Thuringiensis Formulations Research Articles

Comparative Efficacy of UV Screens in Protecting the Activity of a Bacillus thuringiensis formulation

UV inactivation of Bacillus thuringiensis var. israelensis ( B. t. i .) toxin is a common problem encountered with any floating formulation against mosquito larvae. An alginate encapsulated, slow-release, floating formulation of B. t. i. , incorporated with UV screens such as acriflavin or methyl green or congo red was prepared and evaluated for larvicidal activity against Culex quinquefasciatus . The data indicated: i. Encapsulation of B. t. i . toxin in sodium alginate has prolonged its residual activity for 45 days, ii. all the UV screens used gave significant level (F=21.66, df = 3716, P<0.0001) of protection to B. t. i . toxin from inactivation by sunlight even after 180 h exposure to direct sunlight (4 hours exposed to direct sunlight daily till 45th day) and iii. compared to acriflavin or methyl green, congo red provided excellent protection.

Avaliação da eficiência de formulações de Bacillus thuringiensis para o controle de traça-das-crucíferas em repolho no Distrito Federal

A traça-das-crucíferas (Plutella xylostella) é a praga mais importante do repolho no Distrito Federal. Seu controle é feito basicamente com inseticidas. Novos produtos são constantemente avaliados para o controle da praga e neste trabalho duas novas formulações de Bacillus thuringiensis [Bacillus thuringiensis var. aizawai (350 e 500 g/ha)e B. thuringiensis var. kurstaki x B. thuringiensis var. aizawai (350 e 500 ml/ha)] foram avaliadas no período de maio a outubro de 1995. Os tratamentos B. thuringiensis var. kurstaki (500 ml/ha), deltametrina (240 ml/ha) e uma testemunha sem pulverização foram também incluídos no experimento. O delineamento foi blocos ao acaso, com sete tratamentos e quatro repetições. Os resultados mostraram que B. thuringiensis var. aizawai nas duas dosagens avaliadas e B. thuringiensis var. kurstaki x B. thuringiensis var. aizawai (500 ml/ha) foram os produtos mais eficientes. Ao final do experimento larvas e pupas de traça-das-crucíferas foram coletadas no campo e a primeira geração foi submetida a um teste de laboratório onde discos de folhas de repolho foram tratados com as dosagens dos inseticidas a base de B. thuringiensis utilizadas no campo. Larvas de segundo estádio foram colocadas sobre os discos tratados e a mortalidade de larvas avaliada após 72 h. Todos os tratamentos causaram mais de 97% de mortalidade de larvas. O resultado do teste de laboratório sugere que a menor eficiência de B. thuringiensis var. kurstaki x B. thuringiensis var. aizawai (350 ml/ha) e B. thuringiensis var. kurstaki (500 ml/ha) no teste de campo quando comparada aos demais Bacillus, pode ser devido à mais rápida degradação destes produtos no ambiente.

Utilization of Several Biopolymers for Granular Formulations of Bacillus thuringiensis

Bacillus thuringiensis variety aizawai was encapsulated within several biopolymers (gelatin, pectin, chitin, alginate, and cornstarch) and assayed for biological activity against neonate Trichoplusia ni (Hubner). Granules were made with various solvents, and a total of 8 formulations were tested. Nearly 100% mortality occurred with all formulations except those made with chitin. B. thuringiensis formulations made with gelatin, pectin, or cornstarch and stored in the laboratory for 12 mo exhibited no detectable decrease in toxic activity against T. ni larvae. Assays that measured resistance to wash-off demonstrated that granules made with gelatin and pectin were retained on cotton leaves. Experiments were conducted to determine palatability of several formulations in 2-choice preference tests. T . ni larvae preferred granules containing gelatin or pectin.

Relative Activity of Commercial Formulations of Bacillus thuringiensis Against Selected Noctuid Larvae (Lepidoptera: Noctuidae)

Diet incorporation and spray chamber assays compared the activity of three commercial formulations of Bacillus thuringiensis Berliner against Heliothis virescens (F.), Helicoverpa zea (Boddie), Pseudoplusia includens (Walker), and Spodoptera exigua (Hübner). The commercial products evaluated were Condor OF® (Ecogen Inc., Langhorne, PA), Dipel ES® (Abbott Laboratories, North Chicago, IL), and Javelin WG® (Sandoz Crop Protection Corp., Des Plaines, IL). Variation in results of the diet incorporation studies illustrated the importance of including a standard reference formulation in the design of the studies and suggested that some standardization of insect strains used in such assays may be important also. Overall results of the diet incorporation studies were similar to those obtained in the spray chamber studies where insects were assayed on sprayed cotton and soybean. Dose-mortality regressions were developed for each B. thuringiensis formulation applied against each insect species on cotton and soybean over a 28-day observation period. These regressions may be helpful in the development of recommendations for the use of B. thuringiensis on cotton and soybean. They may also have value in establishing base-line levels of susceptibility for future resistance monitoring efforts. Median lethal concentrations (LC50s) tended to be slightly higher on cotton than on soybean. The most susceptible insect species was H. virescens, and the least susceptible was S. exigua. LC50s for H. zea and P. includens were similar and intermediate between those of H. virescens and S. exigua. Javelin WG tended to exhibit the highest activity per unit weight of commercial product, but the relative differences among the commercial formulations were influenced by insect species.

Behaviour of larvae on diets containing Bacillus thuringiensis formulations or endotoxins

Behaviour of larvae on diets containing Bacillus thuringiensis formulations or endotoxins

Bacillus thuringiensis serovar japonensis Strain Buibui for Control of Japanese and Oriental Beetle Larvae (Coleoptera: Scarabaeidae)

Two liquid formulations containing Bacillus thuringiensis serovar japonensis strain Buibui toxin were evaluated in the field for control of Japanese and oriental beetle larvae. One formulation stopped in late sporulation phase where greater than 90% of the cells lysed contained free protein toxin crystals (parasporal inclusions) and live spores. A second formulation contained B. thuringiensis serovar japonensis strain Buibui toxin expressed in killed recombinant Pseudomonas fluorescens. both formulations demonstrated the ability to significantly reduce Japanese and oriental beetle larval populations in turfgrass compared to untreated controls. The B. thuringiensis formulation was more effective than the first prototype of the genetically engineered P. fluorescens, but the potential for development of this technology was clearly demonstrated.

Effect of Surfactants, Bacillus thuringiensis Formulations, and Plant Damage on Oviposition by Diamondback Moth (Lepidoptera: Plutellidae)

Greenhouse and field studies were conducted 1993–1994 to investigate the effects of 2 surfactants, 2 insecticides containing toxins from Bacillus thuringiensis Berliner, and plant damage on oviposition by the diamondback moth, Plutella xylostella (L.). Greenhouse studies showed no significant difference between the number of eggs laid by moths on broccoli plants treated with B. thuringiensis plus surfactant relative to plants treated with surfactant alone. All greenhouse tests, however, showed that 4-8 times as many eggs were laid on plants treated with the surfactants Latron CS-7 or Ortho X-77 compared with control plants. A positive linear relationship was observed between the number of eggs deposited on a plant and the extent to which that plant had been damaged by herbivory before oviposition occurred. Field tests showed that for plants with equal herbivore damage, moths laid significantly more eggs on plants treated with a tank mix of B. thuringiensis plus the surfactant Latron CS-7 compared with nontreated plants. These data indicate that diamondback moths prefer to lay eggs on plants treated with certain surfactants and also show preference for plants with feeding damage.

Spray deposition and persistence of a Bacillus thuringiensis formulation (Foray® 76B) on spruce foliage, following aerial application over a northern ontario forest

Abstract A commercial formulation of Bacillus thuringiensis Berliner subspp. kurstaki, Foray® 76B, was sprayed aerially at a dosage rate of 30 BIU in 1.5 L per ha, over a 500‐ha block in a mixed spruce‐fir forest in northern Ontario, Canada, using two fixed‐wing aircrafts equipped with rotary atomizers. Droplet size spectra were determined on Kromekote® cards at ground level, and spray deposit recovery was assessed on glass plates. Initial deposits and persistence of different components of the formulation were determined on canopy foliage by bioassay using spruce budworm (Choristoneura fumiferana Clem.) larvae as the indicator species, and by different quantification techniques that were newly developed in this study. For quantification of foliar deposits, the total protein content was determined and foliar residues were expressed in ng per g foliage (fresh weight). Foliar extracts were acidified to precipitate the protein. The supernatant was subjected sequentially to n‐hexane and n‐octanol extraction, the components present were quantified spectrophotometrically, and the concentrations equivalent to ng protein per g foliage were determined. Then, the concentrations of “total foliar deposits”; (total protein + n‐hexane fraction + n‐octanol fraction) were calculated. The data on droplet spectra indicated a narrow size spectrum, with number and volume median diameters of 40 and 43 μm respectively. The number of droplets per cm2 was high (92) on the sampling card, and so was the spray mass recovery (about 50 to 60% of the amount applied) on the glass plates. Correspondingly, the initial mortality was high (100%) in insects fed foliage collected from 1.0 h to 3.0 d post‐spray, thus indicating high deposits on canopy foliage. The bioactivity of foliar deposits persisted for up to 18 d (the last day of sampling) post‐spray and the mortality was 33.3%. The prolonged persistence of bioactivity was independent of the type of bioassay conducted. The data on force‐feeding bioassay indicated that spores did not contribute significantly to larval mortality. The supernatant of the formulation showed moderate toxicity. When the soluble protein was removed by precipitation, the toxicity of the supernatant decreased, but measurable toxicity still persisted up to 18 d post‐spray. Thus, the data indicated that formulation ingredients contributed to toxicity against spruce budworm. In parallel with the bioassay results, the total protein concentration levels also persisted for up to 18 d. The mean initial concentration was 1400 ng/g, which declined to 224 ng/g on the 18th day. The n‐hexane‐soluble fraction indicated an initial concentration of 782 ng/g, which was about the same on the 18th day. The n‐octanol‐soluble fraction showed a higher initial concentration (979 ng/g), but this declined over the 18‐d period to 541 ng/g. The “total foliar deposits”; (3161 ng/g) were high initially, but decreased to 1514 ng/g on the 18th day. The half‐life (DT50) of persistence was low (0.84 d) for the total protein, compared to those of n‐octanol fraction (8.3 d) and “total foliar deposits”; (10.3 d), thus indicating a much more rapid disappearance of the protein fraction than that of the n‐octanol fraction and “total foliar deposits.”; These findings showed that the prolonged bioactivity of foliar deposits observed in this study was due to formulation components in Foray 76B. Nevertheless, the present study provided a new methodology to determine “total foliar deposits,”; following aerial application of a Bacillus thuringiensis subspp. kurstaki formulation over a conifer forest.

Evaluation of Microbial and Conventional Insecticides for Control of Larval European Corn Borer on Whorl Stage Corn, Clay Center, Ne, 1995

Abstract Bacillus thuringiensis formulations and conventional insecticides were evaluated for efficacy against larval ECB in whorl stage field corn. All plots were planted without soil insecticide on 16 May. The experimental design was a RCB with 4 replicates. Each plot consisted of a single row, 40 ft long with a 30-inch row spacing. Plots were artificially infested with black-head stage ECB egg masses. The egg masses were deposited on wax paper discs, precounted in the laboratory and placed in the whorl of the infested plants on 30 Jun and 9 Jul. Crop growth stage was 37 and 57 inches extended leaf height, respectively. The same 5 plants in each treatment replicate were infested with 10 egg masses per infestation date. All granular insecticides were applied on 13 Jul. Environmental conditions were: air temperature, 81°F; wind direction and speed, west (250°) at 7 mph; relative humidity, 53%; and crop growth stage, 63 inches extended leaf height. A 10-inch Almaco smooth belt cone rear mounted on a Hahn Hi-Boy was used to apply preweighed amounts of the granular insecticides over the top of the plant whorls (G). Liquid insecticides were applied on 15 Jul. Environmental conditions were: air temperature, 74°F; wind direction and speed, east (80°) at 5 mph; relative humidity, 76%; and crop growth stage, 67 inches extended leaf height. A CO2 pressurized backpack sprayer at 30 psi was used to apply a band application over the top of the whorl (total spray volume = 1050 ml/plot) of premeasured amounts of the liquid insecticides (L). All infested plants were evaluated for ECB larval feeding damage on 14-15 Aug. The stalks of the infested plants were split lengthwise and the accumulated length and number of cavities in the 5 plants per treatment replicate were used to evaluate ECB larval damage. The percent infestation at evaluation was determined by the plants with a minimum of 1 cavity per treatment replicate. Data were analyzed by ANOVA for RCB with mean separation using DMRT.

Integration of Entomopathogenic Nematodes with Bacillus thuringiensis or Pesticidal Soap for Control of Insect Pests

The integration of entomopathogenic nematodes and Bacillus thuringiensis subspecies kurstaki or a pesticidal soap controlled insect pests inhabiting the soil and foliage in the greenhouse. The nematode Heterorhabditis bacteriophora controlled larvae of the masked chafer Cyclocephala hirta or the black vine weevil Otiorhynchus sulcatus in the soil and a commercial formulation of B. thuringiensis (Javelin) controlled larvae of the cabbage looper Trichoplusia ni on foliage. The combination of H. bacteriophora or Steinernema carpocapsae with a pesticidal soap (M-Pede) was effective against larvae of the spotted cucumber beetle Diabrotica undecimpunctata undecimpunctata in soil and all feeding stages of the cabbage aphid Breuicoryne brassicae on foliage. After combining and immediately applying both the nematode and B. thuringiensis or pesticidal soap, positive results were obtained against insects in the soil and on foliage. The combinations of nematode and B. thuringiensis or pesticidal soap were held for 4 days with or without aeration, and the fate of the nematodes was observed daily. Both nematode species survived well in the B. thuringiensis formulations with aeration. Without aeration, S. carpocapsae was unaffected by the B. thuringiensis formulations, but H. bacteriophora showed poor survival in the two commercial formulations (Javelin after 1 day and Biobit after 3 days). With or without aeration, both nematode species were adversely affected in the pesticidal soap, but H. bacteriophora showed a higher mortality rate than S. carpocapsae.

Effect of Bacillus thuringiensis Application Interval on European Corn Borer (Lepidoptera: Pyralidae) Control in Sweet Corn

Ground-applied treatments of two commercial Bacillus thuringiensis subsp. kurstaki formulations (MVP and Dipel ES) and tank-mixes with a pyrethroid (Ambush 2E) were evaluated for control of European corn borer, Ostrinia nubilalis (Hübner), larvae in sweet corn. Treatments were applied at average intervals of 3.4, 5, 7, and 10 days to determine field persistence. Manual infestations of first-instar O. nubilalis were used to augment natural populations. During both years, there were no significant interactions between application interval and treatment for all dependent variables tested, including late instars per ear, percent marketability, yield, and predator density. Regardless of application interval, MVP provided greater larval control than Dipel ES. However, the decline in efficacy of the encapsulated MVP formulation occurred at the same rate as that of the non-encapsulated Dipel ES formulation over the 3.4 to 10-d intervals. Tank-mixes of B. thuringiensis + low-rate permethrin provided no additional control compared with low-rate permethrin alone. Given the infestation levels present in this test, neither B. thuringiensis formulation provided control sufficient to maintain current processor standards of 5–10% infested ears at harvest.

Bioassay, Effect of Commonly Applied Pesticides on C. Florus in North Central Washington, 1994

Abstract Various insecticides were evaluated for direct toxicity and the effects of field-aged residues on adult females of the leafroller parasitoid Cf. The chemicals tested for direct toxicity were those listed in the “Predator Toxicity Guide-Apple” chart in the “1994 Crop Protection Guide for Tree Fruits in Washington.” B. thuringiensis products (Dipel, Javelin and MVP), growth regulators (Comply, Dimilin, RH-5992 and RH-2485) and M-Pede were tested at the full field rate and the neurotoxins at 10% of the field rate. Ten microliters of a wetting agent (Triton B-1956) were added to each of the B. thuringiensis formulations. Cf females were taken from a colony maintained at the WSU Tree Fruit Research and Extension Center for the assay. The age of Cf adults was standardized at 2-5 d after emergence from the pupal stage. Fifty females reared from at least five separate host larvae were selected for each of the chemicals tested. These females were anesthetized with CO2, placed on a piece of 11-cm filter paper and transferred to a Potter spray tower. The tower applied 4 ml of pesticide at 6 psi of pressure to the parasites. Cf were transferred to petri dishes with snap-on lids (Falcon 1006, 50 × 9 mm). Honey water and a small cube of artificial diet used to rear leafrollers were added to the petri dishes. The diet worked very well for controlling the moisture in the petri dishes, and honey water had been shown to extend Cf life span by providing nutrition. Five Cf were placed into 10 petri dishes for each of the chemicals (50 Cf per treatment) and kept at 75°F (±2°F) constant temperature and a photoperiod of 16:8 (L:D) h. Surviving parasites were counted at 24 and 48 h after treatment. Treatments with significant Cf survival at 10% field rate were then tested at 50% of the field rate. Treatments with survivors at 50% of the field rate were tested at the full field rate. The residue degradation test was conducted in an apple orchard at the Tree Fruit Research and Extension Center. The trees were 15-yr-old spur type ‘Red Delicious’ on dwarfing roots. The insecticides were applied at the recommended field rates (see below) with a handgun sprayer at 300 psi to the point of drip, simulating a dilute spray of approximately 400 gal/acre. Each treatment was replicated three times as a single tree. Ten mature leaves were collected from each tree (replicate). One punch (2.3 cm diameter) was taken from each leaf (10 total from each tree), and two were placed in a small petri dish (Falcon 1006, 50 × 9 mm). A small quantity of diluted honey water was smeared on the lid for a carbohydrate source, and a small piece of artificial diet used to rear leafrollers was placed in the petri dish to help keep humidity at acceptable levels. There were five petri dishes for each replicate (15 for each treatment). After the leaves were placed in the petri dish and each dish was labeled with a replicate and treatment code, one was chosen at random and five adult Cf females, age 2-3 d old, were placed inside (75 females per treatment). The petri dishes were placed inside a food storage container and kept at 20°C constant temperature and a photoperiod of 16:8 (L:D) h. The no. of survivors was counted at 24 and 48 h. This bioassay was repeated at 1, 3, 7, 14 and 21 d after treatment (DAT) for treatments where Cf mortality was significantly different than the untreated check.

Bioassay, Effect of Commonly Applied Pesticides on T. Platneri in North Central Washington, 1994

Abstract Various insecticides were evaluated for direct toxicity and the effects of field-aged residues on adult females of the leafroller egg parasite Tp. Tp were received from Rincon-Vitova (Ventura, CA) on a card containing approximately 100,000 parasitized host eggs (Sitotroga cerealella reared on grain). Chemicals tested for direct toxicity were those listed in the “Predator Toxicity Guide-Apple” chart in the “1994 Crop Protection Guide for Tree Fruits in Washington.” The B. thuringiensis products (Dipel, Javelin and MVP), the growth regulators (Comply, Dimilin, RH-5992 and RH-2485) and M-Pede were tested at the full field rate and the neurotoxins at 10% the field rate. Ten microliters of a spreader (Triton B-1956) were added to each of the B. thuringiensis formulations. The card with the parasitized eggs was sectioned into 1-square-inch pieces containing approximately 1,000 Tp. The Tp females used for the tests were reared from these pieces in small petri dishes (Falcon 1006, 50 × 9 mm). The age of Tp females was standardized at 1-3 d after emergence from the pupal stage. Fifty females from one of the petri dishes were selected for each of the chemicals tested. These females were anesthetized with CO2, placed on a piece of 11-cm filter paper and transferred to a Potter spray tower. The tower applied 4 ml of pesticide at 6 psi of pressure to the parasites. Tp were transferred to additional petri dishes (Falcon 1006, 50 × 9 mm). A small cube of artificial diet used to rear leafrollers and a thread dipped in honey were added to the petri dishes. The diet worked very well for controlling the humidity and moisture in the petri dishes, and honey had been shown to extend Tp life span by providing nutrition. Five Tp were placed into 10 petri dishes for each of the chemicals (50 Tp per treatment). Surviving parasites were counted 24 and 48 h after treatment. Treatments with significant survival at 10% of the field rate were then tested at 50% of the field rate. Treatments with survivors at 50% of the field rate were tested at the full field rate. Means from the 10% field rate application covered a wide range of values and the standard deviations were proportional to the means so statistics were run on transformed data (log X + 1). The residue degradation test was conducted in an apple orchard at the Tree Fruit Research and Extension Center. The trees were 15-yr-old spur type Red Delicious on dwarfing roots. The insecticides were applied at the recommended field rates (see below) with a handgun sprayer at 300 psi to the point of drip, simulating a dilute spray of approximately 400 gal/acre. Each treatment was replicated three times as a single tree in each .Ten mature leaves were collected from each replicate (tree). One punch (2.3 cm diameter) was taken from each leaf (10 total from a tree), and two were placed in a small petri dish (Falcon 1006, 50 × 9 mm). A small cube of artificial diet used to rear leafrollers and a thread dipped in honey were added to the petri dishes. There were 15 petri dishes for each treatment (five for each tree). After the leaves were placed in the petri dish and each dish was labeled with a replicate and treatment code, one was chosen at random and five adult Tp females, age 1-3 d old, were placed inside (75 females per treatment). The petri dishes were placed inside a food storage container and kept at 20°C constant temperature and a photoperiod of 16:8 (L:D) h. The no. of survivors was counted at 24 and 48 h. This test was repeated at 1, 3, 7, 14, and 21 d after treatment for those that were significantly different than the untreated check.

Evaluation of Microbial and Conventional Insecticides for Control of European Corn Borer on Whorl Stage Corn, Clay Center, NE, 1994

Abstract Registered and experimental Bacillus thuringiensis formulations, conventional insecticides and a commercially available nematode (BioSafe) were evaluated for their efficacy against ECB in whorl stage field corn. The trial was located in a field which was planted as an adult corn rootworm trap crop (soil insecticide free). The experimental design was a RCB with 4 replicates. Each replicate consisted of a single row 40 ft long with 30-inch row spacing. All plots were planted on 6 Jun. ECB egg masses (black-head stage) laid on wax paper discs were precounted in the laboratory, placed in vials and infested on 8 Jul by placing them in the whorl of the infested plant. Five consecutive plants in each treatment per replication were infested with 10 egg masses each. The crop growth stage was 40—15 inches extended leaf height. All insecticide applications were made on 13 Jul. Conditions at time of applications were: air temperature, 85°F; wind direction and speed, north at 10 mph; relative humidity, 80.2%; subsoil temperature at 4 inches, 76.3°F and crop growth stage, extended leaf height of 52-60 inches. A mason jar with holes in the lid was used to apply preweighed amounts of granular insecticides and the nematode. Granules were applied uniformly to the whorls of the plants by shaking the mason jar. Liquid insecticides were banded over the whorl uniformly with a CO2 pressurized backpack sprayer with a spray volume of 18.4 gpa at 30 psi. The infested plants were evaluated for larval feeding damage on 9-12 Aug, 33-36 d after egg mass infestation. The plants were dissected lengthwise and the accumulated length and number of larval cavities recorded. From the infestation date to final damage evaluation, precipitation totalled 3.79 inches plus irrigation 3.03 inches.

Oak Tannins Reduce Effectiveness of Thuricide (Bacillus thuringiensis) in the Gypsy Moth (Lepidoptera: Lymantriidae)

The effect of host plant on the effectiveness of Thuricide, a commercial formulation of Bacillus thuringiensis sp. kurstaki Berliner, toward gypsy moths, Lymantria dispar L., was examined. Thuricide was administered to second- and fourth-instar gypsy moths on foliage from red oak, Quercus rubra L.; chestnut oak, Quercus prinus L.; and quaking aspen, Populus tremuloides Michaux. Oaks were 2-5 times more inhibitory of Thuricide than aspen. Red oak was more inhibitory than chestnut oak. The differences among host-plant species were greatest at the higher dose of 34 IU per larva. Mortality was correlated negatively with the concentration of total phenolics, gallotannins, and proteinbinding activity in leaves. Purified tannins from the oaks were highly inhibitory, indicating that leaf tannins are primarily responsible for reducing the effectiveness of Thuricide. We conclude that oak tannins reduce the effectiveness of this B. thuringiensis formulation, that stand composition may have a major effect on the effectiveness of microbial control measures, and that tannin inhibition may represent a useful target for formulation improvement.

Persistence of Natural and Genetically Engineered Insecticides Based on Bacillus thuringiensis2

The effects of environmental factors on the persistence of formulations of Bacillus thuringiensis Berliner were investigated in a greenhouse study. The persistence of Dipel™, a conventional formulation of B. thuringiensis, was compared with that of MVP™, a commercial formulation consisting of Pseudomonas fluorescens Migula genetically engineered to express a δ-endotoxin gene of B. thuringiensis subsp. kurstaki. Sprayed foliage bioassayed with third instars of Pseudoplusia includens (Walker) indicated that overall persistence of Dipel™ was significantly better (P &amp;lt; 0.05) than that of MVP™, though the 2.5% difference probably was not meaningful from a practical standpoint. The two formulations had significantly (P &amp;lt; 0.05) better persistence on cotton than on soybean or tomato, though there was still &amp;gt; 25% bioassay mortality on all three plant species after 14 d. Sunlight and a combination of precipitation and ultraviolet light were most detrimental to the B. thuringiensis formulations, followed by precipitation only and ultraviolet light only. The formulations were most stable in the dark with no precipitation.

Evaluation of Diatomaceous Earth (Insecto) and Bacillus thuringiensis Formulations for Insect Control in Stored Peanuts2

Runner variety peanuts treated with four rates of diatomaceous earth (28.4, 56.8, 85.2, and 113.6 g per 12.7 kg peanuts) and Virginia variety peanuts treated with four Bacillus thuringiensis formulations (Dipel, Foil, M-Trak and Trident) were held for 8 months at ambient conditions in south Georgia and infested with stored-product insect pests. No red flour beetle, Tribolium castaneum (Herbst), adults were found in peanuts treated with diatomaceous earth until six months after treatment. After 8 months, red flour beetle populations in peanuts treated with diatomaceous earth ranged from 5.7 ± 1.9 to 32.8 ± 12.0 per kg, as compared to 221.2 red flour beetles per 12.7 kg peanuts in untreated controls. The effect of diatomaceous earth on red flour beetles was described by non-linear regression. Indianmeal moth, Plodia interpunctella (Hübner), and almond moth, Cadra cautella (Walker), populations were not abundant in untreated controls or the diatomaceous earth treatments. After 8 months, red flour beetle populations in peanuts treated with the four biological insecticides were not significantly different from the untreated controls. Low levels of Indianmeal moth and almond moth were present in all treatments.

Drop-size Spectra and Deposits of Four Bacillus Thuringiensis Formulations on Simulated and Natural Fir Foliage

In aerial spray studies reported in the literature using concentrated aqueous formulations, the segments of drops that remained above the foliar surface were sized after impaction. The drop volume that could have penetrated into the foliar cuticle was not taken into account. The objectives of the present study were to spray monodispersed drops over natural and simulated balsam fir needles, to determine drop spreading, to measure the sizes of drop segments above the foliage, and to compute the drop volume that penetrated into the foliar surface. Four aqueous formulations of Bacillus thuringiensis var. kurstaki, containing a dye and a chemical tracer [triethyl phosphate (TEP)], were sprayed in a laboratory chamber over balsam fir branches clipped from field-grown trees. Spray was also applied on aluminum fir branches with and without a coating of the cuticular wax extracted from natural fir foliage. Drop-size spectra, drops/cm2, and deposits (ng TEP/cm2 of foliar area, and ng formulation protein/cm2) were assessed on the natural foliage and wax-coated aluminum foliage (foliar simulator); but only drops/cm2 and deposits of TEP and protein were measured on the uncoated aluminum foliage. Both natural foliage and foliar simulator received similar drop sizes, drops/cm2, and deposits, but the latter two parameters were higher on the uncoated aluminum foliage. The investigation provided a new method to determine the actual sizes of drops deposited on a foliar simulator. The simulator not only had similar size and shape, but also the same surface characteristics. Quantification of protein deposits was also faster on the simulator than on the natural foliage.

Droplet size spectra and deposits of two aerially sprayed Bacillus thuringiensis formulations on artificial samplers and live foliage

Abstract Two commercial formulations of Bacillus thuringiensis var. kurstaki (BTK), Foray® 48B and Thuricide® 48LV, were applied aerially over nine spray blocks in a hardwood forest in West Virginia in 1991. Droplet spectra and spray mass deposits were determined using water‐sensitive paper strips (WSPS), glass micro‐fiber filters (GMFFs), glass plates and castor oil. Mass deposits of BTK were also assessed on natural foliage by two bioassay methods, i.e., feeding of homogenized foliage containing a starch‐sucrose solution and force‐feeding bioassay of foliar extracts containing re‐dissolved protein precipitate. Deposits on canopy foliage and ground samplers were also assessed by total protein assay and enzyme‐linked immunosorbent assay (ELISA). Droplet spectra on the WSPS were different from those on castor oil. Droplets on horizontal ground WSPS were larger than those on vertical ground WSPS. WSPS placed at canopy level collected more droplets than those at ground level. The total protein deposits (ng/c...

Efficacy of Condor of and Dipel 8 L Against the Gypsy Moth, 1988

Abstract Spray trials were conducted in Kent and New Castle Counties, DE, and Salem and Cumberland Counties, NJ. Treatments consisted of oil-based isolates of Bacillus thuringiensis formulated as Condor OF and Dipel 8 L diluted with water, Condor OF applied undiluted and an untreated control. Treatments were replicated five times in a randomized complete block. Woodlots were 10-84 acreas in size and consisted of isolated stands. Fifteen 0.025-acre fixed radius plots were established within each woodlot where treatment effects were measured. A Grumman Ag-Cat 600 aircraft equipped with eight AU-5000 Micronair rotary atomizers on a standard spray boom was used to apply the treatments. All B. thuringiensis formulations were applied at 20 billion international units (BIU)/acre (40 oz formulation/acre). For the diluted applications, Condor and Dipel were applied at a volumetric rate of 128 oz/acre including 2% (v/v) Bond (Loveland Industries, Inc.) as a sticker. The aircraft was operated at an airspeed of 90 mph on a 75 ft swath width, about 50 ft above the forest canopy. The pump pressure was 40 psi and the variable restrictor unit on the nozzles was set at 9 and 5 for the diluted and undiluted applications, respectively. The blade angle on the nozzles nearest the fuselage was set at 65 and 35°, and 70 and 35° for the other six nozzles on the boom, for the diluted and undiluted applications, respectively. Woodlots were treated on 22 and 27 May in Delaware and New Jersey, respectively, when GM was predominately 3rd instar. Pre- (Spring) and postspray (Fall) egg mass counts were made within each of the 15 subplots. GM larvae were counted under burlap bands placed on one dominant preferred tree 25 ft outside each 0.025- acre plot. Estimates of feeding damage were based on examination of each burlapped tree and were rated in one of seven classes: 1, 0%; 2, 1-5%; 3, 6-10%; 4, 11-25%; 5, 26-50%; 6, 51-75%; and 7, &amp;gt;75.