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.     

Effectiveness of spinosad combined with diatomaceous earth against different European strains of Tribolium confusum du Val (Coleoptera: Tenebrionidae): Influence of commodity and temperature

Laboratory bioassays were carried out to assess the effects of combining spinosad at 0.01, 0.1 and 0.5 ppm, with the diatomaceous earth (DE) formulation SilicoSec at rates of 150, 300 and 600 ppm, against larvae and adults of three different populations of Tribolium confusum du Val (Coleoptera: Tenebrionidae), originating from different European countries (Greece, Portugal and Denmark). Tests were conducted on wheat and maize at 25 and 30 °C. Survival of T. confusum larvae was assessed after 7 d exposure and survival of adults was assessed after 7 d and 14 d of exposure. At each dose of spinosad, survival of T. confusum individuals decreased as the rate of DE increased. As temperature increased, the efficacy of spinosad and Silicosec applied either alone or in combination also increased. The efficacy of spinosad alone was slightly higher on maize than wheat, while the reverse was noted for all the tested combinations of spinosad with DE as well as in the case of the application of DE alone. The strain from Portugal was always the least susceptible of the three tested. Our study indicates that it is possible to combine low doses of DE (<600 ppm) with spinosad (<1 ppm) to control adults and larvae of T. confusum, especially at temperatures >25 °C.     

The efficacy of different surface applications of wettable powder formulation of Detech® diatomaceous earth against the rice weevil,Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

In this study, the insecticidal activity of the wettable powder formulation of Detech® diatomaceous earth against the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae), an important stored grain pest, was investigated. Detech® diatomaceous earth was applied on concrete and wooden surfaces at doses of 0.25, 0.5, 1 and 2 g/m² and the mortality of S. oryzae adults was observed at time intervals of 24, 48, 72, 96, 120, 144, 168, 192, 216, 240, 264 and 288 h. In the first 24 h of application on the concrete and wooden surfaces, no death was observed. At the 48^th hour, no effect or very low mortality was observed on the concrete and wooden surface at all doses. While the increase in dose and exposure time on the concrete and wooden surface increased the mortality rate of the adults, complete adult mortality was obtained on concrete surfaces after 288 h. The wettable powder formulation of Detech® diatomaceous earth at a dose of 2 g/m² is highly effective against rice weevils on wood and concrete surfaces at laboratory conditions, though with greater success on concrete, but the longer DE exposures increase the efficacy on both surfaces.     

Efficacy of surface applications with diatomaceous earth to control Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) in stored wheat

Commercial formulations of diatomaceous earth (DE) products labeled for use as grain protectants usually specify on the label the depth for using them as a surface treatment, which is often 30.5 cm. An experiment was conducted at two temperatures (27 and 32 °C) and three exposure intervals (7, 10 and 14 d), at a relative humidity of 57–60% to determine if Rhyzopertha dominica (F.), the lesser grain borer, could penetrate a 30.5-cm layer of wheat treated with the labeled rates of three commercial formulations of DE, and, if so, to measure rates of adult survival and progeny production. When R. dominica adults were introduced to this surface layer of 30.5-cm wheat admixed with DE, they were able to penetrate the DE-treated layer and oviposit in the untreated wheat below. Both adult survival and progeny production were significantly lower in wheat with a surface-layer treatment of Dryacide^® (1000 ppm) as compared to Insecto™ (500 ppm), Protect-It^® (400 ppm) or the untreated control. Temperature and exposure interval had no effect on adult survival or progeny production. The vertical displacement patterns of adults were significantly different among DE treatments, but not for temperature or exposure intervals. More R. dominica traveled a greater distance in the untreated control, followed by Insecto™, Protect-It^®, and then Dryacide^®. Results indicate that R. dominica can penetrate a surface layer of DE-treated wheat and reproduce within and below it, but it is possible that pest suppression is dose dependent, or it may depend on a combination of application rate and specific DE formulation.     

Burning characteristics of ammonium perchlorate-based composite propellant supplemented with diatomaceous earth

For composite propellants, solid-phase thermal conduction is one of the dominant processes of propellant combustion and influences their burning characteristics. In this study, diatomaceous earth (DE) was used as a low-thermal-conductivity material, and the influence of DE on the burning characteristics of an ammonium perchlorate (AP)-based composite propellant was investigated.The ignitability of the propellant was improved by the addition of DE. DE showed both positive and negative effects on the burning rate of the propellant. The negative effect was attributable to the reduction of energy by the addition of DE. The enhancement in the burning characteristics was attributable to the particle shape and size of DE, the catalytic effect of Fe₂O₃, and the physical effect of SiO₂; Fe₂O₃ and SiO₂ are constituents of DE. The mechanism of the physical effect of SiO₂ is as follows. The heat conduction in the solid phase is obstructed by SiO₂ particles in the propellant matrix, and the temperature in the vicinity of these particles becomes higher. Consequently, a hot spot is formed on the burning surface side of the SiO₂ particles, and the burning rate is then increased. Further, the hot spot effect was dependent on the AP interparticle distance in propellant matrix and the specific surface area of AP.     

Persistence of diatomaceous earth,SilicoSec® against three stored grain beetles

The persistence of a commercially available diatomaceous earth (DE) formulation (SilicoSec®) against Sitophilus granarius, Rhyzopertha dominica and Tribolium confusum on wheat at four dose rates (500–2000 mg/kg) during a 360-day period of storage was assessed. Mortality of S. granarius were 76.0, 88.4, 93.2 and 95.6% at 7, 14, 21, and 28 days, respectively at 0 month at a dosage of 2000 mg/kg, whereas the corresponding values were 31.5%,71.3, 87.2 and 96.8 at 12 months with the same dosage. Mortality of R. dominica were 48.0, 79.6, 86.4 and 90.0% at 7, 14, 21, and 28 days, respectively at 0 month at a dosage of 2000 mg/kg, whereas the corresponding values were 82.7, 95.2, 98.0 and 98.8% at 12 months with the same dosage. Mortality of T. confusum were 82.1, 96.8, 98.8 and 100.0% at 7, 14, 21, and 28 days, respectively at 0 month at a dosage of 2000 mg/kg, whereas the corresponding values were 32.8, 99.6, 100.0 and 100.0% at 12 months with the same dosage. The increase in mortalities obtained from 1500 to 2000 mg/kg for each of the three species were mostly insignificant at 28 d exposure. Therefore, wheat treated with SilicoSec® at a dosage of 1500 mg/kg could be satisfactorily protected against S. granarius, T. confusum and R. dominica for a year.     

Factors affecting the insecticidal efficacy of an enhanced diatomaceous earth formulation against three stored-product insect species

An enhanced mixture of diatomaceous earth (DE) with the plant extract bitterbarkomycin (BBM) was evaluated in the laboratory against adults of three major stored-product pest species. This mixture (DEBBM) was applied at three dose levels; 50 ppm, 100 ppm and 150 ppm and on four grain commodities; hard wheat, barley, rice and maize. The species tested were Sitophilus oryzae, Tribolium confusum and Cryptolestes ferrugineus. In order to determine the influence of temperature and r.h. on the efficacy of DEBBM the bioassays were carried out at three temperatures; 20, 25 and 30 °C and two relative humidity (r.h.) levels; 55% and 75%. Mortality and progeny production of each species were assessed after exposures of 7 and 14 d. DEBBM efficacy was increased with the increase of dose, exposure and temperature whereas it was decreased with the increase of r.h. Mortality of all species was higher in treated barley compared to the other grains, although significant differences between barley and wheat were not recorded in all cases. Also, DEBBM performance in maize and rice was lower compared to that in barley or wheat. DEBBM was very effective against C. ferrugineus as mortality of this species that was achieved with 150 ppm was always >85%. Of the remaining species the least susceptible to DEBBM was T. confusum. Although DEBBM caused significant mortality to all three species, progeny production was not totally avoided. However, progeny production was significantly lower in comparison with the untreated commodities.     

溶解氧浓度对硅藻土移动床复合生物反应器处理城市污水的影响

利用硅藻土移动床复合生物反应器处理城市污水。以复配硅藻土作为微生物的载体,在连续流小试中,考察溶解氧浓度对反应器处理城市污水效果的影响。当溶解氧浓度为1.85～2.38 mg/L时,处理出水TN为13～16mg/L,满足《城镇污水处理厂污染物排放标准》(GB 18918—2002)一级B标准,其他出水指标如COD_(Cr)为12～22mg/L,NH_3—N为0.5～2.6mg/L;出水TP为0.2～0.9mg/L,都满足GB 18918—2002一级A标准。表明该反应器在中小规模污水处理方面是一个有前途的污水处理工艺单元。     

Preozonation To Improve And Optimize Diatomaceous Earth Filtration

The benefits of preozonation before diatomaceous earth filtration have been demonstrated in a City of New York research program to develop design criteria for treatment of its 300 mgd Croton water supply. In the treatment of a supply where paniculate matter is predominantly of organic origin, preozonation provides two outstanding advantages that are not possible in diatomaceous earth filtration alone.     

New York City's Ozone Demonstration Plant Design

Designand construction specifications of a 3 mgd (12, 187 m³/day) demonstration plant to treat water by ozonation followed by diatomaceous earth (DE) filtration at New York City's Jerome Park Reservoir are described. The primary treatment objectives are to maintain a treated water quality of turbidity below 0.2 NTU, color below 3 color units, and iron and manganese below 0.3 mg/L. Three process trains will be employed, each operating at a maximum of 1 mgd (3,786 m³/day), to test variousmodificationsof theozone/DE process. The demonstration plant is scheduled to operate approximately one year, beginning in April 1986, to provide data for a full-scale plant to be constructed later in the decade.