Changsha Mandarins: Their Fruit and Their Pests

About four years ago I planted three Changsha Mandarins in my backyard.  Changsha Mandarins (one of the many varieties within Citrus reticulata) are one of the cold hardiest of the citrus family that do not have any Poncirus or Ichangensis in their bloodline.  While this reduces the Changsha's survival in truly cold winter climates, it also means there will be none of the characteristic skunkiness or insipid, puckering flavors that sometimes go hand-in-hand with the entire notion of cold-hardy citrus.

Compared to Satsumas (which otherwise share many of the Changsha's characteristics) my Changsha Mandarins are tall, upright trees, very different from the drooping shape of the Satsumas.  Their vertical growth has been nothing short of spectacular as seen in the photos below:

Changsha Mandarin in 2009.  Total height
about 1.5 feet tall.  It was moved from a
pot to the ground in early April.

Changsha Mandarin in 2010.  Total height
about 3 feet.  It's still mainly a single
shoot at this point, with a few side-
branches just forming.

Changsha Mandarin in 2011.  Total height
about 7 feet.  The single vertical branch
is starting to divide out into multiple
branches.

Changsha Mandarin in 2012.  Total height
about 11 feet.  This particular tree has
17 fruits on it, its first crop ever!

This Spring (2012) I observed flowers covering all three of my Changsha Mandarins, and many of the flowers successfully set fruit.  I was initially disappointed at what appeared to be the small number of fruit on the trees, but as summer wore on I discovered dozens more fruit than I initially saw during the spring.  Now here at the end of September as the fruit are beginning to acquire their first hints of orange color, I can easily count them:  there are 52 covering the three trees.

My first crop of Changsha Mandarins!  Late September 2012.

Since I'm still about a month away from sampling my first Changsha Mandarins I can't give any first-hand experiences with the fruit yet.  The largest are just a bit smaller than tennis balls.  Here's the description from the website of the nursery I bought them from, Woodlanders in Aiken, South Carolina:  "It is a hardy and early fruiting citrus here in Aiken, SC with fruit which is much relished by neighborhood kids!"  

At the Southeastern Palm Society's Citrus Expo held here in Wilmington in November 2010 I had the pleasure of actually meeting up with some folks from Woodlanders Nursery, and I asked them about their Changshas in particular.  I was assured their trees produced excellent, although sometimes seedy fruit.  I look forward to confirming this next month!  Note: All of the citrus from Woodlanders Nursery is grown on its own roots.  This means without a dwarfing rootstock you're likely to get a very large tree as the years ago by.  Plan accordingly!

Changsha Mandarins, as with all citrus, have a few pests you've really got to watch out for.  Here in North Carolina, several hundred miles north of the Florida or Gulf Coast citrus industry, our insect and disease pressures are much lower than backyard or hobbyist growers to my south might endure.  The three insect pests I've observed here are the Citrus Leafminer, Red Citrus Spider Mites, and several varieties of Aphids.

Citrus Leafminer damage.  The
tiny caterpillar inside the leaf
causes the shiny U-shaped trails.

The Citrus Leafminer is active only during the warm, growing season.  The adults are small, unimpressive moths that blend in really well with any of the dozens of moth species you might see flying around streetlights and porch lights at night.  The adults lay their eggs on tender new growth.  The eggs hatch into tiny caterpillars that tunnel inside the new leaves, leaving a very characteristic shiny trail behind that doubles back on itself many times in U-shaped channels as they consume the tasty, inner portion of the leaf.  In most cases the damage they cause isn't severe and probably only becomes a major issue on small or otherwise unhealthy trees.  For control of Citrus Leafminers I visually inspect new shoots every couple of days during the growing season and just pull off and safely dispose of any affected leaves.  If you catch them early enough this should prevent a major outbreak.  I went three years without seeing a single Citrus Leafminer using this method!  Obviously this would not work as in areas near commercial citrus plantings or where nearby neighbors are growing citrus.  Chemical-based or pheromone-based control techniques might work better then.

When a Citrus Leafminer caterpillar is ready to pupate it rolls over a section of leaf and seals it with silk.
These are very important to remove and destroy if you're wanting to exercise chemical-free control of these pests.

The only picture I could find I've taken of Red Citrus
Spider Mites.  There are a few individuals on the leaf
behind the flower buds, and a few more above.

Red Citrus Spider Mites are, at least in my backyard, almost exclusively a Winter and early Spring pest.  They can multiply to astounding numbers during the winter and can heavily damage leaves by their sucking of sap and subsequent dehydration of the leaves.  Interestingly they don't appear to be affected by freezing temperatures even down to 20 degrees F. (-6.5 degrees C)  They congregate most-heavily on the upper surfaces of the leaves but also appear on the lower surfaces in smaller numbers -- look for tiny red dots a little smaller than grains of sand.  If you wipe your finger across them on a leaf surface you'll crush sometimes dozens at a time leaving a pale pinkish streak behind.  I imagine the reason these spider mites are such a problem during the winter is whatever predators may control their numbers during the warmer two-thirds of the year are dormant or absent in winter.  During the summer I rarely, if ever, seen them.  Some control can be achieved by using a horticultural oil spray, but the amount of spray needed and the time spent coating both the upper and lower leaf surfaces could both become enormous if you have more than a few trees.  Be careful using oil spray in the days leading up to a major cold outbreak as it appears the oil can negatively impact the leaves' ability to handle temperatures below 27 degrees F (-3 degrees C) for any length of time.  There are probably chemical control methods that also would work, but I strongly prefer to remain organic in all my gardening endeavors.  

Aphids infesting the undersides of Changsha
Mandarin citrus leaves.

The final citrus pest I've observed in my backyard are Aphids.  If you've raised apples, roses, peaches, or almost anything you've probably experienced outbreaks of Aphids when a plant is producing lots of tender, new growth.  I'm not sure precisely what Aphid species I have on my citrus trees but they follow the pattern observed in other plants exactly:  when a flush of new growth is occurring Aphids numbers will explode for a few weeks, diminishing and then virtually disappearing as the new growth hardens off into mature leaves.  I list Aphids last because they've seldom been a significant enough pest to worry about, and I have taken no actions to prevent or disturb Aphids on my citrus so far.