VOL. 25, NO. 5
IN THIS ISSUE:
Citrus Black Spot
No, we don’t have it in Texas groves, and, yes, we are looking, but the symptoms of citrus black spot are not quite so simple as we thought. I just received some beautiful color posters of the disease from Jamie Yates of the Citrus Research and Extension Center at Lake Alfred and I was surprised at some of the different forms this disease has, especially on oranges.
One of the forms is called ‘hard spot’ which are small, roundish, black lesions with a tan center, overall sort of like a doughnut. This form seems to occur on the sunny side of the fruit and pencil-point-sized dots (the fungal structures) can usually be seen in the inner, tan portion of the spot.
Another form is called ‘false melanose’ which pretty well describes it if you are familiar with melanose lesions on grapefruit. A third form is called ‘virulent spot’ that is perhaps best described as looking very much like irregular oleocellosis (oil spotting). The fourth form of the disease is known as ‘cracked spot’ which is a bit more difficult to describe—mostly larger dark lesions that often coalesce and which develop almost concentric cracks.
Most inoculum comes from leaf litter, very much the way greasy spot does. However, secondary spread is by (rain) splash from infected fruit and is more problematic on late season fruit. Secondary spread means that lower fruit typically show more symptoms than higher fruit.
The disease affects all citrus except Tahiti limes (Persian limes for those who insist on misnaming this fruit). In addition, the fruit symptoms may develop during post-harvest storage.
According to some growers, fruit set appears to be on the lighter side in comparison to last season. While there are still some grapefruit and some Valencias to be harvested, overall production for the 2010-11 season is already higher than that of the previous year, so perhaps a slightly lower new crop is to be expected.
Too, one cannot discount the effect of the February freeze on fruit set, despite the lack of really significant twig damage—perhaps some of the flower buds (which were already formed and ready to bloom) were killed. You‘ve heard of the effect of spring frost on the flowers and flower buds of deciduous crops such as peaches; maybe we had the same effect without being able to see the damage at the time.
HLB in Chiapas
On March 1, 2011, it was announced that citrus greening was confirmed in 23 tissue samples and 6 psyllid samples in a commercial orchard of Persian lime in the state of Chiapas. That brings to four the number of states on the eastern side of Mexico that are now under quarantine for greening. There has been no news of further detections on the western side of the country.
HLB Survey Results in Texas
The combined results of residential and grove survey results of APHIS and other agencies into mid-April show that the Citrus Center has tested 12,278 tissue samples, with 4,684 samples pending and 33,759 ACP samples, with another 8,756 ACP samples pending. To date, 580 of the 1068 orchards have been surveyed. Surveys have been expanded to include citrus black spot and citrus canker.
TDA’s inspections of 20 propagating nurseries and 225 retail establishments selling citrus and/or jasmine resulted in a total of 23 violations for labeling or quarantine violations, plus one “stop sale” for ACP or other quarantined pest.
No samples of tissue or ACP have tested positive for greening or the other diseases being surveyed.
Nursery Movement Rules Change
As published in the Federal Register on April 27, APHIS has established new rules for the interstate movement of citrus trees from quarantined areas to any area in the US. Certificates and limited permits are required for facilities operating under compliance agreement with APHIS, and the facility must meet strict standards for the production of disease-free plant materials.
The rule is viewable at www.aphis.usda.gov/plant_health/plant_pest_info/citrus/index.shtml.
Public comments will be accepted until June 27, which can be posted online at
The five states quarantined for SOS (Arizona, Texas, Louisiana, Mississippi and Florida) cannot ship plant materials to other citrus-producing states, and parts of two counties in Florida which are quarantined for citrus black spot cannot ship plant materials to other citrus-producing states or areas.
Presumably, this rule change does not negate existing regulations regarding the movement of citrus propagation materials between citrus-producing states, which regulations are aimed at other citrus diseases than just canker, greening, CBS, and SOS.
Back in 2001, the Florida Department of Citrus developed a process to separate intact juice sacs from fruit and subsequently licensed the process to CitraPac, Inc. CitraPac created Fruit Pearl frozen snacks, which combine juice sacs from oranges and tangerines with pearl-shaped pieces of other fruit purees. The end product is flash frozen and packaged in 3.25 ounce cups and are available in four flavors: Guava Mango, Tropical, Wild Berries and Cream, and Chocolate Strawberry.
Fruit Pearls are reportedly available in the frozen foods section of supermarkets in several states, including Market Street and Village Market in Texas (I don’t know where those are) and in Barnes & Noble BookSellers in 27 states (I don’t know if that includes Texas). Naturally, they are widely available in Florida. Fruit Pearls should be worth a taste if you find them locally.
THE INFORMATION GIVEN HEREIN IS FOR EDUCATIONAL PURPOSES ONLY. REFERENCE TO COMMERCIAL PRODUCTS OR TRADE NAMES IS MADE WITH THE UNDERSTANDING THAT NO DISCRIMINATION IS INTENDED AND NO ENDORSEMENT BY THE COOPERATIVE EXTENSION IS IMPLIED.
| Valley Citrus Notes Index | Aggie Horticulture |