White County
 Gardening
Podcast
June 24, 2008
Managing Tomato Diseases (Series 3 of 3) (4:29 minutes)
Audio/Video Script:
Sherri Sanders
County Extension Agent - Agriculture
Hi this is Sherri Sanders, County Extension Agent in White county. This is
the final in a series of three podcasts dealing with tomato diseases. Today we
will discuss a few of the fungal diseases that affect tomatoes in Arkansas.
Fungal Diseases are favored by warm, wet conditions and poorly
drained soil. The fungi are common in many soils.
Buckeye Rot occurs on the fruit and first appears as a brown spot on the
skin, usually where the fruit has contacted the soil. Green or ripe fruit may
become infected. As the spot grows, it forms rings of narrow dark brown and
wider light brown bands. Infected fruit remains firm for a time, then rots
rapidly, sometimes with a white, cottony growth in the center of the brown area.
Root rot symptoms include dark brown discoloration of the roots and lower stem,
resulting in death of the plant.
Buckeye Rot management includes: planting in well-drained soils; using deep
tillage to reduce soil compaction and improving internal soil drainage. Rotate
with corn or other grass crops. Mulch beneath plants to reduce soil contact with
fruit. Use fungicides.
Early Blight is a very common disease of Arkansas tomatoes and is
favored by warm, rainy weather. The fungus survives on seed, infected by plant
debris, volunteer tomatoes, or certain other plants like potatoes, eggplants,
horse nettles or black nightshade. Poor fertilization favors the diseases as
well.
Spots form on leaves, stems, and fruit. Leaf spots start as small, dark brown
areas sometimes with a yellow border and grow rapidly under favorable
conditions, forming lighter brown bands with a dark center. Stem spots have even
more noticeable rings than leaf spots and may cause plant death if the stem is
girdled. Fruit spots start at or near the stem attachment and also develop a
dark, ringed appearance. Spots are leathery-feeling and may be covered by a
blackish dust, consisting of numerous, microscopic spores of the fungus.
Infected fruit often drops off soon after infection.
A grower should select resistant varieties, avoid diseased transplants, if
possible, eliminate weeds and volunteer tomatoes and rotate to other areas every
two years. Use proper fertilization and fungicides.
Southern Blight - This is a common problem in Arkansas on soils that have
grown tomatoes for several years. The fungus survives as hard, brown "sclerotia"
that look like tiny BBs in the soil or on infected tomato debris. It is spread
by anything that moves soil or debris in the field. Sclerotia can survive for
several years without a host.
A large, brown to dark brown rot appears on the stem at the soil line, which
spreads up and around the stem causing a rapid wilt of the plant. Usually a
white, cottony growth develops over the surface of the rot area and sclerotia
form on the white growth over a period of a few days. The sclerotia are
spherical, starting out as whitish balls, which turn red then brown and are
about 1/16" across. Many sclerotia form on the infected stem. If young plants
are infected, they may fall over at the soil line.
Rotate with corn or wheat for 1-2 years. Avoid beans or eggplants in the
rotation. Deep plow the soil to bury infected plants. Use only disease free
transplants and soil. Plastic mulch may help somewhat. Fertilize with calcium
nitrate to minimize disease; use fungicides
Verticillium Wilt - This is a sporadic disease in Arkansas, favored by
long-term tomato production, cool weather, and high pH soils. The fungus
survives as micro-sclerotia in infected crop debris and can attack many other
plants. Verticillium wilt is increased by root wounding from cultivators or root
knot nematode feeding.
The wilt symptoms can be confused with Fusarium or bacterial wilt. Infected
plants may wilt only slightly at first, usually during the hottest part of the
day, and recover at night. Later, lower leaves may show whitening or yellowing
between the veins. This discoloration may become fan-shaped and more yellow over
time. Like Fusarium wilt, a brownish discoloration forms under the outer skin of
the lower stem and can be observed if split length-wise. The pith remains white
and healthy.
Grow resistant varieties with resistance to as many races of the fungus as
possible. Rotate out of tomatoes for 2 years. Destroy all weeds on a regular
basis, as they may be hosts for the fungus. Destroy all infected plants
immediately.
For additional information, contact your county office of the University of
Arkansas Cooperative Extension Service. This has been Sherri Sanders with the
Cooperative Extension Service in Searcy.
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