Thuringiensis Treatments Research Articles

Effectiveness of bio-insecticides and mass trapping based on population fluctuations for controlling Tuta absoluta under greenhouse conditions in Albania

Tuta absoluta is a major pest of tomato crops that causes high yield losses. Cultivated areas in Albania have reported high levels of infestations despite the application of control measures. The present study aims to describe population fluctuations of T. absoluta during tomato cultivation for three consecutive years in the winter–summer growing season under greenhouse conditions. Delta traps baited with pheromones were used to monitor the population fluctuations, and the appropriate treatment period was determined. The effectiveness of mass trapping, Indoxacarb and Bacillus thuringiensis treatments at maintaining the pest populations below the economic injury level was tested. Even under greenhouse conditions, the population levels were high during spring and peaked in summer. The infestation rate increased by up to 85% on leaves and fruit. The application of Bt, Indoxacarb, and mass trapping reduced the infestation rate on fruits by approximately 29%, 43% and 52%, respectively, which represented significant differences in effectiveness. In conclusion, the results indicate that performing an intervention that includes combined methods in the proper period might reduce the infestation rate from 80-95%.

Toxicological, biochemical and ultrastructural alterations induced by chlorfluazuron and Bacillus thuringiensis (diple d.f.) on Pectinophora gossypiella (saunders) larvae

Effects of the lethal concentrations of Chlorfluazuron and Bacillus thuringiensis (Diple D.f.) against Pectinophora gossypiella (Saund.) larvae treated as neonate were studied recently. The obtained results indicated that, Chlorfluazuron treatment showed great toxicity compared to B. thuringiensis. The biochemical response of 10-days old larvae was studied by the evaluation of the total soluble protein, total lipids, and transaminases activities: Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST), and the carbohydrate hydrolyzing enzymes (trehalas, invertase and amylase). The total protein content decreased to 43.26mg/dl and 26.24mg/dl for chlorfluazuron and Bacillus thuringiensis treatments, respectively compared to untreated control (100.1 mg/dl). In contrast, the total lipid levels were increased for the same compounds, recording values: 132.73 and 87.87 mg/dl, respectively, compared to control (36.51 mg/dl). Moreover, a high increase in the activity of all Carbohydrate hydrolyzing enzymes induced by both treatments compared to control. Activity of AST enzyme was declined to 5.44 and 12.66 mg glucose released/gm body weight/min for Chlorfluazuron and B. thuringiensis, respectively, compared to control (14.62 mg glucose released/gm body weight/min). In contrary, a great increase in the ALT activity was recorded with values: 129.49 and 159.61 mg/dl for the same compounds, respectively compared to untreated check (85.36 mg/dl). Newly hatched larvae of P. gossypiella treated with Chlorfluazuron as one of chitin biosynthesis inhibitors showed some histopathological alternations of the cuticle layers. The exo-cuticle became thicker with variable staining affinity, while the endo-cuticle became thin and faintly stains. The epidermal layer was formed mostly with irregularly distributed cubical cells varied in height and staining affinity. Furthermore, histopathological alternations, of midgut were obtained for Bt treated larvae of P. gossypiella representing extensive damage of the epithelial columnar cells with increased cytoplasm vacuolation at the Bt toxins. In addition, ultrastructure studies conjugated with observations for both Chlorfluazuron and Bt treated and untreated PBW larvae were massive supported by transmission electron microscopy (TEM).

Efficacy of an alphabaculovirus-based biological insecticide for control of Chrysodeixis chalcites (Lepidoptera: Noctuidae) on tomato and banana crops.

Chrysodeixis chalcites (Esper) is a major pest of tomato in Mediterranean countries and attacks banana in the Canary Islands (Spain). The efficacy of Chrysodeixis chalcites single nucleopolyhedrovirus (ChchSNPV-TF1) was evaluated in plant growth chambers and greenhouse trials performed on tomato and banana plants respectively. Treatments were applied using a compressed air sprayer. Mean (± SE) lethal infection varied from 77 ± 10% to 94 ± 3% in second-instar larvae fed for 2 days on tomato plants treated with 2 × 10(6) to 5 × 10(7) virus occlusion bodies (OBs) L(-1) , increasing to ∼100% infection after 7 days. Mortality of larvae collected from banana at different intervals post-application varied from 54 ± 10% to 96 ± 4% in treatments involving 1 × 10(8) -1 × 10(9) OBs L(-1) , whereas indoxacarb (Steward 30% WG) and Bacillus thuringiensis var. kurstaki (Biobit 16% WP) treatments produced between 22 ± 6% and 32 ± 5% pest mortality. All treatments significantly reduced plant defoliation compared with untreated controls. Application of 1 × 10(9) OBs L(-1) was 3-4-fold more effective than chemical or B. thuringiensis treatments. Larvae acquired lethal infection more rapidly when feeding on tomato than banana plants, but this difference disappeared following >60 min of feeding. This information should prove useful in the registration of ChchSNPV-TF1 as a bioinsecticide in the Canary Islands and Europe.

Effects of Bacillus thuringiensis var. kurstaki and Spinosad on three larval stages 1st, 2nd and 3rd of tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) in laboratory conditions

The tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is considered to be one of the most devastating pests affecting the tomato crops, where crop losses range from 60 to 100%. In this research, two bio-insecticides, Bacillus thuringiensis and Spinosad, were evaluated for their efficacy in the control of T. absoluta, on tomato plant in a laboratory conditions. The LC25 and LC50 values of B. thuringiensis and Spinosad were estimated on larval instars 1st, 2nd and 3rd. Furthermore, LC50 values for B. thuringiensis treatments on three larval stages were 2386.755, 2109.978 and 2757.651 ppm and for Spinosad 1283.915, 1339.862 and 2253.188 ppm, respectively, and LC25 values of B. thuringiensis and Spinosad treatments on three larval stages were 985.440, 1368.202 and 1914.574 ppm and 436.268, 643.788 and 1526.941 ppm, respectively. After determining the LC50 and LC25 values of both agents, to evaluate the combined effects of bacterium and Spinosad, an experiment was conducted in the form of completely randomised design with four treatments including LC50 (Bt), LC50 (Sp), LC25 (Bt) plus LC25 (Sp) and control. Statistical analysis of the results showed that percentage mortality combination of two biological agents treatment on three larval stages 1st, 2nd and 3rd of T. absoluta compared with control, Spinosad and B.t alone treatments have significant differences (P < 0.05). Our results demonstrated that Spinosad was more effective in the control of T. absoluta lethality, than the B. thuringiensis treatment. The LC25 and LC50 values of B. thuringiensis and Spinosad were demonstrated on three larval stages in which first instar larvae was the most susceptible. The results showed that the combination of B. thuringiensis and Spinosad have good additive effect when compared with applied individually treatments. We recommend the combination of two biological agents to control this pest. Our current study indicated that the concept of integrating bio-insecticides, B. thuringiensis and Spinosad, with other control tactics, especially with environmentally acceptable agents has opened further opportunities for their uses as biological control agents of insect pest.

Responses of nematode‐community structure in turfgrass soil to microbial filtrates from municipal–solid waste compost

AbstractActinomycetes,Bacillus subtilis,andBacillus thuringiensiswere isolated from municipal–solid waste (MSW) compost, and different microbial liquid filtrates (MLF) were prepared. Sterile culture media with no microbes were used as their controls. The effects of MLF on soil nematode communities were examined in pot‐grownFestuca arundinaceaSchreb. Fifteen genera of nematodes in background soil were identified, of whichHelicotylenchusandRotylenchuswere dominant. The inoculation of MLF strongly affected the abundance and community structure of soil nematodes. Compared with their controls, lower total nematode numbers following MLF incorporation were found. Actinomycetes inoculation changed community structure of soil nematodes, transforming the dominant genera fromHelicotylenchusandRotylenchusintoCephalobus, Chiloplacus, andAphelenchus.Actinomycetes incorporation resulted in a significant decrease of plant‐parasitic nematodes relative to control pots. Only plant‐parasitic and omnivorous‐predatory nematodes were found in treatments followingB. subtilisinoculation, andHelicotylenchus, Rotylenchuswere dominant genera with relative abundance of 76.2% and 14.3%, respectively. Although the dominant genera were stillHelicotylenchusandRotylenchus, B. thuringiensisinoculation led to a marked decrease in populations of plant‐parasitic nematodes and an increase in populations of fungivorous and bacterivorous nematodes relative to control. Shannon's diversity index (H′), evenness index (J′), richness index (SR), and Wasilewska index (WI) in pots treated with actinomycetes andB. thuringiensisfiltrates were significantly higher than those of their controls, whereas significant lower dominance index (λ) in actinomycetes andB. thuringiensistreatments was observed than their controls. Plant growth was improved in the treatments inoculated with three microbes. The findings highlight that actinomycetes can most effectively suppress plant‐parasitic nematodes, increase community diversity, evenness, and richness, thus improving soil environment for turf growth.

The combined use of Bacillus thuringiensis and Nesidiocoris tenuis against the tomato borer Tuta absoluta

Since Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) was first detected at the end of 2006 in the Mediterranean Basin, several endemic natural enemies have been reported to prey on this exotic pest. The predator Nesidiocoris tenuis Reuter (Hemiptera: Miridae) can regulate T. absoluta populations, because it is able to prey efficiently on T. absoluta eggs. Furthermore, previous studies have demonstrated that first-instar larvae of T. absoluta are highly susceptible to Bacillus thuringiensis (Bt) treatments. In this work, we tested the combination of both approaches under greenhouse conditions. B. thuringiensis formulations were sprayed weekly for two months, three months or throughout the growing cycle, and in all cases, one N. tenuis per plant was also released. Control plants were completely destroyed by the infestation levels reached by T. absoluta. In contrast, all treatments based on B. thuringiensis treatments and releases of N. tenuis reduced leaf damage by more than 97% when compared to the untreated control, with no significant differences among them. Furthermore, yield in the control plants was significantly reduced when compared with all Bt–N. tenuis treatments. Our results demonstrate that when B. thuringiensis treatments are applied immediately after the initial detection of T. absoluta on plants, they do not interfere with N. tenuis establishment in the crop because T. absoluta eggs are available. According to our data, treatments with B. thuringiensis later in the growing season would no longer be necessary because mirids alone would control the pest.

Efficacy of Bacillus thuringiensis (Berliner) in controlling the tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

The tomato borer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is considered to be one of the most devastating pests affecting tomato crops in South America, where crop losses range from 60 to 100%. After its detection in the Spanish tomato-growing area at the end of 2006, it spread quickly to other European and northern African countries. Currently, T. absoluta management in these countries is mainly based on chemical treatments. Nonetheless, special emphasis is being placed on implementing environmentally safe strategies. Commercial formulates based on Bacillus thuringiensis may be a good alternative, as they have been used to control other insect pests successfully. The laboratory, greenhouse, and open-field experiments presented in this work are evidence that B. thuringiensis is highly efficient in controlling T. absoluta. First instar larvae were the most susceptible, while susceptibility was lower in second and third instar larvae. Our results have shown that the impact of T. absoluta can be greatly reduced by spraying only B. thuringiensis-based formulates, with no need for chemical insecticides. Furthermore, the integration of this technology with other biological control methods focused on T. absoluta eggs, such as the use of mirid predators or parasitoids, could reduce the number of B. thuringiensis treatments and the use of chemicals, with the consequent reduction of residues on fruits.

Combination of Bacillus thuringiensis and Habrobracon hebetor for the biological control of Plodia interpunctella

In this paper, we review our work on biological control of Plodia interpunctella (Hubner) (Zhang et al., 1995) in our laboratory over the years. We isolated, screened and evaluated Bacillus thuringiensis strains collected from warehouses against P. interpunctella and determined the lethal concentration for 50% of the population (LC 50 ) of highly toxic isolates and compositions of crystal proteins and the genotypes of these isolates; evaluated the role of host-instar and refuge on the parasitization behavior of Habrobracon hebetor Say (Hymenoptera: Braconidae); investigated the effect of combining B. thuringiensis with H. hebetor for management of P. interpunctella infestation and assessed the influence of B. thuringiensis on H. hebetor during this combination treatment. The results showed that three strains of B. thuringiensis (IMM130, IMM368 and IMM408) were highly toxic to P. interpunctella among 122 B. thuringiensis isolates obtained from 413 field samples (Zhang et al., 2000a); Isolate IMM408 with LC50 1.24 μg/g diet, was most potent (Akinkurolere et al., 2007). It belongs to H 7 serotype and contains ~135kDa crystal proteins and cry1Ab9, cry1Ca1, cry1Da1 and cry2 genotypes (Zhang et al., 2000b). It was observed that H. hebetor could parasitize all larval stages of P. interpunctella , but significantly fewer first and second instars were parasitized under choice and no-choice conditions (Akinkurolere et al., 2009a). Parasitized fourth instars were more profitable to H. hebetor irrespective of refuge or choice factors, as significantly more adult parasitoids emerged from host instars. Therefore, H. hebetor females consistently showed high preference for late instars of P. interpunctella when they were offered a choice between early and late host instars. Refuge significantly hindered H. hebetor from locating the early instars, but not the late instars (Akinkurolere et al., 2009a). Bacillus thuringiensis -parasitoid combination treatment significantly evoked more P. interpunctella mortality than either treatments ( B. thuringiensis or parasitoid) when used singly (Akinkurolere et al., 2009b). Bacillus thuringiensis or H. hebetor alone caused 42% and 35% P. interpunctella larval mortality, respectively. The B. thuringiensis -parasitoid combination treatment significantly evoked more P. interpunctella mortality (86%) than other single treatments. Progeny development of parasitoid wasp was dependent upon its susceptibility to B. thuringiensis contaminated hosts. H. hebetor was able to successfully complete its development on the hosts although, fewer wasps emerged from B. thuringiensis -parasitoid combined treatment than in none B. thuringiensis treatments (Akinkurolere et al., 2009b). H. hebetor showed positive response to acetone and hexane extracts from frass and larvae of P. interpunctella , and the active compounds are mostly hydrocarbons (unpublished data). Keywords : Bacillus thuringiensis, Habrobracon hebetor, Plodia interpunctella , Pest management, Parasitoid.

농약 사용 저감화를 위한 환경 친화적인 파밤나방(Spodoptera exigua)의 방제

파밭에서 발생하는 파밤나방을 친환경적으로 방제하기 위하여 농약저감화 방법중의 하나인 교호방제법을 검토하였다. 파밤나방에 등록되어 있는 살충제 가운데서 시판중인 25개 품목을 구입하여 실내실험에서 약효가 우수한 9종을 선발하여 비닐하우스내의 소포장 시험을 통해 화학 살충제 4종을 선발하였으며, 본 실험실에서 선발한 3종의 BT제의 교호처리를 포장시험에 적용하였다. 처리방법은 같은 약제를 1주일 간격으로 3회 처리한 단일처리와 BT제를 포함하여 서로 다른 약제를 1회씩 3종류를 1주일 간격으로 교호처리 하였다. 그 결과 화학농약과 미생물 농약을 처리한 Indoxacarb WP - Chlorfluazuron EC - B.t. var. kurstaki CAB141과 Indoxacarb WP - Methoxyfenozide + spinosad SC - Chlorfluazuron EC - B.t. var. aizawai CAB109, B.t. var. kurstaki CAB141의 3합이 평균 살충율 78%이상을 나타냈다. 따라서 단일처리의 방제가보다 10% 이상 높았으며 평균피해감소율 43% 이상에 달하여 단일처리한 조합보다 10% 높은 효과를 나타났다. 이와 같은 결과는, 동일한 약제 살포에 의한 저항성발달을 최소화하고, 천연물이나 미생물을 이용한 생물농약을 교호처리함으로서 화학농약의 살포 횟수를 감소시켜 친환경적으로 파밤나방을 방제할 수 있을 것으로 사료된다. For the environment-friendly control of beet armyworm, Spodoptera exigua, in spring onion fields, we have examined an alternative application method. Twenty-five insecticides registered for spring onion were tested for control effect against the beet armyworm in the laboratory, then the best 9 chemical and a single biological insecticides were selected and compared with 2 new isolates of Bacillus thuringiensis in a polyvinyl house. After that, 4 chemical and 3 B. thuringiensis treatments were used in the field for the control of beet armyworm in the spring onion. Two application methods are used: one is triple treatments with the same chemical and the other is alternative application with different chemicals and B. thuringiensis for 7 days intervals. Indoxacarb WP - chlorfluazuron EC - B.t. var. kurstaki CAB141 and indoxacarb WP - methoxyfenozide + spinosad SC - Chlorfluazuron EC - B.t. var. aizawai CAB109, B.t. var. kurstaki CAB141 showed greater than 78% mortality of beet armyworm larvae and greater than 43% damage decrease in spring onions infested by beet armyworm. These results showed that alternative applications had higher control effect than any other applications. It was suggested that alternative applications with microbial biological agents such as B. thuringiensis might minimize the development of insecticide resistance and might be used as the environment-friendly control of the beet armyworm.

Bacillus thuringiensis as a pest management tool for control of the squash vine borer, Melittia cucurbitae (Lepidoptera: Sesiidae) in South Carolina

A commercial formulation of Bacillus thuringiensis (Mattch) was evaluated under field conditions at Clemson, South Carolina, USA for control of the squash vine borer, Melittia cucurb-itae (Lepidoptera: Sesiidae), on yellow crookneck squash, Cucurbita pepo in 1997, 1998 and 1999. Two application methods were used: injection of the B. thuringiensis formulation directly into the main stem and spray foliage application. These were compared to an insecticide standard, endosulfan (Phaser), and an untreated check. In most cases, B. thuring-iensis treated plots had significantly less damage than untreated plots and generally gave control equal to that of the insecticide standard, endosulfan. In a trial 1998, the two methods were directly compared, the foliage sprays gave control equal to or better than the injection treatments. Even during the heaviest pest pressure (second trial, 1998), the B. thuringien-sis treatments were as effective as endosulfan in reducing the squash vine borer damage.

Strategy for orchard use of Bacillus thuringiensis while minimizing impact on Choristoneura rosaceana parasitoids

AbstractTrials were conducted to study how spring Bacillus thuringiensis Berliner subsp. kurstaki treatments on apple may be timed to maximize the survival of parasitoids of the obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), found in the southern interior of British Columbia, Canada. Orchard collections verified that second through fourth instar obliquebanded leafrollers were found in varying proportions from pink through the petal fall stage of apple development when spring B. thuringiensis treatments are applied vs. lepidopteran pests. Laboratory‐reared second through fourth instar obliquebanded leafrollers, unparasitized and parasitized by one of three native parasitoid species, were fed untreated apple leaves or leaves treated with B. thuringiensis. The highest mortality of unparasitized obliquebanded leafrollers occurred when fourth instars were exposed to B. thuringiensis‐treated leaves; B. thuringiensis‐induced mortality in the unparasitized second and third instars was less than 50%. The consumption of B. thuringiensis‐treated leaves by host larvae significantly increased the percentage of dead host larvae in all parasitized and unparasitized treatments. However, because of the low susceptibility of this leafroller species to B. thuringiensis, relatively high numbers (38–43%) of three obliquebanded leafroller parasitoid species were able to survive the consumption of B. thuringiensis by second and third instar host larvae. Fourth instar obliquebanded leafrollers were found at the full bloom and petal fall stage of apple development in the orchard, at which time B. thuringiensis treatments are recommended for optimal leafroller control. The highest parasitoid mortality due to host mortality was recorded in Apophua simplicipes Cresson (Hymenoptera: Ichneumonidae) and Macrocentrus linearis (Nees) (Hymenoptera: Braconidae), when the hosts were treated as fourth instars. Both of these parasitoids emerge from fifth and sixth instar obliquebanded leafrollers. Bacillus thuringiensis did not have as negative an impact on Apanteles polychrosidis Viereck (Hymenoptera: Braconidae), which emerges when the host is in the fourth instar. When leafroller mortality and parasitism were combined, the B. thuringiensis treatment did not significantly increase host elimination above that of parasitism alone, except for larvae parasitized by A. simplicipes that were in the fourth instar. The consumption of B. thuringiensis by unparasitized larvae was shown to slow larval development.

The use of biopesticides to control insect pests of papaya (&lt;i&gt;Carica papaya&lt;/i&gt;)

Laboratory and field experiments were carried out between June 1997 and January 1999 at Paradise farm near Nsawam in the Eastern Region of Ghana to evaluate the effectiveness of neem seed extract and Bacillus thuringiensis (Kurtaski) for controlling insect pests of papaya Carica papaya. Methanol and aqueous neem seed extracts were tested at the following concentrations 0, 50, 75 and 100 g/L. Bacillus thuringiensis was applied at the rate of 0, 0.2, 0.4, 0.6, 0.8 and 1.0 g/L. Percentage mortality and leaf damage caused by insect pests were determined in the laboratory and in the field. The population of the major insect pests, which visited the plants, was also determined. The nature of the damage caused by the insect pests found on the various developmental stages of the plants was assessed by critical visual observation. The major insect pests recorded on papaya at Paradise farm were the variegated grasshopper, Zonocerus variegates (L), mealybugs, Planococcus sp and Mexican bean beetle, Epilachna sp. It was observed in the field that the populations of these insect pests were significantly reduced by the higher doses of methanol and aqueous neem extracts as well as the Bacillus thuringiensis treatments. The neem seed extracts and Bacillus thuringiensis preparations had significant effect on the mortality of adult and nymphs of Z. variegatus in the laboratory and in the field compared to the control. The rate of mortality increased as the dose increases. Hundred grams per litre of methanol and aqueous neem seed extract and 1 g of B. thuringiensis per litre of water were the most effective and induced the highest mortality of adults and nymphs of Z. variegatus compared to the other treatments. The least percentage leaf damage was recorded on papaya plants treated with the highest dosage of neem extract and B. thuringiensis. (Journal of the Ghana Science Association: 2001 3(3): 117-125)

Bollworm (Lepidoptera: Noctuidae) Development and Movement on Bacillus thuringiensis-treated Cotton Leaves

Larval mortality, survivorship and movement of the bollworm, Helicoverpa zea (Boddie), on and away from Bacillus thuringiensis-treated cotton leaves were investigated in the laboratory. Bacillus thuringiensis (Costar®, Novartis Crop Protection, Inc; Greensboro, NC) was applied to the upper surface of cotton leaves via a spray table in five concentrations, i.e., 0.0 (control), 0.14, 0.29, 0.58, and 1.15 kg/ha. Three-day-old H. zea larvae were released on treated leaves, kept at 30°C, and transferred to artificial diet after 12, 24, and 48 h. Significantly higher numbers of larvae were found on the lower than upper leaf surface after all three transfer times, but the numbers surviving in all treatments were similar to the control. Larval movement from the leaf to cup surface was significantly higher in B. thuringiensis-treated leaves than in the control. The mortality of larvae that were transferred from leaves to diet at 7 d after treatment was significantly higher in all treatments than in the control and highest at the highest rates (0.58 and 1.15 kg/ha). Data on survival of larvae at different locations suggest that for the first 24 h, the increase in the percentage of larvae on the inner cup surface in B. thuringiensis treatments was not due to larvae that had consumed a lethal dose, but an attempt to avoid the B. thuringiensis on the upper leaf surface. Highest larval weight was recorded in the control for all transfer times. The length of the larval period increased with the B. thuringiensis rate at the 12-h transfer. The pupal weight was reduced at the highest B. thuringiensis rates at the 48-h transfer.

Field evaluation of Helicoverpa armigera nucleopolyhedrovirus formulations for control of the chickpea pod-borer, H. armigera (Hubn.), on chickpea ( Cicer arietinum var. Shoba) in southern India

Treatment of chickpea with HearNPV 1 Nomenclature is that given in Index Virum of the International Committee on the Taxanomy of Viruses (http://life.anu.edu.au/viruses/Ictv/fs_bacul.htm#Species1). although the name HaNPV is commonly used. 1 at 1.5×10 12 p.i.b. per ha was as effective, or better at controlling Helicoverpa armigera larvae, and increasing yield relative to control, than either a standard chemical insecticide, endosulfan, or Bacillus thuringiensis, in two successive years. Currently high virus production costs make the viral treatments uncompetitive compared with the chemical treatment, but more economic than B. thuringiensis treatments. Several formulations of virus were tested, including an emulsifiable concentrate, a ULV suspension and a microencapsulated preparation, but none were consistently more effective than a filtered but un-purified aqueous suspension of HearNPV. Yield and pod damage correlated with mid and late season number of medium-sized and large larvae. Persistence of all treatments, including endosulfan and B. thuringiensis was short, and six treatments were necessary to provide adequate crop protection. HearNPV was the slowest-acting of the three control agents, with average survival times (AST) of 5.5 days, compared with 3.2 and 4.3 days for larvae fed leaves treated with B. thuringiensis and endosulfan, respectively. Marginal rates of return were not very sensitive to product costs. Further research should focus on formulations designed to prolong virus persistence, and socio-economic studies to design the optimal implementation route for this technology. Supply, cost and quality control issues need to be addressed.

Effectiveness of Diflubenzuron and Bacillus thuringiensis Against Gypsy Moth Populations

Abstract Aerial applications of Bacillus thuringiensis Berliner subsp. kurstaki (74.1 billion international units/ha per application; single and double applications), diflubenzuron [69 g (ai)/ha], and no treatment were evaluated. Treatment effects were estimated from frass collections, defoliation, counts of pupae under burlap, and egg-mass counts. Estimates of larval density in the canopy 20 days after treatment ranged from 318.3 to 55.5 larvae per m² in the control- and diflubenzuron-treated plots, respectively. Larval density was reduced in all treatments, and was lowest in the plots treated with diflubenzuron and two applications of B. thuringiensis. Population density rapidly declined in the control plots, and by June 20, when larvae were predominantly in the fifth and sixth instars, no significant differences in larval density were detected among the treatments. Significantly less defoliation occurred to oak trees in the treated plots, but no differences were detected among the spray treatments. Counts of pupae under burlap, postseason egg-mass counts, and percent reduction in egg-mass density did not differ significantly among treatments or versus controls. These results suggest that diflubenzuron and double B. thuringiensis treatments caused higher levels of larval mortality than occurred with a single B. thuringiensis application, but that with a naturally declining gypsy moth population the final levels of damage were the same under all treatments. North. J. Appl. 14(3):135-140.

Bacillus thuringiensis Alone and in Mixtures with Chemical Insecticides against Heliothines and Effects on Predator Densities in Cotton

Tests were conducted in a cotton field in 1994 and 1995 to evaluate the efficacy of Bacillus thuringiensis var. kurstaki Berliner alone and in mixtures with thiodicarb and cyhalothrin against heliothines and to evaluate the survival of predators on cotton. The heliothine population treated in both years was almost entirely Helicoverpa zea (Boddie) (&amp;gt;97%). In both years, B. thuringiensis alone failed to reduce larval populations over the control plots (P &amp;gt; 0.05). Larval densities were similarly reduced in thiodicarb and thiodicarb-B. thuringiensis treatments. Treatments that contained cyhalothrin and/or profenofos provided the best control. Bacillus thuringiensis treatment of plots did not have any delayed effects on H. zea such as reductions in developmental rates or delayed mortality beyond 3 days after application. In addition, heliothine egg mortality in the 1994 collection 3 days after application did not differ significantly among treatments. Predator density in the B. thuringiensis alone treatment was similar to the untreated control. All treatments that contained conventional chemical insecticides, including thiodicarb at the ovicidal rate, reduced predator densities to low numbers. These data indicate that B. thuringiensis did not provide control of H. zea in cotton fields and did not improve control of H. zea when used in mixtures with an ovicide or larvacide. Therefore, caution should be urged in recommending B. thuringiensis when the heliothine species composition is skewed toward H. zea. Furthermore, when B. thuringiensis was used in mixtures with chemical insecticides, there was no conservation of arthropod predators relative to use of traditional chemical insecticide treatments.

Field Assessment of Trichogramma brassicae (Hymenoptera: Trichogrammatidae) and Bacillus thuringiensis for Control of Ostrinia nubilalis (Lepidoptera: Pyralidae) in Sweet Corn

Field studies conducted in 1992 and 1993 tested the efficacy of using commercially available Trichogramma brassicae Bezdenko and Bacillus thuringiensis to control Ostrinia nubilalis (Hubner) in sweet corn. Shipped T. brassicae displayed good biotic fitness (emergence rates, sex ratios, longevity, and fecundity) in 1992 and 1993, but release rates and emergence profiles of the parasitoids differed in the 2 yr. In 1992, a total of 429,120 female parasitoids per hectare was released over 10 release dates. In 1993, a total of 163,680 female parasitoids per hectare was released over 10 release dates. Parasitoids dramatically affected the fate of O. nubilalis egg masses in both 1992 and 1993. O. nubilalis egg mass survival decreased by at least 45% in T. brassicae plots in both years. When all insect damage was considered, field releases of T. brassicae significantly improved ear quality in 1993 and in plots augmented with O. nubilalis egg masses in 1992. When an effect caused by T. brassicae was observed, the increase in percentage clear ears ranged from 9 to 17%. There was no significant interaction between B. thuringiensis and T. brassicae treatments in 1992 and 1993. B. thuringiensis treatments alone had a significant impact on ear quality only when high O. nubilalis populations were present in 1992. The integration of B. thuringiensis and T. brassicae did not result in additional insect control.

Integration of Host Plant Resistance and Bacillus thuringiensis Insecticides in the Management of Lepidopterous Pests of Celery

J. Econ. Entomol. 88(6) : 1787-1794 (1995) Experiments were conducted to assess the combined effects of host plant resistance in Apium graveolens and Bacillus thuringiensis insecticides on damage caused by the beet armyworm, Spodoptera exigua (Hubner), and the cabbage looper, Trichoplusia ni (Hubner), under field conditions. The celeriac, A. graveolens variety rapaceum, cultivar 'PI 357333' had significantly less feeding damage than another celeriac, cultivar, 'PI 223333'. Celeriac cultivars had fewer petioles with lepidopteran feeding damage compared with celery, A. graveolens variety dulce, cultivars. When B. thuringiensis treatments significantly reduced feeding damage, the combined effect of host plant resistance and B. thuringiensis was additive, suggesting that these are compatible pest management tactics.

On-Farm Efficacy of Aerially Applied Bacillus thuringiensis for European Corn Borer (Lepidoptera: Pyralidae) and Corn Earworm (Lepidoptera: Noctuidae) Control in Sweet Corn

Aerial applications of Bacillus thuringiensis subsp. kurstaki and tank-mixes with synthetic insecticides were evaluated for control of Ostrinia nubilalis (Hubner) and Helicoverpa erpa zea (Boddie) in Minnesota sweet com during 1990-1992. In addition to natural infestations, sweet com was manually infested with first-instar O. nubilalis to investigate optimum timing of applications relative to larval hatch. Efficacy of B. thuringiensis was significantly enhanced when applied 2 d before larval hatch, compared with 2 d after hatch. Treatments with low-rate permethrin + B. thuringiensis or full-rate permethrin followed by B. thuringiensis provided control of O. nubilalis equal to full rates of permethrin or micro-encapsulated methyl parathion. Of the B. thuringiensis treatments, only the tank-mix of low-rate permethrin + Dipel ES significantly reduced H. zea larval infestations and yielded more marketable ears than the untreated check. Based on active ingredient per hectare, low-rate permethrin + B. thuringiensis reduced synthetic insecticide use 66%, compared with full-rate permethrin, or 92% compared with full-rate methyl parathion. Using a four-application program, permethrin followed by three B. thuringiensis applications reduced synthetic insecticide use 75'% compared With full-rate permethrin, or 94% compared with full-rate methyl parathion. Disadvantages of the use of B. thuringiensis for late-season insect management in sweet corn include application timing, incidence of H. zea, and potential for increased risk of larval contaminants in marketable product.

Control of Lepidoptera on Cole Crops, 1993

Abstract ‘Vates’ collards were planted at the Muck Crops Branch, Celeryville, OH, on 17 Jun. The experimental plots were 3 rows wide on 20 inch centers, 15 ft long and separated by 3 ft alleys. Each treatment was replicated four times in a randomized complete block design. A single application was made 22 Jul using a tractor-mounted boom sprayer delivering 50 gal/acre at 50 psi with three D-4 hollow cone nozzles/row. Activator 90 was added at 2 pts/100 gal solution to all Bacillus thuringiensis treatments. Latron B-1956 was added to both RH5992 and RH2485 at 0.06% vol/vol solution. Five plants per plot were randomly selected and inspected for DBM, ICW, and CL small (1 st- 2nd instars) and large (&amp;gt;3rd instars) larvae on 27 Jul.