Sunday, December 18, 2011

A Little Rusty

A couple of weeks ago now I got a phone call from the Master Gardener office asking me about a citrus problem. It is very hard to try and diagnose an issue over the phone. It was described to me as being brown all over the skin. I immediately thought of some kind of rot, but the peel was not soft or mushy. I was going to try and run by the office the next day and see if I could figure it out. In the meantime I got Maggie, the Master Gardener on duty at the time, to look up a few things online that it could be and call me if she found anything that looked like it. Well, that advice saved me a trip downtown. She figured out that it was indeed Citrus Rust Mites. Since this happened, I have actually had a couple of other people mention this same issue to me so once is a coincidence, twice or more is a problem.
Phyllocoptruta oleivora or Citrus Rust Mites are long, wedge-shaped and light yellow, measuring about 0.1 to 0.2 mm long, generally they are not visible to the naked eye.
The rust mite feeds on the outside exposed surface of the fruit. Feeding destroys the rind cells and the surface of the fruit becomes silvery on lemons, rust brown on mature oranges and grapefruits.
It looks like this:

Visible characteristics of injury differ according to variety and fruit maturity. While the primary effect of fruit damage caused by Rust Mites mainly is cosmetic, which causes there to be a reduction in grade of the fruit in the fresh market, there has been other conditions which have been associated with severe fruit injury, including reduced size, increased water loss, and increased drop.
Leaf injury caused by feeding of these mites can exhibit many symptoms on the upper or lower leaf surfaces. When injury is severe, the upper surface can lose its glossy character, taking on a dull, bronze-like color. Lower leaf surfaces often show yellow degreened patches. Complete defoliation is rarely an issue. Very high populations can reduce tree vigor.

I mentioned that these things are very tiny. The mite has an elongated, wedge-shaped body about three times longer than wide and under magnification they look like this:

Rust mites tend to seek out high humidity areas away from direct sunlight but also avoid areas where dew forms. Rust mites overwinter on foliage and in bark crevasses. On foliage, mites are most likely to be found on undersides of dry, inner canopy leaves. They reproduce very quickly also, a generation may be completed in 1 to 2 weeks in Summer, but development slows or stops in Winter, depending on temperature.
A variety of predators and diseases attack citrus rust mites. Several fungal diseases, including Hirsutella thompsonii, occur naturally and, during periods of moist weather, cause tremendous rust mite population crashes. Predators of these mites include thrips mites, coccinellid beetles, dusty wings and other insects.
If you happen to have a severe infestation, or they seem to return year after year, you can use any good miticide. Please make sure you read the label and it has listed both Citrus Rust Mite and that it can be sprayed on Citrus.
The good news is, if you do end up with fruit like the picture above, it is still very much edible. Other than the possibility of loss of tree vigor, this critter only really affects the fresh fruit market. Processed fruit, that is a whole other story. You never see the peel, so what is the difference?
Chances are you will never have a problem with the Citrus Rust Mite, and I hope you never do. I wanted to present the case, just in case you go out to your tree and find the fruit looks like it has a case of the creeping crud!
Happy Growing!

Sunday, December 11, 2011


This time of year, everybody gets busy, it goes with the season. For me, my Master Gardener duties tend to drop off significantly, though I am teaching the Citrus and fruit classes this week to the new class. Where I get really busy now is musically. I am the director of a local brass group and the Christmas season is probably our busiest time. The group does find time to have a Christmas party however, and that is where today's blog begins.
I have a dear couple that I have been friends with for many years, he plays French Horn in my group. I met them both at church back in the 80's. Mary has been asking me to come by and identify a plant in her yard for weeks, time just never seemed to be on my side. She sent me some pictures, but I couldn't make a positive ID that way. Well, the group was discussing the idea of having a Christmas party, but we had no idea of where to have it. Mary graciously offered to have it at their house. Perfect!
I could finally get over to ID this mystery plant. I figured it would be easy because the nursery I work at delivered many of the plants used in that sub-division. Then I got worried, what if I couldn't figure out what it was?!
Well, luckily, I knew the name. It was Strobilanthes dyerianus or better known as Persian Shield.

Persian shield is native to Myanmar (formerly called Burma). It is considered an evergreen in Zones 9-11, here in my Zone 8 the frost will get it, but it does come back, especially if planted in a protected area or mulched well. The plant has soft (not woody) stems which are square in cross section.
It lists as getting 3-4 feet tall with a 2-3 foot spread. I have seen the spread, but not the height, probably because of the cold.
The leaves are variegated dark green and silvery-metallic purplish-pink on top and all purple underneath. If this wasn't pretty enough, as a side note it also flowers. They are funnel-shaped, pale violet, and arranged on short spikes.

This plant thrives in humid climates. It prefers rich, well drained soil, but can adapt to a wide variety of conditions. I mentioned that it can get to be 4 feet tall. When it does, it has a tendency to fall over. To avoid toppling over, pinch it back a few times in the first half of the growing season. This will induce branching and create a thicker, bushier foliage. Maybe THAT is why I have never seen any that tall, people pinching back their plants.
You will want to keep your Persian Shield out of direct mid-day sun in the Summer. It does best with direct sun in the morning and shade in the afternoon. It will do well in partial shade, but will have better color as long as it gets lots of bright indirect light. It can be kept as a houseplant, but it is difficult to maintain since it needs bright light, high humidity, and warm temperatures. It will do well as a container plant outside, just remember, it will need more water. Persian Shield is not at all drought tolerant and should be watered before the soil dries out. Feed about every two to three weeks with a water soluble fertilizer.
When it comes to pests, they are prone to Mealy Bug problems. If you are lucky the natural enemies of mealies will assist you in their eradication. If not, an insecticidal soap will work just fine. Please make sure to follow the label directions.
Okay, lets just say you have fallen in love with this plant, not hard to do so far huh? You have one or know of somebody that has one and you want more. Never fear, more plants are as close as a pair of clippers. Persian Shield can be started from stem cuttings taken in Spring or Summer. If you have a place to do it, you can also take cuttings before the first frost gets it.
There are a couple of ways to do it. You will want to start with a cutting about 4 to 6 inches in length. Use sharp scissors, clippers or shears and make the cut 1/4 inch below a leaf node. A leaf node is the small swelling that is the part of the plant stem from which one or more leaves emerge.
The first way is to place the cuttings in some plain old water. With this method, you take a container such as a plastic cup. Fill it three quarters of the way with water. Cover with cling film and make a hole in the middle. Stick the cutting through the hole until it is in the water. In 3-4 weeks, you should have some pretty decent roots. I do not recommend this method. The roots that are formed are water roots and will have a harder time adapting to growing in soil. It will work and can be done, but you could have a higher percentage of failure however.
The preferred method is to take your cuttings as described above, dip them in a little root hormone and stick them in a mixture of one half peat and one half sand. Keep them in a warm, humid environment by placing them in a large plastic bag. Bright indirect light is everything else you need. The cutting should root within two to three weeks.
Persian Shield makes a wonderful contrast when planted in mass with a bunch of other plants such as Hosta and Coleus.

I hope you give this plant a chance, it might just be the "shield" you are looking for in that hard to grow anything shaded area.
Happy Growing!