Tree Fruit Pests and Controls

Bacterial spotis caused by the plant pathogenic
bacterium Xanthomonas campestris pv. pruni.This
bacterium can attack leaves, twigs, and fruit. Foliar
infection results in angular, grayish lesions about 1/8 inch
in diameter. As lesions age, they become purple and
necrotic, and sometimes abscise, leaving a shot-hole
appearance. Multiple lesions result in leaf chlorosis
(yellowing) and defoliation. Lesions often concentrate
along the leaf midribs and tips, the latter resulting in a tip
burn appearance.
Cankers are visible in early spring as slightly raised,
blister-like areas along the twig. If the terminal bud region
becomes infected, the shoot tip becomes a blackened
canker that may extend downward along the shoot for
about an inch. In this case, the terminal bud is killed.
Fruit symptoms are first observable three to five weeks
after petal fall. Look for small, depressed, brownish
lesions, sometimes accompanied by pits, cracks, or
exuding gum. These lesions may eventually coalesce to
cover large areas of the fruit surface.
Bacterial spot infections occur anytime from petal fall
until after harvest. The two-four week period immediately
after petal fall is critical for both early foliage and fruit
infection. Thus, to properly control fruit infection, sprays
should be applied from petal fall until 15 days before
harvest. Mycoshield (Terramycin) and Tenncop 5E have
provided satisfactorily disease control.
In addition to the protective sprays mentioned above,
there is some evidence that early applications just before
bud-swell and prior to bloom can help to reduce the
overwintering epiphytic inoculum on tree surfaces. These
sprays lower the bacterial population, thereby decreasing
the likelihood of infection of newly emerging leaves and
fruit. Also, autumn applications during leaf drop may be
beneficial in preventing canker formation. Fixed copper
materials can be used at both these times; see section on
Fungicides and Bactericides.

Table 11.1Relative Susceptibility of Varieties to
Bacterial Spot

Ambergem
Belle of
Biscoe
Bounty
Candor
Cardinal
Correll
Cresthaven
Derby
Dixired

Earliglo
Emery
Erly-Red-Fre
Flamin Furey
Flamin Fury 15
Hamlet
Harbelle
Harbinger
Harbrite
Harcrest

Harkin
Harrow Beauty
Harrow
Majestic
Pekin
Ranger
Redkist
Sentry
Scarlet Pearl
Sentinel

Articglo
Bellaire
Blake
Blushing Star
Coronet
Cresthaven
Crimson Snow
Earlired
Earlirio
Early
Easternglo
Elberta
Encore
Fantasia
Garnet Beauty
Glohaven
Golden Jubilee
Harvester

Jefferson
Jerseydawn
Jerseyglo
Jim Dandee
John Boy
Keystone
Late Sunhaven
Laurol
Loring
Madison
Monroe
Norman
NJ 237
Redhaven
Redskin
Richaven
Rio Oso Gem

Ruston Red
Salem
Southaven
Sugar Giant
Sugar May
Summer Beaut
Summercrest
Summergold
Summerqueen
Sunqueen
Sunshine
Surecrop
Triogem
Topaz
Tyler
Washington
White Lady

Autumnglo
Autumn Lady
Babygold 5
Fantasia
Fayette
Flamin Fury
Flavor Top
Flavorcrest
Jerseyland
Jerseyqueen
Lady Nancy

Marglow
Marhigh
Marland
Marqueen
Maygrand
Rancocas
Redcrest
Redgold
Redhaven
Rio Oso Gem
Shippers Late

Slaybaugh
Snow Giant
Springold
Sugar Lady
Suncrest
Sunglo
Sunhigh
Sweet Sue
Tyler
Velvet
White Hale

1998 New Jersey Commercial Tree Fruit Production Guide

105