Overwatering can also cause leaves to yellow and drop. Gardeners can
kill their plants with kindness during hot, dry weather by watering
too much, too frequently. Many plants look a little wilted during
the heat of the day - they curl their leaves slightly to minimize
moisture loss through transpiration during very hot weather - but
recover when the sun sets. Watering them even more when they appear
wilted can lead to root rot. Watering deeply once or twice a week
once the plants are established should be sufficient, even when it
is hot and dry. Apply the water to soil as much as possible, rather
then dousing the plant. This puts it at the root system where it is
needed, and keeps the foliage as dry as possible to reduce the
incidence of disease problems.
Since you have to hand water a large garden, I hope you use mulch to
help conserve soil moisture and moderate soil temperatures during
the growing season. Organic mulches such as straw or shredded leaves
can do a better job of this than plastic mulch during such hot, dry
weather unless you have drip irrigation installed under the plastic.
Plastic or organic mulches can help keep weeds down, too. Weeds
compete with desirable plants for water and nutrients, and can serve
as a source of insect and disease problems. Either plastic or
organic mulches can also cut down on disease problems that spread by
splashing spores up from the soil during rain or irrigation.
Easy on the
If you apply high nitrogen fertilizers - especially during hot
weather when the plants are under drought stress - you can burn
them, which will also cause leaf drop. Fertilizer placed directly
into the hole at planting time can have the same effect on
transplants. This includes organic sources such as uncomposted
manure, blood meal, and fish emulsion.
Although you do not mention any kind of spots on the leaves or
fruits, peppers are susceptible to a number of diseases that can
cause the leaves to yellow and drop prematurely. These include
cercospora leaf spot, a fungal disease whose symptoms include round
or oblong spots on the leaves and stems. These spots often have
light gray centers with dark brown borders. Infected leaves turn
yellow and drop when the disease is severe. The fungus is carried on
infected seed and may survive over winter in the garden on infected
plant material. Long periods of warm, wet weather are ideal for this
disease to develop.
Control options include thoroughly cleaning out
the garden at the end of the season and not saving seed from
infected plants. Dispose of infected plant plants in the trash or by
burning them, rather than tossing them on the compost pile. Purchase
fresh seed or disease-free transplants for next season's garden, and
do not plant them where infected plants were grown this year for at
least two years. Avoid overhead irrigation to keep from wetting the
foliage more than necessary. Spray plants with basic copper sulfate
at the first sign of disease, making repeated applications as long
as weather conditions favor disease development. Follow label
directions regarding intervals between applications.
Bacterial spot is a bacterial disease characterized by leaf and
fruit spots. It is most likely to develop during warm, wet weather.
On the leaves, spots start as irregularly shaped water-soaked spots
on the undersides of the leaves. They become purplish with black
centers, and you may notice a yellow halo around the spot. The spots
appear sunken on the upper leaf surface and raised on the lower side
of the leaf. Affected leaves take on a ragged appearance, often
yellowing and falling prematurely. On fruits, the spots start as
water-soaked areas, that turn brown and raised. They have a corky
feeling. The bacterium is usually transmitted on infected seeds and
the transplants grown from those seeds.
The disease can survive
over winter on infected plant debris, and is transmitted from plant
to plant by splashing water, or on your hands or tools that have
been used on infected plants. Remove severely infected plants from
the garden, and throw them in the trash or burn them. Clean plant
debris from the garden as thoroughly as possible, and practice crop
rotation. Try not to plant pepper and tomato plants in the same
place more than once every three or four years, since they are in
the same family and susceptible to many of the same maladies. Avoid
overhead irrigation to keep from wetting the foliage more than
necessary, and do not work in the garden while plants are wet from
rainfall. Spray plants with basic copper sulfate at the first sign
of disease, making repeated applications as long as weather
conditions favor disease development. Follow label directions
regarding intervals between applications.
Leaf drop on peppers (and other fruit-bearing plants) can reduce the
number and size, as well as the quality, of fruits because it limits
photosynthesis, the process whereby plants manufacture their own
carbohydrates. Reduced leaf cover also opens fruits up to sunscald,
a result of their exposure to full, blazing sun.
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