Insecticidal Effects of Different Application Techniques for Silica Dusts in Plant Protection on Phaedon cochleariae Fab. and Pieris brassicae L.

Abstract

<jats:p>Since the 1900s, diatomaceous earth (DE) has been used as an alternative to chemical insecticides in stored product protection. New silica and DE formulations offer expanded possibilities for use in horticultural crops. However, many crop pests are found on the leaf underside and this is especially challenging when using silica because the substance must have direct contact with the insect to be effective. We tested three application techniques with three formulations of silica to evaluate their efficacy against different developmental stages of mustard leaf beetle (<jats:italic>Phaedon cochleariae</jats:italic> Fab.) and the cabbage worm of the large white butterfly (<jats:italic>Pieris brassicae</jats:italic> L.) on the host plant species pak choi (<jats:italic>Brassica rapa</jats:italic> ssp. <jats:italic>chinensis</jats:italic> L.). Formulations were applied manually with a powder blower, with an electrostatic spray gun, and in a closed chamber also working with electrostatic forces. The silica formulations used in the biotests were Fossil Shield 90.0s®, AE R974®, and a formulation developed at Humboldt University Berlin called AL-06-109. All formulations contained at least 60% silicon dioxide. Significant differences in efficacy were detected with different application methods and/or silica formulations. AL-06-109 electrostatic cabin-applied was the most effective combination. All formulations, if applied electrostatically, resulted in good coverage and in high plant protection against insect pests. Dusts applied manually were unevenly distributed and easily removed by wind from leaf surfaces. Electrostatic application with a spray gun resulted in even particle distribution on plants, but overspray was high. To accomplish even coverage without wasting so much active material, an enclosed mobile chamber with an electrostatic spray system and an attached exhaust system was developed.</jats:p>

Response of Glucosinolate and Flavonoid Contents and Composition of Brassica rapa ssp. chinensis (L.) Hanelt to Silica Formulations Used as Insecticides

“…Nevertheless, both Surround and AL-06-109 induced changes within indole GS in the plants from the first to the second harvest. In studies conducted by Mucha-Pelzer et al with the formulation AL-06-109, the plant still demonstrated reduced leaf damage by insects compared to the control after dust removal. It is, therefore, suggested that the ability of self-defense is developed for certain substances, either from leftover particles or from the induced GS amounts.…”

“…Experimental Design. B. chinensis plants were raised to the age of 35 days, after which time silica formulations were electrostatically applied onto plants as demonstrated by Mucha-Pelzer et al (20). In the experiment presented in Figure 1 we tested whether plants are affected by silica particulate matter.…”

“…It has also been documented that direct applications of fly ash lead to alterations in the secondary metabolite content and composition, as established in experiments conducted by Anderson et al . Plants have to be covered completely to ensure insecticidal effectiveness when using silica formulations, and electrostatic dust application can be used for plant protection . On the basis of the described physical mode of action of silica, the plant cuticle may also be damaged in addition to the insect cuticle.…”

“…*Author to whom correspondence should be addressed (phone þ49-30-31471345; e-mail tanja.mucha.pelzer@googlemail.com). Plants have to be covered completely to ensure insecticidal effectiveness when using silica formulations, and electrostatic dust application can be used for plant protection (20). On the basis of the described physical mode of action of silica, the plant cuticle may also be damaged in addition to the insect cuticle.…”

The effects of insecticides on butterflies – A review

“…Environmental Entomology 39, 1961-1972. Mucha-Pelzer et al, 2010 Pieris napi L Dimethoate, Phosalone, Fenitrothion, Diflubenzuron Pieris rapae L Surfactant, Fluazifop-p-butyl, Sethoxydim, Deltamethrin, Pumpkin leaf acetone extract Polymmatus icarus L Fenitrothion, Clothianidin Goulson, 2018 Proteus urbanus L, A Naled, Malathion Salvato, 2001 Pygrus oileus L, A Naled Pyronia tithonus L Fenitrothion, Diflubenzuron Vanessa Supplementary table 1: An overview of research examining the effects of direct pesticide exposure on different butterfly species. The table displays the species on which direct effects of pesticides have been tested as well as the stage in their life cycle used, the pesticide tested, the method of application and main findings.…”