A sensitive bioassay for spider mite (Tetranychus urticae) repellency: a double bond makes a difference

Area of Science:

• * Entomology
• * Chemical Ecology
• * Organic Chemistry

Background:

• * Spider mites are significant agricultural pests.
• * Understanding their chemical ecology is crucial for developing control strategies.
• * Natural products and synthetic compounds are investigated for repellent properties.

Purpose of the Study:

• * To determine the repellency of homologous n-alkanes and 1-n-alkenes to spider mites.
• * To identify the most effective hydrocarbon repellents.
• * To evaluate the sensitivity of a bioassay for detecting structure-activity relationships in repellents.

Main Methods:

• * Choice bioassays were conducted using homologous n-alkanes (C8-C21) and 1-n-alkenes (C15-C19).
• * Repellency was assessed at a concentration of 400 μg/cm(2).
• * EC50 values (concentration for 50% mite repulsion) were determined for repellent compounds.

Main Results:

• * C15-C19 n-alkanes were highly repellent, with n-hexadecane (C16) showing the strongest effect.
• * 1-Heptadecene (C17 1-n-alkene) exhibited the lowest EC50 value.
• * The bioassay detected significant differences in repellency based on hydrocarbon structure, including the presence of a double bond.

Conclusions:

• * Specific n-alkanes and 1-n-alkenes possess significant spider mite repellent activity.
• * The developed bioassay is sensitive enough to differentiate repellency based on subtle structural variations.
• * Findings contribute to understanding natural product repellents and may aid in developing new pest control methods.