Thrips

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Melon thrips
Photo: Dr. Arnold H. Hara, CTAHR

Problem

The flowers on your gardenia are spotted, misshapen and/or do not open. Or the leaves of your ornamental have silvery streaks on them. They also have tiny black spots on the underside. If you have a silvery sheen and/or white, yellow or brown splotches on your ornamental ginger flowers, see below, under Thrips on Ginger.

Thrips on croton
Photo:  Dr. Arnold H. Hara, CTAHR

Description

There are many different types of thrips in Hawaii. I will address one here, as an example. Western flower thrips attack a wide range of vegetable crops and ornamentals. They use rasping, sucking mouthparts to take sap from leaves, flowers and stems of plants leaving a silvery appearance on leaves. Leaves wither, curl, turn brown, and die. The undersides of the leaves will be spotted with tiny black specks. Flowers become spotted and deformed and buds may not open.

Western flower thrips spread tomato spotted wilt virus which attacks both vegetable and ornamental crops. Thrips are pale tan or dark brown, narrow and flat.

Some of the Thrips active in Hawaii

• Western flower thrips   (Wide range of hosts including many crops and ornamentals. Cultivated crops include beans, burdock (gobo), capsicum, cucumber, eggplant, lettuce, onion, tomatoes and watermelon. Ornamental crops include carnation, chrysanthemum, orchids, pikake, rose and tuberose.)
• Banana rust thrips  (Primary hosts are anthurium, ti, dracaena, and  banana.  Also infest orange, tangerine, tomato, and green beans.)
• Anthurium thrips (Hosts include dendrobium orchid, begonia, bird-of-paradise, bougainvillea, chrysanthemum, night blooming cereus, wandering jew, parsley, citrus, sweet potato, lychee, banana, and corn.)
• Hawaiian flower thrips (Wide range of hosts with a preference for plants in the Legume and Convolvulaceae (Morning Glory) families. Other hosts include Acacia confusa, Acacia farnesiana, Acacia koa, alfalfa, asparagus, Astelia menziesiana, aster, avocado, banana, Batis marinima, beach naupaka, beans, bell pepper, coffee, guava, Hibiscus, kukui flowers, mangoes, orchids, pakalana, peppers, pikake, plumeria, prickly poppy, radish, rose and all squashes.)
• Melon thrips (Wide range of hosts including plants in the Solanaceous family, Cucurbit family, Legume family, as well as amaranth spinach, Chinese wax gourd, Chinese spinach, cyclamen, dahlia, orchid, plumeria, sweet potato and others.)
• Banded greenhouse thrips  (Hosts include banana, beet, celery, Crinum, chrysanthemum, eggplant, grass, orchids, pineapple, tomato, others.) 
• Banana rind thrips (In Hawaii, hosts are banana and papaya. Other hosts outside of Hawaii.)
• Cardamom thrips (This thrips species attacks red and pink ginger flowers in Hawaii. Outside of Hawaii, this pest attacks cardamom and others in the Zingiberaceae family. It also affects edible ginger and Pancium longipes.)
  

Dichromothrips on dendrobium
Photo: Dr. Arnold H. Hara, CTAHR

Banana rust thrips (anthurium, ti, dracaena, banana, citrus, tomato, green bean)
Photo: Dr. Arnold H. Hara, CTAHR

  

Anthurium thrip damage (anthurium, orchids, ornamentals, fruits, vegetables)
Photo: Dr. Arnold H. Hara, CTAHR

Anthurium thrips, adult nymph
Photo: Dr. Arnold H. Hara, CTAHR

Melon Thrips (vegetables, ornamentals)
Photo: Dr. Arnold H. Hara, CTAHR

Thrips on hollyhock
Photo: Dr. Arnold H. Hara, CTAHR

Information

• CTAHR – Crop Knowledge Master – Pests - Thrips
• Thrips: Quick Tips (UC Davis IPM)

Control

There are a number of parasites of the thrips so do not use broad spectrum insecticide to try to kill them as you will kill the good guys. In addition, you may not contact the thrips since they feed in unopened flower buds and in the sheaths of new leaves. Consult an extension agent about pesticide use.

Adult thrips on red ginger
Photo: Dr. Arnold H. Hara, CTAHR

Thrips on Ginger

Problem: Your red ginger flowers have a silvery sheen and/or yellow and brown splotches.

Description:  Cardamom thrips attack red and pink ginger flowers leaving a silvery sheen on the flower bracts. The damage will later appear as white, yellow or brown splotches and streaks on the flowers.

Thrips feed on unopened sheaths and flower bracts so they often are undetected until the damage is done. Thrips are brown and ¼ inch in length and are very difficult to see since they feed in unopened flowers and in the sheaths of new leaves.

Control: Remove plant debris and alternate hosts. Chemical control is difficult because thrips are hidden in leaf sheaths and flower bracts. Talk to an extension agent about pesticide use.

Kendal Lyon, Hawaii Island Master Gardeners