Assessment of diatomaceous earth use potential in Louisiana sugarcane

Authors: Penn, Hannah; Richard, Randy; Dufrene, Dawson

Submitted to: Journal of Kansas Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2025
Publication Date: 1/16/2025
Citation: Penn, H., Richard, R.T., Dufrene, D.J. 2025. Assessment of diatomaceous earth use potential in Louisiana sugarcane. Journal of Kansas Entomological Society. https://doi.org/10.2317/0022-8567-97.4.111.
DOI: https://doi.org/10.2317/0022-8567-97.4.111

Interpretive Summary: Diatomaceous earth (DE) is a powder made from diatoms that has previously been used as an organic insecticide substitute against stored product and household pests. In agriculture, DE may also control insects in two ways: 1) if applied to the soil, the plants may take it up and increase their physical strength against feeding and 2) if applied to foliage, the physical dust damages soft insects like caterpillars. Given that much of the work done on DE has been in other areas, we wanted to determine its potential in in sugarcane against the main pest in Louisiana, the sugarcane borer (SCB). We also wanted to make sure that DE would not harm beneficial insects that eat SCB like the red imported fire ant (RIFA). To test this, we added DE to field soil and measured SCB damage and sugar yield. We then did a laboratory study to see if DE in soil harmed RIFA. We then sprayed DE in sugarcane leaves to see effectiveness against SCB and how well the DE stayed after rain events. We found that adding DE to the soil amendment did prevent SCB damage or increase sugar yields, but neither did it harm RIFA. Unlike the soil treatments, DE leaf sprays decreased SCB damage to stalks when plants were protected from rain, but DE did not last long on plants after rain events. Given that the most used insecticide in sugarcane only requires 1-2 applications per year and also does not harm RIFA while DE leaf sprays will require several expensive applications, we suspect that DE is not a good fit for use in Louisiana sugarcane.

Technical Abstract: Diatomaceous earth (DE) has the potential to decrease pest damage to plants both indirectly by being a source of silica if applied as a soil amendment and directly as a physical barrier if applied to foliage. For applicability in Louisiana sugarcane, DE would need to be effective at controlling the sugarcane borer (SCB), the primary economic pest, while not harming natural enemies like the red imported fire ant (RIFA) that provide biological control. We examined DE formulated for agricultural use by evaluating its potential as a sugarcane soil amendment and a foliar treatment. We determined impacts of a DE soil amendment on SCB damage and yield in a field test then evaluated if the amendment negatively impacted RIFA survival in a laboratory assay. Using potted plants, we assessed efficacy of DE foliar applications against SCB followed by a visual assessment of product longevity in the field. We found that the DE soil amendment did not alter SCB damage or yield but neither did it impact RIFA survival. Unlike the soil amendment, foliar application in a rain-free environment decreased SCB damage to stalks. However, the product did not persist on leaves or stalks under typical Louisiana field conditions. Given that the most commonly used insecticide in sugarcane only requires 1-2 applications per year and does not disrupt biological control while DE would require many costly applications due to plant growth rates and precipitation levels, we suspect that DE is not currently recommended for use with Louisiana sugarcane production.