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April Gardening Topics
Anthracnose in Modesto Ash
Anthracnose is a fungal disease caused by wet spring weather. The disease infects
the new shoots as they emerge in spring. The leaves look scorched, turn brown
and drop off. Dry weather may arrest the disease. Prune out infected twigs and
branches. Fertilize the tree to
stimulate vigorous growth. Fungicidal sprays may give some protection if
properly applied but coverage is difficult. Spray information may be found at
the UC Pest Note on Anthracnose. See below for Verticillium wilt on ash.
Avocado Trees, Brown Spot
The brown patch that looks like a turtle's back is called Carapace Spot. It
is corky and usually cracked into angular divisions. It is caused by rubbing or
brushing of tender young fruit on leaves or stems in the wind, but the fruit in
usually undamaged under the spot.
Just cut out the spot. More
pictures of avocado problems can be found at UC Avocado
information.
Avocado Trees, Pruning
Most avocado trees need little or no pruning except to manage tree size.
Always prune sparingly and don't prune in late summer/early fall. If large branches are removed, it will
stimulate growth all over the entire tree. Pruning should mainly be done on young trees. Remove dead or damaged wood at any time.
Wait until new growth starts in the spring before removing freeze damage. What
looks dead may not be. Avocado trees grow irregularly and can be shaped when
young by cutting back the tip of a branch or pinching back the terminal bud of
the upright shoots. Repeat this
method for the first few years to develop a more compact form.
Citrus Fertilizing
In California, most soils contain adequate nutrients for growth except
nitrogen. A one- year-old tree needs about a tenth of a pound of nitrogen and a
5 year old tree will need one to one-and-a-half pounds for the season. It's
best to divide the fertilizing into 3 applications during April, June, and
August. Purchase a balanced product that contains zinc. Spread the fertilizer evenly over the
entire root area and water in.
Citrus Leaf Drop
Leaf drop from citrus trees is normal. Washington Navel oranges may lose
over 3,000 leaves a day during peak leaf drop in the spring. Valencia oranges may lose about 1500 a
day. Problems that can cause
excessive leaf drop beyond these numbers are lack of water and a heavy
infestation of spider mites. The
trees leaves will have brown spots if affected by the mites. You can wash them
off with a strong water spray. Bud
and small fruit drop is also normal.
Citrus Sooty Leaves
Sooty mold on citrus may be a byproduct of sucking insects such as aphid, mealy
bug, soft scale or whitefly. Ants will protect these pests against predators in
exchange for the honeydew that the pests produce. The sooty mold grows on the honeydew. Try washing off the sucking insects
with a strong water stream. Next step
is control of the ants. Ants may be managed by applying a sticky compound
around the trunk and trimming limbs touching buildings or other access
points. Baits at the base of the
tree also help. For more information
about specific controls, see the UCCE Pest Note on
Sooty Mold.
Codling Moth
Codling moth larvae can cause a great deal of damage to apples, pears, plums
and walnuts by penetrating the fruit and boring into the core. On apples, look
for brown colored holes filled with frass. There are a number of non-chemical steps to control this
pest. For that information, refer
to the UCCE Pest Note on Codling Moths.
Modesto Ash Verticillium Wilt
Infected ash trees can wilt on only one side. The leaves turn yellow, then
brown, and die upward from the base of the branch. The dead leaves may remain
attached. Affected branches often
die back. Verticillium wilt is one
of the most widespread, destructive, soil borne fungal diseases. It attacks through the roots, clogging
up the water conducting tissues. The tree usually recovers with good irrigation
and fertilization. Resistant
species are available.
Oakworm
This is a pest of California Live Oaks. The adult oakworm moth is tan-to-gray colored with a wing
span of about an inch. It lays white eggs twice a year that turn reddish or
brown before hatching. The first hatch is in November and overwinters on the leaves,
growing and eating more as the weather warms. At full size, the larva is about
an inch long with a yellowish green body, dark stripes down the side and large
brown head. Outbreaks occur every eight to ten years in the Bay Area. In late March or April, look for little
green pellets (droppings) falling from oak trees. A second generation of eggs
hatches in mid to late summer. Trees
may suffer no permanent damage beyond being unsightly. If you cannot tolerate
the worms and their mess, further treatment methods are outlined in the UC Pest Note
on Oakworm.
Peach Leaf Curl
It is too late for chemical control in April. This coming winter, use a dormant spray in December and
again at leaf break in February. This years damaged leaves will eventually
fall off and should be disposed of in the trash. The new leaves that are
produced are generally fine, but the vigor of the tree may suffer.
Poison Oak
Poison oak is a California native plant that provides shelter and food for
many native birds and other creatures.
The down side is that at least 75% of humans develop allergic contact
dermatitis to the plant. Removal
of unwanted poison oak can be done by allergy-resistant people by pulling and
digging or by application of herbicides.
Under no circumstances should poison oak be burned. Herbicide application details are found
in the UC Pest Note on Poison Oak.
Powdery Mildew
Powdery mildew fungus is a common disease on many plants and produces a
white powdery appearance on leaves and sometimes other green parts. It can be
found on roses, dahlias, chrysanthemums, peas and squash. Some rose varieties
are so susceptible that you would be better off removing the plant. A homemade
spray with baking soda may be used for control. To each gallon of water, add 2.5 teaspoons of light
horticulture oil (or salad oil) and four teaspoons of baking soda. Use a fine spray on affected plants,
but sparingly as some plants may show some sensitivity. More control methods
are available in the UC Pest Note on Powdery Mildew.
Syrphid Fly
As an adult, it looks like a fly but has yellow and black stripes like a
honeybee. In the larval stage, it looks like a soft, fleshy, green slug-like
worm with a white stripe down the back about a half an inch long, happily eating
aphids. This insect should be treated as a beneficial in the garden and
protected. Photos are available of
the Syrphid fly
or hover fly.
Transplanting Tomato Seedlings
Try to plant your tomatoes after the soil reaches 65F for healthy growth. Some kitchen thermometers will measure
temperatures in this range. Here
are two methods of transplanting tomatoes into the ground. The first is to plant deep vertically,
right up to upper leaves on the plant.
Remove those leaves that would be buried. The second method is to dig a
trench, lay the plant on its side, cover up the roots and stem with soil. The
leaves will start to turn upward and grow vertically. The stem portion that is
underground will develop roots. Either
method will provide you with a husky, healthy tomato plant. A number of tomato staking methods are available for reference.
Updated: 20-Mar-2008
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