جستجوی مقالات مرتبط با کلیدواژه « cotton bollworm » در نشریات گروه « کشاورزی »

Cotton bollworm (Helicoverpa armigera) is a major economic pest worldwide and damaging many crops. Microbial insecticides, botanical insecticides, and insect growth regulators (IGRs) are among the compounds used as biorational insecticides in integrated pest management programs. Due to the high dependence of this pest control on insecticides application, investigating effective and safe insecticides is an important research topic.

To evaluate the effectiveness of different insecticides to control this pest, an experiment was conducted in a randomized complete block design with nine treatments in a cotton field in Golestan province. Treatments included indoxacarb, teflubenzuron+alpha cypermethrin, thiodicarb, cypermethrin, chlorfluazuron, lufenuron+emamctin benzoate, matrin and Bacillus thuringiensis. The control plot was treated with water. The plots were treated 7-10 days after the peak flight of the moths. Sampling was performed one day before and 1, 2, 4, 7, 14, 21 and 30 days after treatment. At each sampling time, 10 plants were randomly selected for each replicate, and the number of live larvae was counted.

One day after treatment, the highest efficacy was recorded for thiodicarb (63.4%) and then for teflubenzuron+alpha cypermethrin, lufenuron+emamctin benzoate and indoxacarb with 58.1, 46.7 and 44.3%, respectively. After four days, when the mean larval population in all 10plants in the control treatment was still at the pre-treatment level, the effectiveness of these insecticides was 77.6, 81.2, 89.9, 79.8, 51.6, 83.3, 47.9, and 46.4%, respectively. Two weeks after the treatments, no larvae were observed in the plots sprayed with thiodicarb, cypermethrin, and lufenuron+emamctin benzoate, and their effectiveness in reducing the pest population was 100%. At the endpoint of the experiments, the efficacy of Bt, Matrin, chlorfluazuron, and Indoxacarb were 48.5, 55.5, 58.2, and 89.8%, respectively. The other four treatments (cypermethrin, lufenuron+emamctin, teflubenzuron+alpha cypermethrin, and thiodicarb) were completely (100%) affected the larvae population.

According to the standard classification of insecticides toxicity provided by the World Health Organization (WHO), the insecticides alpha cypermethrin, emamctin benzoate, indoxacarb, thiodicarb and cypermethrin are all classified as the group with moderate toxicity, lufenuron with low toxicity and teflubenzuron and chlorfluazuron were classified in the group without toxicity. The results demonstrated that two relatively safe insecticides, teflubenzuron+alpha-cypermethrin, and lufenuron+emamctin benzoate, are suitable alternatives to common insecticides, indoxacarb, and thiodicarb. Matrin, plant-derived insecticide, Bt, microbial insecticide, and chlorfluazuron, IGR insecticide, were relatively effective. Due to the adverse effects of using common chemical insecticides, two insecticides, teflubenzuron+alpha-cypermethrin, and lufenuron+emamctin benzoate, are recommended as alternatives concerning the relative safety and simultaneous use of chlorfluazuron with matrin/Bt as entirely safe options.

The physiological feeding reactions of cotton bollworm were investigated by evaluation of nutritional indices and enzyme activity of larvae reared on different rapeseed cultivars including, Sarigol, Rgs003 and Slm046. The experimental plants were treated by amounts of urea fertilizer equivalent to 120, 240 and 360 kg per hectare, in three development stages of plants. The nutritional indices of Helicoverpa armigera on different rapeseed cultivars were calculated by Waldbauer's formula. The total leaf protein in three rapeseed cultivars were significantly increased with increase of nitrogen level. The lowest and highest values of measured nutritional indices were observed in larvae reared on control and treated plants with 360 kg/hec of nitrogen, respectively. Also results indicated that there was not significant difference between larval nutritional indices which reared on plants treated with 120 and 240 (kg/hec). Similar results were obtained for larval digestive enzyme activity.

In the present study, effect of seed protein extracts of Robinia pseudoacacia, Medicago sativa, Lens culinaris and Vica villosa were studied (in vitro and in vivo) on alpha-amylase activity of boll worm, Helicoverpa armigera (Hübner). Effect of 4 concentrations (14, 13.15, 10.05 and 9.7 μg) of protein extract of the mentioned plants showed the greatest inhibitory effect. The highest inhibition of the enzyme was observed under the influence of all four inhibitors at pH value equal to 9. Zymogram analysis in confirmation of enzyme quantification showed inhibition of alpha-amylase in reducing band thickness. At the highest concentration of alfalfa seed protein extract, 49% enzyme inhibition was observed. In the presence of acacia inhibitor at a concentration of 41 μg / ml, 76% of alpha-amylase activity was reduced. Alpha-amylase was assayed at different concentrations of lentil protein extract and a concentration-dependent inhibitory process was obtained at the highest concentration of 51% enzyme inhibition. Also, four different concentrations of hairy vetch inhibitor were measured with enzymatic extract and in the highest concentration of hairy vetch, 61% of enzyme inhibition was observed. Amylase activity in digestive lumen after the second larval instar in acacia treatment showed significant reduction. Total larval longevity in acacia treatment (49.03±1.12) had significantly longer life time in comparison with other treatments. Thus, the seed extract of R. pseudoacacia had high inhibitory activity for the α-amylase of this pest.

The cotton bollworm has been considered as a threatening pest in pistachio orchards in Kerman province especially in Sirjan.  In this study, the nutritional indices of the third instar larvae reared on leaves and fruits of six pistachio varieties including Ahmad Aghaei, Akbari, Ohadi, Jandaghi, Kalehghochi and Momtaz. Experimental containers, containing one larvae and one fruit or leaf incubated at growth chamber with 22±2°C, 55±5% RH and a photoperiod of 16:8 (L: D). The weight of larvae, feces and consumed fruits and leaves were calculated every 24 hours. Data were analyzed by one-way ANOVA using SPSS software. The results showed significant differences in all larval nutritional indices on studied pistachio varieties. The lowest values of efficiency of conversion of ingested food (17.87±0.87%) and the lowest of efficiency of conversion of digested food (21.73±0.69 %) were observed on fruits of Ohadi variety. Also, the lowest of efficiency of conversion of ingested food (11.87±0.89 %) and the lowest of efficiency of conversion of digested food (15.43±0.88 %) were observed on leaves of Ahmad Aghaei variety. Based on the cluster analysis resuls, the highest values of nutritional indices were observed in larvae feeding on fruits of Momtaz, Jandaghi and Kaleghohi varieties. The lowest values were obtained on larvae reared on fruit and leaf of Ohadi and leaf of Ahmad Aghaei varieties.

The Cotton bollworm, Helicoverpa armigera (Lep.; Noctuidae) is one of the most important and most economic pests of cotton. The species is a polyphagous pest and, because of high mobility, high viability under adverse conditions, being multivoltine and resistance to insecticides, it is very difficult to manage. In this study, nutritional effects of chitosan صere studied orally suing different doses of chitosan mixed with an artificial diet. The experiments were carried out under laboratory conditions at six dose rates of 0, 2.5, 4.0, 6.0, 8.0 and 10.0 g/kg of artificial diet. Larval mortality, and anti-growth and antifeedant effects were investigated. In this research, mortality of both third and fifth instars did not observe even by two-days feeding from dose rate of 10.0 g/kg of both chitosan. feeding of third and fifth instars of the Cotton bollworm from different dose rates of chitosan stimulated the growth and feeding of some larvae and inhibited the growth and feeding of some others in each replication. This shows that in dependence on dose rate and larval instar, effects of chitosan on third and fifth instars have been either as growth inhibition or stimulation, and either as feeding inhibition or stimulation. Growth and feeding stimulation of larvae of an insect due to feeding from chitosan is reproted for the first time. This would be led to the better understanding of factors affecting on chitosan efficacy and its effects on different aspects of insect biologies.

The volatiles emitted by herbivorous insects and herbivore-damaged plants play an important role in foraging behaviour of parasitoids that lead to host location of parasitic wasps. The olfactory response of Habrobracon hebetor (Say) (Hymenoptera: Braconidae) to volatile compounds of larvae and larval faeces of Helicoverpa armigera (Hünber) (Lepidoptera: Noctuidae), corn ear and tomato fruits both infested and un-infested by cotton bollworm was studied using a double sided Y-shaped olfactometer in laboratory conditions. Results showed that parasitoid wasps were significantly more attracted to compounds emitted by larvae and larval faeces of the cotton bollworm. Response of parasitoid wasps to volatiles of larvae in comparison with infested tomato and corn ear indicated that 71.74% and 68.09% of wasps were attracted to odors of host larvae, respectively. Wasps did not show response to the odors released from un-infested tomato fruit and corn ear. There was no significant difference in attraction of parasitoid wasps to faeces of larvae that fed on tomato and corn ear. Our results indicated that volatile compounds produced by fifth instar larvae and larval faeces of H. armigera are important agents for attracting parasitoid wasps.

Cotton bollworm, Helicoverpa armigera (Hϋbner) (Lepidoptera: Noctuidae) is a cosmopolitan and polyphagous pest that attacks many plant species including cotton. One of the most important principles of the Integrated Pest Management programs (IPM) is use of non-chemical agents such as natural enemies (parasitoids and predators), and resistant host plant to control pests. Transgenic Bt cotton is one of the substitution ways of chemical pesticide used for control of this insect pest. Production of transgenic crops was a novelty in the method of applying host-plant resistance. Crops that are genetically engineered to express Bacillus thuringiensis toxin are planted in many areas.
Material and

In the present study, effect of transgenic Bt cotton, Coker cultivar, including cry1Ab was studied on biology and digestive protease activity of the bollworm. For bioassays, gut dissection and demographic studies, H. armigera were obtained from the Division of Entomology, Department of Plant Protection, College of Agriculture and Natural Resources, University of Tehran, Karaj, Alborz, Iran. The insects were held in the growth room on the condition of 25 ± 1ºC, 60–70 % relative humidity with a 16-h day length. Proteolysis using general substrate (Azocasein 2%) was assayed after some modification. In this manner, 10 µl enzyme extract and 50 µl Azocasein 2% (substrate solution) were mixed into 40 µl of the 20 mM Tris-HCl buffer pH 8.0 and incubated during 60 min. Protease activity was measured using specific substrate with some modifications. Trypsin- and chymotrypsin-like activities were assayed using 1mM BApNA (Benzoyl-l-arginine-p-nitroanilide) and 1 mM SAAPFpNA (Succinyl-l-Ala-l-Ala-l-Pro-Phe-p-nitroanilide), respectively.

The results illustrated that the second larval instar mortality in the transgenic cotton was 68 percent and in control cotton was 6 percent. Furthermore, larvae in different instars, in transgenic Bt, had significantly lower weight and longer life time in comparison with control. Several biological characters of both treatments including survivorship, development and weight were significantly changed. On the other hand, total protease, trypsin and chymotrypsin activity in digestive lumen, after the second, fifth and sixth larval instar in transgenic cotton showed significant reduction, respectively.

Coker cotton crop with cry1Ab, will have significantly negative effects in insect biology and digestive physiology during the pest life time and can be noticeable in management of important pests such as boll worm. Bt cotton can therefore be useful in an integrated pest management program, because it resulted in a reduction in the number of insecticide applications per season

Cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) is one of the important pests of agricultural products in the world, including Iran. In this study, the sublethal effects of Bacillus thuringiensis Berliner subsp. kurstaki (Bacillales: Bacillaceae) were evaluated on third instar larva of H. armigera under laboratory conditions 26±1 °C, 65±10% RH and 16:8 (L:D) photoperiod. The LC20 value of B. thuringiensis on 3rd instar larva of H. armigera was 9.8 × 105 IU/L. The mean female longevity and fecundity in control and Bt-treatment were 16.63 ± 1.05 and 13.88 ± 1.05 days and 1336.83 ± 147.68 and 1029 ± 147.68 eggs respectively that in both cases, there was a significant difference. In control and Bt-treatment, the net reproductive rate (R0) were 582.22 ± 51.89 and 126.38 ± 27.78 f/f/g, the intrinsic rate of natural increase (rm) were 0.1442 ± 0.002 and 0.1082 ± 0.004 f/f/d, the finite rate of increase (λ) were 1.155 ± 0.003 and 1.114 ± 0.004 f/f/d, the mean generation time (T) were 44.16 ± 0.62 and 44.73 ± 0.62 d and the doubling time (DT) were 4.80 ± 0.08 and 6.41 ± 021 d respectively. Except the mean generation time (T), other population parameters of H. armigera showed a significant difference between control and Bttreatment. The results indicated that the B. thuringiensis have high potential to reduce the cotton bollworm population and can be recommended for reducing the use of pesticides in the areas where the pest is present.

Digestive amylolytic activities in the midgut of 3rd, 4th and 5th instar larvae of Helicoverpa armigera (Hübner) on different host plants including white kidney bean (cultivars Daneshkadeh and Pak), red kidney bean (cultivars Akhtar and Naz), canola (cultivars Okapi, Opera, Sarigol and Zarfam), soybean (cultivars Clark, M7, Sari and Williams) and cowpea (cultivar Mashhad) were investigated under laboratory conditions. The amylolytic activity in 3rd, 4th and 5th instar larvae of H. armigera on different host plants in a broad pH range (pH 2–10) were studied. The results showed that the larva fed on canola cultivar Okapi had the lowest amylase activity on 3rd (0.42±0.005 OD/min), 4th (0.39±0.001 OD/min) and 5th (0.36±0.005 OD/min) instar larva. The highest enzyme activity was in 5th instar larvae of H. armigera on most plant cultivars (white kidney bean cultivars Daneshkadeh, red kidney bean cultivar Naz, canola cultivars Sarigol and Zarfam, soybean cultivars M7 and Williams). The amylolytic activity in 3rd, 4th and 5th instar larva of H. armigera was observed at pH 2.00 to 10.00. But the optimum p Hof amylase activity in the midgut of H. armigera larva was at pH 8.00 to 10.00. The maximum amylase amount in 3rd, 4th and 5th instar larva of H. armigera was observed on cowpea cultivar Mashhad at pH10.00 (1.34, 1.73 and 1.85 U/mg, respectively). Our findings provide useful information and when this information is used in association with other ecological and biological data, it may be valuable in development and implementation of management programs of H. armigera.

During evolution, various compounds against herbivors were developed in plant species. Disturbance in digestive system by plant enzyme inhibitors is one of the effective methods in integrated pest managment programs. In this study, the effects of total Goebelia alopecuroides and Vicia ervilia seed extracts and their fractions were assessed against proteolytic activity of cotton bollworm. Total extracts of G. alopecuroides was effectively inhibited digestive proteinase of cotton bollworm compared with that of V. ervilia. The inhibitory effect of G. alopecuroides on Bovine trypsin and chymotrypsin as well as insects’ trypsin and chymotrypsin was higher than that of V. ervilia. Total seed extracts of V. ervilia significantly decreased digestive chymotrypsin activity. Ammonium sulfate precipitation of seed extract also showed significant inhibitory effect among the fractions. The fifth fraction of G. alopecuroides showed the highest inhibititory efect agianst digestive proteolytic activity of cotton bollworm and bovine trypsin. The first fraction of V. ervilia significantly inhibited total proteolytic activity.The first fraction of both plants seed extracts inhibited digestive trypsin of cotton bollworm compared to the other fractions. The third fraction of V. ervilia and the forth fraction of G. alopecuroides showed higher inhibitory effect on digestive chymotrypsin of cotton bollworm comperd with the other fractions. Comparing crude extracts effects of both plant species on laboratory and wild populations of cotton bollworm showed that wild ones was susseptible compared with the laboratory population.

The effect of different artificial diets based on the seeds of one cowpea cultivar (Mashhad) and four chickpea cultivars (Arman, Azad, Binivich and Hashem) on biological and life table parameters of Helicoverpa armigera (Hübner) was studied at 25±1ºC, 65±5% RH and a photoperiod of 16:8 (L:D) hours. The larval period ranged from 13.26 to 21.54 days on Binivich and Mashhad, respectively. The longest and shortest development time of H. armigera was on Hashem (38.62±1.56 days) and Azad 33.81±0.09 days), respectively. The highest fecundity (total number of eggs laid per female) was obtained on Mashhad 1227.23±10.27 eggs) and lowest value of this parameter was on Arman (351.00±1.29 eggs). The highest net reproductive rate (R0) was on Mashhad 250.60 ±0.25 female offspring) and lowest value of this parameter was on Arman (59.49±0.49 female offspring). The intrinsic rate of increase (rm) was the highest on Azad (0.205±0.001 day-1) and lowest on Arman (0.140±0.006 day-1). In different host plants examined, the value of mean generation time (T) ranged from 24.11±0.25 to 30.41±1.30 days and doubling time (DT) ranged from 3.22±0.5 to 4.88±0.25 days. The results indicated that Azad and Arman were the most suitable and unsuitable cultivars incorporated into artificial diet for population growth of H. armigera, respectively.

Proteases are considered as major digestive enzymes in alimentary canals of most insects، which are responsible for providing amino acids and energy from nutrients for insects’ growth. The substrate azocasein was used for measuring general proteolytic activity of midgut extracts from Helicoverpa armigera (Hübner) larvae reared on different chickpea cultivars (Arman، Azad، Binivich and Hashem) and a cowpea cultivar (Mashhad) when incorporated into artificial diets at different pH values (6 to 12). The experiments were preformed at 25 ± 1Cº، 65 ± 5% RH and a photoperiod of 16:8 (L: D) h. The results showed that the lowest general proteolytic activity of the third، fourth and fifth instar larvae was on Arman، Binivich and Arman (4. 31، 4. 26 and 4. 31 U/mg، respectively)، while the highest rate was in the larvae fed on Mashhad، Azad and Mashhad (6. 68، 6. 31 and 6. 67 U/mg، respectively)، respectively. The general proteolytic activity in H. armigera larvae on all examined cultivars had an increasing trend in pH from 6 to 12. The optimum pH value of proteolytic activity in the larvae fed on different cultivars was 12، suggesting the maximum proteolytic activity of H. armigera larvae at high alkaline pH. Mashhad and Arman cultivars were the most and the least suitable hosts for H. armigera، respectively.

The cotton bollworm, Helicoverpa armigera is a serious pest of different agricultural crops in Iran and other parts of the world. The effect of different corn hybrids including SC700, SC704, SC500, DC370 and SC260 which incorporated into artificial diets on population growth parameters of H. armigera was studied at growth chamber conditions (25±1ºC, 65±5% RH and a photoperiod of 16:8 (L:D) hours). The intrinsic rate of increase (rm) on different hybrids varied from 0.1039 to 0.1394 (day -1), which was lowest on SC700 and highest on SC500. The highest net reproductive rate (R0) was on SC500 (203.90 females/female/generation) andthe lowest value of this parameter was on SC700 (68.30). The results showed that longest doubling time (DT) was on SC700 (6.59 days) and shortest one was on SC500 (4.96 days). Because of the higher coefficient of determination (r2) value in Gompertz model, data from different hybrids had a better fit to this model compared to Weibull model. The survival rate (lx) of individuals developed to adults from the initial cohort was 0.36, 0.44, 0.56, 0.46 and 0.48 on DC370, SC704, SC260, SC500 and SC700. The life expectancy (ex) of H. armigera was 13.55, 16.45, 13.53, 13.43 and 13.76 days, respectively at the first day of adult emergence. Our findings indicated that hybrid SC700 was unsuitable host and hybrid SC500 was suitable host for H. armigera.