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)

 

Rust on Pear Trees

This year has been active for pear rust development.  This disease (Gymnosporangium spp.)  requires two host to complete its life cycle — a pear and a juniper.  There are several related species of this disease that also cause Cedar Apple Rust, Pear Trellis Rust, Cedar Quince Rust, and others.  As you can see in the photo below, orange growth occurs on the leaves and fruit.  Later in the summer spores are released and blown by wind to the nearest juniper host.  On junipers the disease appears as a gelatinous mass on the branches that eventually hardens to a brownish colored gall.

Photo courtesy of Allan Whitehead, MSU-ES

What to do about this disease?  Sanitation is very important.  Clean up all infected leaves, fruit, and other plant parts and dispose of them away from the orchard area.  Prune out infected tissue on both pears and junipers.  Some pears and junipers are resistant to this disease, so choose those varieties if considering a new planting.  The only sure way to eliminate the disease is to get rid of one of the hosts — either the pear or the juniper.  Approved fungicides may help, but it will be a constant battle and timing of application will be critically important.

Some good links on rust diseases that show more photos and suggestions on control:

http://www.ladybug.uconn.edu/factsheets/documents/pear_rust.html

http://pep.wsu.edu/hortsense/scripts/query/displayProblem.asp?tableName=plant&problemID=802

http://www.agf.gov.bc.ca/cropprot/peartrellis.htm

http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/cedar-apple-and-related-rusts

http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/cedar-apple-rust-and-gymnosporangium-rusts/