Cotton Pink Bollworm Research Articles

Laboratory evaluation of toxicity of selected insecticides against egg and larval stages of cotton pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae)

BackgroundThe cryptic nature of pink bollworm Pectinophora gossypiella (Saunders) larvae enables its reduced vulnerability to insecticidal control. Further, the development of resistance against Bacillus thuringiensis (Bt) toxins posed a serious threat to transgenic cotton cultivation. This necessitated determining the critical timing of spray applications on the control effectiveness. This study assessed the influence of egg age (freshly laid vs. three-day-old) and the location of larvae (directly exposed to the insecticide residues on the boll rind vs. burrowed inside the bolls) on insecticide control efficacy.ResultsThe results revealed a significant decrease in the ovicidal activity of tested insecticides with an increase in the age of eggs from one day old to three days old (paired t-test, P < 0.05). The larvae directly exposed to the insecticide residues on the boll rind were more susceptible (> 80% mortality) than the larvae exposed after they had burrowed inside the bolls (< 49% mortality). The inhibitory effects of tested insecticides on developmental biology were more pronounced in the experiment on pre-larval release insecticide treatment compared with insecticide treatment given post-larval release and entry inside the bolls.ConclusionEgg age influences the insecticide susceptibility, as does the larval location, directly exposed vs burrowed inside the bolls. Older eggs and the larvae that had burrowed inside the green bolls of cotton were relatively less susceptible to the insecticide treatments. The toxic effects of insecticides on egg and larval stages were primarily ephemeral. These findings are significant for devising a comprehensive strategy for pink bollworm management on a sustainable basis.

Molecular Investigation Using RAPD-PCR Marker Field Populations of Pectinophora gossypiella Saunders (Lepidoptera: Gelechiidae) Exposed to Some Insecticide

Seasonally the cotton plant cultivated in Egyptian fields is suffering from the cotton Pink Bollworm Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) attacking fruits and buds. Insecticide applications reported control failure by the most recommended conventional classes. Monitoring pest DNA changes after sublethal exposure become the new technique to investigate. Then four insecticide treatments were screened by using the molecular marker polymerase chain reaction (PCR) inspection, using four Random amplified polymorphic deoxyribonucleic acid analysis (RAPD-PCR) primers partitioned based on band reproducibility. Result of LC50 was 0.55, 61.1, 69.3, and 0.23 for spinoteram, novaluron, metaflumezone, and dimeuron respectively. The insecticide treatments band of gel produced detected 47 loci ranging from 87 to 63 % polymorphism. The primer efficiency value of PIC =0.361, 0.34, 0.34, 0.355, and 0.262, RP = 5.30, H = 0.473, 0.434, 0.434, 0.462 and 0.31, and MI = 0.10, 0.1386, 0.138, 0.167 and 0.0582 for the same treated samples respectively. Distance and similarity were quantified based on Nei’s and genetic dissimilarity by the UPMGA method then a phylogenetic tree was constructed and grouped the entire genotypes into 2 major clusters and 6 subclusters. The RAPD primers revealed the number of alleles (Na = 0.324, 0.318, 0.318, 0.326, and 0.328), and the effective number of alleles (Ne = 0.571, 0.569, 0.558, 0.574, and 0.5784). The fixation-index (Fst) analysis narrated a very great genetic diversity (Fst = 0.626, 0.684, 0.684, 0.2, and 0.695) exists within the four treated samples respectively. The level of gene flow was (Nm = 0.239, 0.230, 0.230, 0.233, and 0.2187) respectively across the four genotypes studied. Results proved that the RAPD-PCR technique was suitable for distinguishing between insecticide treatments.

Diagnostic expression of the cotton pink bollworm Pectinophora gossypiella (Saunders) Ace1 exposed to some insecticide by the real-time PCR

The Pink Bollworm Pectinophora gossypiella (Saunders) is a devastating pest in Egyptian cotton field. Insecticide control failure may be happen due to its biological features of hide inside bolls and rarely exposed to insecticide application. Thus, a bulk of bolls infested with larvae collected from fields of Sharkia and Benysuef governorate. Moreover, exposed to py, Op sub lethal concentrations in laboratory bioassay. Toxicity features as LC50, LC90 and the slope, and RR was completed. Whereas the common target site of OP and pyrethroid is the acetylcholinesterase enzyme. Thus, the gene Ace1 encoding AChE relative expression was investigated using molecular marker of real-time PCR procedures via the steps of generating data was RNA isolation and characterization, cDNA synthesis, then generating normalization factors, and Ct data attained and analyzed using 2-ΔΔCT method to quantify the gene expression quantitatively of insecticide treated larvae tissue extracted. Data showed the most expressed ratio of samples was cypermethrin followed by deltamethrin compared with the control and the least was malathion and chlorpyrifos, thus, the most effective insecticide was malathion and the least were cypermethrin according to ct values. Hierarchical clustering combined with Heat map and principle component analysis based on various clustering systems and algorithm as distance measures were completed. Validation of reference gene in addition to gene expression stability analyzed by the three optimal gene finders and showed that deltamethrin and cypermethrin treated genes having lower mean weights and considered transcriptionally stable and ideal reference genes.

Genetic diversity of cotton Pectinophora gossypiella (Saunders) (Lepidoptera, Gelechiidae) population in inferred from mitochondrial COI sequences

The objective was to identify different haplotypes network of pink bollworm and their distribution in south India using the partial mitochondrial COI sequence of pink bollworm populations. Genetic diversity analysis exhibited the presence of 5 haplotypes in COI gene sequences, and among them, Hap_1 was the most common and present in 17 populations. Distributions of pairwise differences obtained with partial COI data from the overall populations were unimodal, suggesting population expansion. A significant neutrality test based on Tajima’s D, Fu and Li’s D and F test presented a haplotype network with multiple haplotypes. The acceptance of the neutrality test with significant positive values validated the theory of demographic expansion in cotton pink bollworm populations with respect to COI. The pink bollworm has a population genetic diversity among the investigated populations collected from south India.

The Role of Entomopathogenic Fungus, Beauveria bassiana (Bals.) Vuill. in Reducing Population Densities of Refugee Insect Pests to Dry Okra Pods During Winter

The present work was carried out during two successive seasons, being 2019/20 and 2020/21 in three locations in Gharbia governorate to explain the role of entomopathogenic fungi (EPF) in decreasing insect pest populations inhabiting okra dry pods during the winter period. Three insect pest species were found in the okra dry pods: the cotton seed bug, Oxycarenus hyalinipennis (Costa) (Hemiptera: Lygaeidae), the cotton pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) and the cotton spiny bollworm, Earias insulana (Boisd.) (Noctuidae: Lepidoptera). The EPF, Beauveria bassiana (Bals.) Vuill. was isolated from the 3 insect species in the winter months. The seasonal fungal incidence percentages were 3.04 and 10.73% in nymphs and adults of O. hyalinipennis, respectively in the first season and were 13.53 and 16.53% in the second one. The seasonal fungal incidence percentages on P. gossypiella larvae were 4.64 and 7.96% for the two seasons, respectively. Natural mortality with the fungus ranged from 4.32 to 14.16 and 4.32 to 20.63% in the two seasons, respectively. Whilst the seasonal fungal incidence percentage on E. insulana larvae were 6.02 and 5.23 % for the first and second seasons and the fungus was isolated for one time in each season. Results explained and approved the role of EPF as natural mortality factors against insect pest species in their winter microhabitats in Egypt. Accordingly, it encourages biological control advocates to utilize such natural enemies as biological control agents.

Evaluation of Sequences of Certain Insecticide Groups and Biocide Application on Cotton Bollworms, Associated Predators and Cotton Yield in Cotton Fields Egypt

Field experiments were conducted during 2019 and 2020 seasons in Sakh Agricultural Station Farm, Kafr El-Sheikh Governorate, to evaluate the sequences of certain insecticide six groups and biocide on cotton bollworms, associated predators in cotton fields and cotton yield. Sequence of Ictafos (chlorpyrifos) of organic phosphorus – Topron (chlorofluoezuron) of insect growth inhibitor – Cyperco (cypermethrin) of pyrethroids resulted in the greatest means of reduction (51.07, 71.57 and 83.58%) in number of cotton pink bollworm, pectinophora gossypiella (Saund.), Spiny bollworm, Earias insulana (Boisd.) and American bollworm, Helicoverpa armigera Hubner larvae, respectively. The least means of reduction (25.87, 30.28 and 37.78%) of number of pink, spiny and American bollworms larvae with sequence of biocide, (Agrein) only, respectively. All treatments of insecticides were associated with the greatest reduction by range of (65.60 – 69.90%) and (70.34 – 76.14%) on the populations of the six insect predators by the application of sequences of insecticides and each insecticide alone, respectively. Contrast, sequence of biocide Agrein had the minimum side effect on beneficial predators with mean of reduction (29.05%). The highly effective insecticidal sequence against cotton bollworms had the highly increase in cotton yield production.

Degree day-based model predicts pink bollworm phenology across geographical locations of subtropics and semi-arid tropics of India

There is a global concern about the effects of climate change driven shifts in species phenology on crop pests. Using geographically and temporally extensive data set of moth trap catches and temperatures across the cotton growing states of India, we predicted the phenology of cotton pink bollworm Pectinophora gossypiella (Saunders). Our approach was centered on growing degree days (GDD), a measure of thermal accumulation that provides a mechanistic link between climate change and species’ phenology. The phenology change was predicted by calculating absolute error associated with DD and ordinal date, an alternative predictor of phenology, for peak moth abundance. Our results show that GDD outperformed the ordinal dates in predicting peak moth abundance in 6 out of 10 selected locations. Using established thresholds of 13.0/34.0 °C, mean DD accumulated between the consecutive moth peaks across different years were estimated at 504.05 ± 4.84. Seven generations were determined for pink bollworm in a cropping season, the length of which varied between 35 and 73 days in response to temperature. Pink bollworm population reached its peak during third generation which can be the target for management actions. The study provides essential information for developing pink bollworm management strategies under climate change.

Environmental friendly technique to control cotton pink bollworm Pectinophora gossypiella in Egypt

The cotton bollworms are major pests that reduce yield and quality of the growing cotton crop all over the world. (PBW) pink bollworm Pectinophora gossypiella onseder acommon injurious bollworms of cotton in Egypt, a field studies were performed to evaluate the management of mercantile bollworm pheromones and/with parasitoid Trichogramma evenecens, compared with recommended bollworms insecticides, carried out at El-Behira, governorate, Egypt, during two cotton seasons (2018 and 2019) to reduce the population’s density of (PBW) pink bollworm Pectinophora gossypiella. The obtained results revealed that the treatment of pheromones and/ with parasitoids induced real reduction of pink bollworm infestation (90%) followed by insecticide (88–87%) in both seasons respectively. Furthermore, the costly economic ratio of pheromones and/with parasitoids was less than insecticides and gave highest cotton yield. Specific friendly technique pheromones and/with parasitoids had good potential for providing effective protection system for Pink bollworm.

A novel Bacillus thuringiensis isolate toxic to cotton pink bollworm (Pectinophora gossypiella Saunders)

In this study, we report a novel indigenous Bacillus thuringiensis (Bt) isolate, T26, which showed spores and crystals under scanning electron microscope and pathogenicity against the pink bollworm (Pectinophora gossypiella Saunders) in artificial diet based bioassay. SDS-PAGE analysis of the spore-crystal mixture of the Bt isolate, T26 revealed presence of three major protein bands of approximate molecular weights of 80, 55 and 40 kDa. The draft genome assembly consists of 56 scaffolds with an entire draft genome size of 5,054,095 bp. NCBI blast analysis revealed that assembled draft genome is spread over in a chromosome (4,818,543 bp) and one plasmid (235,552 bp). NCBI Prokaryotic Genome Annotation Pipeline (PGAP) showed presence of 5033 coding gene sequences and 159 RNAs genes. None of the known lepidopteran active genes (cry1, cry2 and cry9) could be detected with PCR or with whole genome sequence analysis using Bt toxin scanner tool or CryProcessor tool. Thus, presence of protein crystals and toxicity towards cotton pink bollworm and absence of any known cry/vip/cyt type of genes in draft genome indicates it is a novel type of Bt isolate. Further investigation of this genome sequence along with protein sequencing will lead to understand the novel factors responsible for its virulence and could be a useful tool for the insect resistance management in pink bollworm.

Compatibility of entomopathogenic fungi and Azadirachta indica extract against the cotton pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) under controlled conditions

Compatibility of entomopathogenic fungi (EPFs) viz. Verticillium lecanii, Metarhizium anisopliae and Beauveria bassiana with Azadirachta indica extract (alone and in combinations) was evaluated against 2nd instar larvae of the cotton pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) under controlled conditions. Results indicated that maximum mortality rate of P. gossypiella larvae was recorded at combination of the highest conidial concentrations of V. lecanii + M. anisopliae + B. bassiana along with A. indica extract, while minimum mortality rate was recorded at A. indica extract alone, 12 days post exposure interval. Maximum mycosis and sporulation from dead cadavers of P. gossypiella larvae were recorded at the highest concentration of B. bassiana, while the lowest mycosis and sporulation were recorded at the highest conidial concentrations of V. lecanii + M. anisopliae + B. bassiana along with A. indica extract. Maximum percent of pupation and adult emergence in P. gossypiella larvae was observed in the treatment, where A. indica extract was applied alone, while the minimum percent of pupation and adult emergence was observed at the treatment combination of the highest concentration of B. bassiana + V. lecanii + M. anisopliae along with A. indica extract was applied. EPFs proved their enhanced long-term protection potential for cotton crop against P. gossypiella. A. indica extract integrated with the EPFs can be a potential alternative to the chemicals and as an effective component of IPM program against P. gossypiella.

Evidence for population expansion of Cotton pink bollworm Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) in India

Pink bollworm, Pectinophora gossypiella (Saunders) infestation on Bt cotton is a major concern to cotton production in India. The genetic diversity and phylogeographic structure of the insect in light of PBW resistance needs to be revisited. The objective of this study was to identify different haplotypes of pink bollworm and their distribution in India. To achieve this we studied the population structure in 44 cotton growing districts of India. The partial mitochondrial COI sequence analyses of 214 pink bollworm populations collected from 44 geographical locations representing 9 cotton growing states of India were analysed. Genetic diversity analysis exhibited presence of 27 haplotypes, among them Pg_H1 and Pg_H2 were the most common and were present in 143 and 32 populations, respectively. Distributions of pairwise differences obtained with partial COI gene data from the overall Indian populations are unimodal, suggesting population expansion in India. Significant neutrality test on the basis of Tajima’ D and Fu’s Fs presented a star-shaped haplotype network together with multiple haplotypes. The unimodal mismatch distribution, rejection of neutrality test with significant negative values supported the theory of demographic expansion in cotton pink bollworm populations in India. Genetic data not only provides us with a perspective of population genetics, but also that the two populations of pink bollworm, those occurring early in the season are genetically close to the late season populations with respect to their partial CO1 region. Resistance to Cry toxins does not seem to have had an impact on this region of the mt DNA in populations of pink bollworm.

DEVELOPMENTAL THRESHOLDS AND THERMAL REQUIREMENTS NEEDED FOR THE COTTON PINK BOLLWORM PECTINOPHORA GOSSYPIELLA (SAUNDERS)

The present study was conducted on the cotton pink bollworm, Pectinophora gossypiella (Saunders.) (Lepidoptera: Gelechiidae) the most devastative insect pest to cotton cultivations in Egypt. It causes great damage and loss in the cotton yield. All experiments were carried out in the laboratory of the environmental study, Department of Plant Protection, Faculty of Agric., Ain Shams Univ. aiming to estimate some biological parameters of P. gossypiella reared on artificial diet at four constant temperatures 18, 20, 25, 30oC with 65±5% RH, then determine threshold of development and thermal constant for each of the developmental stages and complete generation. Obtained results demonstrated that the duration of each developmental stage of P. gossypiella highly affected by the change of temperature. The incubation period of eggs greatly varied at different temperature, these periods were 10.86, 10.29, 6.00 and 4.00 days at 18, 20, 25 and 30oC, respectively. Threshold of development for P. gossypiella egg stage was 12.1oC. The mean of duration for P. gossypiella larvae, pupae were 30.40, 14.10 days and the durations for male, female and generation were 24.72, 26.99 and 57.95 days, respectively. The longest duration of larvae, pupae, male and female moths were 47.61, 20.13, 33.59 and 33.68 days recorded at 18oC while the shortest durations were 16.60, 7.40, 13.75 and 14.64 days recorded at 30oC for larvae, pupae, male and female moths, respectively. The threshold of development for P. gossypiella larval, pupal, male, female stages was 11.6, 12.1, 9.8, 9.5oC, respectively. The threshold of development for P. gossypiella generation was 11.7oC. Based on the estimated threshold of development and duration of each developmental stage at the respective rearing temperature, the average of thermal constant was estimated as 73.59 for egg stage, 298.76 for larvae, 124.98 for pupae, 299.49 for adult male, 338.96 for adult female and 567.80 DDs for P. gossypiella generation.

Management of cotton pink boll worm Pectinophora Gossypiella (Saunders) with Trichogramma bactrae and T. brasiliensis

Afield trial was conducted at ICAR-CICR research farm, Nagpur, during kharif 2016–2017 and 2017–2018 to evaluate the efficacy of egg parasitoid Trichogramma bactrae (Nagaraja) and T. brasiliensis (Ashmead) along with insecticides as check for management of cotton pink bollworm. In 2016–2017, results showed that the least number of exit holes were in T. brasiliensis treated plots followed by chemical treatment and T. bactrae. However, number of mines was the least in T. bactrae followed by chemical treatment and T. brasiliensis. The reduction in larval population over control was lowest in T. brasiliensis followed by T. bactrae and chemical control. During 2017–18 data revealed that the number of exit holes was the least in the plots sprayed with chemical insecticides and it was at par with T. bactrae. However, the least number of mines on epicarp was noticed in the plots imposed with T. bactrae followed by chemical insecticides. The significantly minimum per cent locule damage was noticed in the chemical treatment. Though the infestation of pink bollworm in the form of boll and locule damage was significantly low in insecticides treated plots it was comparable with T. bactrae and T. brasiliensis released plots.

Ti-catalyzed cross-cyclomagnesiation of 1,2-dienes in the stereoselective synthesis of insect pheromones

The Ti-catalyzed intermolecular cross-cyclomagnesiation reaction of aliphatic and oxygenated 1,2-dienes with Grignard reagents was used as the key step to develop facile stereoselective methods for preparation of the major components of citrus leafminer moth (Phyllocnistis citrella) pheromones as well as cotton pink bollworm (Pectinophora gossypiella) and fruit fly (Drosophila melanogaster) attractants.

Resistance Monitoring of Emamectin Benzoate 5SG in Cotton Bollworms in Tamil Nadu

The median lethal dose (LD50) of emamectin benzoate 5SG when monitored against cotton pink bollworm Pectinophora gossypiella, it was found to be 0.4282 mg larva−1 for F1 generation and 0.1802 mg larva−1 for F9 generation. The LD95 was found to decrease from 3.3760 (F1) to 1.1564 mg larva−1 (F9). The susceptibility index to emamectin benzoate based on LD50 and LD95 was 2.37 and 3.03, respectively. With regard to number of generations required for 10-fold decrease in LD50, it was found to be 27. Considering the F9 populations as the most susceptible, the tentative discriminating dose was fixed as 1.1mg−1. Assessing the level of insecticide resistance as one time survey in summer cotton revealed that the % resistance of H. armigera in five districts ranged from 3.33 to 10.00. The highest resistance (10%) was observed at Coimbatore district. The survivability of fruit and shoot borer Earias vitella varied from 6.66 to 15.00% against emamectin benzoate, with Erode population being highly susceptible. The % survival of pink bollworm varied from 3.33 to 6.66% at 1.1μg larva−1.

Determination of Receptor Binding Properties of Bacillus thuringiensis δ-Endotoxins to Cotton Bollworm (Helicoverpa zea) and Pink Bollworm (Pectinophora gossypiella) Midgut Brush Border Membrane Vesicles

Pesticidal activity and receptor binding properties of Bacillus thuringiensis toxins to cotton pink bollworm (Pectinophora gossypiella) and cotton bollworm (Helicoverpa zea) were investigated. P. gossypiella was susceptible to Cry1Aa, Cry1Ab, Cry1Ac, and Cry2Aa toxins. To H. zea, Cry1Ac and Cry1Ab were more potent than Cry1Aa and Cry2Aa. Cry1Ba, Cry1Ca, Cry1Da, Cry1Ea, Cry1Fa, Cry1Ga, Cry1Ha, and Cry2Ba were not potent against both pests. Binding assays were performed with 125I-labeled toxins (Cry1Aa, Cry1Ab, Cry1Ac, and Cry2Aa) and brush border membrane vesicles (BBMVs) prepared from H. zea and P. gossypiella midguts. Both Cry1Ab and Cry1Ac toxins showed saturable, high-affinity binding to P. gossypiella and H. zea BBMVs. Cry2Aa and Cry1Aa toxins bound to BBMVs with relatively low binding affinity but with high binding site concentration. Heterologous competition binding assays were performed to investigate the binding site cross reactivity. The results showed that Cry1Aa, Cry1Ab, and Cry1Ac recognize the same binding site, which is different from Cry2Aa. Ligand blot assay showed that Cry1Ac toxin binds to a 120-kDa BBMV protein in P. gossypiella and Cry1Ab binds to a major 210-kDa protein.

Pink bollworm control in southwestern desert cotton: III. Strategies for control: An economic simulation study

I. A Field-Oriented Simulation Model A simulation model for pink bollworm (PBW) and cotton was developed, field validated, and incorporated into an industry sponsored regional PBW management program for southwestern desert cotton. The PBW model differs from earlier versions in its incorporation of stochastic development, the expansion of the concept of physiological time to include nutritional influences of the cotton host on larval development, and its ability to simulate the kinds of data typically collected by pest control advisors when monitoring cotton for pink bollworm. II. A Strategic Management Model A simulation model of pink bollworm populations, as affected by insecticide and pheromone applications in cotton, is described. The simulation results compared favorably to field data. The study indicates that use of sex pheromone for control of pink bollworm by mating disruption inversely depends on density and therefore is most effective in the early season when populations are low. Compared to untreated fields, pheromone-treated fields show delayed population peaks and reduced overall infestation. Pheromone applications in the early season delay but do not obviate the need to spray insecticide to limit infestation levels. III. Strategies for Control: An Economic Simulation Study The cotton-pink bollworm model and the management model developed by Stone and Gutierrez (I and II of this series) are used to evaluate different strategies for controlling pink bollworm in the southwestern desert. Pesticide sprays based on an ultraconservative economic threshold of 2 percent infested bolls are found to be the most profitable in the absence of penalties for heavy insecticide use. Insecticide sprayed on thresholds over 8 percent infested bolls did not control pink bollworm. Pheromone in combination with insecticide greatly enhanced profits and was the best workable strategy tested since a 2 percent threshold is probably too difficult to sample accurately in the field. The efficacy of using early season insecticide applications at and before the first hostable squares are present is discussed, as is the possible impact of early season insecticide applications on beneficial insect populations.

Pink bollworm control in southwestern desert cotton: I. A field-oriented simulation model

I. A Field-Oriented Simulation Model A simulation model for pink bollworm (PBW) and cotton was developed, field validated, and incorporated into an industry sponsored regional PBW management program for southwestern desert cotton. The PBW model differs from earlier versions in its incorporation of stochastic development, the expansion of the concept of physiological time to include nutritional influences of the cotton host on larval development, and its ability to simulate the kinds of data typically collected by pest control advisors when monitoring cotton for pink bollworm. II. A Strategic Management Model A simulation model of pink bollworm populations, as affected by insecticide and pheromone applications in cotton, is described. The simulation results compared favorably to field data. The study indicates that use of sex pheromone for control of pink bollworm by mating disruption inversely depends on density and therefore is most effective in the early season when populations are low. Compared to untreated fields, pheromone-treated fields show delayed population peaks and reduced overall infestation. Pheromone applications in the early season delay but do not obviate the need to spray insecticide to limit infestation levels. III. Strategies for Control: An Economic Simulation Study The cotton-pink bollworm model and the management model developed by Stone and Gutierrez (I and II of this series) are used to evaluate different strategies for controlling pink bollworm in the southwestern desert. Pesticide sprays based on an ultraconservative economic threshold of 2 percent infested bolls are found to be the most profitable in the absence of penalties for heavy insecticide use. Insecticide sprayed on thresholds over 8 percent infested bolls did not control pink bollworm. Pheromone in combination with insecticide greatly enhanced profits and was the best workable strategy tested since a 2 percent threshold is probably too difficult to sample accurately in the field. The efficacy of using early season insecticide applications at and before the first hostable squares are present is discussed, as is the possible impact of early season insecticide applications on beneficial insect populations.

Pink bollworm control in southwestern desert cotton: II. A strategic management model

I. A Field-Oriented Simulation Model A simulation model for pink bollworm (PBW) and cotton was developed, field validated, and incorporated into an industry sponsored regional PBW management program for southwestern desert cotton. The PBW model differs from earlier versions in its incorporation of stochastic development, the expansion of the concept of physiological time to include nutritional influences of the cotton host on larval development, and its ability to simulate the kinds of data typically collected by pest control advisors when monitoring cotton for pink bollworm. II. A Strategic Management Model A simulation model of pink bollworm populations, as affected by insecticide and pheromone applications in cotton, is described. The simulation results compared favorably to field data. The study indicates that use of sex pheromone for control of pink bollworm by mating disruption inversely depends on density and therefore is most effective in the early season when populations are low. Compared to untreated fields, pheromone-treated fields show delayed population peaks and reduced overall infestation. Pheromone applications in the early season delay but do not obviate the need to spray insecticide to limit infestation levels. III. Strategies for Control: An Economic Simulation Study The cotton-pink bollworm model and the management model developed by Stone and Gutierrez (I and II of this series) are used to evaluate different strategies for controlling pink bollworm in the southwestern desert. Pesticide sprays based on an ultraconservative economic threshold of 2 percent infested bolls are found to be the most profitable in the absence of penalties for heavy insecticide use. Insecticide sprayed on thresholds over 8 percent infested bolls did not control pink bollworm. Pheromone in combination with insecticide greatly enhanced profits and was the best workable strategy tested since a 2 percent threshold is probably too difficult to sample accurately in the field. The efficacy of using early season insecticide applications at and before the first hostable squares are present is discussed, as is the possible impact of early season insecticide applications on beneficial insect populations.

Controlled Release of Gossyplure for Use in Control of Cotton Pink Bollworm

ABSTRACT PRE-MATING pheromone communication between male and female pink bollworm moths infesting cot-ton can be disrupted by permeating the insects' environ-ment with the synthetic sex pheromone, gossyplure. A theoretical model has been developed to predict the release of gossyplure from a gossyplure-filled fiber sealed at one end. The vapor pressure and diffusivity of gossyplure, key parameters in the above model, have been experimentaly determined for the temperature range of 15 to 50 C. The predicted release of gossyplure is a complex function of temperature and half-power function of time. The model is capable of predicting gossyplure release at a constant temperature and in a diurnal-temperature-cycle environment similar to that encountered in a cotton field in Imperial Valley, CA dur-ing August. The gossyplure releases predicted by the model have been experimentally verified by measuring the displacement of liquid-meniscus level in gossyplure-filled fiber placed in an environmental simulation chamber.