Diatomaceous Earth Formulation SilicoSec Research Articles

Insecticidal effect of diatomaceous earth against Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) and Sitophilus granarius (L.) (Coleoptera: Curculionidae) under laboratory conditions

Laboratory experiments were carried out in order to evaluate the insecticidal effect of diatomaceous earth against adults of Callosobruchus maculatus (F) and Sitophilus granarius (L.), two important stored grain pests in darkness (30°C and 65% relative humidity). Wheat and cowpea were treated with the diatomaceous earth formulation Silicosec® (Biofa, Germany), at five concentrations determined with preliminary tests and compared with untreated wheat and cowpea as control. Dead adults were counted 24, 36 and 48 h later. Results showed that increasing concentration of Silicosec® and days after treatment (DAT) significantly increased the mortality rates of adults to above 90% in both experiments. Regarding LC50 and LC95 values, it was observed that C. maculatus adults are more susceptible to Silicosec® than S. granarius. The results showed that these two pests could be controlled successfully with diatomaceous earth. Key words: Callosobruchus maculatus, diatomaceous earth, Silicosec®, Sitophilus granarius, stored grains, cowpea, wheat, effective concentration.

Insecticidal effect of diatomaceous earth against Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) and Sitophilus granarius (L.) (Coleoptera: Curculionidae) under laboratory conditions

Laboratory experiments were carried out in order to evaluate the insecticidal effect of diatomaceous earth against adults of Callosobruchus maculatus (F.) and Sitophilusgranarius (L.), two important stored grain pests in darkness (30°C and 65% RH). Wheat and cowpea were treated with the diatomaceous earth formulation Silicosec® (Biofa, Germany), at five concentrations determined with preliminary tests and compared with untreated wheat and cowpea as control. Dead adults were counted 24, 36 and 48 h later. Results showed that increasing the concentration of Silicosec® and days after treatment (DAT) significantly increased the mortality rates of adults to above 90% in both experiments. Regarding Lc50 and Lc95 values, it was observed that C. maculatus adults are more susceptible to Silicosec® than S. granarius. The results showed that these two pests could be controlled successfully with diatomaceous earth. Key words: Callosobruchus maculatus, diatomaceous earth, Silicosec®, Sitophilus granarius, stored grains, cowpea, wheat.

Laboratory evaluation of diatomaceous earth deposits mined from several locations in central and southeastern Europe as potential protectants against coleopteran grain pests

Diatomaceous earth (DE) deposits from regions of central and southeastern Europe were evaluated for their insecticidal efficacy against Sitophilus oryzae (L.) (Coleoptera: Curculionidae), Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae) and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) in comparison with the commercially available DE formulation SilicoSec. The effects of temperature, RH, grain commodity (wheat, barley, maize, rice), application method (spraying vs. dusting) were evaluated. FYROM, a DE from the Former Yugoslavian Republic of Macedonia, was the most effective of the DE deposits for grain treatment, whereas the least effective was from Greece (named Crete). However, for surface treatment, Slovenia was the most effective followed by Elassona 1 and Begora. Increase of temperature increased DE efficacy, while the reverse was noted with the increase of RH. Furthermore, the DEs were more effective in barley or wheat than in maize or rice. Neither the mined DEs nor SilicoSec were able to suppress progeny production of the tested species after previous exposure on the treated commodities. Generally, dust application of DEs was more efficacious than spraying against S. oryzae and T. confusum. However, spraying of wheat significantly reduced the bulk density (test weight) compared to dusting. For surface treatment, after 1 d of exposure, Slovenia was the most effective of the mined DEs followed by Elassona 1 and Begora, whereas after 6 d of exposure the mortality was almost complete (>99%) with all three DEs. More than 6 d of exposure were required for an effective control of T. confusum adults with the remainder of the mined DEs.

Effect of Paecilomyces fumosoroseus (Wise) Brown and Smith (Ascomycota: Hypocreales) alone or in combination with diatomaceous earth against Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) and Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

Abstract The insecticidal effect of the entomopathogenic fungus Paecilomyces fumosoroseus (Wise) Brown and Smith (Ascomycota: Hypocreales) was evaluated against adults and larvae of the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae) and larvae of the Mediterranean flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). The fungus was added in stored wheat at two dose rates, 200 and 400 ppm, at two temperature levels, 20 and 25 °C alone or in combination with the diatomaceous earth formulation SilicoSec ® . Mortality of the exposed individuals was measured after 7, 14 and 21 d of exposure. For both T. confusum adults and larvae, mortality was higher at 20 than at 25 °C. In the case of T. confusum larvae, after 14 d of exposure, mortality on wheat treated with the highest dose of P. fumosoroseus with SilicoSec ® was significantly higher than that of SilicoSec ® or P. fumosoroseus alone. At 20 °C larval mortality was 100% after 21 d of exposure in both fungal doses with SilicoSec ® . In contrast, mortality of T. confusum adults was low and did not exceed 34% in any of the treatments tested. Finally, mortality of E. kuehniella larvae did not exceed 56%, while SilicoSec ® alone caused higher mortality in comparison with the other treatments.

Effect of Temperature and Humidity on Insecticidal Effect of SilicoSec Against <I>Ephestia kuehniella</I> (Lepidoptera: Pyralidae) Larvae

Laboratory experiments were carried out to assess the insecticidal effect of the diatomaceous earth formulation SilicoSec against larvae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), in stored wheat (Triticum durum Desf.). Larvae were exposed to wheat treated with SilicoSec at 400 and 800 ppm and held at 20, 25, and 30 degrees C and 55 and 75% RH. Larval mortality was assessed after 24 h, 48 h, 7 d, and 14 d of exposure in the treated wheat. At both dose rates, mortality increased with temperature, but this increase varied with the exposure interval. At short (< or = 48-h) exposures, larval mortality was significantly higher at 30 degrees C than at the other two temperatures. In contrast, no significant differences were noted between 20 and 25 degrees C. At longer exposures (> or = 7 d), the increase of temperature increased mortality at 800 ppm, but no significant differences were noted between 25 and 30 degrees C at 400 ppm. Furthermore, significant differences in larval mortality were noted between the two humidity levels, but only at exposures > or = 7 d. After 14 h of exposure, at both dose rates examined, the increase of temperature significantly decreased mortality. The results of the current study indicate that E. kuehniella is susceptible to SilicoSec, but temperature and relative humidity should be taken into consideration.

Factors affecting the insecticidal efficacy of the diatomaceous earth formulation SilicoSec® against adults of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

The insecticidal efficacy of the diatomaceous earth formulation SilicoSec® (Biofa GmbH) against adults of the rice weevil, Sitophilus oryzae, was evaluated in laboratory experiments on stored wheat. Bioassays were conducted at three temperature levels, 22, 27 and 30°C, two relative humidity (rh) levels, 55 and 65%, and four dose rates, 0.25, 0.5, 1 and 1.5 g of SilicoSec®/kg of wheat. Three different aged-adult groups, 1, 2 and 7 d-old, were exposed. The mortality of exposed adults increased with the exposure interval and dose rate. Also, the increase of temperature increased S. oryzae mortality in all exposure intervals examined. The increase of rh from 55 to 65% caused a significant decrease in S. oryzae mortality. The age of the exposed individuals did not have a direct effect on SilicoSec® efficacy.

Factors affecting the insecticidal efficacy of the diatomaceous earth formulation SilicoSec against adults and larvae of the confused flour beetle, Tribolium confusum DuVal (Coleoptera: Tenebrionidae)

The insecticidal efficacy of the diatomaceous earth (DE) formulation SilicoSec (Biofa GmbH) against adults and larvae of the confused flour beetle, Tribolium confusum DuVal (Coleoptera: Tenebrionidae) was evaluated in laboratory tests. These tests were conducted at five temperatures, 22°C, 25°C, 27°C, 30°C and 32°C, and two relative humidity levels, 55% and 65%. SilicoSec was applied to three types of product, hard wheat, soft wheat and wheat flour, at four dose rates, 0.25, 0.5, 1 and 1.5 g/kg of each product. In order to assess the influence of larval instar on the efficacy of SilicoSec, the larvae were divided into two groups, young and old larvae, corresponding to 1–3 and 4–7 instar larvae, respectively. Similarly, adults were divided into three different groups, 1, 2 and 7-d old adults, respectively. For both adults and larvae, mortality on wheat or flour treated with SilicoSec increased with the exposure interval and the dose rate. Larvae were more sensitive to DE than adults, given that adults could survive exposure intervals and application rates that were lethal to larvae. The mortality of larvae and adults exposed to SilicoSec increased with increasing temperature. In contrast, the efficacy of SilicoSec notably decreased with the increase of relative humidity from 55% to 65%. Significantly, more adults and larvae were dead in SilicoSec-treated wheat than in treated flour. The efficacy of SilicoSec was substantially affected by the age of the exposed individuals. Young larvae were significantly more sensitive than old ones. Adults became significantly less susceptible to SilicoSec as their age increased from 1 to 2 and to 7 d.

Effect of grain type on the insecticidal efficacy of SilicoSec against Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

The insecticidal efficacy of the diatomaceous earth formulation SilicoSec ® (Agrinova GmbH, Germany) against the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) was evaluated on peeled rice, paddy rice, maize and barley in laboratory tests. SilicoSec was applied at five dose rates: 0.125, 0.25, 0.5, 1 and 1.5 g/kg of grain. The treated grains were infested with S. oryzae adults, and the weevil mortality was estimated after 24, 48 h, 7 and 14 d of exposure on treated grain. After the 14 d counts, all the exposed adults were removed and progeny production on treated grains was assessed 45 and 90 d later. Insecticidal efficacy of SilicoSec against the rice weevil was highly affected by grain type, exposure interval and dose rate. In all grains tested, longer exposure intervals increased weevil mortality. The efficacy of SilicoSec on maize was not satisfactory, given that after a 14 d exposure at the highest dose rate the mortality did not exceed 65%. Moreover, progeny production on treated maize was high, regardless of the dose rate. On the other hand, 100% of weevils were dead on barley treated with the two highest dose rates of SilicoSec, after a 7 d exposure. However, a complete suppression of progeny production on treated barley was not achieved, even at the highest dose rate. A satisfactory level of protection was recorded on paddy rice treated with 1 and 1.5 g of SilicoSec/kg. At these two rates, all adults were dead after a 7 d exposure, and no progeny were produced during the 90 d incubation period. In contrast, the mortality on peeled rice treated with 1.5 g of SilicoSec/kg did not reach 100%, even after 14 d of exposure, and a high number of progeny were recorded.