单宁对苏云金芽孢杆菌库斯塔克变种杀棉铃虫效力的作用(英文)

本文报道棉铃虫、苏云金芽孢杆菌库斯塔克变种和单宁三者间的相互作用。苏云金芽孢杆菌芽孢晶体混合粉以6个不同的浓度（0％,0．005％,0．01％,0．015％,0．02％,0．025％湿重）分别加入含0．025％单宁和不含单宁的人工饲料中。初孵幼虫分别在上述饲料中饲养48h后,转入相应的不含苏云金芽孢杆菌的人工饲料上饲养,直到留存的幼虫化蛹。结果表明,单宁与苏云金芽孢杆菌混用可提高苏云金芽孢杆菌对棉铃虫的毒力,LD50降低45％,并可显著抑制该虫的生长发育,但二者在抑制生长发育方面无交互作用。选择取食试验显示,苏云金芽孢杆菌对五龄幼虫有显著的抑食性,但单宁无此作用,单宁与苏云金芽孢杆菌混用不会增强抑食性,但单宁能抑制苏云金芽孢杆菌菌落的生长,浓度高于15mg／100ml还能抑制芽孢的萌发。     

Influence of tannic acid and Cry1Ac toxin of Bacillus thuringiensis on larval survival, growth, and development of Helicoverpa armigera

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) causes huge economic losses in cotton production around the world. Tannin, one of the important secondary substances in cotton plants, can increase the δ‐endotoxin activity of Bacillus thuringiensis ssp. kurstaki. The mechanism of interaction between tannin and Bt toxin on H. armigera is unclear. We investigated the interaction between tannic acid and Cry1Ac toxin in H. armigera, and monitored survival, growth, and development during the larval period after treating the larvae with four concentrations of Cry1Ac toxin (0, 2, 8, and 14 μg^?1) alone or in combination with four concentrations of tannic acid (0, 0.5, 1, and 2 mg g^?1). Mortality of larvae treated with both tannic acid and Cry1Ac was higher than the mortality of larvae treated with tannic acid or Cry1Ac alone. Mortality was 47.5 and 51.5% in larvae treated with 14 μg g^?1 Cry1Ac alone or 2 mg g^?1 tannic acid alone, respectively. In contrast, larval mortality was 75% when treated with the mixture of 14 μg g^?1 Cry1Ac and 2 mg g^?1 tannic acid, suggesting that a mixture of the two enhanced the effectiveness of each one alone. The developmental time of larvae treated with the combination of tannic acid and Cry1Ac was significantly longer than when they were treated with Cry1Ac or tannic acid alone. Larval weight, pupal weight, and pupation rate were also significantly reduced in larvae treated with both toxins, compared with the larvae treated with either toxin alone. These results showed that the interactive effect of tannic acid and Cry1Ac on larval growth inhibition is additive, and that tannic acid improves Cry1Ac toxicity to insects. Tannic acid used in combination with B. thuringiensis might potentially reduce overall insecticide use, thus delaying development of insecticide resistance.     

Host crop influence on the susceptibility of the American bollworm, Helicoverpa armigera, to Bacillus thuringiensis ssp. kurstaki HD-73

Studies on the susceptibility of F₁ neonates of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) collected from chickpea in Delhi and cotton in Punjab, Haryana and Rajasthan in northern India, to Bacillus thuringiensis ssp. kurstaki HD‐73, and the impact of host crop diets on insect susceptibility, were carried out by diet incorporation bioassays. The susceptibility of F₁ neonates of H. armigera to Bacillus thuringiensis ssp. kurstaki HD‐73 ranged from twofold (LC₅₀ 96 h, 84.5–164.2 µg (ai) l^?1) for chickpea to about fivefold (LC₅₀ 96 h, 51.1–247.7 µg (ai) l^?1) for cotton. The F₁ neonates of insects collected from pearl millet were twice as tolerant as those collected from cotton and sunflower at Sirsa to B. thuringiensis ssp. kurstaki HD‐73, suggesting that there was an influence of host crops on insect susceptibility. Insects originally collected from cotton fields at Bhatinda and reared for four generations on a chickpea‐based meridic diet were used to initiate host‐specific colonies of H. armigera. These host‐specific colonies were allowed to complete one generation on meridic diets prepared with different hosts, viz., cabbage, cauliflower, chickpea, green pea, pearl millet, and pigeon pea. Larvae of H. armigera were heaviest on the 15th day, and had a higher growth rate on a pigeon pea‐based diet than all other host diets. The larval period was shorter on chickpea and pigeon pea, with higher percentage pupation than all other host‐diets. The pupal weight of H. armigera was greater on chickpea and pigeon pea diets than on other host diets. The growth and development of larvae was significantly poorer on pearl millet diet than on other host diets. The F₁ neonates of H. armigera belonging to cabbage, cauliflower, and pearl millet host‐specific colonies were more susceptible than those belonging to chickpea, green pea, and pigeon pea host‐specific colonies to B. thuringiensis ssp. kurstaki HD‐73, suggesting the importance of proteinaceous nutrients in tolerance. The F₁ neonates of the pearl millet colony of H. armigera grown on a chickpea‐diet for 4 days were significantly more tolerant to B. thuringiensis ssp. kurstaki HD‐73 than those reared on the pearl millet‐based diet. These studies show the impact of the host diet of H. armigera on tolerance to B. thuringiensis.     

Suspension concentrate formulation of Bacillus thuringiensis var. kurstaki for effective management of Helicoverpa armigera on sunflower (Helianthus annuus)

A local strain DOR Bt-1 belonging to Bacillus thuringiensis var. kurstaki (Bt.k) was multiplied through solid state fermentation and the resulting technical powder was milled and sieved to obtain particles of various sizes. Efficacy of Bt.k. against larvae of Helicoverpa armigera was found to increase with the decrease in particle size. Boric acid was found to be synergistic to DOR Bt-1 technical powder. LC₅₀ of the Bt and boric acid mixture (75:25) was lower at 89.63 mg/100 mL in comparison to Bt alone at 116.75 mg/100 mL. A suspension concentrate formulation with DOR Bt-1 technical was developed using boric acid as an adjuvant. The formulation was found to be highly effective against H. armigera in laboratory bioassays with an LC₅₀ of 185 µL (containing 53.36 mg Bt). The formulation gave effective control of H. armigera on sunflower within 3 days after spray even at the lowest dose of 1.0 mL/L under field conditions.     

EFFECTS OF GOSSYPOL ON GROWTH OF THE COTTON BOLLWORM AND DEVELOPMENT OF ITS PARASITOID CAMPOLETIS CHLORIDEAE*

Abstract The effects of gossypol, an important allelochemical in cotton, on growth of the cotton bollworm Helicoverpa armigera (Hubner) and development of its endoparasitoid Campoletis chlorideae (Uchida) in Huanghe River Valley were studied. Growth of H. armigera larvae was accelerated by adding 0.1% gossypol in the artificial diet, causing 10.75% reduction of the vulnerable period to C. chlorideae while the suppression activity of 0. 5 % gossypol to H. armigera larvae prolonged the vulnerable period by 28.15%. Negative effects of gossypol on the development of the parasitoid were demonstrated by using the artificial diet and cotton varieties WD-151 (glandless) and HG-BR-8 (glanded). Gossypol at 0.1% concentration in artificial diet did not remarkably increase the body weight of adult wasp, but significantly extended the egg-larval time and shortened the pupal time; 0. 5% gossypol and HG-BR-8 remarkably reduced the body weight of adult wasp, also significantly prolonged the egg-larval period and decreased the pupal period. Finally, the coordinate application of high gossypol resistant cotton varieties and C. chlorideae in H. armigera control is discussed.     

Entomopathogenicity of endophytic <Emphasis Type="Italic">Serratia marcescens</Emphasis> strain SRM against larvae of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> (Noctuidae: Lepidoptera)

An endophytic Serratia marcescens strain SRM (MTCC 8708) isolated from the flowers of summer squash was found to be entomopathogenic against the larvae of Helicoverpa armigera. Natural epizootic of this bacterial strain on the larvae collected from summer squash flowers ranged from 19.9 to 72.3%. Under laboratory conditions, a dose of 6 × 10¹⁰ c.f.u./ml diet induced 66.3% mortality of first instar H. armigera larvae. Similarly all other growth and development parameters of the insect were severely retarded in a dose-dependent manner. The bacterium invaded the entire alimentary canal and haemolymph with successful replacement of all other gut-associated microflora. There was a great reduction in midgut proteinase activity due to inhibition of five major proteinase isozymes by S. marcescens infection. Further, a synergistic interaction between chitinases isolated from this strain and Bacillus thuringiensis Cry1Ac toxin was observed. The present findings suggest that this plant-associated S. marcescens strain SRM could be suitably exploited for the management of H. armigera.     

Effect of different additives on the persistence and insecticidal activity of native strains of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis>

The persistence and insecticidal activity of native strains of Bacillus thuringiensis was evaluated in formulations containing different additives such as arrow-root powder, carboxy methyl cellulose (CMC), gum acacia, non-food grade (NFG) starch, and soluble starch. Persistence of B. thuringiensis varied with different additives used in the formulations. Among the different additives used, NFG starch provided maximum protection to B. thuringiensis and native strain 42 showed maximum persistence (83%) which was higher than that obtained in commercial formulation. In commercial formulation, the persistence of B. thuringiensis was 47% only after 3 d of spray. The feeding trials conducted on second instar larvae of H. armigera using leaves sprayed with NFG starch formulation revealed 70% larval mortality while commercial formulation showed 50% mortality during the same period.     

Efficient screening and breeding of Bacillus thuringiensis subsp. kurstaki for high toxicity against Spodoptera exigua and Heliothis armigera

Spodoptera exigua is one of the most renowned agricultural pest insects and relatively insensitive to Bacillus thuringiensis subsp. kurstaki strains which are widely used commercial products to control lepidopterans such as Heliothis armigera. In the current study, we have developed a new and efficient approach to screen and breed a B. thuringiensis subsp. kurstaki strain exhibiting high toxicity against S. exigua while retaining its high toxicity against H. armigera. UV and diethyl sulfate methods were used for mutagenesis, followed by an agar plug plate diffusion assay for preliminary screening of Zwittermicin A over-producing mutants, from which we obtained a mutant strain, designated here as B. thuringiensis subsp. kurstaki D1-23, with high toxicity against S. exigua. The toxicity of D1-23 against S. exigua and H. armigera was improved by 115.4 and 25.9%, respectively, compared to its parental commercial strain BMB005.     

Increased food utilization indices and decreased proteolytic activity in Helicoverpa armigera larvae fed sublethal Bacillus thuringiensis‐treated diet

The cotton bollworm Helicoverpa armigera is one of the most devastating insect pests. A set of protease enzymes allows this species to feed on different host plant species. Control measures in agriculture often involve the application of the pathogenic bacterium Bacillus thuringiensis subsp. kurstaki (Btk). In the present study, the effects of sublethal Btk doses are evaluated with respect to the food utilization indices and proteolytic activities of Helicoverpa armigera. Accordingly, the H. armigera larvae are fed with artificial diet containing sublethal Btk doses (LC₅, LC₁₀, LC₁₅, LC₂₀ and LC₂₅) and a Btk‐free diet as control. All but one of the food utilization indices we measured is observed to increase significantly with increasing Btk doses. By contrast, the specific activity of total protease, chymotrypsin and elastase enzymes decrease significantly with an increasing Btk concentration. We conclude that Btk was not toxic to H. armigera larvae and any damage that it causes can be compensated for by H. armigera larvae via various mechanisms. In conclusion, increased nutritional indices in the larvae fed with Btk diet represent an important issue that needs to be considered to avoid the pest establishing Bt resistant populations. Meanwhile, the lack of effect of Btk sublethal concentrations on trypsin enzyme specific activity can bolster this challenge.     

大豆胰蛋白酶抑制剂与棉酚或丹宁混用对棉铃虫中肠蛋白酶和生长率的影响

本文报告了大豆胰蛋白酶抑制剂(STl)与棉酚、丹宁酸单一和协同作用对棉铃虫Helicoverpa armigera(Hubner)幼虫中肠蛋白酶活性和生长速率的影响。在离体条件下,STI、棉酚和丹宁酸均对中肠蛋白酶有抑制作用,以STI的作用最强。活体试验表明,人工饲料中0.84%(干重)的S丁I对强碱性类胰蛋白酶活力有显著抑制作用;0.3%丹宁酸则对弱碱性类胰蛋白酶和总蛋白酶活力有显著抑制作用;0.3%棉酚对几种蛋白酶活力的影响均不显著。三者均能显著抑制幼虫的生长,而Sn与棉酚或丹宁酸的协同作用比三者的单独作用更能有效地抑制幼虫的生长发育和中肠蛋白酶活性。     

Effects of the Cry1Ac toxin of Bacillus thuringiensis on Microplitis mediator, a parasitoid of the cotton bollworm, Helicoverpa armigera

Interactions between the cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), its larval parasitoid Microplitis mediator (Haliday) (Hymenoptera: Braconidae), and the Cry1Ac toxin of Bacillus thuringiensis Berliner were evaluated under laboratory conditions. The growth of H. armigera larvae was delayed and its pupal rate and pupal weight decreased when they were fed on a diet containing Cry1Ac toxin. Due to the lowered growth rate of the host larvae, the time available for parasitization of H. armigera by M. mediator increased when the host larvae were reared on a diet containing Cry1Ac toxin at concentrations of 0.5, 1, 2, and 4 µg g^?1. The longevity of female and male parasitoids was not significantly affected when newly emerging wasps fed on honey solutions containing three different concentrations of Cry1Ac toxin (125, 250, and 500 µg ml^?1). When female parasitoids were fed on honey solutions containing Cry1Ac, their offsprings’ egg and larval development period, pupal weight, length of pupation, adult weight, and adult longevity did not change significantly in most of the treatments compared with controls. When the female parasitoids parasitized host larvae that had been fed on a diet containing 0.5, 1, 2, 4, and 8 µg g^?1 Cry1Ac toxin, their offsprings’ eggs and larvae were significantly delayed. Their pupal weight, adult weight, and adult longevity were also significantly less than controls.     

Differential effect of tannic acid on two tree-feeding Lepidoptera: implications for theories of plant anti-herbivore chemistry

Summary Feeding efficiencies of ultimate instar larvae of two polyphagous tree-feeding Lepidoptera, Malacosoma disstria (Lasiocampidae) and Orgyia leucostigma (Liparidae), were measured on artificial diets containing from 0% to 8% tannic acid. Relative growth rate (RGR) of O. leucostigma was not affected by up to 8% tannic acid, suggesting that O. leucostigma has evolved an effective counteradaptation to hydrolyzable tannins. In contrast, as little as 0.5% tannic acid caused a significant reduction in RGR of M. disstria, due both to reduced efficiency of conversion of digested food (ECD) and reduced relative consumption rate (RCR), and caused a significant increase in mortality during the pupal stage. Moreover, when reared from hatching on tannin-containing diets, no M. disstria larvae survived past the fourth instar.Although tannins are commonly referred to as digestibility-reducing substances, tannic acid did not reduce the ability of M. disstria or O. leucostigma larvae to digest either the whole diet or nitrogen contained in the diet. For M. disstria, tannic acid acts as a toxin and a feeding deterrent, but not as a digestibility-reducing substance. Growing evidence that tannins commonly act as toxins warrants a reassessment of their role in anti-herbivore chemistry.     

Effects of the mixed biocide Bacillus thuringiensis–abamectin on the development of the parasitoid Microplitis mediator and its host Helicoverpa armigera

The effects of the mixed biocide Bacillus thuringiensis Berliner with abamectin (BtA) on the development of the parasitoid Microplitis mediator (Haliday) (Hymenoptera: Braconidae) and its cotton bollworm host, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), were evaluated in the laboratory. Weight gain in larvae of H. armigera was initially delayed, but larval developmental period increased and pupal weight increased when they were fed on a diet containing BtA. Due to increased longevity of the host larvae, the susceptible period to parasitization of H. armigera by M. mediator increased when the host larvae were reared on diets containing BtA at concentrations of 0.5, 1, 2, and 4 μg g^?1. The longevity of female and male parasitoids significantly decreased when newly emerged wasps were fed a honey solution containing 200 μg ml^?1 BtA in comparison with those fed only a honey solution. Mean longevity was significantly prolonged when parasitoids were fed a honey solution and BtA–honey solution in comparison with those fed BtA–distilled water, distilled water, or nothing. There were no significant differences compared with the control in any biological characteristics for the offspring of female parasitoids fed the honey solutions containing BtA at concentrations of 50, 100, and 200 μg ml^?1; characteristics measured include the egg‐larval period, pupal weight, male and female pupal periods, adult fresh weight, and adult longevity. When female parasitoids parasitized host larvae that had been fed the diet containing BtA, their male and female pupal periods were significantly prolonged compared with the control (without BtA).     

Action of Cu2+ on Bacillus thuringiensis Growth Investigated by Microcalorimetry

By using an LKB-2277 Bioactivity Monitor, ampoule mode, the heat output of Bacillus thuringiensis growth metabolism is determined at 28°C and the effect of Cu²⁺ on B. thuringiensis growth is studied. Copper is regarded as an essential trace element for life. Its deficiency may be the cause of diseases. Cu²⁺ at different concentrations has different effects on B. thuringiensis growth metabolism: a low concentration (0–30 g/ml) of Cu²⁺ can promote the growth of B. thuringiensis, a high concentration (40–120 g/ml) can inhibit growth of the bacteria, and a concentration of Cu²⁺ of up to 130 g/ml completely inhibits B. thuringiensis growth.     

Rosmarinic acid production by <Emphasis Type="Italic">Coleus forskohlii</Emphasis>hairy root cultures

Coleus forskohlii hairy root cultures were found to produce forskolin and rosmarinic acid (RA) as the main metabolites. The growth and RA production by C. forskohlii hairy root cultures in various liquid media were examined. The hairy root cultures showed good growth in hormone-free Murashige and Skoog medium containing 3% (w/v) sucrose (MS medium), and Gamborg B5 medium containing 2% (w/v) sucrose (B5 medium). RA yield reached 4.0 mg (MS medium) and 4.4 mg (B5 medium) after 5 weeks of culture in a 100 ml flask containing 20 ml of each medium. Hairy root growth and RA were also investigated after treatment with various concentrations of yeast extract (YE), salicylic acid (SA) and methyl jasmonic acid (MJA). RA production in a 100 ml flask containing 20 ml B5 medium reached 5.4 mg (1.9 times more than control) with treatment of 0.01 or 1% (w/v) YE, 5.5 mg (2.0 times more than control) with treatment of 0.1 mM SA, and the maximum RA content with 9.5 mg per flask (3.4 times more than control) was obtained in the hairy roots treated with 0.1 mM MJA. These results suggest that MJA is an effective elicitor for production of RA in C. forskohlii hairy root cultures.     

Bacillus thuringiensis isolates from soil and diseased insects in Egyptian cotton fields and their activity against lepidopterous insects

The distribution of Bacillus thuringiensis in Egyptian soils of cotton cultivations represented by 11 governorates was studied. This study aimed to isolate indigenous strains that may be potent against some lepidopterous insect pests. Out of 45 isolates, only 10 were effective and they showed high levels of toxicity against the target insects at 500 μg/ml (80% larval mortality or higher). Among these 10 isolates, two isolates were potent against Spodoptera littoralis, two isolates were potent against Helicoverpa (= Heliothis) armigera, seven isolates were potent against Pectinophora gossypiella, but none were potent against Agrotis ypsilon. LC₅₀ and LC₉₀ values and the potency of the B. thuringiensis isolates have been determined. Trials were conducted to isolate B. thuringiensis from diseased lepidopterous insects collected from the same locations, but all isolates showed low potential activity against the target insects. These findings showed promise for the possible use of some indigenous B. thuringiensis strains in the control of lepidopterous pests in Egypt.     

SEX PHEROMONE COMPONENTS OF HELICOVERPA ARMIGERA:CHEMICAL ANALYSIS AND FIELD TESTS*

Abstract Gas chromatographic and mass spectral analyses were conducted on the pheromone gland extracts of female moth of Helicoverpa armigera (Lepidoptera:Noctuidae). Saturated aldehyde (16:Ald), (Z)-9-hexadecenal (Z-9–16:Ald), (Z)-11-hexadecenal (Z-11–16:Ald), hexade-canol (16:OH) and (Z)-11-hexadecenol (2–11–16:OH) were found from gland extracts in the ratio of 6.1:4. 5 :100:3. 5 :8.8. In field tests of Shandong and Shanxi Provinces, 2 mg blends of Z -11–16:Ald and Z-9–16:Ald (97:3) applied on a rubber dispenser effectively attracted H. armigera males. The addition of 4%-7% 16 :Ald to the binary mixture caused increase over that of the binary mixture. The addition of 1%Z-11–16:OH to binary or trinary mixture may reduce catches, while addition of 5% Z-11–16:OH reduced catches singnificantly.     

Comparative selectivity of pesticides used in greenhouses,on the aphid parasitoid Aphidius colemani (Hymenoptera: Braconidae)

A series of bioassays were conducted under laboratory conditions to determine the relative toxicities of various pesticides (acetamiprid, cypermethrin, chlorantraniliprole and emamectin benzoate, Bacillus thuringiensis var. kurstaki and Helicoverpa armigera nucleopolyhedrovirus, copper oxychloride, iprodione, mandipropamid, a mixture of propamocarb?+?fluopicolide and mixture of fludioxonil?+?cyprodinil) on Aphidius colemani adults and mummies, as well as sublethal effects on female fecundity. Cypermethrin was highly toxic to pupa of A. colemani within host mummies. Acetamiprid, cypermethrin, emamectin benzoate, a mixture of propamocarb?+?fluopicolide and mixture of fludioxonil?+?cyprodinil were also highly toxic to A. colemani adults (92–100% mortality at 48?h post treatment). Mandipropamid, iprodione and copper oxycloride treatments significantly reduced fecundity of the female parasitoids. In contrast B. thuringiensis var. kurstaki, H. armigera nucleopolyhedrovirus and chlorantraniliprole were harmless (<30% mortality) to the parasitoid species tested according to International Organisation for Biological Control toxicity classification and are likely to be compatible with integrated pest management programmes.     

The life parameters of a parasitoid Microplitis mediator (Hymenoptera: Braconidae), reared on cotton bollworm Helicoverpa armigera (Hübner) with Cry1Ac diet

Microplitis mediator (Haliday) is an important endoparasitoid of the cotton bollworm, Helicoverpa armigera (Hübner) in northern China. Interactions among H. armigera, its larval parasitoid M. mediator, and Cry1Ac over two generations were evaluated under laboratory conditions. The results indicated that the developmental period of M. mediator offspring's eggs and larvae were significantly delayed and pupal and adult weight were significantly less compared to the control when the female parasitoids parasitized H. armigera larvae that fed on diet containing 1, 2, 4 and 8 µg/g Cry1Ac. The female parasitoids emerged from the host fed diet containing 8 µg/g Cry1Ac could oviposit in healthy hosts, and their offspring's biological parameters (egg–larval period, pupal weight and adult weight), parasitism rate, abnormal cocoon rate and adult emergence were not significantly affected. Cry1Ac was detected in larvae and hemolymph of H. armigera, but not in the larvae of M. mediator. The results suggest that the observed significant effects on several fitness parameters of the F₁ M. mediator developed from H. armigera fed Cry1Ac diet most likely were host-quality mediated rather than direct effects of Cry1Ac.     

Effects of stilbene optical brighteners on the insecticidal activity of Bacillus thuringiensis and a single nucleopolyhedrovirus on Helicoverpa armigera

The incorporation of certain stilbene optical brighteners into virus-based formulations has been demonstrated to increase viral pathogenicity (as indicated by reduced LD/LC₅₀ values) but their effect on Bacillus thuringiensis activity has been scarcely investigated. We determined the effect of nine optical brighteners on the insecticidal activity of B. thuringiensis ser. kurstaki HD-1 strain (Bt HD-1) on Helicoverpa armigera and also compared the effect of two optical brighteners on the insecticidal activity of Bt HD-1 and occlusion bodies (OBs) of a Spanish isolate of H. armigera single nucleocapsid nucleopolyhedrovirus (HearNPV-SP1). Blankophor CLE, Blankophor DRS, Blankophor ER, and Leucophor SAC significantly increased the pathogenicity of Bt HD-1. In contrast, Tinopal UNPA-GX, Tinopal CBS, Blankophor BA, Leucophor AP, and Leucophor UO had an adverse or no effect on its insecticidal activity. Mixtures of HearNPV-SP1 OBs with Tinopal UNPA-GX or Leucophor UO resulted in 31.4- and 11.4-fold increases in pathogenicity, respectively, at 1%, and 11.4- and 6.3-fold increases in pathogenicity, respectively, at 0.1%, compared to the OBs alone. However, none of these brighteners increased Bt HD-1 activity. These results appear consistent with the hypothesis that the enhancement of HearNPV-SP1 pathogenicity and the null or antagonistic effects observed in Bt HD-1 against H. armigera were due to optical brightener-mediated degradation of the peritrophic membrane, but additional systematic studies involving a broad range of brighteners and electron microscope observations are required to confirm this premise.