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Pumpkin (squash, melon) diseases defined

Still searching for the definitive proof that AGPs are really pumpkins, I
found this on diseases. It's at 
http://cygnus.tamu.edu/Texlab/Vegetables/cantaloupe.html if you want to
look for yourself.

CANTALOUPE, CUCUMBER, SQUASH PUMPKIN AND CRENSHAW

Cucumis and Cucurbita spp.

Downy Mildew (fungus - Pseudoperonospora cubensis): Angular yellow spots
appear on the upper surface of the leaf during periods of high humidity.
The underside of leaves, opposite the yellow spots, becomes covered by a
grayish growth which is the spore producing structures of the fungus. This
growth is more noticeable early in the morning when heavy dew is present.
Spores are easily carried by wind from diseased plants. Cool temperatures
along with free moisture are ideal for mildew infection and spread. Hot,
dry weather may reduce or stop disease development. Resistant varieties
should be used when possible. Preventative fungicide applications should
begin at the time of blooming and continued at 7 to 10 day intervals until
the crop is harvested. 

Powdery Mildew (fungus - Erysiphe cichoracearum and Sphaerotheca
fuliginea): This disease appears on the leaves as a white powdery mass
composed of the spore-bearing structures of the fungus. Severely infected
leaves shrivel and die. The fungus can also grow on petioles and young
stems. Infected plants are yellow, stunted, and may die. Fruits are not
attacked, but are usually small and deformed. Powdery mildew is favored by
cool, dry weather. Spores are air-borne. Varieties of most cucurbits are
available that show some degree of resistance to powdery mildew.
Preventative fungicide applications will effectively control powdery
mildew. New races of the fungus have appeared which are resistant to some
fungicides. Several applications at 7 to 10 day intervals may be necessary
for optimum control. 

Anthracnose (fungus - Colletotrichum lagenarium): First symptoms of this
disease are spots on the foliage that begin as yellowish or watersoaked
area. Spots enlarge and turn brown to black in color. Diseased tissue dries
and the center of the spots fall out, giving the leaf a "shot-hole"
appearance. Symptoms on fruits consist of circular, black, sunken, cankers
varying in size depending on the host plant. When abundant moisture is
present, the center of the spot is surrounded by a gelatinous pink mass.
The fungus overwinters on old cucurbit vines and residues. It may also be
seed-borne. Plants may be infected at any stage of growth. Disease
appearance in the field depends mainly on rainy, cool weather for a period
of several days. All above ground portions may be infected. Seed treatment,
crop rotation and destruction of crop residues are important practices for
the control of this disease. Preventative fungicide applications, as
recommended for downy mildew control, should be made at seven to 10 day
intervals, or more often, if weather conditions are favorable for disease
development. Preventative fungicide applications will protect plants
against infection. 

Gummy Stem Blight (fungus - Didymella bryoniae): This disease affects
leaves and stems, and is more prominent in the crown at soil level. Leaf
symptoms begin with irregular spots that dry and drop out giving the lesion
a ragged appearance. The most conspicuous phase of the disease is the brown
exudation in the crown of infected plants. Vine cankers are found near the
soil line, producing a gummy brown ooze. The fungus overwinters in the soil
and on crop residue. The fungus is seed-borne. Once the fungus becomes
established, millions of spores are produced which can be readily
disseminated to other plants by rain, wind or mechanical equipment. Using
disease-free seed or seed that has been treated with a fungicide will
prevent the disease from becoming established in new fields. Crop rotation
should be practiced. Spraying with some fungicides has also shown to be
effective. 

Angular Leaf Spot (bacterium - Pseudomonas syringae pv. lacrymans): This
disease appears on leaves, stems and fruit. Spots are small, angular,
straw-colored and watersoaked. Leaf spots often dry and fall out giving the
leaf a "shot-hole" appearance, similar to those caused by anthracnose.
Spots on fruit are usually smaller and circular in shape. Bacteria
overwinter in crop residue and on seed. Hard rains splash the bacteria to
stems and leaves. The disease may reach epidemic proportions during periods
of heavy rains, particularly if temperatures remain high. Since the disease
is seed-borne, the use of disease-free seed treated with a fungicide is
recommended. Crop rotation with non-cucurbit crops is also helpful for
control of angular leaf spot. Application of copper fungicide will assist
in control. Cucurbits, however, are sensitive to copper when young, and
repeated applications of copper may cause yellowing of foliage around the
edges of the leaves. 

Alternaria Leaf Spot (fungus - Alternaria cucumerina): Small, circular
watersoaked spots first appear on the leaves, later enlarging to one and
one-half inch or more in diameter. Definite concentric rings and margins
appear giving the diseased area a "bull's eye" appearance. The fungus
overwinters in crop residue and on other cucurbit plants. Numerous
air-borne spores are produced on diseased spots. Crop rotation and seed
treatment help. A preventative fungicide program should be followed when
the disease occurs consistently. 

Choanephora Wet-Rot (fungus - Choanephora cucurbitarum): This disease
occurs almost exclusively on crenshaw, squash and pumpkins. The blossom
ends of fruit turn black, watersoaked, and covered by a fungal growth. The
fungus is usually confined to the end of the fruit, but if conditions
favorable for disease development prevail, the entire fruit may decay.
Greatest damage by this disease is caused during prolonged damp weather. 

Fusarium Rind Rot (fungus - Fusarium roseum): Rind rot of cantaloupes
caused by Fusarium roseum, caused considerable damage in the Rio Grande
Valley in recent years. Rots appear on the melon rind which at first may go
unnoticed. However, after peeling the fruit, large brown decomposed areas
may be found in the flesh. Since the disease may go unnoticed in the field,
melons may be harvested, packed and shipped without the handlers being
aware of the problem. 

Cucumber Mosaic (virus): This virus causes prominent vein clearing in young
leaves, followed by pronounced mosaic mottle on older leaves, and stunting.
With cucumber, the fruit is prominently mottled, misshapen and blistered.
The virus is spread by aphids. It does not affect watermelon. 

Squash Mosaic (virus): This virus does not affect cucumber, cantaloupe,
honeydew and watermelon fruit. Symptoms on leaves are faint mottling and
distortion. On squash, prominent vein clearing and mottling occurs. Yellow
variety fruits are green with isolated yellow zones and misshapen fruit.
The virus is spread by the cucumber beetle. 

Tobacco Ringspot Virus (virus): Chlorotic stippling, ringspots and mild
vein clearing occur on leaves on cantaloupe, honeydew, and cucumber. Squash
leaves are severely affected, often showing leaf perforations. Fruit of
yellow varieties are severely misshapen with irregular sunken or raised
dark green spots. Watermelon plants have shortened internodes and
pronounced upright growth of terminals. On fruits, concentric rings and
pimples are scattered over the green rind. 

Watermelon Mosaic Virus (virus): Vein clearing and mosaic patterns occur on
cucumber, cantaloupe, and squash. Older plants are severely stunted and
leaves are malformed with dark green blisters. Runners are twisted and
stand upright, a symptom expression usually referred to as "snake head."
Fruits are small. Squash fruit develop a typical mosaic pattern. Yellow
squash are green with yellow spots. Infected zucchini squash are rough and
stunted. In cucumbers, the fruit is mottled partially at the stem end. The
virus is spread by aphids and possibly other sucking insects. No resistance
exists among currently used varieties. Early insect control is important
for the prevention of this disease. 

Charcoal Rot (fungus - Macrophomina phaseolina): Symptoms resemble those of
gummy-stem blight and other vine diseases of melons. First symptoms are
dying of leaves close to the crown. As the disease progresses, entire
runners wilt and die. Close observation of the crown will reveal brown
cankers on the stems both below and above the soil line. Black, hard bodies
produced by the fungus, known as sclerotia, are found on the surface of the
cankers. Crop rotation may be of limited use since the fungus affects a
large number of hosts, including corn and grain sorghum. There appears to
be some difference among the varieties. Soil fumigation with either liquid
or gas compounds kept for a few days under a plastic cover may offer
another means of control. 

Fusarium Wilt (fungus - Fusarium oxysporum f. sp. melonis): This is one of
the most severe diseases, especially of watermelons, that causes sudden
wilting and plant death about the time that fruits are beginning to
enlarge. It also attacks the plant at other growth stages especially during
the seedling stage when it may produce damping-off. The causal fungus is
soil and seed-borne. The disease seems to be most severe when infected seed
are used. Serious losses may occur even where watermelons have not been
previously grown. Use disease free seed and utilize long rotational
programs. Some varieties are more resistant than others. 

Root Knot Nematodes (nematode - Meloidogyne spp.): (See nematodes (Root
Knot).

Denise McCann Beck
USDA Zone 7
Sunset Western 4
Coastal Bristish Columbia
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