A low-toxicity baiting program precipitates collapse of Argentine ant and ant-associated hemipteran pest populations in commercial citrus

BACKGROUND: Delottococcus aberiae is an invasive mealybug that produces severe damage in Spanish citrus. This mealybug has established a mutualistic relationship with native Mediterranean ant species that may limit biological control of this pest. Herein, we evaluated the effect of tending ants on the biological control of D. aberiae. To do this, we compared: (i) the density of D. aberiae, (ii) the density of its natural enemies, and (iii) the damage produced by the mealybug in trees with (control) and without ants (ants excluded with sticky barriers) in two citrus orchards across two consecutive years. RESULTS: Lasius grandis was the most abundant ant species in both orchards and represented more than 95% of the ants tending D. aberiae in control trees. Spiders and lacewings were the most abundant predators observed in mealybug colonies, and the exclusion of mutualistic ants increased their abundance. Moreover, in control trees, ant activity throughout the year was negatively correlated with the relative abundance of predators (number of predators per mealybug). No parasitoids were recovered during field experiments. Ant exclusion reduced the density of D. aberiae and the ratio of damaged fruit at harvest across years and orchards.CONCLUSIONS: This work corroborates the previous finding that D. aberiae benefits from its mutualistic relationship with L. grandis, probably because the presence of ants reduced the abundance of generalist predators. This mutualism can be disrupted using physical barriers on on the trunk. Further research should assess other methods of ant control that are more economic and feasible for citrus producers.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Exclusion of Mediterranean ant species enhances biological control of the invasive mealybug Delottococcus aberiae in citrus

Plata

Gómez‐Martínez

Beitia

et al. 2023

“…15 This may lead to increased numbers of sap-sucking homopterans and may negate the positive effects of ants in agricultural systems. [16][17][18][19] To counteract the mutualism between ants and their trophobionts, sugar feeding has been employed. If provided with dispensers containing artificial sugar solutions, ants may choose artificial sugar over honeydew and stop attending homopterans.…”

Section: Introductionmentioning

confidence: 99%

“…In return for the honeydew and to increase productivity, ants protect homopteran partners against their natural enemies, sanitize them by removing their waste products (the honeydew) and transport them to fresh plant tissues 15 . This may lead to increased numbers of sap‐sucking homopterans and may negate the positive effects of ants in agricultural systems 16–19 …”

Section: Introductionmentioning

confidence: 99%

Implementing wood ants in biocontrol: Suppression of apple scab and reduced aphid tending

Jensen

Hansen

Damgaard

et al. 2023

BACKGROUND Ants can become efficient biocontrol agents in plantation crops as they prey on pest insects and may inhibit plant pathogens by excreting broad‐spectrum antibiotics. However, ants also provide a disservice by augmenting attended honeydew producing homopterans. This disservice may be avoided by offering ants artificial sugar as an alternative to honeydew. Here we tested the effect of artificial sugar feeding on aphid abundance in an apple plot with wood ants (Formica polyctena, Förster), and tested the effect of ant presence on apple scab (Venturia inaequalis, Cooke) disease incidence. RESULTS Over a 2‐year period, sugar feeding eliminated ant‐attended aphid populations on the apple trees. Furthermore, scab symptoms on both leaves and apples were reduced considerably on ant trees compared to control trees without ants. The presence of ants on the trees reduced leaf scab infections by 34%, whereas spot numbers on fruits were reduced by between 53 and 81%, depending on apple variety. In addition, the spots were 56% smaller. CONCLUSION This shows that problems with wood ant‐attended homopterans can be solved and that ants can control both insect pests and plant pathogens. We therefore propose wood ants as a new effective biocontrol agent suitable for implementation in apple orchards and possibly other plantation crops. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Corpse‐associated odours elicit avoidance in invasive ants

Wagner,

Czaczkes

2023

BACKGROUNDInvasive ants, such as Linepithema humile (the Argentine ant), pose a global threat, necessitating a better understanding of their behaviour in order to improve management strategies. Traditional eradication methods, including baiting, have had limited success, but the causes of control failure are not always clear. This study aims to investigate whether ants form associations between food odours and corpses, and subsequently avoid areas or food sources with food odours associated with corpses. We propose that ants may learn to avoid toxic baits in part because of their association with ant corpses, which could have implications for pest control strategies.RESULTSAnts were tested on a Y‐maze after exposure to scented corpses or dummies. 69% (n = 64) of ants avoided branches bearing the scent of scented corpses. Colonies neglected food with corpse‐associated odours, with only 42% (n = 273) of foragers feeding from such sources. However, if corpses were produced by feeding ants scented toxicant, focal ants encountering these corpses did not avoid the corpse‐associated scent on a Y‐maze (53%, n = 65). In dual‐feeder tests, ants did not avoid feeding at food sources scented with odours associated with conspecific corpses.CONCLUSIONConspecific corpses act as a negative stimulus for ants in a foraging situation, potentially causing avoidance of toxic baits. This study suggests adding odours to baits and cycling them to disrupt the bait–corpse association may be helpful. Interestingly, although avoidance of baits was observed, feeding preferences were not significantly affected. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.