What does it mean when squash and melons have scabs, rings, and sunken spots?
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| Raised corky bumps caused by a scab infection on winter squash M. Grabowski, UMN Extension |
The long awaited harvest of melons and winter squash has
arrived in Minnesota. Many gardeners are surprised to find sunken spots, rings,
unusual color patterns, or raised corky scabs on the fruit. What caused all of
these unusual spots and can the fruit be eaten?
Fruit spots can be caused by a number of different factors
including fungal and viral plant pathogens. Melons, cucumbers, winter squash,
and summer squash are all in the same plant family, the Cucurbitaceae. As a
result, these crops often suffer from the same plant disease problems. Although
many of the vine crops share disease problems, how severe the disease problem
becomes varies by crop and by variety. Below are a few common disease problems
found on melons and squash at harvest in Minnesota.
Mosaic viruses
Several different mosaic viruses can infect squash and melon
in Minnesota. Viruses may be spread by insects like aphids or cucumber beetles,
on sap on hands and tools, or in infected seed. Infected plants have mosaic
patterns of dark and light greens on the leaves and leaves may be puckered or
distorted. Fruit produced on virus infected plants often have unusual color
patterns, ring spots, and may be malformed.
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| Zucchini with unusual raised spots due to a viral infection. M. Grabowski, UMN Extension |
Are virus infected squash and melons safe to eat?
Yes, you can eat squash and melons that are infected with
mosaic virus. These viruses are not harmful to humans and do not cause the
fruit to rot. Often the discoloration is only skin deep. In cases where fruit
are severely distorted, the texture of the fruit may be affected and may not be
desirable for eating.
Fungal fruit spots on squash and melons
There are several different fungi that cause fruit rot in squash
and melon. Scab and anthracnose are common in Minnesota. Both of these diseases
start as a leaf spot disease and eventually infect fruit. The type of spot that
occurs on the fruit depends on which disease is present and how susceptible or
resistant the plant is. Anthracnose causes sunken round spots in the fruit of
cucumber, squash, and melons. If moisture is present, fluffy fungal
growth and powdery salmon colored spores can be seen within the fruit spot.
Scab causes sunken round spots on cucumber, summer squash, and pumpkin that may
be covered with a dark green to black velvety fungal growth when humidity is
high. Some types of winter squash are moderately resistant to scab and will
develop a raised corky bump on the fruit instead of a sunken spot. Resistant varieties are available for scab and anthracnose in some crops.
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| Cantaloupe infected with anthracnose M. Grabowski, UMN Extension |
Are melons and squash infected with a fungal fruit spot ok
to eat?
Fungal fruit spot diseases will rot the fruit of the squash
or melon. This rot begins just below the sunken spot visible on the outside of
the fruit. In cases where only a few fruit spots occur, rotten areas can be cut
out and the remainder of the fruit can be cooked and eaten. Carefully inspect
winter squash at harvest. Only fruit with no signs of a fruit spot disease
should be stored as rot can progress in storage.
Sometimes so many spots are present that the majority of the
fruit is rotten. In other cases a fruit spot may crack open and secondary
bacteria and fungi or fruit feeding insects will move into the fruit. In both
situations, this fruit should be removed from the garden and buried in a
compost pile that heats up and breaks down plant material completely.
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| Anthracnose spots on pumpkin M. Grabowski, UMN Extension |
