Biohazard II: Japanese Oak Wilt in Niiharu Citizen Forest, update

Homo sapience is in extreme ado about COVID-19 these days. But it’s not only we with infectious diseases. Do you remember I posted the problem of Japanese Oak Wilt last summer (on August 23, and September 6, 2019)? At that time, the City had not decided yet what to do with this infectious disease for mighty oaks in Yokohama. Here’s the update. In the end, they cut the tree standing on the popular strolling way in Niiharu Citizen Forest 新治市民の森. Now there is only a stump where I first found the infection.

There was a lot of wood powder for the infected tree …

At that time, I’ve heard it costs fortune to protect forest from the rapidly spreading disease. (It sounds familiar, doesn’t it?) Once infected, it’s hopeless to rescue the tree. The only possible way for humans to guard the rest is to vaccinate them, with the cost of 10,000 yen (USD 100) per tree. (In this regard, oaks are luckier than we with COVID-19 without vaccine.) For 67ha of Niiharu Forest with countless number of trees in oak family, it’s a fortune. My seniors murmured that the City did not have money to do that (,of course). “Well, they cannot leave the tree situated on the most popular road in the forest, can they?” “No, no.” Ultimately the Office has settled in felling the dying tree, but they did not have money to excavate the roots and sanitize the soil. (It is the standard way to treat this disease. Please see my post on August 23.) Having said that, we are not sure if it is wise to take such a complete measure especially for the area in question.

The stump of an infected oak.
 Inside the oak infested with Raffaelea quercivora,
 the virus spreads like cottony mold
 to clog vascular cambium rapidly,
 just like blood clots for heart attack, stroke, et al.
 Could you see the difference between
 the whitish core and the reddish rim?
 Cambium is the outer part of a trunk,
 and here, they have almost entirely changed the color.
 This is an evidence the tree was infected by the disease.
 It was dying …

Near to that point, there is a place where people could find a plant nearing the extinction and on the red list of IUCN. My seniors told me they have not spotted it for more than 10 years already. But hope springs eternal. If we treat the area chemically, perhaps the probability for us to meet that plant again in Yokohama becomes almost zero ... Though, what would happen this summer in Niiharu without complete treatment against the Oak Wilt? Will we have sudden tree deaths spreading to the entire forest? “Huh, no one knows.” It’s just like us with COVID-19. Who can say for 100% sure Tokyo Olympics and Paralympics will be held in the next year free of global pandemic? Never underestimate viruses …

Still, spring has come … Viola keiskei

If you find environmental issues in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター

657 Nanasawa, Atsugi City, 243-0121
〒243－0121　厚木市七沢657
Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/

Qué será será: Japanese Oak Wilt in Niiharu, after that

The follow-up of my post on August 23^rd. Early August, I found a Quercus serrata affected by Japanese oak wilt in Niiharu Citizen Forest 新治市民の森. I reported it to the seniors of Lovers of Niiharu organization 新治市民の森愛護会, and the City Office. They checked the situation nearby and searched any other tree that was also infected by the disease … Sadly there was another, a very formidable tree far larger and taller than the one I’ve found. The first one I noticed was right next to a very popular road for Niiharu visitors. If that one dies and starts crumbling, as often the case of victims of the disease, it poses VERY high risk of fatal accidents. The second tree we identified as contracted individual is in the middle of the forest away from the trekking route. So, the immediate measure the City and the Lovers organization have chosen is “Cut the one on roadside. Pls give us more time to think what to do with the next.”

The latest photo of a tree affected by
 Japanese oak wilt that I found early August.
 It seems to me the wilted branches are
 going up to the tree crown.

On the foot of the above tree,
 the frass created by Platypus quercivorus was increasing.
 Oh my …

“Look. Treating Japanese oak wilt is difficult. Say, we cut that big one surrounded by another large trees.” “Thank God, they are not oaks!” “We have to carry out all the trunks and boughs from there without spreading the Raffaelea quercivora. If we left logs in situ, that becomes home for more Platypus quercivorus, right?” “Yes. The remnant of the tree can be a cradle for the bugs with the virus and the disease will spread more.” “Now, how can we take out the logs of 80cm or so diameter with 20 or 30m long?” “Heavy machinery cannot enter unless we destroy the forest.” “………..” “Above all where is money to do that?” “Good point.” “Moreover, there is no guarantee only those two are affected in Niiharu Forest.” “Indeed.” “Do we do a research of the entire Forest?” “Some landlords do not allow us to enter their property.” “Yeah. If a large tree is contracted the infection, whose roots reach to the lands of different owners, what to do with it?” “We need permits from all the proprietors to treat the issue.” “Dear, dear …”

Another one found with the disease.
 It really has an impressive shape, but, dying …

The lower trunk of the above tree

The seniors of Lovers organization are a sort of sanguine. Niiharu Forest is not on a public land alone. It’s a combination of lands owned by the city, the prefecture, the national government, religious entities, educational or business institutions, and the private households. The number of owners regarding 70ha of Niiharu is roughly 90. It’s extraordinary we can call the place as “Citizen Forest” where Lovers organization can engage in the maintenance together with the City. Though, when this kind of issue happens, the miracle could end. “So, the eventual conclusion will be just like the way we took for pine wilt disease.” “Yeah … we’re gonna let the forest to endure by itself.” “…”

Niiharu Forest is still OK as of August 31^st.
 Can we keep this green for how long?

As some of you may know, when Dutch elm disease was first recognized as rampant, people spread DDT et al in a vast area of forests to kill the vector insects that were many species. Entire fauna in food chain became casualties, and masterpiece “Silent Spring (1962)” by Rachel Carson was born. With this background, although Japanese government institutionalized the usage of insecticides for pine wilt disease in 1977, aggressive chemical treatment against the infection has not been taken. It’s like we humans are crouching low to wait for very strong storm to go away. Many formidable pine trees have been dead in Japan. Researchers are busy finding resistant pine DNA to replant the affected area. The struggle is going on for decades now. Japanese Oak Wilt was first recognized serious in the 1990s. History-wise, it’s still a young ailment for Japanese Forest, compared with that for pines or elms. And this time, the same approach would be taken. We will just sit and see the green oak forest of Niiharu to die in brown, hoping to replant some other resistant species afterword. “But what else can we do?” “*Sigh* ...”

To begin with, our neglect for Satoyama forest is the reason why we have so many “suitable” big oaks for Platypus quercivorus to nest and multiply. If we have coppiced the Quercus serrata and Quercus acutissima every 10-15 years for daily use, as our ancestors did until some 70 years ago, there would have been a very limited supply for the insects to find home, and hence no fear for pandemic in the forest. During the 1960s, we abandoned such lifestyle and opted for the convenience of petrol energy. Oaks are now inviting big trees for Japanese oak wilt. Our browning forest due to the disease is a consequence of our way of doing. With forest we have to wait for decades to know what the result would be of our action. I’m sad our beloved Niiharu Forest covered with oaks may be all desiccated brown even during high summer. It could happen in a couple of years, just like for Koajiro Forest 小網代の森. We are so sorry we’ve neglected you, Niiharu Forest, for such a long time. Now you’re suffering the trauma, facing the attacks of Japanese Oak Wilt … We irresponsible humans are powerless …

If you find an environmental issues, like Japanese oak wilt, in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター

657 Nanasawa, Atsugi City, 243-0121 〒243－0121　厚木市七沢657

Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/

If you sighting is in the northern part of City of Yokohama, the office you may call is

Office for Northern Parks, City of Yokohama 環境創造局公園緑地部北部公園緑地事務所

Phone: 045-353-1166

FAX： 045-352-3086

ks-hokubukoen@city.yokohama.jp

Or for the southern part, the address to call is

Office for Southern Parks, City of Yokohama 環境創造局公園緑地部南部公園緑地事務所

Phone： 045-831-8484

FAX： 045-831-9389

ks-nambukoen@city.yokohama.jp

We Really thank you, for your kindness to rescue our forest!

Biohazard: Japanese Oak Wilt in Kanagawa Prefecture ナラ枯れ病

In March Last year, I attended a seminar held by researchers for Kanagawa Natural Environment Conservation Center. One of the topics was about Japanese oak wilt, presented by entomologists. Japanese oak wilt is disease of oak trees caused by Raffaelea quercivora virus carried by insects called Platypus quercivorus. So, the presentation was by entomologists. Platypus quercivorus is monogamous ambrosia beetle. Platypus quercivorus has fashionable pockets on their back where they nurture Raffaelea quercivora. The bugs dig lots of tunnels within trunks of oak trees and mate. The female lays their eggs inside their home-sweet-home tunnel. While they are busy in their home, their back rubs the surface of the tunnel, and infects the tree with the virus. Viruses multiply rapidly, which is a good thing for the insect family as their diet consists almost solely of the Raffaelea quercivora. Her eggs soon hatch and the baby worms eat voraciously the virus as their parents. Happy insect-family life. It is a death knell for mighty oaks.

Fashionable back of Platypus quercivorus

Platypus quercivorus is a beetle having a big family life. Their nest within an oak has several egg chambers for thousands of babies. i.e. The bug loves to dwell in a large, established oak. They need at least 30cm of diameter for raising their offspring. Once a parent beetle infests an oak with Raffaelea quercivora, the virus spreads within a body of the tree like cottony mold. It clogs vascular cambium of the oak rapidly, just like blood clots for heart attack, stroke, et al. Big tree has big cambium that can somehow keep a space for water and nutrition to flow if the amount of such liquid is not much, like during rainy season in Japan with moderate temperature. Though, when Japanese summer temperatures skyrocket to 35°C+ with 80%+ humidity, trees get thirsty at once and needs lots of fluid circulating within their body. If Raffaelea quercivora blocks such vital “endocrine system,” large oaks dehydrate and become starved to death rapidly. The researchers for the Centre warned us, “With severe infestation, very large and tall oaks can be blasted within few weeks, even if they looked healthy and vigorous with rich green leaves during rainy season. Japanese oak wilt attacks a tree drastically.”

This photo was taken in Koajiro Forest on August 1^st,
 a bit early to observe autumn leaves in Kanagawa Prefecture.
 The tree was blasted by oak wilt.

Worse, the story does not end here. Tiny worms of Platypus quercivorus with lots of tasty Raffaelea quercivora grow briskly and leave soon parents’ home in masse as adults. A young male immediately tries finding a mate and emits pheromone to attract partners of different DNA. It calls for another flock of Platypus quercivorus to this forest, and move to another oak to build their new nest in droves. Japanese oak wilt would spread rapidly within the forest when the place has lots of established trees of Quercus family, like Quercus serrata, and Quercus acutissima. It is said that the first massive infestation inJapan was recognized in the western part of archipelago around 1990. Since then, the disease devastated the forests in the western Japan, including Kyoto 京都. It now marches to the east.

Another example from Koajiro Forest

Basically, Platypus quercivorus is common in the jungle of South-East Asia, like Vietnam. They are comfortable in tropics. Japan may have had home for Platypus quercivorus for centuries, but within a limited area. It’s no more. The climate change with warmer Japanese winter and lots of rain during spring (like this year) may have provided ideal conditions for the bug to proceed further north. And/or, it would be the result of our neglect of forests. For Platypus quercivorus to have nests, they need large oak trees. When our ancestors used firewood as household energy to cook, to warm, to prepare bath, etc. they coppiced oak trees every 10-15 years to harvest their logs. It was rare to find an oak tree of 30cm of diameter in Japanese villages. In colder places, it could take 50 years for a tree to be that big. Yeah, maybe Platypus quercivorus has lived in Japan for ages, but it was not easy for them to find a suitable home to multiply. Now, no more. When fossil energy replaced firewood in the 1960s, traditional usage of forests was abandoned. An oak forgotten in a forest since the 1960s is nearing 60 years old in 2019. They are big and tall enough for Platypus quercivorus to make holes for thousands of baby worms. Platypus quercivorus of the 21st century Japan find themselves living in a gorgeous place to procreate. The stage is ready for a forest of oaks to die massively. As the disease is caused by virus, once a tree is infested hopelessly, we have to

1. Cut the tree and uproot it entirely to remove the infested body completely.
2. The logs, leaves, etc. must be moved from the site promptly to be incinerated perfectly.
3. The soil where the tree stood should be sanitized entirely.

You see? Once the affected area becomes large, it’s impossible for humans to control the situation.

Also in Koajiro on 1 August 2019, damned hot summer.

In 2017, the Office of Kanagawa Prefecture started to receive reports of Japanese oak wilt attacks in Hakone 箱根 and Miura Peninsula 三浦半島. And so, there was an urgent seminar topic in early 2018. Recently, I’ve been to Koajiro Forest 小網代の森 in Miura Peninsula, aghast to find extensive oak wilt. (More for my adventure in that Forest next week!) When I first posted my blog about Koajiro Forest (on July15, 2016), there was a talk to nominate such royally-loved forest for the 35th National Park of Japan. (It is said that the former Emperor and Empress 上皇 are planning to visit there again with their grandkids before long). I’m not sure if such ambition has any progress now with lots of died oak trees standing here and there. According to a person from the Koajiro Activities Coordination Council NPO法人小網代野外活動調整会議 who guided us at that time, the Prefecture hastily came to the forest and cut the infected trees along the board walk and brought out the logs, leaves, etc. for incineration. There remained rather sorry scenes very near for the visitors to observe. The typical evidence of disease was clear. The remained roots have lots of holes whose mouth is covered by wood powders. Peeled off barks of dying oaks are scattered without mercy. I presume the scientists are caught in a dilemma there. To stop infestation they have to sanitize the place. But Koajiro Forest is proud of its biodiversity and extensive natural underground water system within its tiny 70ha area. If humans chemically treat the soil, even if a bit, what would happen for the creatures, other than Platypus quercivorus, living in the entire forest? It’s a serious problem.

A killing field for oaks

Then, few days later, I found a Quercus acutissima with wood powder in none other than our be-loved Niiharu Citizen Forest 新治市民の森. EMERGENCY. I panicked. I consulted with my seniors of Niiharu Lovers, and called the City Office for my sighting. The chairman of Niiharu Lovers has officially requested the municipality to tackle the problem promptly … Compared with the remnants of oaks in Koajiro Forest, the Niiharu’s oak has, it seems to me, fewer holes, and powder. The crown of the tree was still alive at least a week ago. I hope, I really hope, we have yet time to stop the disease to spread …

Niiharu’s sick oak.
 But it still has green crown.
 We may well be able to save it …

A typical sign of infestation.
 Lots of holes at the bottom of large tree covered by frass.

If you find an environmental issues, like Japanese oak wilt, in Kanagawa Prefecture, please make a contact with Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター

657 Nanasawa, Atsugi City, 243-0121 〒243－0121　厚木市七沢657
Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/


If you sighting is in the northern part of City of Yokohama, the office you may call is

Office for Northern Parks, City of Yokohama 環境創造局公園緑地部北部公園緑地事務所
Phone: 045-353-1166
FAX： 045-352-3086
ks-hokubukoen@city.yokohama.jp

Or for the southern part, the address to call is

Office for Southern Parks, City of Yokohama 環境創造局公園緑地部南部公園緑地事務所
Phone： 045-831-8484
FAX： 045-831-9389
ks-nambukoen@city.yokohama.jp

We Really thank you, for your kindness to rescue our forest!