Lauray asks: We have two kaffir lime trees that are not doing well. I have attached photos of the leaves. Is there is any hope in saving them?
Lauray asks: We have two kaffir lime trees that are not doing well. I have attached photos of the leaves. Is there is any hope in saving them?
Tropical Gardener Answer: (based on a Master Gardener question and answer) You seem to have scale on the leaves of your lime. Go to Google images “scale on lime trees” and compare the photos to confirm that. I am including some information from an article on remedies for scale. It looks like there is some whitefly infestation also and some black sooty mold as well. Treating for the insects is a good start. They can be treated in the same way. The sooty mold can be washed off with soapy water and a little rubbing. Treatment for other possible issues follows.
Scale-damaged plants look withered and sickly. The leaves often turn yellow and may drop from the plant. You may also see black sooty mold on the leaves and/or stems. Heavily infested plants produce little new growth and could eventually die. A mix of oil and soap is low in toxicity and can be quite effective. Neem oil is available at garden centers and can be mixed in water with an insecticidal soap product like Safer Soap which helps it stick to the leaves. Follow the directions on the product you choose depending on the amount of water you use. Spray the mixture directly on the scale and whitefly (underside of the leaves) weekly until you see results. It could take four to six weeks. Spray late in the day to avoid hot sun on the oily leaves which can burn them.
Ants are often part of the scale issue. They “farm” the scale so they can collect the sweet “honeydew” they emit. Placing outdoor ant stakes around your plant will help control the ant population. The sooty mold grows on the “honeydew.”
Though pruning off some of the worst infested areas could help, be sure not to remove more than one third of the trees leaves at a time. Pruning will mean less area to treat and you might get some healthy new growth.
The yellowing leaves in your photo could be chlorosis caused by a nutritional deficiency. Sometimes nutritional deficiencies at lower elevations in Kona are caused by soil that is too alkaline. If you suspect this, you can get lots of information at https://www.grow-it-organically.com/changing-soil-ph.html. Adding elemental sulfur and organic matter can help and you might want to foliar spray with a chelated iron product. A good dose of fertilizer with slow release nitrogen, a high potassium percentage and micronutrients, especially iron, calcium and zinc, can help bring your lime back to health over time if the soil pH is 7 or below. Follow the label instructions on the fertilizer. Over feeding can be as harmful as starving your plant of needed nutrients.
If you decide to replant, be sure to enrich the soil with organic matter as well an organic fertilizer to promote microbial activity and healthy soil. Healthy soil produces healthy plants and healthy plants are less susceptible to insect pressure.
Diana Duff is a plant adviser, educator and consultant living on an organic farm in Captain Cook. Email plant questions to konamg@ctahr.hawaii.edu for answers by Certified Master Gardeners. Some questions will be chosen for inclusion in this column.
Gardening Events
Saturday: “Work Day at Amy Greenwell Garden,” 9 a.m. to 12:30 p.m. Meet at the Garden Visitor Center. Volunteers will help with garden maintenance and should bring a brown bag lunch. Water and snacks provided. Info: Peter, 323-3318.
Farmer Direct Markets
Wednesday: “Sunset Farmers Market,” 2 p.m. to sunset at the north makai corner of the Kmart parking lot.
Wednesday and Friday: “Hooulu Farmers Market,” 9 a.m. to 2 p.m. at Sheraton Kona Resort & Spa at Keauhou Bay
Saturday: “Keauhou Farmers Market,” 8 a.m. to noon at Keauhou Shopping Center
“Kamuela Farmer’s Market,” 7 a.m. to noon at Pukalani Stables
Sunday: “South Kona Green Market,” 9 a.m. to 2 p.m. at Amy Greenwell Garden in Captain Cook
Tuesday through 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