Biology Reference
In-Depth Information
Phomopsis vaccinii Fruit Rot on blueberry.
Phomopsis sp. Fruit Rot on peach.
tuberose, valerian, verbena, violet, wallflower,
wandering jew, water cress, watermelon, yaupon,
yucca and zinnia.
Phymatotrichum root rot occurs from July
until frost. It kills plants in more or less circular
spots, ranging from a few yards to an acre or
more. Death may come within a few days of
first wilt symptoms, and just preceding the wilt
plants actually run a fever, with a higher than
normal temperature. If plants next to the wilted
ones are pulled out, these apparently healthy
plants will often be found to be covered with
yellow to buff mats of mycelium, and under
moist conditions spore mats appear on the surface
of the soil around diseased plants. Such mats are 2
to 12 inches in diameter, first snow white and
cottony, later tan and powdery from spores pro-
duced in quantities. The fungus spreads through
the soil by means of rhizomorphs, smooth, dark
brown strands. The rate of spread may be 2 to
8 feet a month in an alfalfa field, 5 to 30 feet
a season in a cotton field, or around fruit trees.
Sclerotia are formed along the mycelial
strands. They are small, roundish, light at first,
then dark and warty. The fungus winters either as
sclerotia in soil, persisting several years in the
absence of live hosts, or as dormant mycelium in
living roots. The disease is most common and
severe on heavy, alkaline soils. Abundant organic
material reduces rot by favoring antagonistic soil
saprophytes.
Control In ornamental plantings replace dis-
eased plants with some of those given in the
resistant list. Monocotyledons are generally resis-
tant. In locating new orchards, make sure that
root rot has not been present previously by grow-
ing an indicator crop of cotton for a year. Grow
immune crops in rotation with susceptible crops,
and grow susceptible annuals in winter rather
than summer. Try heavy manuring.
Ammonium sulfate can sometimes save
a valuable ornamental tree or shrubs already
infected with root rot. Prune back the top, make
a circular ridge about the plant at the edge of the
branch spread, and work ammonium sulfate into
the soil within the ridge then fill the basin with
water to a depth of 4 inches. The chemical treat-
ment and watering is repeated in 5 to 10 days,
Phymatotrichopsis (Phymatotrichum)
Deuteromycetes, Hypohomycetes
Conidiophores stout with inflated tips bearing
loose heads of conidia; spores hyaline; one-
celled, produced on surface of soil.
Phymatotrichopsis omnivors (formerly
Phymatotrichum omnivorum ). Texas Root Rot ,
Phymatotrichum Root Rot , Cotton Root Rot .
This is the most destructive plant disease in
Texas, a limiting factor in gardening and crop
production. It occurs in the Red River counties
of Oklahoma, the southwestern half of Arizona,
the southeastern edge of Nevada and California,
the southeastern corner of Arkansas and Utah, the
northwestern corner of Louisiana and in most of
Texas except the Panhandle.
The list of susceptible plants flowers, vegeta-
bles, fruits, field crops and trees - is much longer
than that of plants resistant to this omnivorous
fungus, so aptly named. At least 1700 plant spe-
cies are attacked, more than by any other known
pathogen. Because of the wide host range and
destructiveness, the economic losses are enor-
mous, $100 million a year in Texas alone, with
perhaps $50 million in adjacent states.
Crops that either are resistant or escape the
disease are the cereals and grasses, annuals
grown in winter only, and sweet alyssum, ama-
ranth, sweet basil, beauty-berry, bee-balm,
collinsia, diosma, calceolaria, calla lily, Califor-
nia-poppy, candytuft, canna, chicory, cranberry,
cucumber, currant, cyclamen, daffodil, dahoon,
deutzia, dill, fenner, fern, staghorn, foxglove,
freesia, goldentuft, mustang grape, gypsophila,
hackberry, hoarhound, hyacinth, iris, lily, nigella,
marsh-marigold, mignonette, mints, mimulus,
muskmelon, mustard, nasturtium, oak, osage-
orange, oxalis, Indian paint-brush, palms, pansy,
petunia, phlox, Chinese pink, pitcher-plant,
pomegranate, poppy, portulaca, primrose, pump-
kin, red-cedar, sage, scarlet-brush, snapdragon,
snowdrop,
stock,
strawberry,
strawflower,
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