Growing hot pepper for cabbage looper, Trichopulsia ni (Hübner) and spider mite, Tetranychus urticae (Koch) control

Abstract

With the public perception that synthetic pesticides leave harmful residues in crop produce for human consumption, there has been increased interest in using natural products for pest control. The potential of using fruit extracts of hot pepper for controlling the cabbage looper, Trichopulsia ni (Hübner) and spider mite, Tetranychus urticae Koch is explored in this investigation. Crude extracts from fruits of Capsicum chinense, C. frutescens, C. baccatum, and C. annuum, were prepared and tested under laboratory conditions for their insecticidal and acaricidal performance. Mortality was greatest (94%) when fruit extract of accession PI-593566 (C. annuum) was sprayed on larvae of the cabbage looper, while crude extracts of accessions PI-241675 (C. frutescens) and PI-310488 (C. annuum) were repellent to the spider mite. We investigated differences in chemical composition of the crude fruit extracts that may explain the observed differences in mortality and repellency between accessions. Gas Chromatography-Mass Spectrometry spectrometric analysis revealed that capsaicin and dihydrocapsaicin, the pungent components of pepper fruit, were not correlated with toxicity or repellency, indicating that the two capsaicinoids are not likely related to the efficacy of pepper fruit extracts. Major compounds in hot pepper fruit extracts were detected and identified as pentadecanoic acid methyl ester, hexadecanoic acid methyl ester, and octadecanoic acid methyl ester. Spectrometric analysis and toxicity to cabbage looper larvae revealed that pentadecanoic acid methyl ester is likely related to cabbage looper mortality. However, the concentration of pentadecanoic acid methyl ester in some accessions was insufficient to explain the observed mortality of cabbage looper and repellency of spider mite. Fruit extracts of accessions PI-593566 (C. annuum) and PI-241675 (C. frutescens) could be useful for managing populations of cabbage loopers and spider mites, which could reduce reliance on synthetic pesticides. Further study is needed to investigate performance of hot pepper extracts under ultra-violet light and field conditions.