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 WNV was first isolated in Uganda, Africa. It can harm humans,
birds, and other animals. It is transmitted by infected
mosquitoes, primarily the northern house mosquito. The mosquito
becomes infected after biting wild birds that are the primary
host of the virus. The mosquito is actually able to transmit the
virus after 10-14 days after biting the infected bird.
The mosquito life cycle has four life stages (egg, larvae, pupa,
and adult). The female mosquito lays eggs on water or moist
soil. Most of the larvae hatch after 48 hours and the larvae and
pupae live in the water. The females need a blood meal before
they can lay eggs, so only the females bite. They bite every few
days during their adult lives, which may last several weeks.
Preventing mosquitoes is a first step. Homeowners can best
accomplish this by eliminating standing water. Tires and old
containers are obvious places to start, drill holes in the
bottom of recycling containers, clean clogged gutters, don’t
allow stagnant water in anything such as birdbaths, change
landscape slopes to eliminate standing water, and use larvacides
in standing water that can’t be eliminated. B.t. Israeli is the
strain that is effective against mosquito larvae – not the B.t.
kurstaki variety commonly used on trees and gardens to kill
larvae of moths and butterflies! The mosquitoes have already
begun hatching, so treatment time is at hand.
Also protect yourself from bites. Mosquitoes can travel up to
three miles from their breeding sites! Make sure that screens
and doors are tight, use proper outside lighting such as
fluorescent lights, stay indoors at dawn and dusk when
mosquitoes are most active, wear long-sleeved shirt and long
pants when you must go outside, and use insect repellents
properly applied. The Centers for Disease Control is currently
recommending DEET, picaridin, and oil of lemon eucalyptus
(similar to very low DEET concentrations in repelling
mosquitoes). Permethrin for clothing treatment is also available
at stores selling outdoor sports and camping supplies. Read and
follow all label directions. The DEET percentage affects the
length of repelling mosquitoes. For example, a 4.75% DEET lasts
about 1.5 hours and 20% lasts about four hours.
Leaf Diseases Accelerate
As mentioned a few weeks ago, fungal leaf diseases were present.
They are now making their presence felt with a vengeance. These
diseases infected trees and shrubs earlier, and they have
continued to develop rapidly. Some trees are now to the point of
being, well, leafless.
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Anthracnose is the number one fungal disease of good quality
shade trees, and apple scab is hitting apples and crabapples
hard. To give a brief overview, these diseases are preventable
but not curable. They are seldom life threatening to the tree or
shrub, but they can make things look rather unsightly. Many
shade trees losing a large percentage of their leaves will often
set another set of leaves within four to six weeks. Apples and
crabapples are less likely to set another set of leaves, but it
sometimes happens.
Anthracnose has different stages depending on the time of
infection. There is a bud stage, where buds are killed as they
begin to open. Next is a leaf stage, which affects only leaves.
This stage is the one we are commonly seeing, and it infects
leaves and gradually consumes the leaf. And the other stage is
the twig stage which affects smaller twigs on trees and shrubs.
This is one reason why sycamore trees tend to have so many small
branches break. The infection leaves a brittle scar on the
branch which makes it susceptible to breakage.
As I mentioned, once infection has occurred it can’t be cured.
The prevention part needs to begin with a regular spray program
similar to production apples. This means starting when the
leaves are just out of the bud in the early spring. The same
kind of timing applies to ornamental trees. The main harm caused
is the loss of food produced by the lost leaves, and the loss of
energy to set another set of leaves. Fertilizer application at
the lawn rate, to supply a pound of nitrogen per 1,000 square
foot broadcast, will help the tree as much as anything.
[By JOHN FULTON, COUNTY EXTENSION
DIRECTOR SERVING LOGAN, MENARD, AND SANGAMON COUNTIES] |
