Tea, Pests, Disease and Pesticides, Hidden truth of unknown cause.

We hear quite a few incidence of pesticide contamination from Chinese tea.  One might wonder what is really happening with tea grown in China or anywhere else.  I remember a lot of farmers in Japan telling me that tea always attracts pests, and pesticides and tea are always inseparable.  Although it sounds like a reasonable excuse for tea farmers, but I believe there is much deeper cause of this tea, pest and disease relationship.

Tea, pests, disease and pesticides are almost always big topics among tea farmers.  Because there are pests and disease, farmers have to spray or else they lose the crop or the harvest will be heavily damaged.  So the farmers go out and spray once, twice, three times.... and on and on until they are through with their annual cycle.  In Japan, some tea farmers brag about only spraying 5-6 times in one year.  They are considered eco-farmers.

In my past 7 years of tea cultivation, there has never been a time I had to spray.  Should I say, I intentionally let the pests and disease affect the plants so I can observe and find the true cause of pest and disease problems.  Once a farmer start spraying, it becomes a habit to continue to spray to keep any bugs off, both good and bad.  Basically, he is keeping a sterile environment on tea plants much like in a lab, but nature is extremely complex system where each member work crucial role to keep the natural system in balance.

So what are the causes of pest and disease problems?  We'll have a brief look at each cause.

Susceptible Tea variety

Domestication of wild made it more vulnerable to many of nature's friends.  In wild, there is a fine balance.  Plants are not well fed so they have to utilize their friends network often involves bacteria, fungi and various microorganisms and insects.  Even ones considered as pests and diseases can be benefit to establish healthy balance in nature.

To my understanding the biggest problem we have created is that our variety selection weakened natural resistance and imposed judgement of good and bad which didn't exist in nature.  Once we impose value of good and bad, some insects become pests and diseases need to be treated.

Right climate, Right condition

If the growing condition is right for tea, they attract significantly less pests.  For example, Japanese beetle is almost negligible pest in our 2000ft elevation while some tea growers at sea level have never-ending battle with this same pest.

Another example is that since tea thrives in moist environment, drier area tends to make tea plants weaker and has more mite damage.

Soil acidity has an importance in soil chemistry of tea as well.  Often calcium is considered key nutrient in plant growth, but our older field which has more calcium does not necessarily correspond with better growth.  On the contrary, plant vigor decreases as soil pH increases even though there is more calcium available.

Good bugs and bad bugs, they are both inseparable parts of balanced ecosystem.  Without pests there are no foods for natural predators.  Parasitic wasps have no caterpillar hosts and lady beetles have no aphids to feed on.  Yet, finding the right climate and soil conditions for tea significantly reduce disease and pest occurrence and reduce pesticide use.

Over-fertilization

Some farmers consider greater yield as healthier plants and continue to feed the plants more than what they need.  More fertilizers especially nitrogen fertilizer, than soil can hold often get lost and worst case it causes the soil to rot.  I'm sure some farmers experienced that when they dig some bad soil, foul odor hits their nose indicating soil is rotting.  When plants take up rotten nutrient, or just by growing in the soil, plant root suffer and it causes weaker growth.  Consequently, it attracts pests and diseases.

In our trial lot, we had the same results.  In extreme instances, by stopping the use of fertilizer actually made the plants healthier and attracted significantly less pests and diseases.

Consumer preference

Consumer preference is actually a big part of plant material selection.  Because we choose sweeter and richer flavor, subdued milder taste, etc., this sometimes makes plant's defense weaker.  Tea is a type of herb and use its chemicals to defend from pests and diseases.  By selecting plants with less bitterness and more sweetness, this consumer preference makes plants more susceptible.

We have some varieties that taste great, but have terrible disease resistance.  If we want this quality, our compromise is to spray more and prevent the disease.  Or we can select disease resistant varieties and learn to develop and acquire the more subtle flavor note.

How can we improve?

Farmers rely on the harvest and income.  It is best to avoid pesticide use altogether, but when pest problems persist it is better to encourage use safer alternatives and even better to improve the fundamental causes of pest occurance.  Improving soil conditions, planting less susceptible varieties and improving processing skills to make the varieties more desirable.

What else can we do?