Red imported fire ants, Solenopsis invicta Buren (Hymenoptera: Formicidae), which are among the most harmful alien ants, were first detected in Japan in a shipping container from China in May 2017, and continue to enter Japan via this trade pathway. Fumigation is one of the most effective ways to eliminate S. invicta from goods transported in containers. The present study is the first to evaluate the effect of fumigation with allyl isothiocyanate (AITC) against S. invicta. Fumigation using microencapsulated AITC pellets in a gas-barrier bag for 24 h completely killed S. invicta. Furthermore, our fumigation system was able to maintain a high concentration of AITC vapor for at least 13 days. AITC, a naturally occurring compound in wasabi [Eutrema japonicum (Miq.) Koidz], has been demonstrated to be safe for humans and the environment, but its use as a fumigant is limited by its strong volatility and pungency. However, its encapsulation solves this problem by allowing controlled vapor release. Thus, the use of microencapsulated AITC in combination with a gas-barrier bag has considerable potential to provide an effective and easy-to-use protocol for fumigation of S. invicta.

Solenopsis invicta Buren (Hymenoptera: Formicidae; red imported fire ant) is an invasive species in several parts of the world. A major contributor to the spread of S. invicta is infested shipping containers. The vapor of allyl isothiocyanate (AITC), a naturally occurring organosulfur compound, is highly toxic to S. invicta; however, AITC is highly volatile. Microencapsulation of AITC in polyethylene (PE) resin slows the release of AITC, making it a potentially useful material for preventing S. invicta infestations. Here, we examined the efficacy of AITC microencapsulated in PE (mAITC) as a repellent against S. invicta infestation of cardboard boxes, a common containerized cargo. Using baited cardboard boxes, we found that the number of S. invicta individuals entering boxes containing an mAITC sheet was significantly less than that entering boxes without an mAITC sheet. When a PE cover, which is often used to protect carboard boxes during shipping, was used, vapor concentrations of AITC inside the boxes were increased and the number of S. invicta individuals entering the boxes was reduced almost to zero. These findings indicate that mAITC sheeting, especially in combination with a PE cover, is a promising material for the protection of containerized cardboard-box cargo against S. invicta infestation.