Doug asks: Ants are taking over my life both inside and outside. Any suggestions for getting rid of them or at least reducing their numbers?
Tropical Gardener Answer: Nearly 45 species of ants have made their home in Hawaii. None of them are native to the islands. A few of them can be troublesome when they invade your home and garden. Ant control requires multiple plans of attack, persistence, and knowledge of the ants’ preferences.
If any of the ants on your property are very small, red-orange and slow moving they may be little fire ants. These have a painful sting and require immediate action to get rid of them. Go to www.ctahr.hawaii.edu/uhmg/EastHI/little-fire-ant.asp for more information on these and how to deal with them.
Outside, outdoor ant stakes around plants where ants are present can be very effective. If you have aphids, scale or other insects on your plants that suck juices from the host, ants may be “farming” them. When the juices sit on the leaves they sometimes get a black mold called sooty mold. If you see this, ants are almost certainly present. Soapy water can be used with gloves to wash off the mold so leaves can photosynthesize better. A combination of safer soap and neem oil can get rid of the insects and some of the ants.
Several other remedies against ants that are low in toxicity will also work, especially in cases of severe infestation. First you need to figure out if you have ants that prefer sweets or those that prefer protein or grease.
Inside, you can make your own boric acid traps to use in areas away from food where the ants seem to gather. Mix boric acid powder with different foods to see what draws the most ants. For sweet-loving ants, use sugar water, jelly or honey. For grease and fat lovers use peanut butter or regular butter. Mix 1 teaspoon of boric acid with a cup of the food you choose to make a 2 percent solution. If the ants aren’t attracted to your baits, reduce the boric acid to 1/2 teaspoon per cup for a 1 percent solution.
You can place the bait in a 2-inch length of a drinking straw, in a small jar, such as a baby food jar, with a few holes punched in the cap or in a container made of wax paper or tin foil. Ants can find their way into most containers. Place the bait directly in the line of ants that you see. Changing the bait every few days will keep it fresh. Be aware that boric acid can be harmful to pets or small children so be careful of placement. Know that it may take lots of bait stations and some time for the poison to reach the queen and kill the colony.
Several other techniques are also effective at killing ants. They will set up nests anywhere they can. If you see lots of them tending lots of little rice-like eggs, that’s a nest. Disturbing it repeatedly will encourage them to move but if it is in a convenient place to take killing action, here are some suggestions.
1. You can apply diatomaceous earth throughout your yard, focusing on areas of high ant concentration, and pouring it into any ant nests you find. Diatomaceous earth kills ants by working its way into their exoskeleton, suffocating them and drying up their body’s moisture. Be sure to wear a dust mask when applying this product. This is very effective against ants as long as the diatomaceous earth stays dry. If it rains or the product gets wet it is no longer effective against ants.
2. A homemade combination of soap and oil can also be effective. Combine ½ teaspoon liquid dish soap with 1½ tablespoons canola oil and 1 quart of water in a bowl using a whisk. Place the solution in spray bottle and shake it to incorporate the ingredients. Spray areas with high concentrations of ants and pour the solution into their nests. The combination of soap suds and oil enters their exoskeleton and suffocates them.
3. Vinegar kills ants. Pour a 5 percent concentration of white distilled vinegar in the ants’ nests. The acid in the vinegar kills ants on contact. This may not be good to use directly on small plants as the vinegar can burn seedlings.
4. Another effective homemade concoction involves mixing 3 tablespoons cayenne pepper sauce with ½ teaspoon of liquid dish soap in a quart of water. Whisk the ingredients and put the solution in a spray bottle. Spray it on the ants and into their nests. The soap and cayenne pepper sauce kills the ants by smothering and burning them.
If you just want the ants to re-route or relocate, you can spray peppermint oil, on their trails and nests. Other household products that can be used as deterrents include garlic, clove, cinnamon or cayenne pepper powders.
Using multiple approaches over time should get rid of the ants or at least move them away from your home or garden.
Email plant questions to konamg@ctahr.hawaii.edu for answers by Certified Master Gardeners. Some questions will be chosen for inclusion in this column.
Diana Duff is a plant adviser, educator and consultant living in a dryland forest north of Kailua-Kona.
Gardening Events
Saturday: “Work Day at Amy Greenwell Garden” from 9 a.m. to 12:30 p.m. Meet at the Garden Visitor Center across from the Manago Hotel in Captain Cook. Volunteers will be able to help with garden maintenance and are invited to bring a brown bag lunch. Water and snacks provided. Call Peter at 323-3318 for more information
Farmer Direct Markets
Wednesday: “Sunset Farmers Market” 2 to 6 p.m. in the HPM parking lot at 74-5511 Luhia Street in Kailua-Kona (across from Target)
Wednesday &Friday: “Hooulu Farmers Market” 9 a.m. to 2 p.m. at Sheraton Kona Resort &Spa at Keauhou Bay
Friday: “Pure Kona Market” 9 a.m. to 5 p.m. at Amy Greenwell Garden in Captain Cook
Saturday: “Keauhou Farmers Market” 8 a.m. to noon at Keauhou Shopping Center
“Kamuela Farmer’s Market” from 7 a.m. to noon at Pukalani Stables
Sunday: “Pure Kona Green Market” 9 a.m. to 2 p.m. at Amy Greenwell Garden in Captain Cook
Tuesday–Saturday: “U-Pick greens and produce” 10 a.m. to 4 p.m. Tropical Edibles Nursery, Captain Cook.
Plant Advice Lines
Anytime: konamg@ctahr.hawaii.edu
Tuesdays and Thursdays: 9 a.m. to noon at UH-CES in Kainaliu – 322-4892
Mondays, Tuesdays and Fridays: 9 a.m. to noon at UH CES at Komohana in Hilo 981-5199 or himga@hawaii.edu