Q.
I have a group of Italian Cypress in my back yard. I am completely new at this (growing trees
and gardening) because I have lived in apartments and condos until
recently. I planted them, they looked
very happy, but in early summer my gardener pointed out they were being
attacked by spider mites and said I should do something quickly or they will
die. Well, they survived and did not
die, and the new growth on top seems to be green but the growth on the bottom
is still pretty brown. I asked at a
nursery and was told it will never green up and I have never seen needles fall
from the tree, so I suspect he is right (though I am suspicious because
nurseries sell trees). My wife on the
other hand is certain that, given a couple of years the problem will go
away. I was going to replace all the
trees (they are like 15 feet tall and 3 years old, so they grow very fast) but
that is upsetting my wife. I would like
to know who is right, the nursery or my wife (who did grow up around trees).
I have a group of Italian Cypress in my back yard. I am completely new at this (growing trees
and gardening) because I have lived in apartments and condos until
recently. I planted them, they looked
very happy, but in early summer my gardener pointed out they were being
attacked by spider mites and said I should do something quickly or they will
die. Well, they survived and did not
die, and the new growth on top seems to be green but the growth on the bottom
is still pretty brown. I asked at a
nursery and was told it will never green up and I have never seen needles fall
from the tree, so I suspect he is right (though I am suspicious because
nurseries sell trees). My wife on the
other hand is certain that, given a couple of years the problem will go
away. I was going to replace all the
trees (they are like 15 feet tall and 3 years old, so they grow very fast) but
that is upsetting my wife. I would like
to know who is right, the nursery or my wife (who did grow up around trees).
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| Readers Italian Cypress |
A.
I am in the middle on this one. I did look at the original pictures enlarged and it certainly could be spider mite damage. I would be looking for the needles having a “dusty” appearance (tens of thousands dead, cast “skins” of spider mite making a surface “dust” on the foliage. I would also look for perfectly round eggs with a magnifying glass or dissecting scope). Without seeing the branches in person and the extent of the damage
it is hard to judge. If the damage has extended all the way into old growth in
the interior they will not recover but be permanently brown. If the damage is
light and there is some green growth remaining it is possible for them to
slowly recover.
I am in the middle on this one. I did look at the original pictures enlarged and it certainly could be spider mite damage. I would be looking for the needles having a “dusty” appearance (tens of thousands dead, cast “skins” of spider mite making a surface “dust” on the foliage. I would also look for perfectly round eggs with a magnifying glass or dissecting scope). Without seeing the branches in person and the extent of the damage
it is hard to judge. If the damage has extended all the way into old growth in
the interior they will not recover but be permanently brown. If the damage is
light and there is some green growth remaining it is possible for them to
slowly recover.
 |
| Electron micrograph of spider mite feeding |
Take
the branches with dried “needles” and bend them strongly. If they are dry and
snap they will not recover. If they are supple and do not snap like a dry twig
they may recover. That is the best I can tell you. It may not have been spider
mites. I would have to see the foliage very closely and inspect it for mite
“residues”. Not all spider mites make webbing and some webbing is caused by spiders so seeing webbing alone does not guarantee it is spider mites.
the branches with dried “needles” and bend them strongly. If they are dry and
snap they will not recover. If they are supple and do not snap like a dry twig
they may recover. That is the best I can tell you. It may not have been spider
mites. I would have to see the foliage very closely and inspect it for mite
“residues”. Not all spider mites make webbing and some webbing is caused by spiders so seeing webbing alone does not guarantee it is spider mites.
 |
| Webbing like this may or may not indicate spider mites are present. Look for other clues too. |
During
the heat of the summer I would hose down the Italian cypress once a month or so or after any kind of “dirt”
storm. Dirt or dust on the leaves interferes with the natural control of spider
mites by predatory mites and beneficial insects. There is a natural “ecosystem”
at work on cypress that keeps the bad critters under control. Spraying insecticides or miticides can interrupt this natural control system by killing off the beneficials.
the heat of the summer I would hose down the Italian cypress once a month or so or after any kind of “dirt”
storm. Dirt or dust on the leaves interferes with the natural control of spider
mites by predatory mites and beneficial insects. There is a natural “ecosystem”
at work on cypress that keeps the bad critters under control. Spraying insecticides or miticides can interrupt this natural control system by killing off the beneficials.
Do
not irrigate Italian cypress too frequently. If watered often it can cause root
damage and also create the same kind of browning. These are Mediterranean
plants and do not tolerate wet soil during warm weather. Water them no more than about once a week
if you have a “normal” soil but give them a thorough watering when you do.
not irrigate Italian cypress too frequently. If watered often it can cause root
damage and also create the same kind of browning. These are Mediterranean
plants and do not tolerate wet soil during warm weather. Water them no more than about once a week
if you have a “normal” soil but give them a thorough watering when you do.
What do you recommend in regards of treatment… if you do confirm (through white paper test) that the cypress does have spider mites?
If numbers of mites are not terribly high and no browing or dieback is seen wash with soapy water weekly to remove dust or debris interfering with predatory mites or plant oils (petroleum oils, Neem oil, cinnamon oil, etc.) and retest the plant in a week. If the damage is seen they you have no choice but to spray the tree with a miticide and save the tree. Miticides are a type of insecticide that is effective at killing mites. Check product labels at your nursery or farm store to see if it says it kills mites as well. The active ingredients om the label might include Azobenzene, Dicofol, Ovex, and Tetradifon among others.
What if you do find spider mites on the cypress, what do you recommend for treating them?