Question of the Week

Aster Yellow Disease

Q: Have you seen this in your garden?

If you see this, you may have Aster Yellows in your garden. Aster Yellows has been showing up in gardens around the county.  Click here to find out more about Aster Yellows and what to do if you have this on a plant in your yard.


Q: A freeze is predicted for this week.  Should I harvest my lemons now?

A: Predictions are often incorrect so it is best to wait before harvesting all your citrus.  Fruit freezes if the temperatures drops to 26-28 degrees for several hours.  With temperatures of 32 you may have foliage damage but the fruit will be fine left on the tree.  Learn more at https://aggie-horticulture.tamu.edu/newsletters/hortupdate/2011/mar/citrus_freeze.html


Q:Wooly aphids on a dwarf peach tree.  I have white powdery stuff on my dwarf peach tree. What can I do?

A:  The problem you see on your dwarf peach is woolly aphids.  Woolly aphids are tenacious little creatures but can be treated effectively with low-impact methods of control.  These aphids are a mixture eggs, larva, juvenile and adults.  The good news is they have lost their wings and cannot fly away.  Normally, we would suggest you leave them for nature to take care of but this is a huge infestation so it’s time to take measures to knock down their numbers.

The first action should be to take a cloth or simply put on a glove and wipe the majority off the limb and twigs.  Secondly, use a strong blast of water to wash as many off as possible.  Be sure to spray the trunk, limbs, twigs and under leaves.  This should remove the majority of aphids.  You can now decide to leave them to predators or take further action.  If you decide to continue, you should use a horticulture oil such as Neem oil.  Mix it as directed and follow the instructions on the bottle.  The purpose of the oil is to smother the remaining aphids and any eggs that may hatch.  Saturate under the leaves and in all the nooks and crannies of the trunk.  Should they reappear, just repeat these steps.  Most likely, some aphids will be able to overwinter on the plant so be prepared to use these methods in the spring.


Bark lice webbing on oak

Q:  I looked out at my lawn this morning and saw this shiny, gauzy white web all over my trees?  How can I remove it? Is it harmful? 

A:  Well, you are the lucky winner of the Bark lice Lottery.  We have two types of bark lice in this area, Archipsocus nomas and Cerastipsocus venosus.  Both are small soft bodied insects, rarely seen.  They are often referred to as tree cattle because they herd together as they feed around the tree truck and limbs.  They are rarely found on the foliage.  Bark lice are a great clean-up crew feeding on fungi, bacteria, dead insects and lichens.

Although some think they are unsightly, they are highly beneficial and should be left alone.  Eggs are laid under the protective web, the insect then goes through five to six instars.  With the first fall frosts, the group will begin to decline, along with the web.


Sooty Mold Q:  What is this black stuff on my lemon tree leaves?  How do I get rid of it?

A:  What you have on your leaves and fruit is black sooty mold.   We have a number of people complaining of sooty mold this year because we had a cool, mild, wet winter followed by high heat and humidity.  Perfect growing conditions.

Sooty molds are fungi growing and feeding on honeydew.  Honeydew is produced by sap sucking insects feeding on your plant.  These insects include white fly, scale, meaylbug, psyllids, aphids, just to name a few.  It is important to deal with the insect as well as the sooty mold.

Sooty mold can be a real problem for plants by restricting the sun’s ability to penetrate to the leaf reducing the plant’s ability to perform photosynthesis.  This reduces tree vigor and can result in leaf and fruit drop.

First step is to identify the insect.  Should it be scale or aphids, look for fire ants at the bottom or near to the tree trunk.  Fire ants will farm the insect in order to harvest and eat the honeydew.  You must control both the sap sucking insect and the ants.

Non-chemical control of the insects will be difficult but not impossible.  Do hit the foliage with a hard water spray early in the morning for several days and then several times a week thereafter.  You can also use an insecticidal soap but only if you don’t see any beneficial insects such as lady bugs or predators such as lizards.  A dormant oil can be used to suffocate the insects if the temperature is under 85 degrees.

Purchase a good fire ant poison and use as directed.  Should you need to use a chemical for insect management, do read the label, make sure it includes control of the insect you are targeting, then use as instructed.


Oak Leaf BlisterQ:  My oak tree is dropping leaves and looking bad.  What can I do? 

A:  It appears you have Oak Leaf Blister. This is a fungal disease that attacks most all varieties of oak .  Although the symptoms may begin after a cool, wet spring, most homeowners don’t notice the problem until leaves begin prematurely falling in late summer.  New leaves may have blisters and lesions while older leaves just look dry and blistered.

A good regimen of fertilization and watering will enhance tree vigor throughout the year.  It is useless to spray the tree unless you’ve had repeated years of symptoms.  In this case, you can spray the tree with a dormant oil before bud break in early spring.  Additionally, remove all fallen leaves and destroy to minimize reinfection.  If this is not possible, mow the leaves repeatedly then add a nitrogen fertilizer to add in a quick breakdown.

 

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