O-M-G # 2

Our second OMG moment is that Michigan had a great harvest in 2016 but it was tainted by IKB. Are we going to let this sink the reputation of Michigan’s chestnuts?

Yes, we have a new OMG for the month. While we want to think and believe that Michigan-grown chestnuts are the best tasting in the world, some of our chestnuts do have a problem. Some growers are reluctant to admit it and therefore it has become a bigger problem than it needed to be. This problem is caused by Chinese chestnut pollinizing our European X Japanese hybrid cultivars like Colossal and others. When this happens at least 30 percent of the chestnut kernels can look decayed (the outside looks great). There are some doubting this now in Michigan. They think that floating can take all of the bad nuts away. Not true. They think that another pathogen has come in and is rotting their nuts. Not true. They think that the nuts are rotting because of poor storage conditions. Not true.

They are rotting because they have IKB. IKB shows up in the orchard and it progresses during storage. Some molds can get into decaying kernels for sure, but the kernels started their decay with IKB and IKB will continue. Look at some of these photos of kernels still in the burs at harvest time. It is there at harvest and stays there during storage causing rot in the nuts.

Figure 1.  Three chestnut kernels still in their bur prior to harvest time showing typical symptoms of internal kernel breakdown (IKB). Two of the nuts are showing full blown IKB, while the third nut is just beginning to show symptoms. What do you think these chestnuts will look like in 2 to 3 months?

Figure 2.  Two healthy kernels surrounding a kernel showing symptoms of IKB in the bur at harvest time.  Is it possible that the two healthy nuts will begin to show IKB?  It is possible, but at this point it seems these will be two good nuts.

Figure 3. The large darker yellow area in the center appears to be the beginning of IKB but it is the dark spots in the middle of the dark yellow that confirms this kernel will begin to decay in time.

Figure 4. This kernel is the only one that was pollinated in this bur and it has IKB. This is prior to harvest time, September.  What do you think this kernel will look like in 2 months?

Figure 5.  Typical IKB symptoms in a chestnut kernel during storage.

Figure 6. A chestnut found during storage with severe IKB. As nasty as this looks there are no fungi found in this kernel. These types of nuts are only found when Chinese chestnut trees pollinize European X Japanese hybrid cultivars.

Figure 7. On the peeling line, floating chestnuts are peeled and show their IKB symptoms. Unfortunately, not all chestnuts with IKB float.

The facts are, some countries like Italy have 6 major problems with their nuts. Two fungal rots and 4 insects penetrating the shell. Some countries, like Australia have only 1 problem with their nuts, a fungal rot–but it is very serious. These countries can’t do anything about their problems in the kernels.

We have one problem and we can do something about it. Don’t let Chinese chestnut trees pollinize the European X Japanese hybrid cultivars. If you continue to allow this, you will jeopardize the Michigan chestnut industry. Customers do not want to pick up a perfect looking chestnut and have a decaying kernel inside. The biological experimentation to figure this out was tough, but getting growers to act on this information has been tougher.

It is now up to the growers to manage their orchards to reduce the presence of IKB in nuts harvested from their orchards.


Our very first O–M–G goes to a meeting to be held in Iowa this winter.

The actual meeting is not the O–M–G. The O–M–G is the use the expression “seedling chestnut trees of superior genetics” in advertising the meeting. It is an O–M–G because this is a meaningless term that almost destroyed the Michigan chestnut industry in the 1980’s and 90’s before the industry finally took off with higher production from high quality grafted trees.

It is not surprising that in Iowa this term is used as some Iowa chestnuts orchards can be traced back to the Michigan-based Chestnut Alliance, a disbanded chestnut group that created a litany of failed chestnut orchards across Michigan due to the planting of Chinese chestnut seedlings.

A seedling tree is a tree that is from a seed. It has nothing to do with age. If a 20-year-old tree is from a seed, then it is a seedling. The alternative is a grafted tree. A seedling is grown and the top cut off and the high quality tree of known genetics is grafted to the rootstock.

A Pattern We Noticed Years Ago in Michigan Seedling Orchards

Imagine orchards with weak seedling trees of unknown genetics where less than half the trees went into production in most years and only 10 percent of the trees had any value.  Imagine having an orchard of 100 trees, where you must care for each tree equally but only about 10 trees provide you with large amounts of high quality chestnuts.  The other 90 trees just take your energy, money and give back nothing much. One grower recently told COS that he once planted 300 Chinese seedling chestnuts—today, only two remain—the only two that produce anything worthwhile. That might not be the way it is in Iowa, Illinois and Missouri, but that is that way it is in Michigan.  Some of our best chestnut orchardists today started their orchards as Chinese chestnut seedling orchards but they had to abandon those failed orchards. In the 1990’s, Michigan chestnut orchards became the laughing stock of the horticultural world as cherry growers and apple growers watched Michigan Chinese seedling chestnut growers care for trees and orchards that never gave much yield in return.  A nice hobby orchard, maybe, but no way to create a professional commercial orchard.

Another part of this O–M–G is the rare chance of finding superior genetics in a seedling tree.  If you indeed, did find superior genetics in a seedling tree, it will be lost while propagating that tree as a seedling. The purpose of a plant to produce seed is to produce new off spring with diversity–something you want in a forest, but not an orchard. Ask those who bet on horses.  Most of the foals of champions do not become champions.  Most of the children of athletes do not become athletes. There is no way of knowing which trees will be superior without them becoming adults and then you will need to graft it to maintain its superior genetics. The only way to put superior genetics in your orchard is to graft superior cultivars.

Knowing if a young chestnut seedling has superior genetics is impossible with the level of knowledge we have on chestnut genetics today.  It would be very damaging to our industry in Michigan if Michigan chestnut growers started planting chestnut seedlings again. Remember that the late Mr. Don Welling started a Chinese seedling chestnut orchard on his land near New Era, but he quickly saw the failed trees and changed to grafted European X Japanese hybrid trees.  His former 12- to 16-year old orchard is now one of the best in Michigan. Don’t let the Iowa meeting and similar meetings alter this message!

Iowa and surrounding states have been planting chestnuts for years, and to collect 49,000 pounds from orchards in 3 states is a wonderful thing, but in Michigan, our younger single orchards in Michigan with grafted European X Japanese cultivars produce that much and more.  Individual chestnut orchards in Michigan with grafted European X Japanese cultivars produced 30,000 pounds, 40,000 pounds and even 50,000 pounds in 2016.

Why is COS so passionate about this?

Because non-productive chestnut orchards hurt the chestnut industry’s reputation. We once were the laughing stock of the horticultural industry, and once we finally start producing hundreds of thousands of pounds people are tempting our growers with the “seedling chestnut trees of superior genetics” argument again.  The current cultivars in use came from years of research and data collection, showing that they work well in Michigan’s climate and we are always looking for more. Apparently, this is going to be a continuous struggle and we will continuously provide education on this and more. See you on March 18th at the Clarksville meeting. 

Figure 1. Foreground, right: A grafted European X Japanese hybrid tree producing burs on its branches.  Background to the left: A large seedling tree with only a few burs on its branches.  The seedling tree is 5-years older than the grafted tree. This was the typical outcome of seedling orchards versus grafted orchards. Of course, it is important to know what the best cultivars are for a specific area.  The location of these trees was the Traverse City horticulture station.