Jack asks: I think I have aphids on my gardenia. The plant looks anemic and there are lots of little green bugs on the leaves. What should I do?
Tropical Gardener answer: Aphids are among the insects that suck juices from plants. In their feeding process, these insects excrete sweet “honeydew” that attracts ants to protect or farm them. In addition to ant food, the sweet excrement provides a medium for sooty mold to grow. If you see either the ants or the black mold on the leaves, you need to deal with this as a three-part problem.
The mold covering the leaves reduces photosynthesis and can cause the plant to weaken from lack of food. Put on some cotton gloves, soap them up and rub off the mold. If you see ants, plant some outdoor ant stakes at the base of the plant and hopefully you’ll trap most of the “farmers.”
Aphids and other sucking insects like scale, thrips and whitefly can be dislodged, and lose their sucking mouthparts in the process, when subjected to a strong blast of water. If you have only a few and are into hand removal, use some sticky tape. Wrap it around your fingers and with the sticky side out, blot the bugs off the leaves. If you have a mild infestation these are totally non-toxic ways to start. You could also consider planting ginger, onions, chives or garlic near vulnerable plants in your garden. These strongly scented plants can help deter insect pests.
You can also get rid of these sucking insects with a combination of soap and oil that sticks to them and suffocates them. The nontoxic combination needs to contact the insects so be sure to spray everywhere you see them, especially on the underside of leaves. A good combination consists of a tablespoon of safer soap and a teaspoon of neem oil mixed completely with water in a quart sized sprayer. Spray late in the day to avoid the sun burning the oily leaves. Repeat this weekly until you no longer see any insects.
Of course, the most natural way to deal with these pests is to let the predators do the work. If you see ladybugs, lacewings or parasitic wasps eating the aphids hold off on the spray which can deter or harm them as well. If you don’t see any ladybugs try putting in plants that have flowers that attract beneficials like alyssum, nasturtiums, marigolds, lemon balm, borage, fennel, comfrey, dill and cilantro.
Diana Duff is a plant adviser, educator and consultant living on an organic farm in Captain Cook. Some questions that appear here were originally directed to Kona’s Certified Master Gardeners. You may contact them with questions at konamg@ctahr.hawaii.edu.
Gardening Events
Monday: “Tropical Fruit Growers meeting” from 7 to 9 p.m. at 81-6393 Mamalahoa Highway in Kealakekua. White wooden building on makai side across from the Department of Transportation yard. Park in front or on the north side. Ken Love, Brian Lievens and Eli Ednie will discuss the Autocarpus genus that includes breadfruit, jackfruit and others. For more information contact Brian Lievens at 895-8753 or greenwizard@hawaii.rr.com.
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. Call Peter at 323-3318 for more information.
Farmer Direct Markets
Wednesday: “Ho’oulu Farmers Market” 9 a.m. to 2 p.m. at Sheraton Kona Resort &Spa at Keauhou Bay
Wednesday: “Sunset Farmers Market” 2 p.m. to sunset at the north makai corner of the Kmart parking lot.
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: “South Kona Green Market” 9 a.m. – 2 p.m. at Amy Greenwell Garden in Captain Cook
Tuesday–Saturday: “U-Pick greens and produce” 10a.m. to 4p.m. Tropical Edibles Nursery, Captain Cook.
Plant Advice Lines
Anytime: konamg@ctahr.hawaii.edu
Tuesdays &Thursdays: 9 a.m. to noon at UH-CES in Kainaliu – 322-4892
Monday, Tuesday and Friday: 9 a.m. to noon at UH CES at Komohana in Hilo 981-5199 or himga@hawaii.edu