Control Of Ants Research Articles

Fipronil-infused sodium polyacrylate gels provide effective management of Argentine ants in conservation areas.

Various types of hydrogel compounds have recently been developed for controlling invasive and pest ants in a range of environmental settings including agricultural, urban and natural areas. The current study evaluated the potential of sodium polyacrylate (ACR) hydrogels to effectively deliver liquid baits to Argentine ants. Relative to standard polyacrylamide (PAM) hydrogels, individual ACR hydrogel particles were approximately five-fold heavier; this may affect how ants interact with the bait particles, and further influence bait uptake and efficacy. Additionally, ACR hydrogels had significantly higher water absorption capacity and significantly slower rate of water loss, especially during the first 2 h. The efficacy of ACR hydrogel bait containing 0.005% fipronil and various attractants was evaluated on laboratory colonies. Results demonstrated that ACR hydrogel acceptance is significantly increased by the addition of feeding attractants. In addition, a field trial was performed in a nature reserve invaded by Argentine ants to evaluate the efficacy of ACR hydrogel bait. The field trial demonstrated that ACR hydrogel bait containing 0.005% fipronil with various attractants is highly effective and that ant densities throughout the baited plots declined by >99% within 7 days. The results of this study demonstrate that: (i) fipronil is highly effective for Argentine ant control in natural areas when used in low concentrations (0.005%); (ii) ACR hydrogels are an effective tool for delivering liquid baits to Argentine ants; and (iii) hydrogel baits augmented with various attractants including salt, protein and pheromone are highly attractive to Argentine ants. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

When to monitor or control: Informed invasive species management using a partially observable Markov decision process (POMDP) framework

Abstract Resource allocation for invasive species management requires information about the size of the invasive population, which may be expensive and time‐consuming to obtain. The trade‐off between investment in monitoring and control efforts is a challenging decision problem, and existing mathematical tools are often difficult to interpret, and/or limited to a specific case study. We propose a partially observable Markov decision process (POMDP) framework to help decision‐makers understand effective monitoring and control policymaking. POMDPs can deal with uncertainty in both the model and state of the system but are more challenging to solve due to the continuous and high‐dimensional state space. Rather than limiting the possible states of the system, as do most previously proposed methods, we work through the development of a density projection approach, which reduces the dimensionality of the space of beliefs by restricting them to a parametrised family of probability distributions. This serves to align the mathematical representation of the problem with the real‐world quantities relevant to human decision‐making. The result of our model is a sequence of actions, which minimises the expected cost incurred in managing the invasive species, where the recommendation depends on an estimate of the species' abundance, and the uncertainty in this estimate. We demonstrate the effectiveness of our proposed framework with a case study on tropical fire ant (Solenopsis geminata) control and two generic case studies of varying complexity. Furthermore, we investigate sensitivity of the results to the choices of control cost and efficacy, and monitoring cost and error. The framework proposed by this paper makes the powerful machinery of POMDPs available to environmental managers. It computes the optimal course of action to manage a growing population of an invasive species, incorporating a varying time horizon and multiple control interventions. We sidestep the computational difficulties of general POMDPs to provide a clear, visual overview of decision‐making recommendations, and how these decisions change in new situations. Initial results and scenario‐based analysis show promising results, and the framework could be extended to the related field of disease management.

Field evaluations of biodegradable boric acid hydrogel baits for the control of Argentine ants: Promising results in vineyards and citrus orchards

Argentine ants are a major pest in California. In this study, a biodegradable calcium alginate hydrogel with an aqueous boric acid bait was tested against Argentine ant populations in a citrus orchard and a vineyard. A new continuous method was developed to produce large quantities of hydrogel bait for the field test. Foraging activity levels of ants were compared between baited and untreated zones. For both study sites, four to five monthly bait applications throughout summer provided a greater than 80% reduction in ant activity. Based on spatial analyses by distance indices, the baited areas were characterized by gaps (areas with lower ant counts) and the untreated control zones were characterized by patches (areas with higher ant counts). This indicated area-wide suppression of Argentine ants. For the citrus orchard, post-baiting panel trap monitoring showed reductions of both ants and Asian citrus psyllid in the baited zone compared to the control. For the vineyard, mid-season soil analyses indicated that the impact of boric acid baiting on soil boron concentration was negligible. In sum, the calcium alginate hydrogel bait with boric acid as an active ingredient may provide a promising solution for Argentine ant baiting.

Isocycloseram: A new active ingredient for leaf-cutting ants control.

Leaf-cutting ants are the most important pests in several cropping systems in the Neotropics. Granulated baits containing active ingredients, considered hazardous by the Stockholm Convention, are the usual method to control these ants. Isocycloseram is a new insecticide molecule with high safety margin for mammals, but without registration for the ants in general. Thus, this study investigated the effectiveness of granulated baits with isocycloseram in leaf-cutting ants control under laboratory and field conditions. Initially, the mortality of Atta sexdens workers, fed with dehydrated citrus pulp paste containing different concentrations of isocycloseram was evaluated in the laboratory for 21 days, for toxicological classification. Subsequently, the loading, devolution, and incorporation of baits with different concentrations of isocycloseram and the mortality of A. sexdens colonies were evaluated in the laboratory. After that, the percentages of loading and devolution of baits, foraging activity, and colony mortality treated with 0.05, 0.1, 0.2, and 0.3% of isocycloseram were evaluated for the species A. sexdens, A. laevigata, and Acromyrmex lundii in field conditions. All concentrations of isocycloseram killed more than 15% of ants in 24 h and more than 90% in 21 days in the laboratory, being classified as a fast-acting and highly effective active ingredient. Baits with 0.001 to 0.03% of isocycloseram were highly loaded and exhibited low rate of devolution. The mortality of A. sexdens colony was higher at concentrations between 0.075 and 0.3%, in the laboratory. Baits containing isocycloseram at concentrations of 0.2 and 0.3% were highly loaded, presented low devolution rates, and were highly efficient in controlling A. sexdens, A. laevigata, and A. lundii in the field, at dosages of 6, 10, and 12 g/m² of nest. This is the first report of the use of isocycloseram against leaf-cutting ants, contributing to the development of efficient and toxicologically safer ant baits.

New lethal liquid bait for control of pest ants

New lethal liquid bait for control of pest ants

Effects of macro- and micro-nutrients on momentary and season-long feeding responses by select species of ants

Few studies have investigated the relative contribution of specific nutrients to momentary and season-long foraging responses by ants. Using western carpenter ants, Camponotus modoc, and European fire ants, Myrmica rubra, as model species, we: (1) tested preferential consumption of various macro- and micro-nutrients; (2) compared consumption of preferred macro-nutrients; (3) investigated seasonal shifts (late May to mid-September) in nutrient preferences; and (4) tested whether nutrient preferences of C. modoc and M. rubra pertain to black garden ants, Lasius niger, and thatching ants, Formica aserva. In laboratory and field experiments, we measured nutrient consumption by weighing Eppendorf tubes containing aqueous nutrient solutions before and after feeding by ants. Laboratory colonies of C. modoc favored nitrogenous urea and essential amino acids (EAAs), whereas M. rubra colonies favored sucrose. Field colonies of C. modoc and M. rubra preferentially consumed EAAs and sucrose, respectively, with no sustained shift in preferred macro-nutrient over the course of the foraging season. The presence of a less preferred macro-nutrient in a nutrient blend did not diminish the blend’s ‘appeal’ to foraging ants. Sucrose and EAAs singly and in combination were equally consumed by L. niger, whereas F. aserva preferred EAAs. Baits containing both sucrose and EAAs were consistently consumed by the ants studied in this project and should be considered for pest ant control.

Toxicity and Behavior-Altering Effects of Three Nanomaterials on Red Imported Fire Ants and Their Effectiveness in Combination with Indoxacarb.

The red imported fire ant (Solenopsis invicta Buren) is one of the 100 worst invasive alien species in the world. At present, the control of red imported fire ants is still mainly based on chemical control, and the most commonly used is indoxacarb bait. In this study, the contact and feeding toxicity of 16 kinds of nanomaterials to workers, larvae, and reproductive ants were evaluated after 24 h, 48 h, and 72 h. The results showed that the mortality of diatomite, Silica (raspberry-shaped), and multi-walled carbon nanotubes among workers reached 98.67%, 97.33%, and 68%, respectively, after contact treatment of 72 h. The mortality of both larval and reproductive ants was less than 20% after 72 h of treatment. All mortality rates in the fed treatment group were below 20% after 72 h. Subsequently, we evaluated the digging, corpse-removal, and foraging behaviors of workers after feeding with diatomite, Silica (raspberry-shaped), and multi-walled carbon nanotubes for 24 h, which yielded inhibitory effects on the behavior of red imported fire ants. The most effective was diatomite, which dramatically decreased the number of workers that dug, extended the time needed for worker ant corpse removal and foraging activities, decreased the number of workers that foraged, and decreased the weight of the food carried by the workers. In addition, we also evaluated the contact and feeding toxicity of these three nanomaterials in combination with indoxacarb on red imported fire ants. According to contact toxicity, after 12 h of contact treatment, the death rate among the red imported fire ants exposed to the three materials combined with indoxacarb reached more than 97%. After 72 h of exposure treatment, the mortality rate of larvae was more than 73% when the nanomaterial content was above 1% and 83% when the diatomite content was 0.5%, which was significantly higher than the 50% recorded in the indoxacarb control group. After 72 h of feeding treatment, the mortality of diatomite, Silica (raspberry-shaped), and multi-walled carbon nanotubes combined with indoxacarb reached 92%, 87%, and 98%, respectively. The death rates of the three kinds of composite ants reached 97%, 67%, and 87%, respectively. The three kinds of composite food had significant inhibitory effects on the behavior of workers, and the trend was largely consistent with the effect of nanomaterials alone. This study provides technical support for the application of nanomaterials in red imported fire ant control.

红火蚁防治的双重预防机制构建及实践应用研究

红火蚁防治的双重预防机制构建及实践应用研究

Spinosad‐infused biodegradable hydrogel beads as a potential organic approach for argentine ant, Linepithema humile (Mayr) (hymenoptera: Formicidae), management in California citrus orchards

AbstractArgentine ant, Linepithema humile (Mayr), disrupts biological control services in California citrus orchards, leading to economically damaging densities of honeydew‐producing hemipteran pests. With the elimination of chlorpyrifos, the sole registered insecticide for L. humile control in California citrus, the development of effective alternatives is necessary. One alternative is aqueous sugar baits laced with minute concentrations (0.0001%) of insecticide. Field trials were conducted to assess the efficacy of spinosad and thiamethoxam‐infused alginate hydrogel beads (HGBs) for L. humile control. Thiamethoxam‐infused HGBs have previously shown high efficacy against L. humile in citrus. Spinosad is approved for organic use, while thiamethoxam, a neonicotinoid, along with other neonicotinoid insecticides, might soon face deregistration in California, underscoring the need for alternative insecticide chemistries for ant control. Therefore, this study aimed to optimize spinosad‐loaded HGBs by identifying efficacious concentrations, application rates, and deployment frequency, and to compare with thiamethoxam‐infused HGBs, the standard reference treatment. Results showed that spinosad‐infused HGBs significantly reduced high‐density L. humile populations in citrus orchards. Notably, the highest spinosad concentration tested (0.01%) demonstrated comparable control to both 0.0001% and 0.01% thiamethoxam concentrations. A tri‐weekly application schedule for spinosad‐infused HGBs provided best control. Trees treated with 125 or 250 g of hydrogels infused with 0.01% spinosad at weeks 0, 3, and 6 displayed significantly reduced ant activities compared to plots treated solely during weeks 0 and 6, as well as control plots lacking HGB applications. Spinosad‐infused HGBs may offer an effective alternative to thiamethoxam‐infused HGBs for control of L. humile in California citrus orchards.

Repellency of Carvacrol, Thymol, and Their Acetates against Imported Fire Ants.

In the United States, imported fire ants are commonly referred to as red imported fire ants (Solenopsis invicta Buren), black imported fire ants (S. richteri Forel), and hybrid imported fire ants (S. invicta × S. richteri). They are significant pests, and their control heavily relies on synthetic insecticides. The extensive use of insecticides has led to public concern about their potential negative effects on human health and the well-being of wildlife and the environment. As an alternative, plant-derived natural compounds, particularly essential oils (EOs) and their main constituents, show promise as safe and environmentally friendly products for controlling fire ants. Repellants are useful in managing fire ants, and plant-derived natural repellants may serve as a safer and more environmentally friendly option. This study investigates the repellency of EO-derived compounds carvacrol, thymol, and their acetates against imported fire ant workers. The results revealed that carvacrol, a GRAS compound (Generally Recognized As Safe), was the most potent repellent against S. invicta, S. richteri, and their hybrid, with minimum repellent effective doses (MREDs) of 0.98 µg/g, 7.80 µg/g, and 0.98 µg/g, respectively. Thymol also exhibited strong repellency, with MREDs of 31.25 µg/g, 31.25 µg/g, and 7.8 µg/g, respectively. Furthermore, thyme-red essential oil, characterized by a thymol chemotype containing 48.8% thymol and 5.1% carvacrol, was found to effectively repel the hybrid ants with an MRED of 15.6 µg/g. In contrast, thyme essential oil, characterized by a linalool chemotype lacking thymol and carvacrol, did not exhibit any repellent effect, even at the highest tested dose of 125 µg/g. This study provides the first evidence of the potent repellency of carvacrol and thymol against imported fire ant workers, indicating their potential as promising repellents for fire ant control.

Formicidal Potential of Thymol Derivatives: Adverse Effects on the Survival and Behavior of Acromyrmex balzani

Leaf-cutting ants are important pests of agricultural and forest crops. Currently, few insecticides are registered for the control of these insects. Natural bioactive molecules can serve as models for the synthesis of new insecticidal compounds. Such ant killer products must be sustainable and efficient, considering not only lethal effects, but also sublethal effects, which can interfere with behavior and communication between colony members. In this study, we analyzed the toxicity of the monoterpene thymol and its derivatives, as well as the sublethal effects of these compounds on the behavior of the leaf-cutting ant Acromyrmex balzani. These effects were compared with the conventional synthetic insecticide deltamethrin. Although deltamethrin showed higher toxicity (LD50 = 0.87 × 10−5 µg/mg), all other tested compounds increased ant mortality, with thymyl chloroacetate being the most toxic derivative (LD50 = 1.41 µg/mg), followed by thymol (LD50 = 2.23 µg/mg). These three most toxic compounds interfered differentially in the behavior of ants. Thymyl chloroacetate caused increased self-cleaning and reduced allogrooming, which may be related to an attempt to avoid contamination between nestmates. In general, thymol caused greater avoidance among ants, reduced walking speed and caused disorientation in workers. On the other hand, thymyl chloroacetate (LD30) considerably increased the walking speed of the group, without changing the orientation of the individuals. Such changes may interfere with basic activities such as foraging and altering colony cohesion via different mechanisms. Thus, despite the desirable effects of deltamethrin on ant control, this insecticide is highly toxic and should be discontinued soon. Our results show that thymol and its structural modification in thymyl chloroacetate may represent potential ant killers to be used in the management of A. balzani.

Production of Escovopsis weberi (Ascomycota: Hypocreales) Mycelial Pellets and Their Effects on Leaf-Cutting Ant Fungal Gardens

The maintenance of the symbiosis between leaf-cutting ants and their mutualistic fungus Leucoagaricus gongylophorus Singer (Moller) is vital for the survival of both species. The specialist fungal parasite Escovopsis weberi Muchovej & Della Lucia is a threat to this symbiosis, causing severe damage to the fungal garden. Mycelial pellets are resistant fungal structures that can be produced under laboratory conditions. These structures were studied for use in biological pest control, but the production of mycelial pellets has not previously been documented in Escovopsis. One of the aims of this study was to induce Escovopsis weberi to produce mycelial pellets and investigate the potential of these pellets for the control of leaf-cutting ants. We compared the pathogenicity of Escovopsis weberi mycelial pellets and conidia against mini-colonies of Acromyrmex subterraneus subterraneus Forel when applied in the form of baits. Worker ants were able to distinguish mycelial pellets from conidia, as baits with mycelial pellets were more attractive to workers than those with conidia, causing a greater negative impact on colony health. All types of baits containing Escovopsis weberi influenced the foraging activity but only treatments with viable fungal propagules resulted in an increase in the quantity of waste material, with a significant negative impact on the fungal garden biomass. The results provided novel information regarding Escovopsis recognition by worker ants and differences between conidia and mycelial pellet dynamics in leaf-cutting ant colonies, with new perspectives for the biological control of these important pests.

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

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. 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. 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. © 2023 Society of Chemical Industry.

Genetic fine‐mapping of anthracnose disease‐resistance allele Co‐14 present in the Andean common bean cultivar AND 277

AbstractAnthracnose (ANT) is among the common bean fungal diseases responsible for significant yield and grain quality losses. Durable genetic resistance is the primary ANT control method due to the pathogen's high variability. Genetic studies showed that the common bean chromosome Pv01 contains multiple disease resistance genes, including the ANT resistance loci Co‐1 (Co‐12, Co‐13, Co‐14, Co‐15, Co‐1HY, and Co‐1x), Co‐AC, Co‐14, Co‐Pa, Co‐Perla, Co‐w, Co‐x, and CoPv01CDRK. This work aimed to: (i) perform the genetic fine‐mapping of the Co‐14 allele present in the cultivar AND 277, using recombinant inbred lines derived from the cross between Rudá × AND 277; and (ii) identify candidate resistance genes in the Co‐14 allele based on the common bean reference genome. Initially, the Co‐14 allele was mapped between the single‐nucleotide polymorphism markers ss715645251 and ss715645250 at a distance of 2.0 and 19.6 cM, respectively. Fine‐mapping localized Co‐14 between the markers ss715645251 and BARCPVSSR01356, spanning a 40.51 kb region at the end of Pv01. Two genes are described within the Co‐14 region in the reference genome, Phvul.001G243800 and Phvul.001G243900. The linkage between the Co‐14 allele and the markers ss715645251 and BARCPVSSR01356 will be essential for plant breeding programs during the resistance gene transfer to elite cultivars via marker‐assisted selection (MAS). Identifying and functionally analyzing candidate resistance genes in this region will allow more efficient MAS by developing accurate markers for ANT resistance.

Toxicity and horizontal transfer of bifenthrin and dimefluthrin against the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), and the efficacy of their dust applications in the field

The red imported fire ant, Solenopsis invicta Buren, poses a significant threat to biodiversity, agriculture, and public health in its introduced ranges. While chemicals such as toxic baits and dust are the main methods for S. invicta control, toxic baits are slow, requiring approximately one or two weeks, but dust can eliminate the colony of fire ants rapidly in just three to five days. To explore more active ingredients for fire ant control using dusts, the toxicity of bifenthrin and dimefluthrin, the horizontal transfer of bifenthrin and dimefluthrin dust and their efficacy in the field were tested. The results showed that the LD50 (lethal dose) values of bifenthrin and dimefluthrin were 3.40 and 1.57 ng/ant, respectively. The KT50 (median knockdown time) and KT95 (95% knockdown time) values of a 20 μg mL–1 bifenthrin dose were 7.179 and 16.611 min, respectively. The KT50 and KT95 of a 5 μg mL–1 dimefluthrin dose were 1.538 and 2.825 min, respectively. The horizontal transfers of bifenthrin and dimefluthrin among workers were effective. The mortality of recipients (secondary mortality) and secondary recipients (tertiary mortality) were both over 80% at 48 h after 0.25, 0.50 and 1.00% bifenthrin dust treatments. The secondary mortality of recipients was over 99% at 48 h after 0.25, 0.50 and 1.00% dimefluthrin dust treatments, but the tertiary mortality was below 20%. The field trial results showed that both bifenthrin and dimefluthrin exhibited excellent fire ant control effects, and the comprehensive control effects of 1.00% bifenthrin and dimefluthrin dusts at 14 d post-treatment were 95.87 and 85.70%, respectively.

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

The Argentine ant, Linepithema humile Mayr (Hymenoptera: Formicidae), disrupts biological control agents which induces population outbreaks of honeydew-producing hemipteran pests infesting agroecosystems. A multi-season liquid baiting program was evaluated for control of L. humile and ant-associated hemipteran pests in six commercial citrus orchards in southern California. Ant activity in treated trees fell by 96% within three months of treatment and was, on average, 95% lower in treated plots than untreated plots across the 18-month study period. Ant control resulted in the near elimination of hemipteran pest populations on trees in treated plots. Pre- and post-treatment estimates indicated that hemipteran pest infestation of twigs, flush, and fruit decreased by 97, 84, and 99% one year after treatment, respectively. Furthermore, cumulative infestation frequency was 10 times lower and cumulative colony size was 5 times lower on treated trees than control trees across the final year of study. Examining individual hemipteran pest species, the mean infestation rate by Diaphorina citri Kuwayama (Hemiptera: Liviidae) was 75% lower, Coccus hesperidum L. (Hemiptera: Coccidae) 95% lower, Planococcus citri Risso (Hemiptera: Pseudococcidae) 98% – 100% lower, and Aonidiella aurantii Maskell (Hemiptera: Diaspidae) 70 – 80% lower in treated trees relative to untreated trees. A surge in generalist predator activity and parasitism following ant bait deployment appear to be the driving forces behind the marked decrease in pest infestation observed in treated trees. Results underscore the importance of L. humile control for integrated pest management programs targeting ant-associated hemipteran pests in commercial citrus.

Alien vs. herbivore: ant-mediated plant defense as an option for biological control of leafcutter ants

Leafcutter ants are a major pest in vineyards in Argentina, but their damage to vine plants has not been sufficiently quantified. Biological control against leafcutter ants has not been successful so far. Sugary rewards can trigger ants to act as plant bodyguards against a wide range of herbivores. The Argentine ant Linepithema humile (Mayr) is a common invader of vineyards worldwide and has a strong preference for carbohydrates. In a first 10-week field experiment, we attracted L. humile ants to a group of plants using sugar feeders, while no feeders were used for a second group. Ant-excluded control plants were also deployed. We quantified the damage inflicted by the leafcutter ant Amoimyrmex bruchi (Forel) on potted vines with and without L. humile ants. In a second short field experiment, we evaluated the impact of L. humile on A. bruchi foraging through the quantification of foraging activity and the amount of transported material as a function of L. humile presence. We found that A. bruchi caused >90% leaf area reductions in plants without L. humile, while plants where the species was present were rarely attacked and leaves developed similar to those of ant-excluded controls. Active interaction with L. humile decreased A. bruchi’s foraging activity and the amount of material transported by it. This is the first report of A. bruchi as a vineyard pest and the first quantification of the damage inflicted by a leafcutter ant on organic grapevines. We demonstrate that L. humile defends vine plants against herbivore pests and artificial sugar sources boost can this defense service. The development of biological control strategies that include the ecological services of ants as natural enemies of herbivorous pests could become a useful tool in sustainable viticulture and horticulture.

Chemical control of Acromyrmex lundi (Hymenoptera: Formicidae) in anthropic ecosystems.

Leaf-cutting ants are pests in agriculture, forests and pasture and, usually, controlled with toxic baits. The management and control of leaf-cutting ants is complex as a consequence of its sociability and behavior. We tested three toxic baits with abamectin, fipronil and sulfluramid to control colonies of Acromyrmex lundi Mayr, 1865 (Hymenoptera: Formicidae), in two seasons: 'Spring 2020' and 'Summer 2020/21', in Argentina. The percentage of effective bait carried in the spring was similar between treatments with 80%, 80% and 90% for those with abamectin, fipronil and sulfluramid. The ant flow of A.lundi decreased after toxic bait applications compared to the control through time in all treatments. This activity was higher in the spring than in the summer. The baits reduced the foraging activity of A.lundi from 5 to 96 days after application (DAA). Abamectin and fipronil baits controlled 50% and 67% of the nests in the spring, and 20% and 43% at 96 DAA in the summer. Sulfluramid was the best treatment, killing 90% of A.lundi nests. The baits decrease the foraging activity of A.lundi until 96 DAA, with total or partial death of its colonies varying between treatments. The ant symptoms with the sulfluramid bait appeared faster than with fipronil and may be a result of the low level of carry-over or differences in the chemical quality of the active ingredients. © 2022 Society of Chemical Industry.

Long‐term quantification of leaf‐cutting ant damage in willow forestations in the lower delta of the Paraná River, Argentina

Abstract Leaf‐cutting ants are major pests of Neotropics forest plantations. The lower delta of the Paraná River contains the main Argentine Salicaceae production, strongly attacked by Acromyrmex lundii and Acromyrmex ambiguus. Nevertheless, there is no damage quantification in willow plantations attributed to leaf‐cutting ant species. In an area without leaf‐cutting ant control, we installed 15 blocks with eight willow stakes each: four clones × two treatments; with and without leaf‐cutting ant exclusion. We used two traditional (Americano, Nigra 4) and two new (Géminis, Yaguareté) commercial clones. During 2014–2018, we measured the damaged foliage, height and diameter of each tree. Foliage was damaged intensely during the first 2 years. After 1537 days, the loss in height and diameter was greater in Americano (70%), followed by Géminis (50%–60%), Yaguareté (40%–50%) and Nigra 4 (45%–40%). Stake survival with exclusion was greater (>80%) than stakes without exclusion (<50%). Total loss of wood volume was 93% for Americano, followed by Géminis (77%), Yaguareté (66%) and Nigra 4 (51%). Although the new clones were heavily attacked, they produced two to three times more wood volume than Americano; replacing Americano with the new clones would help to reduce leaf‐cutting ants impact on plantations and pesticides released into the environment.

Regional and caste‐specific variation in insecticide susceptibility in odorous house ants, Tapinoma sessile (Hymenoptera, Formicidae)

AbstractAnts consistently rank as the number one household pest, and many species are pests in agricultural and natural habitats. Despite economic and ecological impact of pest ants, effective management still faces many challenges and control failures with liquid spray insecticides are common. The odorous house ant (Tapinoma sessile Say) is an adaptive and widespread pest ant found in North America. This study examined regional variation in T. sessile insecticide susceptibility to three classes of insecticides commonly used in ant control. T. sessile showed significant regional variation in insecticide susceptibility on a relatively small geographic scale. A comparison of colonies collected in urban vs. natural areas showed no significant difference in susceptibility in tests with lambda‐cyhalothrin and fipronil. In tests with dinotefuran, urban colonies were significantly more tolerant relative to natural colonies. These results suggest that habitat type and previous insecticide exposure do not reliably predict susceptibility levels in individual populations. Queens were significantly more tolerant relative to their worker counterparts across all insecticides. Higher insecticide tolerance in queens may explain why T. sessile is such a persistent pest in urban environments. The results provide a foundation for the development of more effective and efficient control methods for T. sessile and warrant further investigation of spatial and potentially temporal variability in insecticide susceptibility in ants.