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Monday, April 16, 2012

Purple Leaf Plum with Pink or Pale Leaves

Iron chlorosis on purple leaf plum


Q. I have two purple leaf plum trees, both about 2 years old. They started the year beautifully. One continues to look normal but the other one has all of a sudden taken a turn that bothers me. The leaves are getting pale and see-through-ish. It is a nice full tree, yet young. Is this as simple as not enough water or something else? It had a great year last year.

A. It is most likely iron chlorosis. On purple leaf plum, an ornamental, the leaves turn a pinkish color and eventually very pale instead of the yellow or light green color with green veins we see in plants with green leaves.

            If you want to see if a lack of iron is the problem, then make five liquid applications of an iron chelate to the same leaves, using a spray bottle, several days apart. Add a few drops of Ivory liquid detergent to the spray bottle to improve the penetration of iron through the leaf surface.
Severe chlorosis on fruiting (green leaved) plum

            If it is an iron problem, the leaves will eventually, and progressively with each spray, begin turning their normal dark purple color. It will take several applications with a spray bottle to the same few leaves to make this happen.

            Liquid applications to the leaves are not typically as effective as applying it to the soil but you will see the results sooner. One or two applications applied to the leaves will not be enough.

            Otherwise, buy some iron chelate containing the EDDHA chelate and apply it to the soil. Do this by dissolving the iron chelate in a bucket of water and wash it in around the roots. You should see a response in the new leaves that come out after the application has been made. This discoloration is also possible if the tree roots are being kept too wet (poor drainage) or if they are damaged.


Worms in Onions and Garlic

Q. I noticed that some of the leaves of my elephant garlic are wilting to one side. I pulled two plants and saw maggots, which I believe are called onion maggots. I have garlic that never sprouted and they had maggots as well. I then decided to pull out all my elephant garlic and most of them were infested and rotten. These maggots also seemed to feasting on my organic fertilizer that I applied.
            What do I do next? Is it okay to plant other plants in there? Will these maggots be damaging to plants such as peppers, tomatoes, squashes and other non-root crop plants? What is the best way to prevent something like this from happening again?

A. I am surprised you have onion maggots. This is the first time this has been reported to me in our climate. This is usually a cooler climate problem as they don't seem to like high summer temperatures very much.

            There are other maggots that attack seedlings. But if this maggot has attacked an onion bulb as it is bulbing up then it is probably onion maggot. Onion maggots need a source of food, onions, nearly continuously to survive.
            Most control recommendations are to make sure that all onions and remnants of onions are totally removed from the garden area at the time of harvest. You cannot leave anything in the ground that is onion related.

            Onion maggots don't like garlic very much so it surprises me that they are in garlic as well. Your observation is correct, onion maggots do like heavily composted soils particularly when the compost has not had a good chance to break down.
            Onion maggots cannot survive in the garden without some source of food for them. However, they can survive during the winter for a longer period of time without food than they can in the warmer months.
            I would recommend that you plant garlic and onions in rotation with other crops and not plant them continuously in one spot. It is okay to replant onions and garlic in the same spot after about three years. Make sure during your growing season that you have a good solid break from all onion related crops for at least two months before replanting onions or their relatives.  

            I am told that you can plant radishes as a trap crop, attracting the maggots to the developing radishes rather than the onions. The radishes are harvested when infested and destroyed.

Onion and Garlic Maggot Control

What Does Onion Maggot Damage Look Like?

Joshua Tree Blew Over in the Wind

Joshua tree that blew over



Q. I've attached a few photos of our Joshua Tree - on the ground! The trunk completely broke during a strong wind on March 25. We planted it 4 years ago and it has grown almost 18" in that time. Can we replant it in the ground even if it has broken off? Is there any way to save it? Re-grow it? We are heart-broken that it might not be salvageable.

A. Unfortunately your Joshua tree is gone. I have never heard of anyone propagating Joshua from above ground stem pieces of the plant. 
Base of Joshua tree in the ground

            I am curious about why it blew over in the wind. This is not normal for a Joshua tree and makes me wonder if there was another problem associated with the plant. Some people have reported the agave weevil attacking Joshua tree. The agave weevil normally attacks agaves (Joshua is a yucca) with American agave being a favorite of theirs.

            This insect is a small snout-nosed beetle that lays its eggs normally at the bases of leaves of the agave. The eggs hatch producing the immature beetle form, a larva or leggless grub. These grubs feed on the stems of agave, normally at the base causing the agave to begin to collapse and rot at the base.
Agave weevil in agave crown
            If these grubs were present on your yucca (Joshua) it might also cause the base of the tree to rot and collapse as well with the upright part falling on the ground. Visual damage and collapse of yuccas is usually reported in early to midsummer in my experience.

            You might look in the remaining stump on the ground and bottom of the blown over portion for 3/8 inch brown to gray snout-nosed beetles or legless off-white grubs of a similar size.

Think Twice About Planting Pecan in the Desert


Q. We want to plant a pecan tree. Would you please recommend one for Las Vegas? If we plant one, can we cut it way back and keep it small like we did our other fruit trees?

A. Think twice about it. Pecan is a big tree requiring lots of water. If you want to proceed, then pick a Western variety that is self-fruitful and low chill such as Mahan, Mohawk, Tejas or Western Schley.

            Pecans are so big that cutting them back may result in a tree that is about 2/3 of its mature size, maybe 60 to 100 feet tall, but you will not get it much smaller than this. The reason you can keep trees like almonds and pistachios small is because they are not big trees to begin with. The larger fruit trees, like apple and pear, are usually put on dwarfing rootstocks.
            Pecan is a big tree and is not on any dwarfing rootstock so it will be hard to keep its size small. Pecans tend to get anywhere from 70 to 150 feet tall and can have a 6 foot diameter trunk. Normal spacing between pecans is 60 feet apart.

Estimating Water Use for Pecan Trees

Siamese Twin Peaches; Double and Triple Peach Fruits

Double and triple peaches

Q. I have small peach fruits now on my newly planted peach tree and some of the fruit are like Siamese twins; there are double fruits coming from the same spot. In some cases there are three fruits.

A. Double peaches are thought to be from drought stress at the time of flower bud formation which would have been from last July or August (2011).

Double peach mature

Double apple

Double fig

            I usually remove one of the “doubles” so that, when possible, only one fruit remains.  You have to do this when the fruit are young and small and they can still recover. The remaining fruit will heal if the damage is not severe. If the double fruit cannot be split apart then remove the entire fruit.

            At this stage of your tree’s life I would probably leave only a handful of fruit on the tree depending on its size. I would estimate that about 50 leaves are needed to support one fruit. I am not asking you to count the leaves but just estimate it when determining how much fruit to leave on a branch.