tea notes

These notes are maintained by Ben Discoe.

< How to grow tea in Hawai‘i?

Pests and Diseases

• Not much is known yet about what might attack tea plants in Hawai'i.  The common rose beetle has been mentioned as a potential pest.  Some kinds of leaf blight can be an issue.  Both of those have been seen at Mealani, but Milton says they were not major problems.
• General reference: APS Plant Pathology: Diseases of Tea lists 70 species.
• CTAHR publication PD-33 Oct. 2006: Identification Guide for Diseases of Tea (pdf)
  • Descriptions and pictures of: Algal leaf spots, Brown blight, grey blight, Blister blight, Horse hair blight, Twig dieback, stem canker.
• CTAHR publication PD-34 Oct. 2006: Zinc Deficiency in Tea (pdf)
  • One page, shows a picture of what can happen with insufficient Zinc: new leaves are small and bunched-up.
• I have encountered the following problems:
  1. Aphids.  Large, dark aphids are brought in by ants.  I was able to control this by repeatedly removing (squishing) the aphids and ants by hand, and cutting off access by ants to the greenhouse tables as well as i could.  Eventually, the ants gave up; in January 2007, aphids in our greenhouse are rare.
     Dwight Sato says these are the common melon aphid:
     
  2. Some kind of armored scale, an insect which attacks the nodes and stems, weakening the plant until it dies.  This especially likes to attack my Yutaka Midori, Bohea and CSO, although it's appeared on all of the 5 USDA cultivars.  Here are pictures of diseased plants and close-up of the organism.  It takes a long time to kill the plant.  Some have had the scale on them for more than a year, dying very slowly.  Once a plant gets it, i have not seen any recovery.
     
     It's not "tea scale" (Fiorinia theae) which grows thinly on leaves, not thick on stems.  I also consulted Ghosh Tea Cultivation and my plants do not match the descriptions of any of the 8 stem diseases in that book.
     Dwight Sato says: "[Keep the plants well-fertilized and healthy so they're not as susceptible to pests like this.] For younger potted plants, if you don't have much, simply and gently wipe or scrape them off the stem with your finger.  A balanced nutrient program appears to be the key factor."
     I found some general guidelines at How to Manage Pests in Gardens and Landscapes: Scales although it only talks about scales commonly found in California.  Of those, my scale looks most like their pictures of greedy scale (Hemiberlesia rapax).  Another reference calls greedy scale "tropical camellia scale" so that sounds very likely.
     Bumps on My Plants is a good introductory page on scales.
  3. I've seen a little bit of the blights and spots mentioned in the CTAHR publications, although they are relatively minor, mostly on plants that have already been weakened by the scale.
• Mike Longo writes:
  • Generally, I would say that Camellia Sinensis has a hard time in pots, and they are more vulnerable to pests, especially when they are in a greenhouse. [..] Once you get a bloom of anything, it quickly spreads throughout the greenhouse. We tried soap sprays and neem with some success. We even tried ladybugs and lace wing insects at one point. Ultimately it took taking the plants out of the greenhouse and planting in the ground to correct the problem. I think that the small rooted Tea cuttings are particularly vulnerable to these problems and it can be real effort getting these plants to grow large enough to get them planted in the field.
    In our field, we have found that insect problems come and go, but that plants usually grow out of the damage. We have had temporary, minor problems with rose beetles, aphids, scale and spider mites. None of these problems lasted for very long at all. For example, spider mites can make the whole plant, usually just the smaller plants,  look dead. The leaves turn completely brown and the plants look like you should just throw them out. However, in every case where mites had caused this kind of damage, the plants grew out of the problem in a couple of months, with no treatment at all. I have seen spider mite damage also at Mealani, a couple of years ago, in the field on some small plants. When I returned for a visit there a few months later, the plants were all healthy and green again and I was told that they also just grew out of it with no treatment. I think that we are finding that Camellia Sinensis, once established in the ground in fairly well-drained soils, is proving to be a very hardy and resilient plant in Hawaii.
• That indicates that a good strategy to avoid pests would be to move tea out of the greenhouse and into the ground as soon as possible.  In fact, in one case a grower even put some baby tea plants in oasis cubes directly into the ground, and they survived and established!
• February 9, 2007.  I found more scale growing on a freshly planted Benikaori rooted cutting (only one plant).
  • These are growing on the top of the leaf, rather than on the stem, and they look rather different than the previous scales, although that might be because they are fresh:
  • 
  • I was able to easily scrape them off with a plastic plant label.  Their bodies were soft, so might be either a soft scale or a very immature hardened scale.