Frost and Asian Chestnut Gall Wasp Meeting

UPDATES FOR MICHIGAN CHESTNUT ORCHARDS

MID-MAY TO MID-JUNE 2017

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  1. Asian Chestnut Gall Wasp Field Trip

An Asian chestnut gall wasp (ACGW) education session combined with field trip will be held at the MSU Southwest Michigan Research and Extension Center (SWMREC) on Sunday, June 4th from 1:00 to 3:00 pm. Everything a grower needs to know about the ACGW will be presented during the Sunday meeting including what to look for, what to do when if/when it arrives, opportunities for experimental treatments, and spread of the parasitoid. We will explain the infestation process, the biological control parasitoid that is following the infestation and the outcomes of this infestation. See for yourself the galls, the damage, and parasitoids. As always, clients (owners of the same farm) and family members of clients are free and non-clients are $25. Water and snacks will be provided. We guarantee that if you don’t take any parts of the chestnut trees home, you will take the insect back to your orchards!

  1. Coming out of the May 8th and 9th frost events

In the early morning hours of May 8 and then repeated on May 9, a serious frost struck the Michigan landscape. Many different types of fruit trees, were advanced because of the warm weather experienced earlier in the spring. After driving around looking at various orchards it is obvious there is little pattern to the severity. In southwest Michigan, which was supposed to miss the frost, serious damage was done to trees in low lying areas. Orchards on high land in southwest Michigan, did not suffer as much as those where the frost drained or settled. In the northern lower peninsula, the trees were not advanced enough to experience severe damage, similar to the frost event of 2012. Between southwest Michigan and northern regions, a large range of frost damage can be observed from light damage to heavy, severe damage.

Focusing on the MSU Clarksville Research Center plot is probably the best way to describe what was seen around the state as Clarksville is 50 miles from the coast of the climate moderating Lake Michigan, 80 miles north of the Indiana state line, and on the 42nd parallel.

In the two tables below, from the MSU Enviroweather program, you can watch the temperatures drop during the morning hours of May 8 and then again on May 9.

Figures 1 and 2. Tables on temperatures May 8 and May 9 (https://enviroweather.msu.edu)

With as many weather stations they have reporting, you would think we would have specific knowledge regarding the low temperatures experienced in orchards those mornings, but it is not that simple. In Shelby for example, a grower, using multiple independent thermometers recorded temperatures in the low 20’s in his orchard and he was 5 miles from the reporting weather station. Another factor is that the station reporting may malfunction or be in the process of malfunctioning. Finally, the actual damage to the plant is based on a series of factors such as stage of bud development, microorganisms present on the plant tissue, length of temperature experienced, moisture, wind speed, dew point, height from the ground and topography of the orchard including elevation.

Taken together, it is no wonder why we see a spotty picture of severe and moderate frost events across the state with severe to moderate amounts of damage on chestnut trees.

Look at the figures below to assess the type of damage you may have had in your orchard. What we already know is that we will not be breaking any yield records in 2017. Some orchards will be reduced in yield, some severely. But some orchards have not been touched. Learn how to determine how much the frost hurt your trees, then determine how much per tree and then in October determine the final amount of yield from those trees.

In most cases damage is obvious after a frost with damaged leaves, dead buds, and with new buds pushing up and down the stems.  Sometimes it is best to go back and review how the chestnut tree would have grown without a frost like in 2016.  Below is a photo of a Colossal tree at the MSU Clarksville Research Center breaking bud without any significant frost damage.  Just below the blue arrowhead is the growing bud that is continuing to extend and push, showing no damage.  But this branch did go through the frost as the frost damage can be seen inside the red circles, so we know that this branch was involved with the frost, but it was either not cold enough long enough to kill the bud and the main stem continues to elongate. A lot of frost damage was seen at the CRC and yields will be reduced in 2017.

Trees with not much frost damage included those in the north where the buds were not pushed far enough to have received damage. Examples include the MSU Northwest Michigan Horticulture and Research Center on the Leelanau Peninsula, an established orchard in Kewadin close to the 45th parallel, and a new orchard in East Jordan on the 45th parallel.

No frost damage observed on one-year-old trees at the MSU Northwest Michigan Horticulture and Research Center (photo taken on May 16th a week after the frost), below.

No damage observed on 15-year-old Colossal trees in an orchard near Kewadin (photo taken on May 16th a week after the frost), below.
No damage observed on one-year-old grafted trees in a new orchard near East Jordan (photo taken on May 16th a week after the frost), below.
Damage was observed in Southwest Michigan, spotty along Lake Michigan coast line, frequent in mid-Michigan. Above are mature trees in Oceana County. No severe damage was noticed on any large mature 15-year-old Colossal chestnut trees in this orchard, below 2 photos.

Similar to the photo above, not only was this Colossal tree not damaged by frost, it was already pushing its sterile catkins, called catkin initials. The few dead branches that can be seen on the stem were dead before the frost.

However, in this same orchard in Oceana County, you can see some damage on the younger trees, but they were planted in a lower area. Therefore, it is difficult to determine if it was the location in the orchard, the fact that they were young, or a factor of them being young, that is short with branches more involved in lower, colder air. In the photo below you can see the dead bud circled in red, and all the surrounding laterals buds that break on make new branches, some with catkins. It becomes a mess of leaves and catkins, until there is enough growth to sort it out.

What’s going on inside the the buds that had pushed but ran into the frost? In the photo below, you can see the dead internal tissue. Those buds are dead and new lateral buds surrounding the dead bud will initiate growth. Even through the outer tissue may look green, if they tissue inside the stems die, then the bud will cease to elongate. Remember, the branch grows from the tip. Behind the dead bud, the leaves may enlarge, but that stem is not elongating from that bud, but from the buds that break around it.

The buds that break around the dead buds are called the lateral buds. They may have broken sometime during the season, but that they begin to push now is a sign that the terminal buds were damaged and the lateral buds will form the new leader. Here you see in red either dead buds or stems that pushed and then the buds died. Only the blue lines show the buds and stems that will grow into this summer.

Here is a stem from a Colossal tree at the MSU Clarksville Research Center. The red circles surround dead buds, the blue circles and lines show living buds and growing tissue. The circles show damaged leaves from the frost, not from insect damage. Later, this frost damage may look like insect damage. Here are catkin initials being produced, indicating a chance for female flowers being produced on the stem growing from lateral buds.

Here are buds on young trees (2-year-old) Bouche de Betizac where the bud died in the frost, but for every bud there are at least 2 more in that bud area ready to break. Odds are that young strong, young healthy trees that run into a frost, these lateral buds will break, push and grow into a new leader for the tree. As usual, red circles are dead buds and blue lines show living buds.

 

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