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Green-Seeds.com
Fruits
& Others
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Citrus Production and Marketing Newsletter
Editor: Jim Ferguson
Extension Horticulturist
Horticultural Sciences Department
University of Florida
PO Box 110690
Gainesville, FL 32611-0690
JJFN@GNV.IFAS.UFL.EDU
UPCOMING FLORIDA EVENTS IN 2000
American Society for Horticultural Science
http://www.ashs@ashs.org/events/ashs2000/ashs2000.html
July 23-26, 2000
Coronado Springs Resort
Orlando, Florida
Colloquia on Biotechnology: Accomplishments and Benefits; Adapting Extension
to Help Horticultural Businesses Service; Global Carrying Capacity: Food
and Future World Population
International Society of Citriculture (ISC)
December 3- 7, 2000
Coronado Springs Resort
Walt Disney World
Orlando, Florida
Pre-, Mid- and Post-Congress tours; oral and poster sessions; program
in development; proceedings to be published.
OTHER CITRUS NEWS
Florida State Horticultural Society (FSHS): Summaries
I have developed brief summaries of selected papers from the 1999 FSHS that
could apply to production practices. Only the primary author is listed.
Further details in papers to be published in the proceedings.
Fertilization
 Can foliar nutrient
sprays increase yield?
Climatic stress such as temperature (in Florida: below 25C or 77F for
several weeks) or drought stress (for 30 days in the tropics) are needed
for flower induction. In California urea sprays have increased the number
of flower buds and yields. In Florida sprays of urea during the winter
(Dec. 25 to Jan. 5) at 25 to 28 lbs N/acre increased flowering, yields,
and lbs solids/acre of Valencias for 4 consecutive years. Sprays of Nutriphite
(a source of P03 and K) at rates of 2 lbs P/acre applied in the winter
or before full bloom also increased flowering, yields, and lbs solids/acre
in 3 of 4 years. - Gene Albrigo
Can nitrate (NO3) leaching
be reduced by reducing the area wetted by microsprinklers?
When young Hamlin orange trees, grown in tanks, were fertigated (27x/year)
at recommended N rates for 5 years with 180 or 360 degree microjets, there
were no differences in tree growth, fruit yield and quality or total N
leached into drainage water which had less thatn 10 ppm. Less N also leached
from trees fertigated 56X/year than trees fertigated 27X/year, indicating
that with frequent fertigations (27 to 56X/year) young trees can be grown
at recommended rates in vulnerable soils without leacheate exceeding 10ppm.
- Jim Syvertsen
Economics of controlled-release
fertilizers 
When controlled-release (CRF)and water soluble, granular fertilizers were
applied to Valencia orange trees from planting to six years of age, the
cost of fertilizing with controlled-release fertilizers at the full recommended
rate was 4X the cost of conventional fertilizers and the return was 15%
greater. Current costs for CRFs make them impractical as the primary nutrient
source in solid plantings. - Bob Rouse
Nutrient Availability in Composts
When composted organic
wastes are applied as a soil amendment, especially in vegetable production,
knowledge of the nitrogen mineralization rates can help determine application
rates. When the field mineralization rate of four commercial Florida composts
was evaluated, nitrogen immobilization occurred when composts had less than
1.6% nitrogen and a carbon:nitrogen ratio greater than 20:1; mineralization
occurred when composts had greater than 1.6% nitrogen and a carbon:nitrogen
ratio lower than 20:1.
Mineralization is the
conversion of an element from an organic to an inorganic form as a result
of microbial decomposition, making that element available for uptake by
plants. Immobilization is the conversion of an element from the inorganic
to the organic form in microbial tissues or in plant tissues, thus making
the element not readily available to other organisms or to plants. M. Ozores-Hampton
Growth Regulator Effects
on Juice Yield and Quality
Gibberellic acid (GA) sprays applied to mature Hamlin orange trees at
or near color break at about 18 a.i./acre plus a surfactant appeared to
enhance peel quality and juice yield but the effect of GA on juice yield
did not persist late into the harvest season. - Fred Davies
Mature Valencia oranges treated with Ecolyst, a new plant growth regulator,
at peak bloom, had increased brix the following harvest season without
affecting other fruit characteristics. - Craig Campbell
Cold Protection
During moderate windy freezes (20F with winds 11 to 17 mph) preliminary
results suggest that leaf damage in mature Hamlin orange trees in a small
grove was affected more by tree location in the grove than by microsprinkler
treatment. Trees in the nortwest sector of the grove had greater damage
than trees in the center of southeast sector. - Jim Ferguson
Pest Management
Economics of Weed Control
When seven pre-emergent herbicides and one post-emergent herbicide were
compared in terms of cost for greater than 80% control on an annualized
basis, costs ranged from $2.09 to $4.55. This cost analysis approach for
weed control can provide a tool to develop more economical production
practices. - Steve Futch
Fungi as Biological
Control of Weeds
When three species of fungi were applied in an emulsion, 54 to 99% disease
severity was recorded 4 to 6 weeks after the initial application on large
crabgrass, crowfootgrass, guineagrass, johnsongrass, southern sandbur,
Texan panicum and yellowfoxtail. Emulsions containing a fungus alone or
a mixture of all three fungi almost completely killed guineagrass. - S.
Chandramohan
Spiders Feed on Citrus
Leafminer
Predaceous spiders outnumbered green lacewings, coccinellids and ants
in lime orchards. Four spider species were found feeding on citrus leafminer
and may be important predators of citrus leafminer, especially in unsprayed
groves. - D. Aalin.
New Cultivars
New Rootstock Release
US 852, a new rootstock released by the USDA in 1999 is a cross between
Changsha mandarin and a large flowered trifoliate orange. Resistant to
Phytophthora nicotianae, tristeza, and some nematodes, Hamlin trees on
this rootstock had only minimal twig damage in the 1989 freeze and , in
one field trial, have produced medium-sized trees with large crops of
high quality fruit. - Kim Bowman
Nursery Practices
Failure of buds on Swingle citrumelo rootstock has been associated with
leaf symptoms of citrus bacterial spot associated with different isolates
of Xanthomonas axonopodis pathovar citrumelo. Nursery practices that control
citrus bacterial spot should also reduce such bud failure problems. These
practices include judicious timing of irrigation, increasing air drainage
to promote rapid drying of foliage and performance of budding activities
after the tree dries. - Jim Graham
What is the Citrusnews
Listserve?
The citrusnews listserve
is a way for Florida citrus growers and others interested in citrus to communicate
with each other, share information and send/receive announcements of general
interest. Essentially it is an email list in which all messages to the listserve
address are sent to everyone who has indicated they wish to be added to
the list. Anyone can add themselves to the list and any member of the list
can post messages to the list for everyone else to read.
Hopefully, this listserve
can improve statewide communication about citrus production practices, problems
and resources. Give it a try!
How1 do I subscribe?
To subscribe to the
listserve, you must have an email account and access to electronic mail.
1) Log in to your email account and invoke mail.
2) To subscribe to the citrusnews listserve mailing list, send an email
message to:mailserv@gnv.ifas.ufl.edu
3) Type the following message as the message text: sub citrusnews
4) Send the mail message.
5) You will receive an email confirmation of your subscription to the
listserve (with your email address). For example: The address: jjfn@GNV.IFAS.UFL.EDU
has been added to the citrusnews mailing list by Jim Ferguson
6) To send a message to the listserve, the address is: citrusnews@gnv.ifas.ufl.edu
7) To remove your email address name from the citrus listserve, send
the following command: unsub citrusnews to: mailserv@gnv.ifas.ufl.edu
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