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Inspection Report Week of March 12, 2018

At a pest workshop in Mobile last fall, Dr. Kassie Conner from the Auburn Plant Lab spoke about tip blight on arborvitae, cryptomeria, and junipers caused by phomopsis and kabatina disease organisms.  These diseases are devastating to young plants while plants more than five years old are less seriously damaged.  Here's a really good write-up from Alabama Extension about these diseases published in 2004: https://www.aces.edu/pubs/docs/A/ANR-1173/ANR-1173.pdf   A list near the bottom details resistant and susceptible varieties.

Kassie said that the pathogens infect through wounds caused by insects or mechanical damage.  A possible insect suspect might be the juniper paria.  I find these on many junipers and 'Black Dragon' cryptomeria where tiny bites have been taken out of the tips of foliage.  I have records of trapping them in late February and early June.  I have never put the two together until Kassie mentioned it.  This might be a situation to keep an eye on.  Kassie suggested spraying for the beetle if they were found in significant numbers.

The beetles can be monitored by tapping foliage over a white surface.  My white Frisbee works best for this because beetles often fold their legs in and drop when disturbed.  The edges of the disc help capture the beetles and hold them where they can be observed.

Kassie said that the timing for control differs.  For phomopsis, begin in early spring and continue at 10-14 day intervals.  For kabatina, fungicide applications should begin in the fall.

The brown tips are in themselves not bad or very noticeable.  They are just dried up feeding sites where beetles have taken out the growing tip.  However, these can be wound sites for pathogens to enter on susceptible varieties.

Maskell scale can be a serious problem on ‘Blue Point’ juniper.  This scale is extremely small. It sometimes looks like the plant has mites.  Often a hand lens is needed to see it.  An extension article from Maryland says: “The exact number of generations per year is not clear. First instar crawlers emerge in June, and there is a second generation in August. In Maryland adult males and females are present in September through October. Eggs, crawlers and adults are all present in the early to mid fall.”  Temperature differences here in the south probably have these dates moved up earlier.

Girdling roots can be a serious problem, especially if plants are left too long in a liner pot.  The picture shows a camellia.  In this case the roots are above ground.  They are often circled underground as well.  It's important to look for this before planting.

Albert Van Hoogmoed 

AL Dept of Agriculture, Mobile County



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