Previous diet affects the amount but not the type of bait consumed by an invasive ant

Abstract

BACKGROUND Recent research on multiple invasive ant species has revealed the importance of carbohydrates for achieving high activity levels and outcompeting native ants. However, comparatively little is known about the role of diet and macronutrient preferences for uptake of insecticidal baits used to control invasive ants. We tested whether diet affected yellow crazy ant (Anoplolepis gracilipes Fr Smith) survival and behavior, and whether bait preference would be complementary to past diet. RESULTS We found that colonies fed only crickets for 28 days had fewer live workers and queens, and less brood per live queen than colonies fed crickets + honeydew but did not differ significantly from colonies fed only honeydew. Colonies that had been fed only crickets were more active (as assessed by interaction with a novel object), retrieved 16–17 times more bait per worker overall, and consumed more of the six bait types than cricket + honeydew and honeydew‐only fed colonies. However, prior diet did not affect bait choice. The two highest sugar bait formulations combined accounted for most of the bait consumed across all treatments (cricket‐only 74.8% ± 28.1; cricket + honeydew 69.2% ± 12.4; honeydew‐only 62.5% ± 30.4). CONCLUSION Yellow crazy ant colonies fare better without protein than without carbohydrates. Yellow crazy ants ate the most bait when fed only crickets but did not choose baits complementary to their previous diet. Baits in a sugar‐rich carrier may be most effective for the control of yellow crazy ants, regardless of the relative availability of macronutrients. © 2019 Society of Chemical Industry

Native and non-native sources of carbohydrate correlate with abundance of an invasive ant

“…These three species are widely distributed across Australia (Fletcher 2009) and therefore, may facilitate other yellow crazy ant populations should efforts to control them fail. Our study, along with the only previous report of yellow crazy ants tending native honeydew-producing insects, the whitefly Neomaskellia bergeii in sugarcane fields in northern Queensland, Australia (Lach et al 2019), suggests that lack of non-native honeydew producers does not impede yellow crazy ant invasion. This suggestion is also supported in Western Australia, where another invasive ant, Paratrechina longicornis (Latreille), was found in high abundances while tending native Sextius sp.…”

“…We have little knowledge of whether access to carbohydrate resources is linked to invasive ant abundance when invasive ant abundance is low or populations are just establishing (Helms 2013). Evidence from laboratory experiments suggest that access to carbohydrates is fundamental to colony growth and activity (e.g., Grover et al 2007;Wilder et al 2011a;Wittman et al 2018;Lach et al 2019). If invasive ant abundance is low, the ants may not be able to outcompete other resident ant species to gain access to resources (sensu Drescher et al 2011).…”

Low reduction of invasive ant colony productivity with an insect growth regulator

“…At a typical field application rate of 2 kg ha –1 , 0.1 g would be the quantity of bait distributed over an area of ≈0.5 m 2 . The corn‐grit matrix previously has been shown to be attractive to A. gracilipes 38 . Nests had access to the bait for one week, during which time no other food resources were available.…”

“…We then photographed the occupants for later counting of larvae, pupae and workers, before replacing the box contents. We assessed colony activity levels by quantifying the interactions of ants with a novel object 38 . We stood a clean steel wire spring (12 cm height × 12 cm diameter, with six coils) vertically in each colony box, taking care not to disturb the occupants, and then counted the number of A. gracilipes that were in contact with the object at 15 s, 30 s, and 1, 5 and 15 min after its introduction.…”

“…The corn-grit matrix previously has been shown to be attractive to A. gracilipes. 38 Nests had access to the bait for one week, during which time no other food resources were available. Additionally, we set up 30 0.1 g baits (50% active, 50% blank) outside the colonies to determine changes in bait mass unrelated to ant consumption (such as evaporative water loss).…”