Effects of plant chemicals on the Cotton Bollworm,Helicoverpa armigera (Hübner): A multi-generation study

We studied the effects of feeding on different cotton cultivars with different gossypol contents on the development, reproduction and food plant utilization of three successive generations of Cotton Bollworm, Helicoverpa armigera (Hübner). Significantly higher larval survival rates were observed in three successive generations of H. armigera fed on cotton cultivar “ZMS13”compared with cultivars “M9101” and “HZ401”. There was a significant decrease in fecundity in the first generation compared with the second and third generations of cotton bollworms fed on “M9101” and “ZMS13”. Cotton bollworm generation significantly influenced mean relative growth rate, relative growth rate and relative consumption rate. The relative growth rate significantly decreased in three successive generations of H. armigera fed on the high-gossypol cultivar “M9101” compared with those fed on low-gossypol cultivar “ZMS13”. However, a significantly higher relative growth rate was recorded in the third generation than in the first generation fed on “M9101”. Measurements of development and food utilization at the individual and population levels over more than one generation ought to provide a more meaningful prediction of long-term and population dynamics of the cotton bollworm.     

棉铃虫Helicoverpa armigera(Hübner)精母细胞减数分裂研究

采用压片法HSG显带技术,对棉铃虫精母细胞减数分裂进行了研究,描述了其减数分裂各时期的特征。同 时通过C-带处理表明棉铃虫染色体单倍数目为n=31,染色体长度从2.05μm至6.20μm不等。     

Sub-lethal influences of different insecticides on oviposition preference of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on cotton in relation to altered plant morphology

We investigated the sub-lethal influences of spinosad, chlorpyriphos, endosulfan, acephate and cypermethrin on the oviposition responses of Helicoverpa armigera (Hübner) to cotton plants, under cage and laboratory conditions. The rank order of toxicity (LC₅₀ values as a per cent) of test insecticides against third instar larvae using the leaf disc method was: spinosad > chlorpyriphos > endosulfan > acephate > cypermethrin. On whole plants, females laid more eggs on acephate LC₅₀-, acephate LC₃₀- and cypermethrin LC₅₀-treated cotton plants than on the control. The chlorpyriphos-treated plants were least preferred for oviposition. When excised cotton leaves from different treatments were used in a multiple-choice test, cypermethrin LC₅₀- and endosulfan LC₃₀-treated leaves received more eggs than the control. The repeated application of sub-lethal concentrations of different insecticides reduced plant height in the case of acephate LC₃₀ and cypermethrin LC₅₀, while plant spread and upper canopy leaf area were reduced in both treatments of acephate and cypermethrin. Reduced plant spread, upper canopy leaf area followed by plant height were found associated with oviposition preference by H. armigera females.     

The effect of piperonyl butoxide on pyrethroid-resistance-associated esterases in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Pyrethroid resistance in field populations of Australian Helicoverpa armigera (Hübner) is primarily a consequence of the overproduction of esterase isoenzymes which metabolise and sequester pyrethroid insecticides. Biochemical studies have shown that pyrethroid-resistance-associated esterases in H armigera are inhibited by the insecticide synergist piperonyl butoxide (PBO). Esterase inhibition by PBO did not occur immediately after dosing, but exhibited maximum inhibition 3-4 h after dosage. Esterase activity subsequently recovered until full activity was restored by 24 h. Topical bioassays using a pre-treatment of PBO showed that maximum H armigera mortality was achieved with pre-treatment times corresponding to maximum esterase inhibition. These results demonstrated that, with correct temporal application, PBO can restore pyrethroid efficacy against H armigera. It would also be expected that restoration of efficacy with other conventional insecticides, currently compromised by esterase-based resistance mechanisms, would occur.     

Long-term selection for resistance to transgenic cotton expressing Bacillus thuringiensis toxin in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Selection experiments for resistance to transgenic Bt cotton expressing Cry1Ac toxin in Helicoverpa armigera (Hübner) were conducted using a leaf-feeding method with 42 selection episodes over 45 generations. The cotton bollworm developed resistance to transgenic Bt cotton after 12 generations (F12) of selection. The survival rate of F12 neonates feeding on leaves of seedling stage for 4 days and boll-opening stage for 5 days of R19 line were ca 34 and 72%, respectively, compared with ca 0 and 40% for a non-selected sister strain (NYCS), but lower than or similar to that of F12 feeding on leaves of non-Bt cotton, Sumian 12 (ca 87 or 76%). Resistance to B thuringiensis HD-1 Dipel in neonates (F12) was ca 6-fold. After 42 generations of selection, the strain developed a very high level of resistance to Cry1Ac protoxin, 210 g kg(-1) MVPII wettable powder and 200 g litre(-1) MVPII liquid formulation, the resistance ratios being 1680-, 1780- and ca 1200-fold, respectively, compared with a laboratory susceptible strain (HZS). When compared with the non-selected NYCS, the resistance ratios to the above toxins were ca 540-, 580- and 510-fold, respectively, but to Dipel only ca 16-fold. The results indicated that it is very important to develop and implement effective resistance-management strategies and to detect early resistance to Bt cotton in field populations.     

Effects of Cry1Ac toxin of Bacillus thuringiensis and nuclear polyhedrosis virus of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on larval mortality and pupation

In the laboratory, the percentage mortality and pupation of Helicoverpa armigera (Hübner) were investigated when larvae were exposed to Cry1Ac of Bacillus thuringiensis Berliner, nuclear polyhedrosis virus of H. armigera (HaNPV) or Cry1Ac and HaNPV together. The results revealed that interactions between Cry1Ac and HaNPV varied with bioassay method and concentration of the suspension. When larvae were infected using a suspension containing both HaNPV and Cry1Ac, most combinations of Cry1Ac (62.5, 125 and 250 microg mL(-1)) and HaNPV (1.2 x 10(6), 6.0 x 10(6) and 3.0 x 10(7) PIB mL(-1)) showed an antagonistic effect. In the bioassay procedure where larvae were force fed diet containing Cry1Ac 48 h after being infected by HaNPV, interaction between Cry1Ac (0.5, 1, 2, 4 and 8 microg mL(-1)) and HaNPV (6.0 x 10(6) and 3.0 x 10(7) PIB mL(-1)) showed an additive effect, while combinations of Cry1Ac (0.5, 1, 2 and 4 microg mL(-1)) and HaNPV (1.2 x 10(6) PIB mL(-1)) showed an antagonistic effect. In the bioassay procedure where larvae being infected by HaNPV were fed on Cry1Ac diet from neonate to death or pupation, the results suggested that Cry1Ac and HaNPV showed an additive interaction. The percentage mortality was lower in the treatment of larvae infected by transgenic Bt cotton leaf discs containing HaNPV suspension than in the treatment of larvae by conventional cotton leaf discs containing HaNPV, while the pupation rate was higher. The combination of Bt cotton and HaNPV showed antagonism. The present results showed that a combination of Cry1Ac and HaNPV usually resulted in mortality levels greater than in the case of Cry1Ac but not greater than with the virus alone.     

Changes in susceptibility to conventional insecticides of a Cry1Ac-selected population of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

The changes in the susceptibility of the cotton bollworm, Helicoverpa armigera (Hübner) to three insecticides (lambda-cyhalothrin, phoxim and endosulfan) commonly used for control of this pest in China were monitored by bioassays at various generations. The insects were originally collected from Bt cotton fields and selected with Cry1Ac over 44 generations. In comparison with a susceptible strain, the larval resistance of the Bt-selected populations to Cry1Ac toxin increased 106-fold. Simultaneously, the resistance levels to lambda-cyhalothrin, phoxim and endosulfan declined dramatically. The results indicated no positive cross-resistance between Cry1Ac toxin and the insecticides. Evidence of the lack of cross-resistance to three commonly used synthetic insecticides in our laboratory-derived Cry1Ac-resistant population may suggest that growers can confidently use these insecticides if and when resistance to Cry1Ac cotton does occur.     

Inheritance of resistance to Bacillus thuringiensis Cry1Ac toxin in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) from India

BACKGROUND: The cotton bollworm, Helicoverpa armigera (Hübner), is one of the most serious insect pests of cotton. It has developed resistance to almost all groups of chemical insecticides because of their intensive use. The failure of insecticides to control H. armigera has been a strong incentive for the adoption of transgenic cotton (Bt cotton). However, the value of Bt could be diminished by widespread resistance development to Bt toxins in insect populations. Therefore, understanding the genetic basis of resistance is essential for developing and implementing strategies to delay and monitor resistance. RESULTS: A resistant strain designated as BM‐R was obtained from the cross of adults from Bathinda () and Muktsar (), Punjab, India, which showed the highest survival (60.68%) and LC₅₀ value (1.396 µg mL^?1 diet). Similarly, a laboratory‐maintained strain from Hoshiarpur, Punjab, showed maximum susceptibility to Cry1Ac toxin with the lowest LC₅₀ value (0.087 µg mL^?1), and was designated as HP‐S. The genetic purity of both strains was confirmed by RAPD profile analysis at each generation, and genetic similarity reached more than 90% after the third generation. Continuous maintenance of the resistant BM‐R strain on Cry1Ac resulted in an increase in LC₅₀ from 0.531 µg mL^?1 in F₀ to 4.28 µg mL^?1 in F₁₄ and 7.493 µg mL^?1 in F₁₉, while the LC₅₀ values for HP‐S larvae on diet without Cry1Ac increased to 0.106 and 0.104 µg mL^?1, which lay within the fiducial limits of the baseline LC₅₀ value. The mode of inheritance of resistance was elucidated through bioassay response of resistant, susceptible heterozygotes and backcross progeny to Cry1Ac incorporated in semi‐synthetic diet. CONCLUSION: Based on dominance, degree of dominance and backcross values, resistance was inferred to be polygenic, autosomal and inherited as a recessive trait. Copyright © 2011 Society of Chemical Industry     

Effectiveness of two insect growth regulators against Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) and Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) and their impact on population densities of arthropod predators in cotton in Pakistan

Field efficacies of two insect growth regulators (IGRs) at two recommended application rates, buprofezin at 370 and 555 g AI ha(-1) and lufenuron at 37 and 49 g AI ha(-1), were determined against the sweet potato whitefly, Bemisia tabaci (Gennadius), and the cotton bollworm, Helicoverpa armigera (Hübner), in experimental plots of cotton at the Directorate of Cotton Research, Faisalabad, Pakistan. Adverse effects of the IGRs on populations of associated arthropod predators, namely geocorids, chrysopids, coccinellids, formicids and arachnids, were also assessed. Both IGRs significantly reduced populations of B. tabaci at each application rate 24, 48 and 72 h after treatment, and higher doses were more effective than lower doses. Buprofezin was not effective against H. armigera at any tested dose for any time of treatment in any spray. Lufenuron applied at 37 and 49 g AI ha(-1) effectively suppressed H. armigera populations, resulting in significant reductions in crop damage. At lower doses, both IGRs appeared safe to predator populations, which did not differ significantly in IGR-treated versus untreated control plots. Population densities of formicids and coccinellids were significantly lower at high concentrations of both IGRs in treatment plots, possibly as a result of reduced prey availability. The potential role of buprofezin and lufenuron for control of B. tabaci and H. armigera in a spray programme and the likelihood of direct toxic effects of IGRs on predatory fauna of cotton are discussed.     

Azadirachtin-A and tetrahydroazadirachtin-A concentrates: preparation, LC-MS characterization and insect antifeedant/IGR activity against Helicoverpa armigera (Hübner)

A 60% azadirachtin-A concentrate has been obtained through repeated precipitation with hexane from a methanolic solution of a 20% concentrate. Azadirachtin-A (90%) has been obtained by medium-pressure liquid chromatography of the 60% concentrate with an RP-18 column and a methanol + water (1 + 1 by volume) solvent system. Catalytic hydrogenation of the 60 and 90% azadirachtin concentrates yielded the corresponding tetrahydroazadirachtin concentrates. Dihydroazadirachtin and tetrahydroazadirachtin formed during the first 5 h of hydrogenation were identified by LC-ESI-MS on the basis of their unique mass fragmentation pattern. The efficacy of tetrahydroazadirachtin concentrates in inhibiting the feeding and growth of Helicoverpa armigera (Hübner) larvae has been compared with that of azadirachtin concentrates. They were in general more active and deterred larvae from feeding at all concentrations. Tetrahydroazadirachtin-A (90%) and azadirachtin-A (90%) with respective IC(50) values of 280 and 390 mg L(-1) were effective as insect growth regulators, while tetrahydroazadirachtin-A (90%) displayed higher antifeedant activity (AI(50) 14 mg L(-1)) against the test insect.     

Use of pyrethroid analogues to identify key structural features for enhanced esterase resistance in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

It has been reported previously that the major resistance mechanism to pyrethroid insecticides by the cotton bollworm Helicoverpa armigera (Hübner) in Australia is a consequence of overproduction of esterase isoenzymes. This paper reports structure-activity relationships that support such a view, based on in vivo bioassays conducted with a range of pyrethroid structures containing a variety of acid and alcohol moieties and the correlation with in vitro esterase inhibition assays against the same structures, and identifies the critical regions of the molecule with regard to esterase inhibition, and hence resistance. The implications of this work in terms of possible resistance management are evaluated and discussed.     

棉铃虫(Heliothis armigera Hübner)的天敌及其对棉铃虫的控制作用

棉铃虫为世界性的害虫,也是我国当前棉花主要害虫之一。近年来,随着抗药性的产生,一些常用农药对棉铃虫的防治效果逐渐下降,用药次数、浓度和药量都不断增加,造成环境污染和棉田农药成本逐年上升。为了开展棉虫的综合防治,保护和利用棉虫的天敌,几年来,我们对湖北省棉铃虫的天敌进行了田间调查和室内观察试验。现将初步的结果报告于下。     

Gamma radiation sensitivity of the eggs, larvae and pupae of Indian meal moth Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

BACKGROUND: This study focused on determining the minimal effective gamma radiation dose that prevents commodity damage caused by the Indian meal moth Plodia interpunctella (Hübner). The study was also designed to assess the effect of releasing either partially sterilized males alone or both partially sterilized males and females on the reproductive potential of P. interpunctella populations. RESULTS: The dose of radiation required to prevent larval emergence from irradiated eggs was 350 Gy, and the same dose was also required to prevent adult emergence from mature larvae. A dose of 300 Gy was not able to prevent adult emergence from irradiated pupae. The dose at which 100% sterility was achieved in treated females mated to treated males was 300 Gy for the parental generation of irradiated pupae. Fertility of the parental males from irradiated pupae was 48.17% at 300 Gy in treated males crossed with untreated females, but male progeny of irradiated male parents had a residual fertility of 11.06% at the same dose. CONCLUSION: F(1) males from irradiated pupae were more sterile than parental males. To prevent larval emergence from irradiated eggs, a dose of 350 Gy is required. The same dose is required to prevent the larvae from reaching the adult stage.     

Effects of nC24 and nC27 petroleum spray oils on oviposition and egg survival of Ostrinia nubilalis Hübner (Lepidoptera,Pyralidae) and Trichogramma brassicae Bezdenko (Hymenoptera,Trichogrammatidae) adults on maize plants

Abstract

The study determined the effectiveness of nC24 and nC27 petroleum spray oils (PSOs) to reduce oviposition of Ostrinia nubilalis and survival of O. nubilalis eggs and Trichogramma brassicae adults. Under choice and no-choice tests, maize treated with 3, 5 and 10% (v/v) of both oils deter O. nubilalis oviposition on maize. The study also showed that treatment of 1 – 3-day-old O. nubilalis eggs with 1 and 2% (v/v) nC24 oil caused 6% mortality compared with 99.5% when treated with 3, 5 and 10% (v/v) oil. In contrast, treatment with 1 – 10% (v/v) nC27 oil caused 99% mortality. Trichogramma brassicae is a major parasitoid of O. nubilalis. The mortality of T. brassicae 24 h after exposure to maize sprayed with 2% (v/v) nC24 and nC27 oils was 8.3 and 12.7%, respectively. At 5% (v/v), the mortalities were 24.9 and 23.5%, respectively. Therefore, application of 3% (v/v) PSO may deter O. nubilalis egg lay, egg mortality and survival of T. brassicae on maize.     

Maize defence mechanisms against the European corn borer,Ostrinia nubilalis Hübner (Lepidoptera: Crambidae)

Maize is arguably the most widely grown crop in the world, but it is often associated with one of its major insect pests, the European corn borer (ECB). The damage caused by this species to maize production is generally variable, but in many cases it is economically significant. This review paper provides an overview of the research findings on the natural plant defence mechanisms against ECB larvae published till now. What is resistance and how it is achieved, what is the chemical response of maize plants to insect feeding and how tolerance can be increased. A short introduction in breeding for resistance and a discussion if the mentioned traits can be used in conventional breeding in order to create maize hybrids less affected by ECB are given.     

Assessment of resistance risk in Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) to chlorantraniliprole

BACKGROUND: Beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), is a major pest of numerous cultivated crops. Chlorantraniliprole, the first commercialised ryanodine receptor insecticide from the anthranilic diamide class, has exceptional insecticidal activity on a range of lepidopteran pests. The aim of this study was to assess the resistance of S. exigua to chlorantraniliprole in the laboratory. RESULTS: A field‐collected population of S. exigua was selected after repeated exposure to chlorantraniliprole to determine the risk of resistance evolution. After 22 generations of selection, there was a 12.0‐fold increase in LC₅₀. The realised heritability (h²) of resistance was estimated as 0.1082 by using threshold trait analysis. The projected rate of resistance evolution indicated that, if h² = 0.1082 and 70% of the population was killed at each generation, then a tenfold increase in LC₅₀ would be expected in 21.7 generations for chlorantraniliprole. CONCLUSION: These results show that the risk of resistance development to chlorantraniliprole exists in S. exigua after continuous application. Copyright © 2011 Society of Chemical Industry     

Biological studies on the olive leaf moth, Palpita unionalis Hübner (Lepid., Pyralidae), and the olive moth, Prays oleae Bernard (Lepid., Yponomeutidae)

Abstract The biology of two important lepidopterous pests, Prays oleae Bernard and Palpita unionalis Hübner, was studied. The target pests were reared on olive plants, Oleae europaea L. (Oleaceae) under laboratory conditions for two successive generations, from March to June 2002. For P. oleae, the duration of larval stage development in the first generation was 21.4 ± 0.18 days at 19.3–20.9 °C, 65–68 % R.H, while in the second generation it was 14.8 ± 0.10 days at 20.8–24.2 °C, 65–69 % R.H. The number of eggs laid per female ranged from 58 to 109 eggs in the first generation, and from 47 to 113 in the second. The larval stage duration of P. unionalis was 16.3 ± 0.12 days at 16.8–22.9 °C, 65–69 % R.H. and 15.5 ± 0.12 days at 21.6–25.5 °C, 66–69 % R.H. for the first and second generations, respectively. Also, the number of eggs laid per female ranged from 630 to 653 eggs, and from 425 to 493 eggs in the second generation under the same previous laboratory conditions. P. oleae laid eggs at night mostly singly on flower-buds, more on the calyx. than on the petals. The larvae mined on leaves and damaged groups of flowers. P. unionalis adults were active at night, laid eggs singly at twilight usually on the lower surface of foliage. Larvae fed on leaves spinning several leaves together to form shelter for the pupa.     

Biological studies on the olive leaf moth, Palpita unionalis Hübner (Lepid., Pyralidae), and the olive moth, Prays oleae Bernard (Lepid., Yponomeutidae)

Abstract The biology of two important lepidopterous pests, Prays oleae Bernard and Palpita unionalis Hübner, was studied. The target pests were reared on olive plants, Oleae europaea L. (Oleaceae) under laboratory conditions for two successive generations, from March to June 2002. For P. oleae, the duration of larval stage development in the first generation was 21.4 ± 0.18 days at 19.3–20.9 °C, 65–68 % R.H, while in the second generation it was 14.8 ± 0.10 days at 20.8–24.2 °C, 65–69 % R.H. The number of eggs laid per female ranged from 58 to 109 eggs in the first generation, and from 47 to 113 in the second. The larval stage duration of P. unionalis was 16.3 ± 0.12 days at 16.8–22.9 °C, 65–69 % R.H. and 15.5 ± 0.12 days at 21.6–25.5 °C, 66–69 % R.H. for the first and second generations, respectively. Also, the number of eggs laid per female ranged from 630 to 653 eggs, and from 425 to 493 eggs in the second generation under the same previous laboratory conditions. P. oleae laid eggs at night mostly singly on flower-buds, more on the calyx. than on the petals. The larvae mined on leaves and damaged groups of flowers. P. unionalis adults were active at night, laid eggs singly at twilight usually on the lower surface of foliage. Larvae fed on leaves spinning several leaves together to form shelter for the pupa.