Citrus Production topics that are the focus of Dr. Roka's area are- Huanglongbing, also known as citrus greening, and a Citrus Yield Case Block Study.
- Huanglongbing (HLB) Greening
HLB (Greening) Huanglongbing (HLB), also known as citrus greening, is one of the most serious citrus diseases. It is a bacterial disease that attacks the vascular system of plants. Once infected, there is no cure for the disease and the fruit is bitter and inedible. The economics of the alternative ways of management strategies are:
- A standard program means that the grove is scouted 4x/yr and infected trees are removed immediately, or
- A foliar HLB program applies nutritional elements to treat HLB induced symptoms and infected trees are NOT removed.
This worksheet allows you to enter your information to determine the net present value of each method for your grove.
Fritz Roka, Robert Rouse, and Phil Stansly. Presented at Future of the Global Orange Juice Industry Workshop, April 6, 2010.
- A Citrus Yield Case Block Study
This is an ongoing study with participating growers in the SW Florida region. We have been collecting yield information for Hamlin and Valencia blocks that were initially stabled in the 1980’s, with some of the blocks having 19 year old trees. The two graphs representing the accumulated data can be viewed below. The published paper can also be read below.
Comparison of Yields by Tree Age and Rootstock in Southwest Florida Orange Groves, F.M. Roka, R.E. Rouse, R.P. Muraro, 2000. Proc. Fla. State Hort. Soc. 113:115-119.
As a result of not having a more current source of information, citrus managers often base production expectations on the Savage yield tables developed 40 years ago. This paper presents the first analysis of citrus production data collected in southwest Florida for eight scion/rootstock combinations. The results reflect trees planted since 1984 with high density tree spacing.
SW Florida, before the late 1970’s was not a large contributor to overall citrus production in Florida. During the 1980’s there were freezes that impacted the production of citrus by killing the trees, especially in central Florida which caused a shift for more planting to be done in SW Florida.
Oranges were the largest part of citrus production in the beginning and still remain the same. After 2005, oranges became an even larger part of SW Florida citrus because of the drop in grapefruit production. The 2004-2005 season saw a great drop in production, due to the effect of the many hurricanes that hit Florida that year. 1990 is when SW Florida really expanded their role in the citrus industry, production was almost doubled.
There is a steady incline until 1980 when production drastically dropped. Effect of the freezes, except for the grapefruits, caused a decline in oranges and specialty fruit (tangerines, tangelos). Then during the 2004-2005 season the toll of the many hurricanes knocked production down further. The high winds of a hurricane caused fruit drop.
Early/mid oranges usually played a bigger role in Florida's citrus production throughout the years. However, in the mid 2000’s, the Valencia (late) oranges and the early/mid oranges became a more evenly split contribution to production.
This graph follows a pattern you would expect. Generally, if the price went up the production went down and vice versa. In the 1980’s however it seemed to not follow that pattern, possibly from the effects of the harsh freezes.
Around the 1970’s acreage in Florida rose drastically, but as soon as the 80’s came acreage dropped quickly. Freezes during this decade killed many bearing trees reducing the acreage by more than 30%. Then in the 90’s the bearing acreage rose again just to come back down in the mid 00’s. the drop was because of the multiple hurricanes that hit Florida on 2004.