obtain sterile to near-sterile product (T > 134C) required the use of a two-step process. Feed at 45 to 50% moisture was heated to the treatment temperature; then additional water was added to 63% moisture. One or more pairs of restriction discs were required between the heating and dilution sections. Products with rough surfaces were formed by steam expansion or air atomization. No significant losses of thiamine occurred during processing. The process is now in operation in a large scale mass rearing facility.

Effects of Temperature and Wind Speed on Pink Boll worm (Lepidoptera: Gelechiidae) Moth Captures During Spring Emergence

Numbers of pink bollworm moths, Pectinophora gossypiella (Saunders), captured daily in California’s Palo Verde Valley during spring emergence were recorded in 6 data sets: 1985 emergence cages; 1986, 1987, and 1989 pheromone traps in cotton fields; and 1986 and 1989 valley wide pheromone survey traps. For 5 of the 6 data sets, numbers of moths were positively correlated with mean temperature for the interval 1800-2200 hours and minimum temperature for the interval 1800-0600 hours, and negatively correlated with mean wind speed for the interval 1800-2200 hours and the time at which wind speed fell below and stayed 22°C. Although temperature and wind affect dispersion of the pheromone plume, there appears to be a direct effect on the moths themselves because regression model parameters were similar in nonpheromone-baited emergence cages and in pheromone traps.

Relationships Between Environmental Factors and Capture Time of Male Pink Bollworm (Lepidoptera: Gelechiidae) Moths in Traps Baited with Sex Pheromone

Peak capture time of male pink bollworm moths, Pectinophora gossypiella (Saunders), was determined from 16 pheromone traps placed at the edges of several cotton fields and monitored at 45-min intervals on each of 42 nights during the cotton growing season from April through November 1990-1992 in California’s Palo Verde Valley. Peak time of capture correlated significantly with times of sunset, sunrise, and wind speeds falling below 2.68 m/s, minimum temperature of the same and previous nights, and maximum temperature. Stepwise and backwards elimination regressions were used to develop a model of predicted capture time, which showed that minimum night temperature, time when wind speed fell below 2.68 m/s, and moon age provided a good fit. By including minimum temperature in the model, time of sunset did not correlate significantly with capture time. Predicted peak capture time occurred 30 min later for each degree increase in minimum night temperature up to 20°C and was delayed by as much as 2 h by wind speeds above 2.68 m/s before 2100 hours and by 1 h during new moon compared with full moon.

Regulation of pheromone production by female pink bollworm moths Pectinophora gossypiella (Sanders) (Lepidoptera: Gelechiidae)

Abstract. We present in this study data which indicate that there is a diel periodicity in the pheromone production of the pink bollworm moth Pectinophora gossypiella (Sanders) (Lepidoptera: Gelechiidae) but that it is not well defined. Moreover the control mechanism of pheromone production differs somewhat from that reported for other moths. No pheromonotropic response was obtained when photophase females were injected with synthetic Helicoverpa zea pheromone biosynthesis activating neuropeptide (Hez‐PBAN). After decapitation for 24 h, Hez‐PBAN did not induce pheromonotropic activity above control levels, which themselves remained relatively high. No effect on pheromone production was observed after treatment with the non‐steroidal ecdysone agonist (RH5999). Decapitation for 72 h resulted in a significant drop in the control levels of pheromone titres. After decapitation for 72 h, stimulation by injections of Hez‐PBAN and pink bollworm head extracts was observed. In addition, an enhancement of the PBAN stimulation was observed when combined with severance of the ventral nerve cord before injection. On the other hand, pink bollworm head extracts did not cross‐react with Hez‐PBAN antiserum in a radioimmunoassay, indicating that the pheromonotropic factor present is sufficiently different from Hez‐PBAN and does not recognize the antigenic binding sites. In studies using isolated abdomen and pheromone gland cultures in vitro, no stimulation of de novo pheromone biosynthesis was observed but a 3‐fold increase in the de novo fatty acid biosynthesis was detected in pheromone gland cultures.

Pheromone trap catches as a means of predicting damage by pink bollworm larvae in cotton

The male moth catches in gossyplure-baited traps were used to predict larval infestation of pink bollworm, Pectinophora gossypiella (Saunders), in cotton fields during 1988 and 1989. The mean moth catches per trap per night were positively correlated with percentage larval infestation. The moth counts in traps and larval infestation in green bolls increased with advance in reproductive stage of the cotton plants. A mean trap catch of 9–12 pink bollworm moths per night was associated with economically damaging infestation. It is, therefore, inferred that insecticidal sprays may be scheduled when 9–12 moths are captured per trap per night.

Stage-structured populations: sampling, analysis, and simulation

Stage-structured populations sampling for population estimation maximum likelihood estimation of models analysis of multi-cohort stage-frequency data - the Kiritani-Nakasuji-Manly method of analysis, the Kempton method of estimation, the Bellows and Birley mode Analysis of single cohort stage-frequency data matrix and other models for reproducing populations - the Bernadelli-Leslie-Lewis model, Lefkovitch's model for populations grouped by life stages Usher's model key factor analysis - the Varley and Gradwell graphical method of key factor analysis extensions to the Varley and Gradwell approach the Manly model for key factor analysis case studies - the sheep blowfly lucilia cuprina the nematode patatrichodorus minor, the pink cotton bollworm moth pectinophora gossypiella, the southern pine beetle dendroctonus frontalis, the grey pup seal halichoerus grypus.

Selection for increased pheromone titre in the pink boll worm moth, Pectinophora gossypiella Lepidoptera: Gelechiidae)

ABSTRACT The genetic basis of pheromone titre in the pink bollworm moth, Pectinophora gossypiella (Saunders), was examined through artificial selection for females that produce greater amounts of the sex pheromone [a mixture of (Z, E)‐ and (Z, Z)‐7,11 ‐hexadecadieny 1 acetates]. Mean (±SD) pheromone titre increased by 91%, from 24.0±8.1 to 45.8±7.9 ng per female, in six generations of selection. No change in component ratio was observed within the selected line. The duration of male wing fanning, measured in a still‐air bioassay, did not change in the female‐selected line.

Upwind Flight to Cotton Flowers by Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Wind tunnel bioassays were performed to examine upwind flight by pink bollworm moths, Pectinophora gossypiella (Saunders), to different parts of the cotton plant ( Gossypium hirsutum L.). More moths approached and landed on flowers than on flower buds, bolls, or leaves. Mated female moths were more readily attracted to flowers than were unmated female or male moths. Attraction of moths to flowers was virtually eliminated by washing flowers in pentane, suggesting that the attraction was mediated by olfactory cues. Moths also responded to a hexane extract of flowers and to flowers without petals. We propose that flower volatiles act as a food lure attracting moths to extrafloral nectaries.

Selection for increased pheromone response in the male pink bollworm,Pectinophora gossypiella (lepidoptera: Gelechiidae)

The genetic basis of the duration and incidence of male wing fanning to pheromone in the pink bollworm moth, Pectinophora gossypiella (Saunders), was examined by artificial selection. Using a still-air bioassay, males from a laboratory colony were selected for increased duration of wing fanning when exposed to a 65:35 blend of (Z,E)- and (Z,Z)-7,11-hexadecadienyl acetates. The mean (+/- SE) duration of wing fanning in the selected line increased from 5.4 +/- 1.4 to 17.4 +/- 2.7 s after six generations. The increase in wing fanning duration was the result of an increase in response duration among responders and not the percentage of males that responded. Realized heritability of wing-fanning duration was 0.16 +/- 0.02. The amount and ratio of pheromone produced by females in the male-selected line did not change.

Wing fanning as a measure of pheromone response in the male pink bollworm,Pectinophora gossypiella (Lepidoptera: Gelechiidae)

A still-air, wing fanning bioassay measured male pheromone response in the pink bollworm moth,Pectinophora gossypiella (Saunders). As pheromone concentration was increased, the duration of wing fanning increased while its latency decreased. Response duration was longest for the natural pheromone blend [44∶:56 (Z,E)- and (Z,Z)-7,11-hexadecadienyl acetates], although responses to 38% and 50%Z,E blends were not significantly briefer. Preexposure to pheromone had no effect on wing fanning in males retested after 24 hr. Wing fanning was highly correlated with upwind flight and other responses observed in a wind tunnel. Wing fanning duration provides a continuous measure of pheromone response and allows a large number of males to be tested in a short time; these two characteristics of the wingfanning assay are helpful for genetic analyses of male response.

Heritable variation in pheromone response of the pink bollworm,Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Heritability of variation in male pheromone response by pink bollworm moths,Pectinophora gossypiella (Saunders), was examined using a still-air, wing-fanning bioassay. Heritability (±SE) of overall responsiveness, as measured by the mean duration of wing fanning to the blend of pheromone components produced by females [44∶56 ratio of (Z, E)- to (Z, Z)-7,11-hexadecadienyl acetate], was 0.385 ± 0.095. Heritabilities of wingfanning duration to blends with 25 and 65%Z, E isomer were 0.377 ± 0.113 and -0.145 ± 0.103, respectively. These findings indicate an asymmetry in the genetic component of variation in response to pheromone blends with high and low proportions of theZ, E isomer. An index of response specificity for individual males was developed based on the response to an off-blend (either 25 or 65%Z, E isomer) relative to the response to the 44%Z, E blend. Heritabilities of response specificity were 0.117 ± 0.059 and -0.043 ± 0.067 for the 25 and 65%Z, E blends, respectively.

Selection for altered pheromone-component ratios in the pink bollworm moth,Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Female pink bollworm moths, Pectinophora gossypiella(Saunders), were selected for altered component ratios of the long-distance sex pheromone, (Z, E)-and (Z, Z)-7,11- hexadecadienyl acetate. Selection for 12 generations increased the mean (± SD) percentage of the (Z, E)isomer from 42.9 ± 1.0 in the parental generation to 48.2 ± 1.2. Although statistically significant, a change of this magnitude may be transparent to males because of their relatively broad response spectrum. Selection for a lower percentage of the (Z, E)isomer yielded no change in the mean pheromone ratio. The total amount of pheromone produced declined in both selected lines. In the line selected for females producing a high percentage of the (Z, E)isomer, the duration of wing fanning by males to high (Z, E)blends was elevated.

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.

Temperature modulation of behavioural thresholds controlling male moth sex pheromone response specificity

ABSTRACT. The response specificity of male Oriental fruit moths, Grapholita molesta (Busck) and pink bollworm moths, Pectinophora gossypiella (Saunders), to different blends and doses of pheromone is altered dramatically by temperature. When acclimated and tested in a flight tunnel at 20oC males of both species exhibit a high degree of specificity, with peak response levels occurring to a narrow range of blend‐dose combinations close to the natural blend. When tested at 26oC, however, males exhibit a significantly lower degree of specificity, with peak response occurring to a broader range of treatments. The change in response specificity results from shifts in behavioural threshold effects influencing plume orientation and initiation of upwind flight, as well as from arrestment of upwind flight, occurring later in the flight sequence. The observed changes in male behaviour suggest that the effect of temperature is directly on neural pathways involved in the perception of odour, and not simply the result of an increase in motor activity or a significant change in the release rate of the pheromone. The results support the threshold hypothesis for pheromone perception (Roelofs, 1978) as a general principle in the Lepidoptera, but also show that the degree of response specificity can be significantly affected by temperature.

Effects of Gamma Radiation on Pink Bollworm (Lepidoptera: Gelechiidae) Pupae: Adult Emergence, Reproduction, Mating, and Longevity of Emerged Adults and Their F1 Progeny

Reproduction of pink bollworm, Pectinophora gossypiella (Saunders), male and female moths from 10- or 15-krad irradiated pupae mated to untreated females or untreated males was reduced 88% or more. Numbers of spermatophores per female from male moths emerging from irradiated pupae were significantly reduced. Percentages of males mating was not different from that of untreated insects except for females from 15- krad pupae paired with untreated males. Inherited sterility was exhibited in both male and female progeny of irradiated parents but was much more apparent in progeny from irradiated male parents. Generally, moths from irradiated pupae and their progeny had reduced longevities. Overall averages across all mating combinations indicated that age of pupae at the time of irradiation treatment and treatment by sex significantly affected oviposition, egg hatch, mating, and longevity. Results varied in some instances and significant interactions of age and mating combinations occurred.

Pheromone Trap for Monitoring Insecticide Resistance in the Pink Bollworm Moth (Lepidoptera: Gelechiidae): New Tool for Resistance Management

A rapid technique using sex pheromone and insecticide-laced traps was developed for measuring insecticide resistance in pink bollworm moth, Pectinophora gossypiella (Saunders). This method was developed in the laboratory by allowing males to fly upwind to a sex-pheromone source in a wind tunnel, and then trapping them on sticky cards (laced with various doses of pyrethroid insecticides) inserted into standard delta traps. Using this technique, populations of adult male P. gossypiella trapped in the field were shown to be more resistant to permethrin and fenvalerate in fields frequently treated with pyrethroids than in fields with little or no exposure to these insecticides. The new method eliminates handling of insects that is involved in other methods of assessing toxicity, and is compatible with the current practice of monitoring populations with pheromone traps. It was important to test and standardize duration of males' postcapture exposure to insecticide-laced sticker, temperature that males were exposed to after capture, quantity of sticker used, and age of males when captured.

Monitoring insecticide resistance with insect pheromones

A novel pheromone-baited sticky trap laced with insecticides proved to be a simple and effective means of monitoring insecticide resistance in the pink bollworm moth. Adult males from fields treated frequently with pyrethroid insecticides showed up to 20-fold resistance to permethrin and up to 14.5-fold resistance to fenvalerate.

Control of Pink Bollworm Moth (Lepidoptera: Gelechiidae) with Insecticides and Pheromones (Attracticide): Lethal and Sublethal Effects

Effectiveness of combinations of insecticides with pheromones (attracticides) for control of Pectinophora gossypiella (Saunders) may depend on, among other factors, males freely contacting attracticide sources, insecticide-induced mortality, and sublethal interference with the mate-locating sequence in poisoned males. In flight-tunnel tests, males readily contacted pheromone sources containing permethrin, fenvalerate, or cypermethrin and suffered significant mortality. Moreover, after 24 h survivors were lesslikely to complete the normal behavioral sequence involved in sex pheromone-mediated mate location. The latter sublethal effects may contribute substantially to the effectiveness of the attracticide technique at the doses of insecticides used in the field. Cypermethrin induced lethal and sublethal effects at a lower concentration than other insecticides tested. Chlordimeform appears to be a poor candidate for attracticide formulations because males avoided contact with this insecticide. Recovery from sublethal effects of cypermethrin occurred after 48 h, and represents a potential limitation to sublethal modification of behavior for population control. However, repeated contact with a moderate concentration of permethrin attracticide enhanced sublethal and lethal effects.