Rita's Monthly Gardening Tips, February 5, 2013
Ants are a part of nature, but it is rarely a pleasure to come upon them. Ants and their honeydew-producing insect partners are a well-known example of mutually beneficial behavior. Understanding more about the life cycles and feeding needs of both these insects will help us to come up with a plan for managing their potential destruction in our garden.
Ants’ primary food preferences are the sugars and proteins that come from plant or animal sources, while aphids, scale, mealy bugs, and whiteflies are all insects that suck the sugar-rich fluids from their host plants. Because these liquids are low in nitrogen, the aphids must consume large quantities of them to gain adequate nutrition. The aphids then excrete equally large quantities of waste, called honeydew, which is high in sugar content. Where there’s sugar, there’s bound to be ants. Some ants are so hungry for the honeydew that they’ll actually “milk” the aphids to make them excrete it. The ants use their antennae to stroke the aphids, stimulating them to release the honeydew. Some aphid species have lost the ability to defecate on their own and now depend on their caretaker ants to milk them.
When the host plant is depleted of nutrients, the ants carry their aphids to a new food source, encouraging the spread of these pests in your garden. If predatory insects or parasites attempt to harm their wards, the ants will defend them aggressively. Some honey ants even go so far as to destroy the eggs of known aphid predators like lady beetles.
Some species of honey ants continue to care for their aphids during winter. The ants carry the aphid eggs home and tuck them away in their nests for the winter months. They store the precious aphids where temperatures and humidity are optimal and move them as needed when conditions in the nest change. In spring, when the aphids hatch, the ants carry them to a host plant to feed.
While it appears the ants are generous caretakers of their aphid charges, they’ve really got their own interests in mind. Aphids are almost always wingless, but certain environmental conditions will trigger them to develop wings. If the aphid population becomes too dense, or food sources decline, the winged aphids can fly to a new location. Not wanting to lose their food source, honey ants may prevent aphids from dispersing. Ants have been observed tearing the wings from aphids before they can become airborne.
Breaking the cycle of ants and aphids requires measures to control both types of insects. Look for indoor nesting sites, such as potted plants. If ants are found in potted plants, remove the containers from the building, then place the pots for 20 or more minutes in a solution of insecticidal soap and water at a concentration of 1 to 2 tablespoons of insecticidal soap per quart of water. Submerge so the surface of the soil is just covered by the water-soap solution.
Ants can be discouraged from invading trees to assist honeydewproducing insects by using Tanglefoot, a sticky nontoxic product. Trim branches to keep them from touching structures or plants so that ants are forced to try to climb up the trunk to reach the foliage.
When using Tanglefoot on young or sensitive trees, protect them from possible injury by wrapping the trunk with a collar of heavy paper, duct tape, or fabric tree wrap and coating this with the sticky material. Check the coating every one or two weeks and stir it with a stick to prevent the material from getting clogged with debris and dead ants, which will allow ants to cross.
Ant stakes with bait can also be used around trees.
Another way to reduce aphid populations on sturdy plants is to knock them off with a strong spray of water. Most dislodged aphids will not be able to return to the plant, and their honeydew will be washed off as well. Using water sprays early in the day allows plants to dry off rapidly in the sun and be less susceptible to fungal diseases.
Life in an Ant Colony
A new ant colony begins when winged reproducing queens and males fly away from the colony where they were hatched to establish a new colony. This activity generally takes place on a warm sunny day after a rain, when temperature and humidity are right. Timing of the flight is specific to individual species, with some migrating as precisely as from 10 a.m. to 11 a.m. Migrating ants don’t fly a great distance—maybe only 50 feet—attracted by specialized pheromones that call mates together. The potential queen can mate several times, storing enough sperm packets within her body to last a lifetime. Males then either die or are eaten by predators. After mating, the queen rubs off her wings and digs to get underground quickly to avoid predators. Out of 1,000 new queens, only two or three will survive to create a successful colony. The new queen lays her eggs, and once they hatch she tends and cleans the young. She feeds them using fat stored in her flight muscles. Once the first set of young goes through its complete metamorphosis from egg to larva to pupae to adult, the worker daughters take over and the queen begins to lay more eggs. It is the job of worker ants to enlarge the nest, carrying the dirt to the surface in their jaws. Ant nests are generally 8 to 24 inches underground, but in hot desert climates they may go deeper to where the soil is cool. The mound serves to maintain the temperature of the nest. The higher the mound the more heat is brought into the nest. In very hot weather other holes may be opened to let some of the heat out. Disturbing the mound with a careless foot quickly may change the temperature within the nest, jeopardizing the eggs. In cool weather ants may sunbathe at the entrance, then return to the nest to give out the heat stored in their bodies.
Interesting facts about ants:
- Ants enrich and turn more soil than earthworms.
- Ants disperse seeds of an estimated 30% of all herbaceous (non-woody) plants.
- Ants are an important food source for many animals from woodpeckers to bears.
- Ants are the primary predators of other insects.
- A single colony of ants can consume as many as 10 million insects per year. Fewer bugs to bug you!
- Ants make up 10% to 15% of the world’s animal biomass!
- If we could weigh all the humans in the world and all the ants in the world, they would weigh roughly the same.
- Ants are a model organism for many scientific fields.
- Ants are social insects that are excellent models for the study of cooperation and conflict in nature. By studying insect societies, researchers can better assess the various degrees of complexity of biological social systems.
Ants have led to important advancements in the study of evolution, sociology, and medicine. Even the Pentagon has studied army ant formations for war strategies.
Check back next month for the March Gardening Tip!