Bug-bitten teas: why are leafhoppers only sometimes a good thing?

Leafhopper responsible for bug bitten teas

For most crops, insect damage is a bad thing—both for yield and quality.  With tea, however, we have this somewhat unique case of the so-called “bug-bitten” teas where attack by an insect actually improves the quality compared to an un-attacked plant by inducing chemical changes that are said to improve the aroma of the finished tea.  Famous examples of this are Oriental Beauty (东方美人, dong fang mei ren), Concubine Wulong (贵妃, gui fei), and Honey-Aroma (蜜香, mi xiang) black teas.  All three of these teas are originally Taiwanese, so is there something special about Taiwan?  Well, when you dive into the scientific literature on leafhoppers on tea plants, most of the studies done in Taiwan are on a species of leafhopper known as Jacobiasca formosana, while most of the studies in mainland China talk about a leafhopper known as Empoasca vitis.  So it seems safe to assume that maybe one of these insects causes “good” chemical changes in the tea leaves that increase the quality and the other species causes “bad” chemical changes that decrease quality, right?  Well, according to a few recent studies, it turns out there is very strong evidence that they’re all the same species (Empoasca onukii), so the leafhopper responsible for Oriental Beauty is actually quite widespread!

And it’s not something specific about geography either, as farmers in mainland China are beginning to adopt this technique to produce bug-bitten teas as well. So why is it that insect damage is a good thing only for these few teas? Why aren’t there any bug-bitten green teas on the market?  I’ve done a bit of thinking about this, and it seems like there are only a handful of ways to explain why leafhoppers are considered pests on green teas, but can improve the quality of some wulongs like Oriental Beauty.

  1. The leafhopper causes the same chemical changes in all tea plants, but those changes are considered “good” in wulongs and “bad” in green teas.  Green teas and wulong teas obviously have different criteria for judging, so maybe what makes an wulong good is actually undesirable in a green tea. This seems unlikely to me since there is a lot of overlap in the list of characteristics that make green tea and wulong tea good, but it is certainly the simplest explanation for this phenomenon. It may also be a simple matter of leaf appearance which is more important for a green tea like Longjing where any blemishes are easy to see compared to an oxidized, twisted leaf tea like Oriental Beauty.
  2. The effect of the leafhopper depends on processing method. In this scenario, the leafhopper still causes exactly the same chemical changes in all tea plants, but those chemicals get modified by different processing methods to create differences in the processed tea. For example, a leafhopper might cause a tea plant to produce some compounds that when left   unoxidized—as they would be in a green tea—produce undesirable flavors, but when they are oxidized in wulong processing they become compounds with desirable characteristics in the finished tea.
  3. Leafhoppers do different things to different cultivars. Maybe different cultivars of tea plant respond differently to leafhoppers.  For example, maybe Longjing #43 defends itself by producing more caffeine (an insecticide), which would lead to a more bitter tea, but Qing Xin defends itself by producing hotrienol, a chemical that smells nice to us and maybe attracts predators of the leaf hoppers.*
  4. Leaves of different ages react differently to leafhopper damage.  Ok, bear with me on this one. Most green teas are produced with only one or two leaves and a bud while most wulongs are produced with even older leaves included in the plucking. Maybe the leafhopper produces undesirable chemical changes in young leaves and desirable changes in older leaves.  Then, if you make a green tea, you’re only getting the bad changes, but if you pluck for an wulong, maybe the good changes outweigh the bad ones.  This one might seem like a stretch, but research shows that it is common for young leaves to respond to damage differently (and more intensely) than older leaves, so I think this is entirely possible.

I’m hoping that you—the knowledgeable tea buyers, farmers, and consumers of the tea world (AKA Tea Geeks)—can rule out some of these possibilities or maybe add some that I’ve missed.  Please let me know what you think in the comments!

*These are just examples! Leaf hopper damage has been shown to increase hotrienol concentrations in wulong cultivars, but as far as I know, no one knows what it does to caffeine or what leaf hoppers do to chemicals in green tea cultivars.

Image credit: By HectonichusOwn work, CC BY-SA 3.0

Please Share!
Share on Google+Tweet about this on TwitterShare on FacebookShare on RedditShare on LinkedInShare on StumbleUponDigg thisBuffer this page

Published by

Eric Scott

Eric is a graduate student at Tufts University studying the impact of climate change on the quality and chemistry of tea.

11 thoughts on “Bug-bitten teas: why are leafhoppers only sometimes a good thing?”

  1. There are different variables to consider. The season life of the bugs, and the optimal picking time for wulong and the optimal time for green tea are very different. The picking standard for these to classes are also very different, green tea optimal plucking is early in the spring, the leaf size small. The wulong picking does not occur until the new leaf growth has stopped. The plants protective reaction is very different, as is the proportional damage to the leaf. The new growth damage is more consequential to the plant that the small bites taken from the more mature and larger leaf. The insect bite, what ever the bug might be, has more of a concentrated bitterness that the small bite to a large leaf. Carelessness in picking a green tea or breaking a leaf in processing can make for an unpleasant brew. There aren’t a lot of insects around in the early spring when the amount of amino acid is the highest and the tea at it sweetest natural flavor. This is not the case with summer longing. #34, known for it ability to create new growth well into the summer, is already sprouting power quality tea leaves, and the bug bites increase the bitterness.

    Wulong leaves have a completely different chemistry. The plant sends chemicals to the new growth that tells the new growth that it is time to stop producing new buds/leaves. These chemicals have aromatic properties that enhances the smell and taste of wulongs. The small bites add a fragrant oxidation while the leaves are still I unpicked. Oriental beauty’s fragrance can be detected while it is still on the bush, unlike any other leaf. The fragrance is the leaf usually is not apparent until the leaf has been withering for a couple of hours after picking. Obviously the early oxidation of this tea works in its favor.

  2. Great write-up, Eric.

    I’ve given some thought on the same subject. Mainly focused around the idea of bug-bitten green teas. I think it’s more than possible, and I think that it’s – in some informal capacity – already been done. Certainly not vocationally in Taiwan, but rather in South Asia. Darjeeling, to be precise.

    As you know, there already exists some evidence that Darjeeling teas get that wonderful “muscatel” flavor from the involvement of buggy li’l pests in the area. Well, some estates do produce the occasional seasonal green teas, and – oftentimes – they possess a lot of those same muscatel notes. Makaibari green tea comes to mind.

    Another country that’s been experimenting with the style of bug-bitten teas is Japan. While they’ve mainly been exploring it from an oolong route, I can only assume they’re using cultivars specifically designed for green teas – Yabukita, Ujikihari, et al. More than possible that those are well-suited to a bug-bitten green treatment.

    Great read . . . makes me want to try a bug-bitten Long Jing someday.

  3. Yeah, I didn’t mention Darjeeling because I’ve had less first-hand experience with it. In China, I’m told the leafhopper population is pretty low until late May—after most green teas are harvested. Perhaps Darjeeling is a better place to answer this question.

  4. As soon as the leaf is broken or bitten the raw edges begin to oxidize. Green tea wants a completely unoxidized leaf so anything bitten and showing signs of oxidizing prior to harvest would need to be discarded or go into a different type/grade of tea. This is besides all the chemistry changes but speaks to why leaf biting bugs are not welcome in green tea gardens.

  5. Awesome post! I did some research, too, after realizing that a 2nd flush darjeeling I enjoyed had the same muscatel note as some of my favorite Taiwanese oolongs, and I realized both owed the flavor to the biochemical cascade caused by the leaf hopper injury described in your write-up (which makes me disfavor hypothesis #2). I hadn’t preciously encountered the opinions on how this negatively affects green teas, though! I’d be interested to see why that’s the case…perhaps because the flavor profile of some chinese greens—I personally prefer the nuttier/creamier greens—is not compatible with the floral/sour fruit finish?

    I think my guess would be some combination of #3 and #4.

  6. If I were to pick one of these to test, I would pick #4, especially after reading Austin’s comments about differences in harvest time. Wulongs aren’t harvested during a ‘flush’ (when most of the shoots are all growing rapidly and synchronously). But I’m honestly a bit confused after being in Hangzhou for the spring. I haven’t really seen any leafhoppers at all yet. Last year they were fairly common in June, but that’s well after the plucking season for most high quality green teas. So now I’m just wondering where in China they are considered a major pest to green teas.

  7. So I asked this question of a tea farmer in Shaxian, Fujian Province who grows oriental beauty. He said the main reason he doesn’t make bug-bitten green teas is just that the appearance of the tea would be ruined, but if someone commissioned a bug-bitten green, he could totally make it.

  8. Eric, super excited that you’ve opened up this topic for discussion, and it inspires me to consult with professionals here to get more solid information on it. I need to review your points made in your post again when I’m not on my phone, but for now I’ll begin with these comments:
    In Taiwan, the green leaf hopper is most prevalent during summer months. As I have been told by several farmers, this insect only affects the leaves during their early growth phase and is only interested in them when the leaf buds are still very small and tender. The effect on the leaf is for the most part only noticeable in the coloration of the leaves when they are still on the tree. The leaves have a distinctly yellowish hue .The insects do not leave a visible scar or discoloration where it actually bites the leafbud . As I understand it, in the Hsinchu region where oriental beauty is traditionally produced, it is a combination of the effect of the insect and the hot summer weather that results in a short growing season. The leaves must be picked before they reach maturation or else they simply die and fall off. In general, for mainstream industry – at least until recent years, the decreased yield is the biggest reason why most conventional farmers do not want the green leaf hopper to affect their crap. It is simply an unreliable prospect. It is also much trickier to process the tea and achieve the desired results. Even in postproduction roasting it is very inconsistent and seems to be batch-specific. I have heard of as little as one quarter of the normal yield after crop has been affected by the green leaf hopper,more typically farmers say it reduces the yield to about half. The leaves are stunted in the growth and will not grow to maturity. In Taiwan, leaves are harvested before they reach full maturity, so they are still in their growth phase – at least the smallest growing tip of the new growth “sprout”, so I disagree with Austin’s statement that leaves are harvested after they stop growing . If the leaves have reached full maturity they are too “old” and will produce much less quality tea. It appears that the insects come and go quickly within a two-week period or so. Furthermore, I’ve been told that in order to achieve the honey fragrance quality, the leaves need to be picked before the next rain. The chemical compounds that result from the insect’s effect will be diluted and the leaves will not produce the flavor profile that can – but does not definitely – result from the green leaf hopper’s presence.

Leave a Reply

Your email address will not be published. Required fields are marked *