Subterranean termite colony elimination can be achieved even when only a small proportion of foragers feed upon a CSI bait

Abstract

Termite bait products that contain chitin synthesis inhibitors (CSIs) protect structures from subterranean termites via colony elimination. A hallmark of CSI baits is their dose-independent lethal time, as workers exposed to a CSI do not die until they initiate the molting process. Due to this mode of action and termite behaviors such as trophallaxis and cannibalism, a relatively small quantity of ingested CSI can spread throughout an entire colony before secondary repellency or avoidance behaviors occur, ultimately resulting in total colony elimination. In the field, only a portion of a subterranean termite colony actively forages upon a CSI bait at any given time, suggesting that only a relatively small proportion of workers may need to feed upon a CSI bait for a colony to be eliminated. In the present study, we used varying proportions of workers from whole four-year-old laboratory-reared Coptotermes gestroi (Wasmann) colonies (~ 62,500 termites/colony on average) to determine what proportion of workers need to feed upon a CSI bait in order to achieve colony elimination. A range of 0% (control), 0.5%, 1%, 2.5%, and 5% of the total worker population of colonies was allowed to feed on a formulated 0.5% noviflumuron bait for five days before being returned to their colonies. Colony elimination was observed for all 5%-fed and four out of six 2.5%-fed colonies by 107 days after CSI exposure. Our results confirm that only a small subset of the worker population of a colony must feed upon a CSI bait to achieve subterranean termite colony elimination.

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Journal of Pest Science (2022) 95:1207–1216
https://doi.org/10.1007/s10340-021-01446-4
ORIGINAL PAPER
Subterranean termite colony elimination can be achieved even
whenonlyasmall proportion offoragers feed uponaCSI bait
JohnalynM.Gordon1,2 · JosephF.VelenovskyIV2· ThomasChouvenc2
Received: 4 June 2021 / Revised: 14 September 2021 / Accepted: 29 September 2021 / Published online: 21 October 2021
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021
Abstract
Termite bait products that contain chitin synthesis inhibitors (CSIs) protect structures from subterranean termites via colony
elimination. A hallmark of CSI baits is their dose-independent lethal time, as workers exposed to a CSI do not die until
they initiate the molting process. Due to this mode of action and termite behaviors such as trophallaxis and cannibalism, a
relatively small quantity of ingested CSI can spread throughout an entire colony before secondary repellency or avoidance
behaviors occur, ultimately resulting in total colony elimination. In the field, only a portion of a subterranean termite colony
actively forages upon a CSI bait at any given time, suggesting that only a relatively small proportion of workers may need to
feed upon a CSI bait for a colony to be eliminated. In the present study, we used varying proportions of workers from whole
four-year-old laboratory-reared Coptotermes gestroi (Wasmann) colonies (~ 62,500 termites/colony on average) to determine
what proportion of workers need to feed upon a CSI bait in order to achieve colony elimination. A range of 0% (control),
0.5%, 1%, 2.5%, and 5% of the total worker population of colonies was allowed to feed on a formulated 0.5% noviflumuron
bait for five days before being returned to their colonies. Colony elimination was observed for all 5%-fed and four out of six
2.5%-fed colonies by 107 days after CSI exposure. Our results confirm that only a small subset of the worker population of
a colony must feed upon a CSI bait to achieve subterranean termite colony elimination.
Keywords Coptotermes gestroi· Bait transfer· Chitin synthesis inhibitors· Termite control
Key message
• 5% of workers feeding on a commercial CSI bait is suf-
ficient for colony elimination.
• True feeding threshold likely between 2.5% and 5% of
the worker population.
• Minimum threshold of bait consumption is lower than
previously estimated.
• Study conducted at the colony level – over 1.68 million
termites used.
Introduction
Subterranean termite species within the Heterotermes, Retic-
ulitermes, and Coptotermes genera (Rhinotermitidae) are
responsible for a significant portion of the structural damage
caused by termites, and resulting economic impact, around
the world (Bourguignon etal. 2016; Chouvenc etal. 2016;
Evans etal. 2013; Krishna etal. 2013; Rust and Su 2012).
Although liquid termiticides remain widely used, the control
of subterranean termites through the use of baits has become
a prominent industry standard since baiting systems that uti-
lize chitin synthesis inhibitors (CSI) were first introduced in
the mid-1990s (Su 1994, 2019). CSI baits meet the three cri-
teria for achieving colony elimination: They are slow-acting,
they are non-repellent, and they have a dose-independent
lethal time (Su and Scheffrahn 1996; Su 2003). Current
commercial formulations can provide a cost-effective and
Communicated by Antonio Biondi.
* Johnalyn M. Gordon
johnalyn@uky.edu
1 Department ofEntomology, University ofKentucky,
Lexington40546, KY, UK
2 Entomology andNematology Department, Ft. Lauderdale
Research andEducation Center, Institute ofFood
andAgricultural Sciences, University ofFlorida, 3205
College Ave., Ft.Lauderdale, FL33314, USA
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