Diatomaceous Earth Formulation Research Articles

Evaluation of diatomaceous earth formulations enhanced with natural products against stored product insects

The insecticidal effect of prepared insecticide formulations labelled as Natural P, Inert Natural P and Py EC on Sitophilus oryzae, Rhyzopertha dominica and Tribolium castaneum have been evaluated on wheat grains. Formulation Natural P contains diatomaceous earth (DE), amorphous silica gel (3%), pyrethrin, flax oil, lavandin essential oil (EO) and un-activated yeast. Formulation Inert Natural P contains DE, amorphous silica gel, lavandin EO and food grade bait whereas formulation Py EC contains pyrethrin, piperonyl butoxide (PBO), flax oil, polysorbate, methyl oleate and amorphous silica gel (5%). Celatom® MN-51 (diatomaceous earth – DE) was used as a standard insecticide. Inert Natural P and Natural P were applied as dust at four different doses and Py EC was applied as emulsions on grain by spraying. All three formulations showed higher insecticidal efficacy and higher progeny inhibition on all three tested insect species and had lower impact on wheat bulk density reduction compared with Celatom® MN-51. The LD50 and LD90 values of Inert Natural P were 48.7 and 163.7 ppm respectively for S. oryzae, 15.2 and 178.0 ppm for R. dominica and 115.2 and 171.3 ppm for T. castaneum. The LD50 and LD90 values of Natural P were 83.6 and 97.9 ppm respectively for S. oryzae, 19.5 and 97.9 ppm for R. dominica and 75.4 and 105.6 ppm for T. castaneum. Applied Py EC at concentration of 2.0 ppm a.i. pyrethrin exhibited 100% mortality after 2 d of S. oryzae and T. castaneum and after 6 d of R. dominica. In addition, all three formulations caused significant reduction of progeny (F1) population compared to control, providing promising approach of integrated pest management strategy.

Lethality and kinetic of diatomaceous earth uptake by the bean weevil (Acanthoscelides obtectus [Say] Coleoptera: Bruchinae): Influence of short-term exposure period

Laboratory bioassays were carried out to assess the lethal effect of the diatomaceous earth (DE) formulation Fossil-Shield® against males and females of adult bean weevils (Acanthoscelides obtectus [Say]). Kinetics of the DE uptake experiment was determined by using manganese as a trace element. The adherence of DE to the common bean was also measured in this study. The mortality of weevils was evaluated after exposure to eight different DE dosages (400–4000 mg/kg) after 1, 2 and 4 days, respectively. DE dust was more lethal to male than female weevils within shorter exposure period at low DE dosages (<2400 mg/kg). However, LD99 values did not show a significant difference (P > 0.05) between sexes. DE adherence ratio ranged between 73% and 98% at the highest (3600 mg/kg) and the lowest (400 mg/kg) DE dosages, respectively. The maximum saturated amount of DE retention on the bean surface was approximately 7.14 μg/mm2. The amount of DE uptake by a weevil was significantly increased (P < 0.05) with DE dosage and exposure time. The two-compartment kinetic model fitted well to the experimental data as a two-site reaction model over the range of DE dosage between 500 and 2000 mg/kg. According to the model, bean weevils can take-up 2.3–3.1 μg/mm2 of DE based on their corresponding LD99 values depends on the exposure period. It was observed that DE particles were incorporated into the epicuticle lipid layer at a rate of 1.18 × 10−3 μg mm−2 min−1 during DE uptake by a weevil. This indicates that from the total body weight, approximately 2% of DE taken-up by an insect within a given exposure period was more decisive for insect mortality than the rate of DE application.

Adhesion of diatomaceous earth dusts on wheat and corn kernels

Insect infestations are a major threat to the quality of stored grain. One method of insect control is to apply diatomaceous earth (DE), a non-chemical, inert dust that is composed of the ossified remains of diatoms. Diatomaceous Earth kills insects via abrasion and desiccation when the insect is exposed to a sufficient quantity of DE from contact on the grain surface. Therefore, good dust adhesion is desirable to ensure that the DE will come in contact with insects in sufficient quantity to provide the insect control expected. This study considered the adhesion ratio of three types of DE, Celite, Dryacide, and Diafil, on wheat and corn kernels. All three types of DE adhered better to wheat than to corn, and to higher moisture grain than lower moisture grain, and moisture content affected the adhesion on corn more than wheat. Dryacide had the lowest adhesion of the three DE tested at each condition. Dryacide's adhesion was significantly lower than at least one other DE in each test and was lower than both other DE for 12% moisture corn and 15% moisture wheat. Celite had the highest adhesion measured in each trial except for 15% moisture corn but was only significantly higher than Diafil for 12% moisture wheat. Additionally, higher surface roughness correlated with higher adhesion percentages, indicating that rougher diatomaceous earth formulations will be better at adhering to grain particles.

First Trial to Assess Gamma-Irradiation and Diatomaceous Earth Combination on Mortality of some Stored Product Insects

This study was designed to characterize the combination of gamma-irradiation and food grade diatomaceous earth (Wolf Creek ranch, California, USA) as diatomaceous earth formulation treatment against three of stored product insect pests [Sitophilus granarius (L), Tribolium castaneum (Herbst.) and Rhyzopertha dominica, (F)] in the laboratory. The study was assessed the killing effect of gamma-irradiation at 50,100 and 250 Gray against these pests. As well as 0, 0.5, 1.0 and 1.5 g/kg (w/w) concentrations of diatomaceous earth formulation alone or in combination with irradiation were assessed. The obtained results indicated that the mixing between two insect control methods had the combined advantages of quick speed of killing and a high level of safety. Where, the LT50 have a wide range of values and the combined treatments of gamma-irradiation and treatment with diatomaceous earth maybe were the most influencing factors reducing lifespan after treatments. In this laboratory study the combination between diatomaceous earth (1.5 g/kg) and irradiated the tested pests with (250 Gy) of gamma ray produced an antagonistic interaction, except in the case of Rhyzopertha dominica F. adults. Our finding stated that the use of ‘control method’ gamma-irradiation in conjunction with diatomaceous earth could be a feasible strategic component in Insect Pest Management; IPM in operational modality might be ‘sequential’ against the tested pests. That is to apply irradiation to eliminate existing census personnel. This is then followed by the addition of DE to the grain to prevent the infection from occurring again

EFFICACY OF DIFFERENT DIATOMACEOUS EARTH FORMULATIONS IN THREE WHEAT VARIETIES AGAINST THE LESSER GRAIN BORER RHYZOPERTHA DOMINICA (F.) (COLEOPTERA: BOSTRICHIDAE)

Laboratory tests were conducted to evaluate the efficacy of three diatomaceous earth (DE) formulations; Celite 209, DiaFil 610 and SilicoSec in three wheat varieties, Atilla-Gan-Atilla, Cetia and Seri M82, against Rhyzopertha dominica (F.). The DE formulations were applied at four dose rates; 250, 500, 750 and 1000 mg/kg. Bioassays were carried out at 26-34°C and at 32-45 % relative humidity (RH). Efficacy was evaluated by recording adult mortality after 7 and 14 days, and progeny production at 56 and 112 days after treatment (DAT). Adult mortality levels significantly differed among varieties, exposure periods, DE formulations and their dose rates, ranging from 27.7 to 100 %. With all DE formulations and wheat varieties, complete adult mortality was achieved at 1000 mg/kg and 14 days of exposure. SilicoSec was more effective, proving higher mortality within shorter exposure period than other formulations. Progeny production was significantly higher in untreated Cetia than in the two other varieties and always greater in untreated than treated grains. Complete progeny suppression was recorded at ≥750 mg/kg. Generally, the performance of all DE formulations was greater in Atilla-Gan-Atilla and Seri M82 compared to Cetia.

Evaluation of the potential value of the F 1 H and F 2 H Diatomaceous earth formulations as grain protectants against Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae):

An insecticidal efficacy of two newly developed grain protectant formulations were assessed against lesser grain borer Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae) on wheat and corn after 6 months period of. Tested formulations, marked as F1H and F2H, based on inert dust, laurel leaves, lavender essential oil, corn oil, silica gel (both F1H and F2H) and pyrethrin (only F2H) were tested at six doses (from 100 ppm to 600 ppm) depending on formulation and type of grain. The appropriate weights of each formulation, were added seperately to plastic containers containing 10 kg of wheat or corn. An initial population of 200 adults of R. dominica were added into each container and left under natural environmental conditions for up to 6 months. A commercial diatomaceous earth (DE) insecticide, Celatom® Mn 51, was used for the comparison of the results, in addition to the untreated control. After six months, both formulations showed higher insecticidal effect than DE Mn 51 in corn and in wheat. Furthermore, the initial population of R. dominica, introduced in wheat was suppressed almost completely, with only 0.7%-5.3% live adults found, depending on formulations and dose. The order of efficacy was F1H>F2H>DE Mn 51. Similar suppression of the initial population was recorded in corn, where F2H was slightly more effective than F1H with 2.0%-10.6% and 4.1%-9.5% live adults found, respectively. At the same time, in the treatments with DE Mn 51 there were 4.7%-74.7% and 33.4%-56.1% live adults in wheat and corn, respectively.

Evaluation of insecticidal efficacy and persistence of Nigerian raw diatomaceous earth against Callosobruchus maculatus (F.) on stored cowpea

The insecticidal efficacy and persistence of Nigerian raw diatomaceous earth (DE) were evaluated in the laboratory on cowpea against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae). The raw DE was applied to 1.5 kg lots of cowpea seeds at 0 (untreated control), 250, 500, 750, 1000 and 1500 mg/kg, and a commercial DE formulation (Protect-It®) applied at 1000 mg/kg was included in the test as positive (treated) control. The treated cowpea seeds were kept under ambient laboratory conditions (26 - 34°C and 24 - 93% RH. Bioassays were conducted on samples taken from each treatment at the day of storage and every 30 d for 6 consecutive months. Adult C. maculatus were exposed for 3 and 5 d to the samples and adult mortality was assessed over this exposure interval and progeny production and seed damage were assessed after additional 30 d. On freshly treated cowpea, both the raw DE and Protect-It® were highly effective against C. maculatus causing 100% adult mortality following 5 d of exposure. In general, the raw DE was less persistent on cowpea providing complete adult mortality only for two months. Protect-It® on the other hand was stable over the 6- month period of storage causing 95.8 to 100% adult mortality. None of the treatments completely inhibited progeny production after 2-3-moths storage period. The results of this study indicated that Protect-It® may provide suitable protection for 6 months against C. maculatus, but the raw DE in its present state is not suitable for long-term protection against this insect pest.

Comparison of three different wood ashes and diatomaceous earth in controlling the maize weevil under laboratory conditions

We studied the insecticidal effects of ashes from three different tree species (common beech, Norway spruce, and black locust) on the mortality of Sitophilus zeamais adults under laboratory conditions. A diatomaceous earth formulation, SilicoSec® was used as a positive control. We studied the contact effects of ashes on adults and the insecticidal effect of ash mixed with wheat grain. The experiment was carried out at three different temperatures (15, 20 and 25 °C) and at two different relative humidity [r.h.] values (55% and 75%). The study on contact effects (immediate mortality and delayed mortality) was carried out in Petri dishes, where we applied ash in two concentrations, 10 and 20 g/m2. After 7 d there was more than 97% mortality for the beetles in all three wood ashes at 25 °C and 55% R.h., while after 14 d wood ash of Norway spruce showed the highest effectiveness (87%) at 20 °C and 55% R.h. 96% mortality was recorded at 20 °C and 55%, when SilicoSec® was applied. The experiment with the mixture of ashes and grains was performed by mixing 2.5 or 5 w% of ash with wheat. In both approaches, we established that lower R.h. in combination with higher temperatures led to higher adult mortality rates. Regardless of the approach, the preparation concentrations did not influence adult mortality. The most efficient ash was that of Norway spruce, yet we attribute its effectiveness not only to its highest content of SiO2 (11.68%) but also to the other ingredients in ash, which can enhance its hygroscopic properties. Our research demonstrated that wood ash can efficiently protect stored crops from maize weevils. However, before introducing wood ash into the systems of protecting stored wheat grains against harmful insects, the influence of concentrations of ashes and their hygroscopic properties should be studied.

Effectiveness of an improved form of insecticide-based diatomaceous earth against four stored grain pests on different grain commodities.

The effectiveness of Grain-Guard, an improved form of diatomaceous earth (DE), with low risk to the environment, was evaluated against the storage pests Liposcelis paeta, Cryptolestes ferrugineus, Rhyzopertha dominica, and Tribolium castaneumon four grain commodities, wheat, rice, maize and sorghum. The overall mortality of stored grain pests increased with the rise of application rate and exposure intervals of diatomaceous earth and decreased over 120 daysof post-treatment period. Our results revealed that mortality of adults 14days post-disclosure was > 80% on wheat at the start of post-treatment than rice, maize, and sorghum, respectively. During the first 60days of post-treatment, adult mortality increased, whereas later on, a steady decrease in adult mortality was observed. Considerable differences in dose rates were observed on mortality levels along with grain commodities. Following 14days of exposure, all adults of four species were dead on wheat at 100ppm and on rice at 150ppm except maize and sorghum. The suppression of progeny was noticeably higher at the beginning of post-treatment duration while after 60-days of post-treatment, progeny numbers started to increase with the rise in post-treatment durations. This new improved DE formulation was found to be effective at dose rates that are extensively lower than required with previous DE formulations and will contribute to lower the risk of health and environment.

Effect of grain type on the insecticidal efficacy of Paya® against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

The objective of the current study was to determine the insecticidal effectiveness of diatomaceous earth formulation (DE) Paya®. The effects of grain commodity (wheat, barley, maize and rice), exposure times and dose rates were evaluated. The efficacy of diatomaceous earth (DE) against 1–7 days old adults of Tribolium castaneum (Herbst) was evaluated on wheat, rice, maize and barley at 26±1 °C and 60±5% RH in darkness. The mortality of adults was tested at five concentrations: 0.125, 0.25, 0.5, 1 and 1.5 g/kg of grain and different exposure times (24, 48 h, 7 and 14 d). To evaluate the progeny production, dead and alive adults were removed from containers after 14 days and these containers were kept at above-mentioned conditions for 45 days. The results obtained indicated that the highest adult mortality was observed after the longest exposure period on barley and wheat so that the two highest DE dosages caused 100% mortality of T. castaneum. The efficacy of Paya® on maize and rice was not satisfactory, given that after a 14 days exposure at the highest dose rate the mortality did not exceed 37% and 66% in the case of maize and rice, respectively. The results demonstrated that the mortality increased with rises in concentration and exposure time and also highly affected by grain type.

Laboratory studies on the behavioral responses of Tribolium confusum and Ephestia kuehniella to surfaces treated with diatomaceous earth and spinosad formulations

Laboratory bioassays were conducted to determine the behavioral responses of adults and larvae of Tribolium confusum Jacquelin du Val and larvae of Ephestia kuehniella Zeller to surfaces treated with two diatomaceous earth (DE) (Insecto, SilicoSec®) and one spinosad formulations, applied alone or in combinations. Five series of bioassays were carried out by using petri dishes with their bottoms separated into two equal parts. The dishes contained different treatments of combinations of the DE or spinosad formulations or one part left untreated. After the preparation of the treatments, ten insects were released in the center of the dish and observations were taken for 60 min at 5-min intervals. In general, the released insects showed positive preference upon contact to the DE-treated wheat as compared with the untreated substrate. There was no negative preference upon contact to the presence of DEs, with very few exceptions. Interestingly, a strong positive preference upon contact was observed for the spinosad formulation. When the tested DEs were applied in combination with spinosad, the presence of spinosad generally negatively affected the preference upon contact, especially in the case of larvae. The results of the present work indicate specific behavioral responses of stored-product insects to insecticidal formulations, which can strongly affect the efficacy of control strategies and should be taken into account.

Persistence and Efficacy of Four Iranian Diatomaceous Earths Against Three Stored Grains Beetles

Persistence and efficacy of four Iranian diatomaceous earth formulations was assessed against Sitophilus oryzae (L.), Tribolium castaneum (Herbst) and Tribolium confusum Jacquelin du Val. on barley, rice and wheat. Three diatomaceous earth samples were collected from Maragheh, Mamaghan, and Khorasan Jonoobi mines and Sayan® formulation was obtained from Kimia Sabz Avar Company. Mortality of the exposed individuals was recorded after 2, 5, 10 and 14 days of exposure. The mortality of all tested species was higher on wheat followed by barley. The insect mortality increased with increasing concentration level. In most cases, Khorasan was the most effective diatomaceous earth deposit. LC50 values of Khorasan deposit was 155.3, 201.5 and 293.7 ppm for S. oryzae, T. castaneum and T. confusum, respectively when exposed for 7 days on treated wheat. Adults of S. oryzae were the most susceptible species to diatomaceous earths. Subsequently, the persistence of diatomaceous earths was assessed after 1, 2, 3, 4, 6 and 8 months of storage. Mortality of all the tested species was high in first four months of storage but decreased rapidly overtime.

Influence of temperature and application rate on efficacy of a diatomaceous earth formulation against Tribolium castaneum adults

Unsanitary storage bins can harbor grain-infesting insects, including the red flour beetle, Tribolium castaneum (Herbst). In a previous study involving heat treatment of empty bins, temperatures in the range of 50–55 °C for 2–4 h were effective in completely killing stored-product insects. Previous research in flour mills showed improved efficacy in killing stored-product insects by using diatomaceous earth (DE) dusts at temperatures below 50 °C. In the current study, the efficacy of a diatomaceous earth formulation (DiaFil® 610) applied to concrete arenas, to simulate floor of empty bins, was examined at three application rates (0, 2.5 and 5.0 g/m2) to control T. castaneum adults at five constant temperatures (28, 36, 42, 44, and 46 °C). Ten adults of T. castaneum were placed on individual untreated and DE-treated concrete arenas for 4, 8, 12, and 24 h at each of the five temperatures. The efficacy of DE against T. castaneum adults increased with an increase in temperature and exposure time. Generally more adults died at 5.0 g/m2 when compared with 2.5 g/m2. In 2.5 and 5.0 g/m2 DE treatments, exposure for 12 h at a temperature of 42 °C resulted in 73–77% mortality of adults with 100% mortality observed after 24 h. At 44 and 46 °C, 100% mortality of adults was observed after 24 h of exposure at both DE rates. At these two temperatures, the high mortality in untreated arenas (controls) at 8, 12, and 24 h exposures ranged from 27 to 100% confounding the true effects of DE. Our results suggest that combined use of DE and temperatures below 50 °C can be used as an integrated approach for controlling insects in empty bins prior to storage of newly-harvested grain.

Insecticidal effect of the combined application of spinosad, Beauveria bassiana and diatomaceous earth for the control of Tribolium confusum

ABSTRACTLaboratory bioassays were carried out to evaluate the insecticidal effect of Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales) germinated conidia, a commercial formulation of diatomaceous earth and a liquid formulation of spinosad, applied alone or in all possible combinations on wheat, against adults of the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae). Diatomaceous earth was applied at one (200 ppm), the fungus at two (100 and 300 ppm) and spinosad at three (0.01, 0.1 and 0.5 ppm) dose rates, whereas all combinations of two or three of the insecticide concentrations were also tested. Insect mortality was determined after 2, 7 and 14 d of exposure. The simultaneous use of B. bassiana germinated conidia with diatomaceous earth notably increased mortality of T. confusum adults by sixfold 7 d after exposure, as compared with either B. bassiana or diatomaceous earth alone. When diatomaceous earth and spinosad were combined, diatomaceous earth did not increase the efficacy of spinosad. In general, the combination of all three agents did not differ from either the application of the agents tested alone, or their binary combinations, in most treatments examined.

Diatomaceous earth impairment of water balance in the maize weevil, Sitophilus zeamais

As water balance is a fundamental component for insect homeostasis, inert dusts such as diatomaceous earth (DE) are physical insecticides that allegedly impair water balance causing insect death by desiccation. Death by desiccation and water loss were indeed reported when using DE against a few stored product insects at discreet relative humidities, which may vary with species, strain, and DE deposit. Here we assessed the activity of two DE formulations from distinct deposits, Insecto® and KeepDry®, against the maize weevil (Sitophilus zeamais), a key pest species of stored cereals in warmer climates. We tracked their action on the insect integument, and impairing water balance in a range of relative humidity, assessing their effect on insect water content and rate of water loss. Both DE formulations compromised insect survival at the full range of relative humidities tested (i.e., from 0 to 100 %) reducing in a third the median survival time. Both DE formulations damaged the insect tegument surface, including sensilla and pores, and compromised water balance reducing body water content and increasing the rate of water loss in over twofold. However, such activity and efficacy differed between DE formulations with KeepDry® leading to greater insecticidal activity and impairment of water balance in the maize weevil than the Insecto® formulation.

Overview of undesirable effects of using diatomaceous earths for direct mixing with grains

Despite numerous advantages of diatomaceous earth (DE), its use for direct mixing with grains to control stored-product insects remains limited because of some very serious obstacles and disadvantages. The main obstacles preventing a wider use of DEs for mixing with grain, such as health concerns, the reduction in bulk density, differences in insect species tolerance to the same DE formulation, the effects of grain moisture and temperature on the effectiveness against insects, the influence of various commodities on DE efficacy, the use of DEs in some other fields, and possible solutions for overcoming DE limitations during direct mixing with grains are described in this manuscript. The same attempts have been made to discover new ways of increasing significantly the effectiveness against insects when much lower concentrations are used for direct mixing with grains. If these newer enhanced formulations can respond to the existing limitations of diatomaceous earth, a wider utilization of diatomaceous earth may be expected to control stored-product insect pests.

Does Diatomaceous Earth Control Leaf-Cutter Ants (Hymenoptera: Formicidae) in the Eucalyptus Plantations?

Genus Atta includes some of the most important Formicidae leaf cutter ants which cause extensive damage to the eucalyptus plantations. Atta sexdens rubropilosa Forel, one of the chief pests in Brazilian reforestation, can restrict and reduce forest productivity by its intense and constant leaf-cutting activities on plants at all stages. Therefore, the demand for new products to control A. sexdens rubropilosa indicates the study of the utilization of the dry powder formulation of diatomaceous earth (DE) against this pest in the eucalyptus cultivars. The study was conducted using 120 colonies of A. sexdens rubropilosa in Eucalyptus grandis Hill ex. Maiden x Eucalyptus urophylla Blake (Myrtaceae) (urograndis) stand. The randomized block experimental design was used with six treatments (1, 10, 25, and 50 g/m2 of DE, 6.0 g/m2 sulfluramid bait per square meter of loose soil, and the control) with five replications, each with four colonies of this ant. Diatomaceous earth was applied to the active A. sexdens rubropilosa ant holes, and the sulfluramid bait was applied in bulk in a localized manner. The control efficacy of A. sexdens rubropilosa with DE was low, showing values similar to that of the control, and, for this reason, it cannot be used to control this ant. The bait with sulfluramid showed higher efficacy than those of the other treatments.

Diatomaceous earth used against insect pests, applied alone or in combination with Metarhizium anisopliae and Beauveria bassiana

Abstract Laboratory bioassays were conducted to assess the insecticidal efficacy of the formulation SilicoSec® used alone or in combination with isolates of entomopathogenic fungi, Metarhizium anisopliae (Metschinkoff) Sorokin and Beauveria bassiana (Balsamo) Vuillemin. SilicoSec® is a commercial diatomaceous earth (DE) formulation. Wheat was treated with 200 mg/kg of DE, 400 mg/kg of each isolates alone or a combination of them, against Tribolium castaneum Herbst, Rhyzopertha dominica (F.), and Oryzaephilus surinamensis L. The experiments were carried out at 27±1°C and 65±5% relative humidity (RH) in continuous darkness. The pathogenicity of all isolates was significantly low even after 7 days of exposure, with the exception of R. dominica. The isolates were virulent to the beetles, but the efficacy of the isolates was enhanced in combination with the DE. Tribolium castaneum was the most resistant species, followed by R. dominica. The findings indicated that the addition of the DE to the isolates increased the pathogenicity especially at the highest exposure interval. The addition of DE may provide satisfactory control of the insect-pests of stored products.

Efficacy of diatomaceous earth formulations against Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in Kersting’s groundnut (Macrotyloma geocarpum Harms): influence of dosage rate and relative humidity

The pulse beetle, Callosobruchus maculatus F. is a key pest to stored Kersting’s groundnut, Macrotyloma geocarpum Harms. There are many reports evaluating various diatomaceous earths (DEs) against stored product pests, but there is limited information on the efficacy of these materials against C. maculatus and none on Kerstings groundnut. Laboratory experiments were conducted to evaluate the efficacy of the DEs, Diatomenerde, Probe-A, Fossil shield, and Damol-D1 against C. maculatus in seeds of M. geocarpum. Each DE was applied at 0.50, 1.00, 1.50, and 2.00 g kg−1, and each treatment infested with newly emerged C. maculatus in petri dishes. The set up was maintained at 50 and 80 % RH regimes at ambient temperature. Data were collected on adult mortality (at 24 h, 48 h, 7 days, and 14 days), oviposition, and progeny emergence of the beetles, and their effects on weight loss and viability of seeds. Probe-A proved the most effective against the beetle, followed by Damol-D1 and Fossil shield. Adult mortality increased progressively with the increasing dosage of DE and exposure time. Seeds treated at 2.00 or 1.50 g kg−1 recorded significantly lower number of eggs and F1 emergence compared with the lower dosages in all DEs. Increased DE concentration consistently decreased seed weight loss due to low beetle infestation, but there was no significant effect on seed viability. DEs were more effective at 50 % RH than at 80 % RH. Probe-A or Damol-D1 applied at 1.50 or 2.00 g kg−1 at 50 % RH is a viable alternative for preventing C. maculatus infestation in stored Kersting’s groundnut.

Mixing of Isaria fumosorosea with enhanced diatomaceous earth and bitterbarkomycin for control of Rhyzopertha dominica

AbstractThe virulence of Isaria fumosorosea alone and integrated with an enhanced formulation of diatomaceous earth (diatomaceous earth + bitterbarkomycin, DEBBM) was tested against the lesser grain borer Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) under laboratory conditions on stored wheat. The fungus was applied to wheat grains at various concentrations of 3.60 × 106, 3.60 × 108, and 3.60 × 1010 conidia/kg alone, or in combination with 15 and 30 ppm of DEBBM. R. dominica was held at 20, 25 and 30°C and two RH regimes (56 and 75%) and mortality was registered after 5, 10 and 15 d. Generally, I. fumosorosea was most effective at 25°C caused the highest mortality of R. dominica at 56% RH. The increase of temperature, concentration and exposure interval increased the insecticidal effect of DEBBM at low RH level. The DE alone suppressed the progeny emergence at higher dose rate as compared I. fumosorosea alone, but their simultaneous use further reduced the progeny production of R. dominica. The integrated use of both tested bio control agents synergized the effect of each other and caused the highest mortality at 25°C and 56% RH. The results clearly demonstrated that I. fumosorosea and new enhanced DEBBM can be integrated to be an effective control measure for R. dominica in stored wheat.