Of course, tomatoes need
sunlight but as with most everything, there can be too much of a good
thing. Sun scald is common in plants(video) that
are suffering from leaf loss from a leaf spot disease, insect damage, or
over-pruning. The problem often occurs when defoliation or pruning of leaves is
heavy. Sun scald results in a pale yellow to white spot on the side of the
fruit facing the sun, this area may become a flattened, grayish-white spot. The
surface may dry out to a paper-like texture. Sun scald spots are frequently
invaded by decay-causing fungi and bacteria that further rot the fruit.
There are several biological and physical methods to reduce sun
scald damage. One simple approach is to identify and plant sunburn-resistant
cultivars (that produce more foliage or that have a fruit color that reflects
more sunlight). Second, use good agricultural practices to grow healthy plants
because good leaf cover will naturally shade the fruit. Provide adequate water,
fertilizer, and monitor plants closely for insects and diseases that can cause
defoliation or leaf curling. Large healthy leaves provide good shade if the
fruits set and grow within the plant canopy. Over-pruning can also lead to sun
scald if too much of the leaf canopy is removed and the fruits are subject to
direct sun.
Shade cloth is a highly effective option to reduce sun scald. Tomatoes are most susceptible to sun
scald at the mature-green stage and somewhat susceptible at the immature-green
stage. When tomatoes turn red, they are more resistant to sun scald. Shade
cloth can be applied earlier but waiting until fruit set ensure plants grow to
their maximum vegetative capacity before sun scald protection is needed. Shade
cloth is available at garden centers or online. Before purchasing, evaluate the
percent of light reduction. For most fruits and vegetables, 20 to 40% shade is
ideal. For a home garden, create a simple frame around tomato plants using wood
or row cover hoops, then drape with shade cloth and securely attach to the structure.
A structure that is open to the east will allow the plants to receive morning
sun.
Now enjoy those healthy tomatoes straight from
your garden!
