两种杀虫真菌制剂与低用量吡虫啉对温室粉虱的协同防效评价

在昆明市郊蔬菜基地4间大棚(5m×100m·间^-1)栽培的生菜上,用球孢白僵菌(Beauveriabassiana)和玫烟色拟青霉(Paecilomyces fumasonoseus)的纯孢子乳悬剂(有效含孢量10^10·ml^-1)及其与1％和3％(w／v)的吡虫啉10％WP的混配剂对温室粉虱(Trialeurodes vaporariorum)进行了协同药效试验,吡虫啉添加量仅相当于推荐用量的6．4％～9．5％和19．1％～28．6％,试验含6个菌剂处理、2个低用量吡虫啉处理和1个清水对照,各有3个小区(7m×5m·小区^-1)重复,随机区组排列,稀释1000倍的菌液(含孢量10^7·ml^-1)和吡虫啉液于生菜移栽后第11d首次喷雾,15d后喷第二次,首次用菌前调查初始粉虱密度,用菌后每隔5d调查活虫数和死虫数,从8月20日起历时30d,结果表明,连续2次用菌有效地控制了粉虱对当季大棚生菜的危害,各菌剂处理的最终相对防效和虫口减退率均达到95％以上,极显著地高于低用量吡虫啉处理,其中,玫烟色拟青霉制剂对粉虱的控制效果一般优于球孢白僵菌制剂,且与吡虫啉的添加量呈正相关,但是,各菌剂处理间控虫效果的差异主要发生在首次用菌后第5d和10d,此后差异逐渐缩小,至第二次用菌后第10d各菌剂处理间无显著差异,本试验结果表明,两种真菌的孢子乳悬剂均可用于温室粉虱的防治,添加微量吡虫啉可增强菌剂的防效。     

白僵菌孢子悬乳剂田间控蚜效果与常温货架寿命测定

将高纯度球孢白僵菌分生孢子粉兑入一种含悬浮稳定剂及紫外保护剂的矿物油中,配成含孢量为100亿/ml的孢子悬乳剂(纯菌剂),再添加3%的吡虫啉10%可湿剂而得菌药混配剂,于2003年5月在浙江余姚进行了防治蔬菜蚜虫的田间药效试验和农户示范。在两块夏熟白菜地中,纯菌剂和菌药混配剂均用1000倍稀释液(107个孢子/ml)常规喷雾2次,并设清水对照和低用量吡虫啉对照。结果表明,混配剂在两块菜地的相对防效分别达94.5%和86.2%,纯菌剂分别达86.4%和73.1%,而低用量吡虫啉处理的最高防效仅为50%左右。在入夏豇豆、甘蓝、白菜、萝卜及梨树上用菌药混配剂1000倍稀释液对多种蚜虫进行的农户示范试验中,一次性喷雾后5~10d内对菜蚜防效为48%~68%,尤对梨二叉蚜的防效高达99%。在对含有和不含添加剂的两配方孢子悬乳剂进行的常温避光18个月贮存中,活孢率在头7个月均稳定在95%左右且未受配方影响,第10个月活孢率仍有75%左右。而后,含添加剂配方的活孢率下降加速,至16个月时基本失活;而不含添加剂配方的活孢率在第16、17及18个月时还有57%、51%和42%。     

两种杀虫真菌制剂对茶小绿叶蝉的田间防效评价

于2002年盛夏在浙江遂昌一高山茶园对茶小绿叶蝉(Empoasca spp．)进行了真菌杀虫剂的田间药效试验。所用菌剂为球孢白僵菌(Beauveria bassiana)和玫烟色拟青霉(Paecilomyces fumosoroseus)的纯孢子悬乳剂及其与3％吡虫啉10％可湿剂的混配剂．各菌剂稀释500倍喷雾2次,间隔12d．结果表明。两种真菌的混配剂明显优于纯菌剂,其中球孢白僵菌混配剂的最高防效达83．4％,而玫烟色拟青霉的最高防效为71．3％．根据25d期间历次调查结果计算平均防效,球孢白僵菌混配剂达66．8％,玫烟色拟青霉混配剂为62．1％,含微量吡虫啉的矿物油为50．3％,球孢白僵菌和玫烟色拟青霉的纯菌剂分别为49．5％和19．0％,结合试验期间气候及田间种群结构特征,讨论了各处理问差异的来源及提高真菌杀虫剂控制茶小绿叶蝉效果的可能途径。     

Cuticular lipids and silverleaf whitefly stage affect conidial germination of Beauveria bassiana and Paecilomyces fumosoroseus

Beauveria bassiana and Paecilomyces fumosoroseus are generalist entomopathogenic fungi that infect the silverleaf whitefly (Bemisia argentifolii). We found second and third instar whiteflies to be the most susceptible larval stage to both fungi. Conidia of B. bassiana germinated most readily on the cuticle of second instars (54% germinated) and P. fumosoroseus germination was highest on third instar cuticle (45%). Fourth instars (the ultimate instar) had low susceptibility to these pathogens, and spore germination on the cuticle of fourth instars was very low for B. bassiana (7%) and intermediate for P. fumosoroseus (33%). Cuticular lipids were found to have toxic or inhibitory effects on conidia of B. bassiana and P. fumosoroseus when the spores were germinated on nutrient agar in the presence of the lipids. In the absence of added nutrients, P. fumosoroseus conidial germination increased in the presence of the lipids. To test if the inhibitory effects of the lipids were due solely to hydrophobicity (preventing water from coming into contact with the conidia) we tested the effects of synthetic long-chain wax esters. The synthetic wax esters inhibited germination of P. fumosoroseus to a degree that was similar to the effect of the cuticular lipid extracts, but the synthetic lipids did not have a significant effect on B. bassiana. Thus, the thick coating of long-chain wax esters produced by whitefly nymphs affect spore germination of fungal pathogens, but whether they play a significant role in defense against disease is not clear.     

常用化学杀螨剂对两种生防真菌孢子的相容性测定

用营养液萌发法和平板萌发法测定了10种常用化学杀螨剂与球孢白僵菌（Beauveria bassiana）和玫烟色拟青霉（Paecilomyces fumosoroseus）分生孢子的生物相容性.结果表明,营养液萌发法比平板法灵敏.以24 h内的孢子萌发率作为指标,供试杀螨剂的常用浓度及其5和10倍稀释液对活孢率的影响在不同杀螨剂间差异极显著,并在两种真菌间也存在差异.三唑锡、浏阳霉素、三氯杀螨醇和阿维菌素对生防真菌孢子的抑制力很强,不宜混用.速螨酮、克螨特、乐斯本、尼索朗及双甲脒等杀螨剂与真菌孢子的相容性优良,可与菌剂田间混用.将速螨酮、克螨特和乐斯本分别按3种浓度与白僵菌的孢子悬乳剂混配后在4 ℃恒温和室内变温下长期共贮,结果显示,3种杀螨剂对孢子活力的影响迥异,混配制剂在室内变温下的贮存期均未达到12个月,离商品化的要求差距较大.乐斯本的长期相容性相对较优,与菌剂低浓度混配可在常温下贮存6.5个月,中浓度和低浓度混配在4 ℃下可贮存12个月.     

Antagonism between Beauveria bassiana and imidacloprid when combined for Bemisia argentifolii (Homoptera: Aleyrodidae) control

Imidacloprid and the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin are both used to control the whitefly Bemisia argentifolii Bellows & Perring. We tested whether the two control strategies acted additively, synergistically, or antagonistically when combined for whitefly control. We found antagonism in that B. bassiana inhibited the effectiveness of imidacloprid. When B. bassiana was combined with imidacloprid, insect response was either less than or similar to (depending on B. bassiana rates) that when imidacloprid was used alone. Adding imidacloprid to B. bassiana treatments always increased mortality, but the increase was less than additive. Beauveria bassiana spore germination and colony formation were not inhibited by imidacloprid in vitro, and B. bassiana did not adsorb or degrade imidacloprid in a tank mix. We hypothesize that B. bassiana caused a behavioral response that reduced insect feeding and uptake of imidacloprid.     

Effects of exogenous nutrients on conidial germination and virulence against the silverleaf whitefly for two hyphomycetes

Exogenous protein and sugar sources were tested for their impact on conidial germination of two silverleaf whitefly (Bemisia argentifolii) pathogens: Beauveria bassiana and Paecilomyces fumosoroseus. In liquid culture, sugars stimulated only 5-27% germination of B. bassiana and < or =11% germination of P. fumosoroseus, whereas, yeast extract or peptone stimulated 95-100% germination. In the absence of additional nutrients, agar alone stimulated approximately 50% germination. Storing spores for different periods of time did not alter their general response to exogenous nutrients. When spores were germinated before being applied to third instar B. argentifolii, mortality was as much as 2.45 times greater and occurred more rapidly than that for fresh spores. For ungerminated conidia, the mean time to death from infection was 5.45 (SE = 0.16) and 4.74 (SE = 0.08) days for application rates of 37 and 144 conidia x mm(-2), respectively. When conidia were germinated before application, infection times dropped to 4.58 (SE = 0.16) and 4.45 (SE = 0.10) days, respectively. A likely explanation for the greater pathogenicity and virulence of germinated over ungerminated B. bassiana conidia is that only a fraction of the spores applied to whitefly nymphs actually germinate on the cuticle. For some specialized applications, such as greenhouse production systems, it may be beneficial to germinate spores immediately prior to application.     

Sprays of emulsifiable Beauveria bassiana formulation are ovicidal towards Tetranychus urticae (Acari: Tetranychidae) at various regimes of temperature and humidity

Aerial conidia of Beauveria bassiana in an emulsifiable formulation germinated by >95% after 24 h exposure to the regimes of 20, 25 and 30 degrees C with 51%, 74% and 95% RH. Ovicidal activities of the formulation towards two-spotted spider mite, Tetranychus urticae, were assayed at the concentrations of 0, 18, 160 and 693 conidia mm(-2) sprayed separately onto fava bean leaves including 39 (25-76) eggs per capita. All the sprayed eggs on the leaves were directly exposed to the different regimes for hatch after 24 h maintenance in covered Petri dishes. Generally, hatched proportions increased over post-spray days and decreased with the elevated fungal concentrations; no more eggs hatched from day 9 or 10 onwards. Based on the counts of the hatched/non-hatched eggs in the different regimes, the final egg mortalities were 15.0-40.4%, 48.9-66.6% and 62.9-87.5% at the low, medium and high concentrations, respectively, but only 5.6-11.3% in blank controls. The RH effect on the fungal action was significant at 20 and 25 degrees C but not at 30 degrees C whereas the effect of temperature was significant at 51% and 74% RH but not at 95% RH. Probit analysis of the egg mortalities versus the fungal sprays generated median lethal concentrations (LC(50)) of 65-320 conidia mm(-2) at all the regimes, and of only 65-78 conidia mm(-2) at 25-30 degrees C with 74-95% RH. The results highlight ovicidal activities of the emulsifiable formulation against the mite species at the tested regimes and its potential use in spider mite control.     

Effects of inoculation method on efficacy of wettable powder and oil dispersion formulations of Beauveria bassiana against Colorado potato beetle larvae under low-humidity conditions

The effects of inoculation method on efficacy of two formulations of Beauveria bassiana strain GHA against Colorado potato beetle larvae were investigated. Under dry greenhouse conditions, ca. 58% mortality was observed among second-instar larvae exposed directly to sprays of B. bassiana conidia, whereas mortality among larvae exposed to similarly treated foliage (either leaf dorsal or ventral surfaces) was <10%. Mortality was ca. 64% among larvae exposed to both direct sprays and foliar spray deposits. Equivalent rates of mortality were observed among larvae treated with a clay-based wettable powder versus an emulsifiable oil-based formulation of B. bassiana conidia; however, this was observed despite application of an approximately 40% greater dose of WP-formulated conidia, indicating greater efficacy of the emulsifiable oil formulation. These results suggest that, under dry conditions, potato beetle larvae do not readily acquire an effective dose of conidia from treated foliage and that development of improved application technologies to more effectively target the larvae may ultimately prove more beneficial than development of formulations with greater foliar persistence.     

新型球孢白僵菌孢子悬乳剂的高效杀蚜活性及其评价方法

用球孢白僵菌（Beauveria bassiana）SG8702的孢子悬乳剂与未剂型化孢子粉对桃蚜进行了杀蚜活性对比测定。孢子悬乳剂与孢子粉分别用水稀释成5个序列浓度,对甘蓝叶片上蚜虫进行相同时间的弥雾接种,前者孢子附着量分别为1.5～701.1个孢子/mm2 ,后者附着量分别为2.8～1005.9个孢子/mm2。蚜虫接种后置于23℃和12L：12D条件下饲养,定时观察8d。经时间—剂量—死亡率模拟分析,悬乳剂的剂量效应参数明显高于孢子粉,且杀蚜时间效应提前。用模型参数估计悬乳剂和孢子粉的LC50,接种后第4天分别为9.0和634个孢子/mm2,第7天为3.3和5.3个孢子/mm2。悬乳剂和孢子粉的LT50随叶面孢子附着量增大而下降,在100个孢子/mm2下为3.2d和4.5d。这表明孢子悬乳剂的杀蚜活性比未剂型化的孢子粉显著增强。作者讨论了杀虫微生物制剂评价的技术规范问题。     

Evaluation of synergistic interactions between the Colorado potato beetle (Coleoptera: Chrysomelidae) pathogen Beauveria bassiana and the insecticides, imidacloprid, and cyromazine

Laboratory studies investigated the interaction between the fungal entomopathogen Beauveria bassiana (Balsamo) Vuillemin and sublethal doses of the insecticides imidacloprid and cyromazine when applied to larvae of the Colorado potato beetle, Leptinotarsa decemlineata (Say). When second instars were fed potato leaf discs treated with sublethal doses of imidacloprid and a range of doses of B. bassiana, a synergistic action was demonstrated. Similar results were observed when larvae were sprayed directly with B. bassiana conidia and immediately fed leaf discs treated with imidacloprid. No synergistic interaction was detected when larvae were fed leaf discs treated with sublethal doses ofimidacloprid 24 h after application of B. bassiana conidia to larvae. However, a synergistic interaction was detected when larvae were fed leaf discs treated with imidacloprid and sprayed with B. bassiana conidia 24 h later. Although sublethal doses of both imidacloprid and the triazine insect growth regulator (IGR) cyromazine prolonged the duration of the second instar, only imidacloprid interacted with B. bassiana to produce a synergistic response in larval mortality. In leaf consumption studies, the highest dose of B. bassiana tested promoted feeding in inoculated second instars. Feeding was inhibited when larvae were fed foliage treated with sublethal doses of imidacloprid and significantly reduced when fed foliage treated with a sublethal dose of cyromazine. Starvation of larvae for 24 h immediately after B. bassiana treatment produced a similar result to the combined treatment of B. bassiana and imidacloprid and increased the level of mycosis when compared with B. bassiana controls. Imidacloprid treatment affected neither the rate of germination of B. bassiana conidia on the insect cuticle nor the rate at which conidia were removed from the integument after application. The statistical analysis used to detect synergism and the possible role of starvation-induced stress factors underlying the observed synergistic interactions are discussed.     

Ovicidal and Larvicidal Activity of Conidia and Blastospores of Paecilomyces fumosoroseus (Deuteromycotina: Hyphomycetes) Against Bemisia argentifolii (Homoptera: Aleyrodidae) with a Description of a Bioassay System Allowing Prolonged Survival of Control Insects

Fungi are the only effective entomopathogens of members of the Aleyrodidae and other homopterans because of the piercing and sucking feeding strategy of these insects. The laboratory assessment of the entomopathogenic activity of fungi often requires a prolonged period of observation. Leaf quality can be the limiting factor in bioassays of fungi against whiteflies that require longer observation periods or those that require conditions that are as close to natural ones as possible. A bioassay system is described that utilizes rooted cabbage leaves infested with the highly polyphagous whitefly, Bemisia argentifolii . Using this method, discriminating dosages of aerial conidia and blastospores of two isolates of Paecilomyces fumosoroseus (Pfr) were bioassayed against eggs and nymphs of B. argentifolii . Low, but significant, mortality (10-20%) of eggs was observed 14 days after exposure to 3.8 104 blastospores/cm2 for the Pfr 97 and European Biological Control Laboratory (EBCL) Pfr 42 isolates. Additionally, the majority of crawlers that had hatched from treated eggs died on the surface of the leaves. Exposure of early second-instar nymphs of B. argentifolii to 3.8 103 conidia or blastospores/cm2 of Pfr 97 resulted in mortalities of 27 and 77% respectively. Identical dosages of conidia and blastospores of the Pfr 42 isolate resulted in mortalities of 59 and 68% respectively. The bioassay method described enables the comparative evaluation of entomopathogenic fungi against whiteflies under diverse biotic and abiotic conditions.     

Potential of fungi as biocontrol agents of polyphagotarsonemus latus (Acari: Tarsonemidae)

Infection of broad mites, Polyphagotarsonemus latus, by conidia of Beauveria bassiana, Hirsutella thompsonii, and Paecilomyces fumosoroseus conidia was investigated in the laboratory under controlled temperature and moisture conditions. Infection of P. latus by the fungus (LC₅₀) was related positively to the 1.16 × 10⁶ B. bassiana conidia per ml, 2.39 × 10³ H. thompsonii conidia per ml, and 1.29 × 10⁵ P. fumosoroseus conidia per ml. Mortality caused by B. bassiana occurred the fastest among densities fluctuating between 65 and 125 mites per leaf. The pathogens B. bassiana and P. fumosoroseus, adjuvants (oil and molasses), and the acaricide ABG6364, a microbial insecticide containing the Beta-exotoxin of Bacillus thuringiensis were evaluated for efficacy against P. latus in a greenhouse test. The B. bassiana treated plants had the greatest and most persistent effect on percentage mortality of total broad mites present per leaf (88 %) followed by the acaricide ABG6364. Use of adjuvants (oil and molasses) did not increase infection of P. latus.     

Effect of combining imidacloprid and diatomaceous earth with Beauveria bassiana on mole cricket (Orthoptera: Gryllotalpidae) mortality

Sublethal doses of three orthopteran-derived strains of Beauveria bassiana (Balsamo) Vuillemin were topically applied to adult southern mole crickets, Scapteriscus borellii Giglio-Tos (Orthoptera: Gryllotalpidae), and tested in combination with substrate treatments of diatomaceous earth (DE) and imidacloprid. Crickets treated only with the high doses (10(8) conidia per cricket) of each of the three B. bassiana strains exhibited the shortest survival times as well as the highest percentage mortality at 28 d after treatment. However, these treatments did.not differ significantly from any of the diatomaceous earth combination treatments. Two of the strains tested, 5977 and 3622, exhibited synergistic interactions with DE, whereas the third strain, GHA, was not significant for synergy. Mortality caused by the combination treatment was still greater than the expected additive effect. DE abrades the insect cuticle and absorbs cuticular lipids, aiding the entry of germinating conidia into the mole cricket hemocoel. None of the three strains exhibited synergy when combined with imidacloprid, and mortality of all combination treatments was less than additive. For strain 5977, there was an antagonistic interaction with imidacloprid. It was difficult to obtain <30% mortality for imidacloprid only treatments, which was considered the upper limit for sublethal doses. The mean percentage mortality caused by imidacloprid was 37.5%, and this high percentage made it difficult for any combination treatment to cause significantly more mortality than the expected additive effect. These results clarify the interactions of other control products with B. bassiana and provide a basis for a reduced pesticide approach to mole cricket control.     

Combining azadirachtin and Paecilomyces fumosoroseus (Deuteromycotina: Hyphomycetes) to control Bemisia argentifolii (Homoptera: Aleyrodidae)

Both azadirachtin and Paecilomyces fumosoroseus (Wize) Brown & Smith have been used to control the whitefly Bemisia argentifolii Bellows & Perring, but with only moderate effectiveness. Azadirachtin is a botanical insecticide derived from the neem tree, and P. fumosoroseus is an entomopathogenic fungus. To test whether these two agents might be more effective for whitefly control if used together, different rates of each were combined in laboratory bioassays in factorial treatment. Both tank mixes and separate sprays were tested. Up to 90% nymphal mortality was obtained when both the fungus and azadirachtin were combined, a significant increase over the 70%, or less, mortality obtained when only one agent was used; however, the combined effects were less than additive. Azadirachtin had moderately inhibitory effects on growth and germination of P. firmosoroseus, which may explain this antagonism.     

Impact of two treatments of a formulation of Beauveria bassiana (Deuteromycota: Hyphomycetes) conidia on Varroa mites (Acari: Varroidae) and on honeybee (Hymenoptera: Apidae) colony health

Bee colonies in southern France were treated with conidia (asexual spores) from two strains of Beauveria bassiana, an entomopathogenic fungus. One strain was commercial (GHA) and the other had been isolated from Varroa mites in the region (Bb05002). Objectives were to evaluate treatment effect on colony weight, adult bee mass, capped brood, and on Varroa fall onto sticky boards. Treatments included conidia formulated with either carnauba or candelilla wax powder, candelilla wax powder alone, or control; in two treatment groups formulation was applied a second time after one week. Treatment did not affect colony health. Colonies treated twice with Bb05002 conidia and carnauba wax powder had significantly higher mite fall compared to colonies treated with blank candelilla wax powder. The proportion of fallen mites that were infected in both conidia treatments was higher than controls for 18 days after the second treatment. The number of fungal propagules on the bees themselves remained elevated for about 14 days after the second treatment. These results were compared to published results from previous experiments with regard to infection duration.     

Development of a Spray-drying Technique for Submerged Spores of Entomopathogenic Fungi

The stability of blastospores or submerged conidia of entomopathogenic fungi is one of the key problems associated with the practical use of fungal biopreparations. A spray-drying technique was developed which allows the drying of blastospores and/or submerged conidia, here called submerged spores, without a significant loss of viability and with only a slight delay in eY cacy. The method was tested successfully using the fungal species Metarhizium anisopliae , M. flavoviride, Beauveria bassiana and Paecilomyces fumosoroseus . For all experiments, a laboratory spray dryer was used. The optimum inlet and outlet temperatures were found to be 64 2oC and 48 2oC respectively. The best protective agent for submerged spores was skimmed milk powder at concentrations of 10 or 20%. The addition of sugars, especially 2.5% sugar-beet syrup, slightly improved the viability after spray-drying. Submerged spores of eight isolates of M. anisopliae, M. flavoviride, B. bassiana and P. fumosoroseus were suspended in 20% skimmed milk powder and 2.5% sugar-beet syrup, and spray-dried. Germination rates of about 90% were achieved, which were comparable to those of freshly produced submerged spores. Finally, the virulences of spray-dried submerged spores of M. anisopliae (Ma 97) and M. flavoviride (Mfl 5) were tested in bioassays using third- and fourth-instar nymphs of the African locust, Locusta migratoria . In contrast to M. flavoviride , there was no significant diVerence in the median lethal time between spray-dried and fresh submerged spores of M. anisopliae . The investigations demonstrated that spray-drying is possible to preserve sensitive submerged spores of entomopathogenic fungi.     

A Proposed Role for the Cuticular Fatty Amides of Liposcelis bostrychophila (Psocoptera: Liposcelidae) in Preventing Adhesion of Entomopathogenic Fungi with Dry-conidia

Maximum challenge exposure of Liposcelis bostrychophila to Beauveria bassiana, Paecilomyces fumosoroseus, Aspergillus parasiticus or Metarhizium anisopliae resulted in no more than 16% mortality. We investigated several of L. bostrychophila's cuticular lipids for possible contributions to its tolerance for entomopathogenic fungi. Saturated C14 and C16 fatty acids did not reduce the germination rates of B. bassiana or M. anisopliae conidia. Saturated C6 to C12 fatty acids that have not been identified in L. bostrychophila cuticular extracts significantly reduced germination, but the reduction was mitigated by the presence of stearamide. Cis-6-hexadecenal did not affect germination rates. Mycelial growth of either fungal species did not occur in the presence of caprylic acid, was reduced by the presence of lauric acid, and was not significantly affected by palmitic acid. Liposcelis bostrychophila is the only insect for which fatty acid amides have been identified as cuticular components. Stearamide, its major fatty amide, did not reduce germination of B. bassiana or M. anisopliae conidia or growth of their mycelia. Adhesion of conidia to stearamide preparations did not differ significantly from adhesion to the cuticle of L. bostrychophila. Pretreatment of a beetle known to be fungus-susceptible, larval Oryzaephilus surinamensis, with stearamide significantly decreased adhesion of B. bassiana or M. anisopliae conidia to their cuticles. This evidence indicates that cuticular fatty amides may contribute to L. bostrychophila's tolerance for entomopathogenic fungi by decreasing hydrophobicity and static charge, thereby reducing conidial adhesion.     

Germination of the entomopathogenic fungus Verticillium lecanii on scales of the glasshouse whitefly Trialeurodes vaporariorum

In a series of laboratory experiments, tobacco leaf discs infested with scales of the glasshouse whitefly Trialeurodes vaporariorum, were immersed in suspensions of conidia of three strains of the entomopathogenic fungus Verticillium lecanii. The germination of conidia on the insect was recorded and compared with the germination of conidia applied to Czapek—Dox Complete Medium. Laboratory bioassays were performed to record the mortality of whitefly scales exposed to conidia of all three fungal strains. The rate of germination of conidia on the whitefly scales was much reduced compared to that oh complete medium. Differences were recorded in the rate of germination of the three strains on complete medium, but not on the whitefly scales. There was no correlation between the pathogenicity of the strains to whitefly scales in laboratory bioassays and the rate of germination on the host.     

Protection of entomopathogenic conidia against chemical fungicides afforded by an oil-based formulation

We evaluated the protection afforded by an oil formulation against non-compatible fungicides in mixtures with conidia of the entomopathogenic fungi Metarhizium anisopliae (Ma) and Beauveria bassiana (Bb). Under laboratory conditions, viability of unformulated (aqueous suspensions) Ma conidia was harmed by recommended label doses of carbendazim (not tested for Bb), and both Ma and Bb conidia were affected by triadimefon. On the other hand, effect of fungicides was usually nil or minimal on conidia formulated as oil-containing suspensions (emulsifiable oil + water). Germination rates for unformulated and oil-formulated Ma conidia subjected to carbendazim were reduced by 77.3 and 12.1%, respectively, compared to their fungicide-free counterparts. Germination rates at 16 h post-inoculation for unformulated and oil-formulated Bb conidia subjected to triadimefon were reduced by 20.5 and 5.5%, respectively, compared to their fungicide-free counterparts. No differences were observed at 20 h post inoculation, indicating a fungistatic action of this compound on Bb conidia. Virulence of unformulated conidia amended with fungicides against third instar Diatraea saccharalis larvae was negatively affected compared to their formulated counterparts. These results suggest that oil-formulated conidia can be effectively protected from damage caused by chemicals, which could have applications in tank mixing or alternate applications with shared spraying equipment, being especially relevant for IPM programs in which mycopesticides and chemicals are simultaneously sprayed.