- Author: Dong Hwan Choe
- Author: Chow-Yang Lee
- Author: Michael K Rust
Ants are one of the major seasonal pests around structures in California's urban environments. Pest management companies throughout the state report that ants are responsible for a significant proportion of their pest control services. In urban residential areas of California, the Argentine ant, Linepithema humile, is the most common nuisance ant species treated by pest management professionals (PMPs) as well as the public themselves (Figure 1).
While contact insecticides are frequently used to control Argentine ants, they also contribute to environmental contamination via drift and runoff. However, insecticide applications following California's recent regulatory changes and label updates may fail to control target pest ants consistently potentially resulting in repeated insecticide applications (Choe et al. 2021).
Baiting for ant control
Baiting (Figure 2) can reduce the need for insecticide spray applications. Active incorporation of baits in a management program may help to lower the risk of environmental contamination caused by insecticide drift and run-off. For Argentine ants, which often form large colonies with multiple nest sites and reproducing queens, the initial application of perimeter spray would still be needed to provide a quick knockdown of foraging ant populations during peak season (June or July). However, baits are particularly useful for subsequent maintenance visits (monthly or bimonthly). In fact, baiting has been demonstrated to be an effective tool for maintenance services for Argentine ants (see References).
Many bait products are available for professional use, and when strategically used, they can be effective at keeping ant numbers low (at acceptable levels) following the initial spray treatment. Gel / liquid / granular bait products containing boric acid, indoxacarb, and thiamethoxam are effective for Argentine ant control.
Importance of bait placement
If PMPs choose to incorporate baits as a main tool for maintenance visits, there is an important question to be answered: Where to place the bait? Unless bait stations are already installed in specific locations and periodically serviced (e.g., cleaning and refilling), PMPs must determine where the baits need to be applied during their visit.
Unlike insecticide sprays, the ants must consume the bait to be effective. Baits placed in just any location cannot be expected to work. Strategic placement of baits is critical to maximize the bait consumption by foraging ants and control of the pest ant populations. In fact, baits start losing their palatability (attractiveness as food) from the moment they are applied in the environment.
Since all ant foragers are liquid feeders, keeping the bait hydrated (minimal water loss) is vital to maximize bait consumption. Contamination and degradation might also impact bait palatability over time. Placing baits in the areas where the ants are currently traveling or foraging will ensure maximum bait consumption. Baits are typically more expensive than insecticide sprays (based on the product cost to treat a unit area), so strategic placement of baits is also crucial from an economic standpoint.
Label information on bait products usually includes specific tips regarding bait placement. For example, one commercial ant bait product label states, “place bait on, into, or adjacent to structures where ants are observed, adjacent to ant trails and to areas suspected of ant activity.” Another product's label instruction states, “locate areas around the building where ants are seen trailing. Apply [the bait] in areas inaccessible to children and pets. For a perimeter defense system, place bait stations near the foundation or where ant trails are found.” In essence, these instructions require knowledge of the locations where the ants are currently active or likely will be within a day or two.
Finding ant trails might be easy if customers have already observed or reported the ant infestation. However, finding active ant trails could be time-consuming, and time for careful inspection to discover active ant trails around the structure during a service visit is often limited.
Ant trail location study
Is there a quick and reliable way to identify the most likely places where Argentine ants would trail and forage in residential outdoor settings? Knowing this would make it possible to quickly determine the best sites for bait placement without looking for ant trails. Argentine ants are known to rely on chemical signals (trail pheromone) as well as structural features (structural guidelines) when maneuvering in the environment (Klotz et al. 1997). Many residential settings share some common structural features such as concrete, lawn, mulch, plant, and soil. If common features can be used to reliably locate the foraging ant trails, that could reduce the time needed to look for ant trails during bait applications.
Site types | Surface/characteristics |
---|---|
L | Lawn |
C | Concrete |
D | Dumpster/trashcan |
T | Tree |
V | Vegetation/bush |
LC | Lawn – concrete interface |
SC | Soil – concrete interface |
MC | Mulch – concrete interface |
BS | Building (vertical surface) – soil interface |
BC | Building (vertical surface) – concrete interface |
A simple field experiment was designed to identify the best sites for bait placement. The study was conducted in October on the University of California, Riverside campus. Several site types were identified based on structural characteristics. Five of these site types were characterized by the presence of a single surface type or a single characteristic item—lawn (L), concrete (C), dumpster or trashcan (D), tree (T), vegetation/bush (short plant without trunk, V). Five other site types were characterized by the presence of two surface types and the interface between them – lawn and concrete (LC), soil and concrete (SC), mulch and concrete (MC), building and soil (BS), and building and concrete (BC). The list of site types is provided in Table 1.
The experiment was replicated 5-13 times for each of the site types. Small squares of cotton (monitoring squares) soaked in 25% (wt:wt) sucrose solution were placed in these sites. The monitoring squares were collected after one hour, and Argentine ants on the cotton squares were counted. The number of ants on the monitoring square was used as the quantitative indicator for ant foraging activity.
The overall data suggest the interface between lawn and concrete (LC) was the location with the highest level of Argentine ant foraging activity (Figure 3). The interface between lawn and concrete (LC) had a much higher number of ants than its single-surface counterparts (L, lawn only or C, concrete only). Bases of the tree (T) and dumpster site (D) also had a good amount of ant activity, but there can be significant amounts of variation in ant activity, especially for dumpster sites (i.e., hit-or-miss). Open concrete surface (C) had the lowest level of foraging activity. Lawn (L), vegetation/bush (V), and four other interface types (SC, MC, BS, and BC) showed intermediate levels of ant activity.
Certain structural and landscape features can be used to quickly determine the best locations for inspection and bait (liquid or gel) placement against Argentine ants. Interfaces between lawns and concrete are among the most common structural features of residential outdoor settings. For example, they are found between lawns and various concrete surfaces, such as driveways, sidewalks, patios, and landscape curbing (Figure 4).
There are possible reasons why the Argentine ants prefer to trail along the interface between lawn and concrete. Preferred microclimate conditions (moisture, temperature) may exist in that location. The absence of heavy vegetation along the lawn and concrete interface (ease of travel), but still with some level of protection (partially shaded), may also be preferred by trailing ants. Environmental factors such as relatively high humidity and partial protection from direct sunlight would also be advantageous in keeping the liquid or gel bait palatable for extended periods.
Take-home message
It is vital to effectively manage pest ants in urban environments with minimal impacts on human health and the environment. To help reduce our reliance on repeated application of insecticide spray products, baiting should be considered for maintenance service visits for pest ants. To maximize the impact of baiting, the baits should be placed along lawn and concrete surfaces. Of course, a control program should not rely only on baiting but also be supplemented with non-chemical techniques such as exclusion, sanitation, removal of honeydew sources, and water management.
It is important to note that the information and data discussed in this article are focused on Argentine ants and sugar-based bait products targeting this species. Thus, the information may or may not directly apply to other ant species with different feeding habits, foraging strategies, or population structures.
For more information about ant management, see the UC IPM Ant page https://ipm.ucanr.edu/PMG/invertebrates/links.ants.html.
References cited
Choe D-H, Paysen, E, Greenberg L, Campbell K, Rust MK. 2019. A closer look: Argentine ant control. Pest Control Technology. GIE Media, Inc. p. 130-135. Vol. 47. No. 10.
Choe D-H, Tay J-W, Campbell K, Park H, Greenberg L, Rust MK. 2021. Development and demonstration of low-impact IPM strategy to control Argentine ants (Hymenoptera: Formicidae) in urban residential settings. J. Econ. Entomol. 114: 1752–1757.
Klotz JH, Greenberg L, Shorey HH, Williams DF. 1997. Alternative control strategies for ants around homes. J. Agric. Entomol. 14: 249-257.
[Originally featured in the Spring 2024 edition of the Green Bulletin Newsletter for structural and landscape pest professionals.]
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- Author: Belinda Messenger-Sikes
During the holiday season, the only creatures you want stirring in your home are your family, friends, and pets. But as temperatures drop, and the rain returns, some pests may seek shelter indoors with you. Rats and mice can be problems all year but in the cold weather, they prefer the warmth of your home to being outdoors and you might see more in your home.
Pests invade homes for varying reasons during autumn and winter. Common outdoor species such as Argentine ants, Oriental (or Turkestan) cockroaches, sowbugs and pillbugs, springtails, and earwigs, may simply be escaping harsh conditions such as freezing temperatures or small-scale flooding. Some insects, especially true bugs (Hemiptera); such as boxelder bug, bordered plant bug, milkweed bug and other seed bugs, false chinch bug, and various stink bugs, naturally seek out dry, protected cracks and crevices to spend the winter. In the landscape, such sites may be beneath loose tree bark or deep within firewood piles, but structural gaps, cracks and crevices may be warmer, drier, and more attractive to these overwintering bugs.
It's generally easier to keep pests out before they become a problem than to try and get rid of them once they infest your home. Exclude pests by sealing up possible entry points around doors, windows, foundations, chimneys, roof joints, shingles, and vents. Install door sweeps and threshold seals to get rid of gaps under and around doors. If you have gaps around windows, you can close them with weather stripping and expanding foam or install new screens.
Clean up the landscape around your home so pests have fewer places to live and breed. Move wood chips and other organic mulches, and firewood piles away from your home's perimeter and entryways. Drain any excess moisture near structural foundations and entryways.
If you spot nuisance pests like boxelder bugs, earwigs, springtails, and centipedes indoors, they can be simply swept up, vacuumed, or taken outside. Other pests like mice and rats need to be dealt with differently.
Ideally, mice and rats should be managed before they get inside. Check the exterior of your home for signs of a mice or rat infestation including droppings, gnaw marks, feeding damage, and rub marks. For mice and rats, tight fitting lids on garbage cans and compost containers will keep these rodents from finding a food source near your home and eventually coming indoors. Thin vegetation between shrubs and buildings and trim back overhanging trees. Roof rats will use climbing vegetation to scale buildings and seek shelter. Seal any cracks or gaps into your home that are larger than 1/4 inch. Screen or block potential entrances under eaves or overlapping roof sections. Use sheet metal or 1/8-inch wire hardware cloth to keep out mice and rats since rodents can gnaw through softer material like plastic or wood.
Snap traps are the safest, most effective, and most economical way to manage rats and mice. You can place traps outside the home to catch rodents before they enter. You can also place them inside if you spot signs of them there. Be sure to use the correct-sized traps and place them in secluded areas along walls, behind objects, in dark corners, and in places where droppings have been found.
Keep pests from ruining your holiday fun by denying them food, water, and shelter in your home. For more details about specific pests and their management, see the UC IPM website https://ipm.ucanr.edu/PMG/menu.homegarden.html.
[Originally featured in the Winter 2023-2024 edition of the Home & Garden Pest Newsletter.]
The past few weeks have been “fun” with pest challenges in our garden and home. In the kitchen we battled ant infestations and pantry moths. In the yard the milkweed plants have been covered with oleander aphids, the California lilac (Ceanothus) was attacked by mealybugs accompanied by ants, and paper wasps (Polistes) have been trying to build a nest on the front porch.
How to tackle each of these issues? UC IPM (University of California Integrated Pest Management) Pest Notes and Quick Tips is my go-to for all these issues.
Inside the House:
Pantry Moths
Ants
In the garden:
Milkweed and oleander aphids (Aphis nerii)
I hoped I had escaped getting the detested orange oleander aphids this year, since in recent years they usually showed up earlier in the summer, but ultimately, they appeared. Most established plants can tolerate some aphids, but all aphids produce honeydew, which can attract ants and sooty mold. Since milkweed is the sole food source for the Monarch butterfly caterpillar, pesticides are not recommended. Thus, using strong sprays of water every couple of days helps manage them. Based on previous experience, I know they will reach the end of their life and ultimately disappear. https://ipm.ucanr.edu/QT/aphidscard.html
Mealybugs (Pseudococcidae)
Paper wasps (Polistes gallicus)
Thanks to UC IPM, which provides information on garden issues and pests, along with giving scientifically researched options on how to deal with them, I have managed to either control or eliminate these pesky pests.
UC IPM Resources:
The above links are to Quick Tips, short, to-the-point cards on each topic. They are available for free at local UC Cooperative Extension offices. The references below are for Pest Notes, which may have multiple pages and offer more detailed information about each topic.
Ants: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7411.html
Pantry Pests: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7452.html
Aphids: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7404.html; https://ipm.ucanr.edu/PMG/PESTNOTES/pn7410.html
Mealybugs: https://ipm.ucanr.edu/PMG/PESTNOTES/pn74174.html
Wasps: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7450.html
Denise Godbout-Avant has been a UC Cooperative Extension Master Gardener with Stanislaus County since 2020.
/h3>/h4>/h4>/h4>/h3>/h4>/h4>/h3>- Author: Ben Faber
UC IPM supports research and extension programs in integrated pest management (IPM). UC Agriculture and Natural Resources scientists adapt research for practical application, and Cooperative Extension advisors and specialists develop and deliver IPM programs to a variety of clientele, including professional pest managers, growers, residents, and agencies. UC IPM staff work with UC ANR scientists to develop "how-to" materials that help the clientele carry out programs and solve pest problems.
To complement the extension programs, UC IPM staff members coordinate development of a variety of materials that explain how to carry out pest management tactics and strategies. Working with UC ANR experts, program staff produce and maintain an extensive array of print and Web-based publications, databases, training materials, and interactive tools for decision making.
Examples are the pest management guidelines and a home and landscape database of pest solutions for residential audiences, IPM manuals for specific crops, books about IPM in landscapes and gardens, a variety of books on pesticide safety, and an extensive weather database that supports interactive pest models.
And now they are happy to announce the publication of a new update to the Citrus PMG. The Year-Round Program has been updated, Ants, Asian Citrus Psyllid, and Huanglongbing
And to learn more about Ant control in citrus, cherimoya and passion fruit, look into the upcoming workshops, September 19 and 21:
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=57442
https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=57622
- Author: Sandipa Gautam
Are you interested in learning about the management of sap-sucking pests and ants in citrus orchards? Lindcove is organizing a full-day workshop to bring you recent research advances on sap-sucking insects and ant management. The workshop will focus on ants.
Ants, especially the invasive Argentine ant and the native grey field ant, are serious pests because they protect sap-sucking pests infesting citrus, grapes, and other perennial tree and vine crops, from their natural enemies. In return for protection, hemipteran pests like Asian citrus psyllid mealybugs, soft scales, aphids, and whiteflies reward ants with honeydew, a sticky sugar-rich waste product that ants imbibe and return to nests to feed nest mates. This is an example of food-for-protection mutualism that is highly disruptive to biological control and IPM programs. This workshop will cover the latest developments in ant monitoring and management and will provide overviews of the benefits of ant control and how reductions in ant densities result in very high levels of biological control of important hemipteran pests.
When: 19 September 2023
Where: Conference room, Lindcove Research and Extension Center, 22963 Carson Ave, Exeter, CA 93221
Meeting Registration Link: https://surveys.ucanr.edu/survey.cfm?surveynumber=41086
Workshop Agenda:
Time |
Presenter |
Topic |
8:30am |
|
Registration |
9:00am |
Mark Hoddle, UC Riverside |
Overview of the Asian citrus psyllid biological control program and the need to control pest ants |
9:30am |
Mark Hoddle, UC Riverside |
Use of biodegradable hydrogel beads and bait stations for controlling pest ants in citrus |
10:00am |
Mike Lewis, UC Riverside |
Infrared sensors and the Internet of Things to automate ant counts in orchards |
10:30am |
|
Coffee Break |
10:45am |
David Haviland, UCCE Farm Advisor, Kern County |
Ant management research and applications in the San Joaquin Valley |
11:15am |
Soon Il Kwon, UC Riverside |
Cultural control of ants in orchards |
11:45am |
Nicola Irvin, UC Riverside |
Flowering cover crops to promote natural enemy ecosystem services |
12:15pm |
|
Lunch |
1:00pm |
Sandipa Gautam, UCCE Area Citrus IPM Advisor |
Hemipteran pests and their management in SJV citrus |
1:30pm |
All presenters |
Table visits and posters to observe technologies that were discussed and to interact with presenters and ask questions |
2:00pm |
David Haviland/Hoddle Lab |
Field demonstration of hydrogel applications for ant control |
3:00m |
|
Workshop Ends |