Toxicity and protectant potential of Piper guineense (Piperaceae) and Senna siamea (Fabaceae) mixed with diatomaceous earth for the management of three major stored product beetle pests

ABSTRACT

There is a dearth of knowledge on the available sources of botanical products for smallholder farmers in Africa and their bioactivity against stored-product pests. Many locally available plants across Africa exhibit both promising insecticidal, medicinal activity and are nutrient rich yet remain underutilized. Laboratory studies on toxicity of powders of Senna siamea and Piper guineense alone or combined with diatomaceous earth (DE) to adult Sitophilus granarius, Tribolium castaneum and Acanthoscelides obtectus were conducted in stored grains. Adult mortality was observed up to 7 d while progeny production was recorded 6–10 weeks. Adult A. obtectus were most susceptible (LD₅₀ 0.0084% and 0.0696% wt/wt for S. siamea and P. guineense, respectively), followed by S. granarius. T. castaneum was most tolerant (LD₅₀ 0.6589% and 0.6829% wt/wt for S. siamea and P. guineense, respectively). Combination of plant powders and DE controlled the beetles faster compared to the plant powders alone. LT₅₀ ranged from 20 h to 101 h for T. castaneum exposed to 1.0% S. siamea and 1.0% DE, and 0.5% P. guineense and 1.0% DE, respectively. Botanicals caused significant reduction of F₁ adults compared to the control. The potential of using botanicals combined with DE to control stored-product insects is discussed.

KEYWORDS:

• Senna siamea
• Piper guineense
• diatomaceous earth
• Sitophilus granarius
• Tribolium castaneum
• Acanthoscelides obtectus

Acknowledgments

Charles Adarkwah was financially supported by the DAAD Program for Research Stays for University Academics and Scientists. The staff of Humboldt University of Berlin, Faculty of Life Sciences, Division Urban Plant Ecophysiology and Biologische Beratung Ltd., Berlin, Germany assisted in various ways, for which we are most grateful. We are most grateful to the Federal Research Centre for Cultivated Plants (JKI), section Plant Analysis and Stored Product Protection, Berlin, Germany who assisted in various ways.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Deutscher Akademischer Austauschdienst [grant number 50015559].