Mississippi Fruit Problems 2015

Every year the Mississippi State University Extension Plant Diagnostic Lab published a list of the pathogens/problems that were identified.  The Lab can be found online here: msucares.com/lab.  In 2015 several pathogens/problems were seen on fruit crop plants in Mississippi.  Below is the run-down. The number after the name indicates how many times it was diagnosed in 2015:

Apple (Malus x domestica)
 Abiotic (Potassium deficiency suspected) (1)
 Alternaria blotch (Alternaria mali) (1)
 Bitter rot (Colletotrichum sp.) (1)
 Burrknot (genetic) (1)
 Cedar apple rust (Gymnosporangium juniperi-virgianae) (1)
 Cedar apple rust resistance reaction (Gymnosporangium juniperi-virgianae) (2)
 Flyspeck (Schizothyrium pomi) (1)
 Leaf spot (Gloeosporium sp.) (1)
 Leaf spot (Pseudocercospora sp.) (1)

Banana, Japanese (Musa basjoo)
 Root rot (Pythium sp.) (1)

Blackberry (Rubus sp.) ‘Arapaho’
 Abiotic (herbicide injury) (1)

Blueberry (Vaccinium sp.)
 Canker (Fusicoccum sp.) (1)
 Leaf and Fruit Spot (Exobasidium maculosum) (1)

Cherry (Prunus sp.)
 Leaf spot (Cercospora circumscissa) (1)
 Shot-hole (Wilsonomyces carpophilus) (1)

Chestnut, Chinese (Castanea mollisima)
 Abiotic (high pH) (1)

Fig, Common (Ficus carica)
 Fig canker suspected (Diaporthe eres) (1)
 Web blight (Rhizoctonia solani) (1)
 Wood boring beetles (1)

Lemon (Citrus limon)
 Alternaria leaf spot of rough lemon suspected (Alternaria sp.) (1)

Mayhaw (Crataegus aestivalis)
 Rust (Gymnosporangium sp.) (1)

Muscadine (Vitus rotundifolia)
 Leaf blight (Pseudocercospora vitis) (1)

Peach (Prunus persica)
 Bacterial spot (Xanthomonas arboricola pv. Pruni) (1)
 Brown rot (Monilinia fructicola) (4)
 Shot-hole (Wilsonomyces carpophilus) (1)

Pear (Pyrus sp.)
 Bacterial shot-hole disease (Pseudomonas syringae) (1)
 Cedar quince rust (Gymnosporangium clavipes) (2)
 Leaf spot (Phoma sp.) (1)
 Spot anthracnose (Elsinoë pyri) (2)

Pecan (Carya illinoinensis)
 Aphid injury suspected (1)
 Burl (undetermined cause) (1)

Plum (Prunus sp.)
 Black-knot (Apiosporina morbosa) 91)
 Gummosis (Botryosphaeria sp.) (1)
 Shot-hole disease (Wilsonomyces carpophilus) (1)
 Shot-hole borer suspected (1)

Satsuma (Citrus reticulata)
 Abiotic (nutrient deficiency suspected) (1)
 Abiotic (alternate bearing) (1)
 Fruit drop (abiotic) (1)
 Fruit split (abiotic) (1)
 Sweet orange scab suspected (Elsinoe fawcettii) (1)

Strawberry (Fragaria sp.)
 Abiotic (acetochlor plus heavy clay soil plus cold wet weather suspected) (1)
 Abiotic (nutrient deficiency suspected) (1)
 Abiotic (root stress-too wet) (1)
 Bacterial leaf scorch (Xylella fastidiosa) (1)



What’s Going on Here?

I have been watching this kumquat tree outside the hallway window here in my office building.  It seems that it is really growing fast — faster than the kumquat right next to it.  Is it a variety difference?  Doubtful.  Look at the photo below and see what you think.

Tall growing kumquat tree.

Tall growing kumquat tree.

Upon closer inspection, I see a couple of things that really stand out — the taller portion has no fruit on it and the leaves are different.  Could it be a bud mutation?  Citrus trees are notorious for mutations and reversions.  But then I see another telling trait — can you see it in the next photo?

Leaf size differences on kumquat tree.

Leaf size differences on kumquat tree.

If you look closely, you can see thorns.  Uh oh.  When I saw the thorns, coupled with the larger leaves I knew right away what was going on.  I followed the larger growth on down the trunk and found this.

Rootstock suckers taking over a kumquat tree.

Rootstock suckers taking over a kumquat tree (two on the left).

Nearly all fruit trees are grafted onto a rootstock to ensure the clonal nature of the variety.  Citrus trees are no different.  In this case above, the rootstock has produced suckers that have grown large and threaten to overtake the kumquat tree.  All of the benefit, and energy, of the rootstock should be going into the kumquat scion; however, the sucker shoots are robbing the kumquat of essential energy.  If allowed to continue, because the suckers are so vigorous they will overtake the kumquat tree and end up reducing its production over time.  Therefore it is crucial to monitor fruit trees for unwanted suckers that are detrimental to the scion plant.  The best course of action here is to remove both of the suckers and then monitor the tree occasionally for new suckers, removing them when they are small.  On this tree pictured, it is not too late to remove the suckers and for the tree to remain healthy, but the suckers should not be allowed to continue for much longer.  Suckers can be removed at any time of the year, but it is certainly preferable to remove them when they are small, succulent, and able to be taken off by hand.