Gesunde Pflanzen (2008) 60, 29-34

Christian Ulrichs, Tanja Mucha-Pelzer, Ekkehard Scobel, Lothar Kretschmer, Reinhard Bauer, Erich Bauer and Inga Mewis (2008)
Silikate im Pflanzenschutz: Elektrostatische Applikation und Abhängigkeit der Wirksamkeit von der Schichtdicke
[Plant protection with silica particles: Electrostatic application and impact of particle layer density on the insecticidal efficacy]
Gesunde Pflanzen 60 (1), 29-34
Abstract: Natural occurring amorphous silica is ubiquitous on the earth in soils and sediments. Both, natural derived silica and synthetically produced amorphous silica are used against stored product pests and parasites in animal houses. New formulations, active even under higher relative humidity's can be possible used against horticultural arthropod pests. Since many horticultural pests hide on the undersides of leaves and silica is a physical contact insecticide, an appropriate application method is needed. This paper reviews electrostatic application of natural derived amorphous silica to Brassica chinensis leaves. Due to the inherent high volume resistivity of silica powder, induction charging was ineffective for electrostatic powder coating. Corona charging involves a reliable current source, but typically is inefficient in charging the powder particles and creates a high density of free ions between the gun and grounded substrate as well as within the coating layer. These factors resulted in poor coating quality and inefficient particle deposition. The best leave coating was archived using tribo charging. Here we have been able to apply coatings with different thickness. While a silica coating of 25-50 μm in petri dish experiments resulted in a reduced mortality of the granary weevil, Sitophilus granarius (L.), there was no difference between mortality with coatings of 50-100 μm and 100-125 μm. Silica applications on B. chinensis leaves resulted within two hours in a 45% reduction of the CO₂-absorption. Absorption level stayed reduced over a period of seven days and was between 45 and 73% compared to the control. Even after removing silica dust using pressurized air CO₂-absorption was between 19 and 28% reduced. This might be the case because silica particles where so small that they could possible clog the stomata opening resulting in a reduced transpiration and photosynthesis rate.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
(original language: German)
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Database assignments for author(s): Christian Ulrichs, Inga Mewis

Research topic(s) for pests/diseases/weeds:
control - general

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Sitophilus granarius