Short Version
Yes, naphthalene balls (mothballs) in the crowns of Royal Palms and Coconut can instantly stop beetles from entering, ovipositing and causing damage. Our trials with three balls in one 450ml water bottle show that there are no attacks for 12–14 weeks once the balls are in place.. However, to be clear, this is not a recommended practice, as naphthalene is not approved for use as a pesticide nor for use near crops. It is also water soluble, so it will (there is no question here) enter the palm's sap and tissue if used in the crown.
🛑⚠️ Warning ⚠️⚠️⚠️⚠️⚠️⚠️
Again, although placing mothballs is a widespread practice - we cannot recommend this.
🛑 https://www.youtube.com/watch?v=2SoyZd7Icjo
🛑 https://www.youtube.com/watch?v=Y_FoZOnQu4Q
Long Version
Believe it or not, using a vapor cloud to repel pests from plants is established art. What is not established is whether it’s better to attract and trap the pests inside or around the infected area or repel them away. But what we have established is that stakeholders are pretty clear - they overwhelmingly request the latter.
We were so fascinated by naphthalene's ability to protect coconut seedlings from rhinoceros beetles, as presented by Sadakathulla and Ramachandran (1990) and Singh (1987), that in 2020 we began developing passive, contactless pest control techniques for both greenhouses and open fields.
For coconut, we first tested naphthalene’s ability to protect 12 palms in Erin, in a field known to have South American palm weevils (Rhynchophorus palmarum) present. However, unlike the trials conducted in India, we eliminated direct contact with the palm by inserting three naphthalene balls into an empty 450 mL water bottle with 3 mm holes—two at the base and one on the cap. Two of these bottles were inverted (cap down to allow any water or condensation to drain) and then positioned in the palm's crown. The naphthalene balls with the restricted opening in the bottle lasted 14–16 weeks, and no beetles were observed near any of the 12 palms - implying it is theoretically possible to build a "slow release" system that can last 52 weeks.
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| P1 - Juvenile palm with napthalnene balls housed in vented 450ml bottle | P2 - Juvenile palm with napthalnene balls housed in vented 450ml bottle |
However, naphthalene, for now, is not suitable for plant protection as it is not approved by the US EPA or the EU EFSA for use in pest control or near food. More importantly, naphthalene is water-soluble, meaning that rain or irrigation water can dissolve it, allowing it to enter the plant through the leaves, roots, or other parts. But naphthalene is a naturally occurring compound that is actually produced by some organisms, as presented in Shimizu et al. (2002), implying that it is highly likely to be synthesized in plants and not show up in the fruits. Only further research will tell us.
In response, we developed the STIM31 Vapor Cloud Cartridge, designed to repel beetles and moths from entering and ovipositing in the palm's crown, while simultaneously attracting pollinators—a crucial feature for allogamous coconut varieties. Plant extracts are used for the repellant cocktail and to date, we have observed no infections in the 26+ trees we have been testing.
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| P3 - STIM31 Vapour Cloud Cartridge Production Prototype (ENP02) |
