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Vegetarian Newsletter
A Horticultural Sciences Department Extension Publication
on Vegetable Crops
Eat your Veggies!!!!!
Issue No. 552 December 2009
Evaluation of Strawberry Cultivars in Florida: 2007-09
By: Bielinski M. Santos, Assistant Professor, Craig K Chandler, Professor,
Maricruz Ramirez-Sanchez and Teresa P. Salam6
Gulf Coast Research and Education Center-Balm
INTRODUCTION
Strawberry (Fragaria x aananssa Duch.) production in Florida is the second largest in
the U.S. after California, with about 3360 hectares and gross sales over $330 million. Florida is
the largest supplier of strawberries during the winter months in the U.S. and the majority of the
strawberry production occurs in the west central part of the state. Strawberry yields in Florida
have increased over the years due to the use of soil fumigation, raised beds with polyethylene
mulch, defined fertilization practices, and planting pest-free stocks from northern nurseries.
Some of the benefits of the annual hill system are improved weed control, high early yields and
large fruit size, and ease of harvest. The west central Florida strawberry industry sets fresh
transplants, with active crowns and intact and functional leaves during early October. Ripe fruit
is harvested from mid-December until mid-March or later, if the market prices are favorable.
The goal of a successful breeding program is to develop cultivars to satisfy market and
grower requirements. From the market point of view, among the most important strawberry fruit
characteristics are uniform shape, size, firmness, flavor, color, and prolonged shelf life. On the
other hand, growers are interested on having cultivars with disease resistance, high yields under
different weather conditions, and acceptable yield earliness, which allow them to supply the
market when premium prices are available. Planting different cultivars in the same farm is a
common practice among strawberry growers in Florida. The purpose is to complement the
production peaks of each cultivar in order to maintain a steady supply through the season,
especially during the early part of the fruiting season.
There is current need for cultivars to complement the harvests peaks of 'Strawberry
Festival', which is the most planted cultivar in Florida. However, the performance of the
strawberry cultivars need to be investigated in Florida to determine adaptability and performance
among cultivars and advanced breeding lines. The objective of this study was to compare the
performance of several strawberry cultivars in west central Florida.
MATERIALS AND METHODS
Two trials were conducted during the 2007-08 and 2008-09 strawberry seasons at the
Gulf Coast Research and Education Center of the University of Florida, located in Balm, Florida.
The soil at the experiment site is classified as a Myakka fine sand siliceous, hyperthermic,
Oxyaquic Alorthod. The organic matter content and the soil pH of the experiment site were 1.5%
and 7.3, respectively, and were measure 4 weeks before transplanting. Planting beds were pre-
formed with a standard bedder, 69 cm wide at the base, 61 cm wide on the top, and 25 cm high,
and spaced 1.22 m apart on centers. The soil was fumigated with 398 kg/ha of methyl bromide +
chloropicrin (67/33 v/v). Simultaneously, beds were covered with black high-density
polyethylene mulch (0.04 mm-thick). No preplant fertilizer was used. Fertilization and pest
control were done according the requirements of the crop. Fertigation was applied through a
single-drip tape line (237 L/ha per min) buried between 2 and 5 cm deep, and the experimental
area was equipped with 15 L/min sprinklers for frost protection and crop establishment.
During the 2007-08 season, the cultivars tested were 'Winter Dawn', 'Florida Elyana',
'Florida Radiance', 'Strawberry Festival', 'Treasure', and 'Camarosa', whereas in the 2008-09
season, 'Winter Dawn', 'Florida Elyana', 'Florida Radiance', 'Strawberry Festival', 'Treasure',
'FL 05-73', and 'FL 05-107' were planted. The experimental design was a randomized complete
block design with 4 replications. Bare-root strawberry transplants from certified nurseries in
Nova Scotia, Canada were planted in 15 Oct. 2007 in double rows 38 cm apart, 20 plants per 7.6
m plot. Sprinkler irrigation was used 8 h/day for 10 days to ensure plant establishment.
Strawberry marketable fruit weight and number were collected two times per week,
beginning on mid-December of each season and using every plant of each plot. A marketable
fruit was defined as a fruit without visible blemishes and with at least 75% of red skin. Early
yield consisted on the cumulative yield from the first six harvests, whereas the total yield
included the twenty-four harvests through the season. The weight per fruit was determining by
dividing the fruit weights by the fruit numbers of the early and total yields. Cultivar means were
compared with a Fisher's protected least significance difference (LSD) test at the 5%
significance level.
RESULTS AND DISCUSSION
2007-08 Season
There were significant effects of cultivars on the fruit number, fruit weight, and weight
per fruit during the 2007-08 and 2008-09 seasons. During the first season, the highest early fruit
number was found in plots planted with 'Strawberry Festival' with 243,900 fruit per ha, whereas
there were no early fruit number differences among 'Treasure', 'Winter Dawn', 'Florida Elyana',
and 'Camarosa', ranging between 125,800 and 166,100 fruit per ha (Table 1). However, there
were no significant differences among plots planted with 'Strawberry Festival', 'Treasure', and
'Winter Dawn' in the total fruit number during the season, while the lowest number was found in
the 'Camarosa' plots.
Early fruit weight was the highest in plots planted with 'Strawberry Festival' and
'Treasure', ranging between 3.3 and 3.5 t/ha (Table 1). Other cultivars produced early fruit
weights between 1.9 and 2.4 t/ha. There were no differences in early fruit weight among the
remaining cultivars. Plots planted with 'Strawberry Festival', 'Treasure', and 'Florida Radiance'
did not differ in total fruit weight, with yields above 12 t/ha. The lowest total fruit weights were
found with 'Camarosa' and 'Florida Elyana'. The heaviest fruit were obtained in plots planted
with 'Treasure' during the early harvests, averaging 19.7 g per fruit, followed by 'Florida
Elyana', 'Florida Radiance' and 'Camarosa', whose fruit ranged between 16.5 and 17.4 g. The
smallest fruit were produced by 'Strawberry Festival' and 'Winter Dawn'. Fruit size changed as
the planting season progressed, as shown by the season-total weights per fruit. There were no
significant differences in the weights per fruit of five out of six cultivars, ranging between 18.4
and 22.3 g per fruit (Table 1).
Table 1. Comparison of fruit number, yield and weight per fruit of different strawberry cultivars,
2007-08 season, Balm, Florida, USA.
Fruit number Fruit weight Weight per fruit
Cultivar Earlya Total Early Total Early Total
no. x 103/ha t/ha g
Strawberry Festival 243.9 a 820.6 a 3.5 a 12.7 ab 14.3 c 15.5 b
Treasure 166.1 b 730.7 ab 3.3 a 15.0 a 19.7 a 20.5 a
Winter Dawn 125.8 bc 647.4 ab 1.9b 11.9b 15.3 c 18.4 ab
Florida Elyana 137.2 bc 567.4 b 2.4 b 11.5 bc 17.4 b 20.3 a
Florida Radiance 113.8 c 600.0 b 1.9 b 12.2 ab 16.5 b 20.3 a
Camarosa 134.5 bc 399.1 c 2.3 b 8.9 c 16.8 b 22.3 a
Significance *
(P<0.05)
aValues followed by the same letter do not significantly differ at the 5% level according to
Fisher's protected LSD test.
2008-09 Season
Plots transplanted with 'Strawberry Festival' and 'Winter Dawn' resulted in the highest
early fruit number, with values of 183,600 and 184,900 fruit per ha, respectively. The lowest
early fruit weights were obtained with the advanced line 'FL 05-107', and with 'Florida Elyana'
and 'Florida Radiance' (Table 2). However, the advanced line 'FL 05-107' produced the highest
total fruit number along with 'Strawberry Festival', both exceeding 710,000 fruit per ha. In
contrast, 'Winter Dawn' and 'Florida Elyana' had the lowest values for this variable with less
than 400,000 fruit per ha.
'Strawberry Festival' and 'Winter Dawn' produced the highest early fruit weight among
all the cultivars, with 3.9 and 3.7 t/ha, respectively (Table 2). There were no significant
differences on early fruit weights among the remaining cultivars, which ranged between 2.2 and
2.8 t/ha. Plots planted with the advanced line 'FL 05-107' provided the highest total fruit weights
during this season (21.3 t/ha), followed by 'Strawberry Festival', 'Treasure', and 'Florida
Radiance', which produced between 13.0 and 15.4 t/ha. The lowest total fruit weight was
obtained in plots planted with 'Winter Dawn'. 'Florida Radiance', 'Florida Elyana', and the
advanced line 'FL 05-107' produced the heaviest early and total weights per fruit during the
season, ranging between 26.3 to 32.7 g per fruit (Table 2). In most cases, there were no
significant differences on early weight per fruit among the remaining cultivars. 'Strawberry
Festival', 'Treasure', and 'Winter Dawn' had weight per fruit between 19.8 and 24.2 g.
Table 2. Comparison of fruit number, yield and weight per fruit of different strawberry cultivars,
2008-09 season, Balm, Florida, USA.
Fruit number Fruit weight Weight per fruit
Cultivar Earlya Total Early Total Early Total
no. x 103/ha t/ha g
Strawberry Festival 183.6 a 710.6 a 3.9 a 15.4 b 21.2 b 21.7 b
Treasure 121.2 bc 537.4 b 2.7 b 13.0 bc 22.3 b 24.2 b
Winter Dawn 184.9 a 388.1 c 3.7 a 7.7 d 20.0 b 19.8 bc
Florida Elyana 67.6 d 323.8 c 2.2 b 10.6 c 32.5 a 32.7 a
Florida Radiance 86.6 cd 510.4 b 2.8 b 13.4 bc 32.3 a 26.3 ab
FL 05-73 130.8 b 592.0 b 2.6 b 11.0 c 19.9 b 18.6 c
FL 05-107 69.9 d 787.0 a 2.2 b 21.3 a 31.5 a 27.1 a
Significance (P<0.05) *
aValues followed by the same letter do not significantly differ at the 5% level according to
Fisher's protected LSD test.
During both growing seasons, 'Strawberry Festival' consistently produced the highest
early and total fruit numbers among all tested cultivars. Similarly, the same cultivar had the
highest early fruit weight. With regards to total fruit weight, 'Florida Radiance', 'Treasure' and
'Strawberry Festival' resulted in the highest values among all cultivars tested during both
seasons. The advanced line 'FL 05-107' seemed to be a promising germplasm that produced the
highest fruit weight in the 2008-09 season, but more testing is needed to confirm that result.
There was no consistency on specific cultivars producing the largest early fruit, while 'Florida
Radiance' and 'Florida Elyana' had the largest total weight per fruit during both seasons.
These results indicated that 'Strawberry Festival' is an adequate choice as a main cultivar
for production under Florida's conditions, which could be complemented during low production
periods with other promising and late producing cultivars, such as 'Florida Radiance' and
'Treasure'. The performance of the advanced line 'FL 05-107' needs to be further investigated
because of its elevated total fruit weight during the only season when it was tested.
Vegetarian Newsletter
A Horticultural Sciences Department Extension Publication
on Vegetable Crops
Eat your Veggies!!!!!
Issue No. 552 December 2009
Attracting Beneficial Insects to Your Farm
By: Robert Hochmuth, Multi County Extension Agent
North Florida Research and Education Center Suwannee Valley
Earlier this fall Carolyn Saft, Suwannee County Extension Agent and I were preparing to
teach a workshop on "attracting beneficial insects to your farm". I wanted to collect samples of
these insects for farmers to see and learn to identify. What happened next made a major impact
on me! I searched several areas here on our farm at the North Florida Research and Education
Center Suwannee Valley. Most areas on the farm are kept clean and mowed and provided little
hope for finding many beneficial insects. However, I found two small areas that were "gold
mines" for discovering several species of "good bugs". The first site was a planting of both
native and introduced landscape plants and flowers. The native flowering plants like butterfly
weed, frost weed, Rudbeckia, salvia (tropical sage), and swamp sunflower all had lots of good
bugs. In addition, a popular non-native, crepe myrtle, was also loaded with good bugs. The
second good collection site was a fall watermelon planting used for insect research purposes.
One of the research trial requirements was "no insecticide sprays" to allow the silverleaf whitefly
to build natural populations so Dr. Susan Webb, UF/IFAS Entomology Specialist could observe
their feeding patterns. Well, as you can imagine, the whitefly populations did very well. But
also, other beneficial such as lacewing, lady beetles, and big eyed bugs were very easy to find.
So the impact on me was the realization that we could do a lot more to attract beneficial
insects to our farm. Here are a few key points to consider when trying to attract beneficial
(from "Habitats for Beneficial Insects", Cornell University,
http://www.nysaes.corell.edu/pp/resourceguide/appendix/appendix b.php and "Natural
Enemies and Biological Control", UF/IFAS, http://edis.ifas.ufl.edu/inl20).
Any organism that feeds on another organism is a natural enemy. Insects that are natural
enemies of pests are called beneficial insects. Other arthropods such as spiders and certain mites
also are beneficial. There are two main types of beneficial arthropods, predators and parasitoids.
Predators, such as ladybugs and spiders, will attack several different kinds of insects, and will
consume several types of prey throughout their life cycle. Parasitoids are wasps or flies that lay
their eggs on or inside other arthropods; they are also called parasites. The egg hatches and the
immature parasitoid feeds on the victim, called a host, eventually killing it. Each developing
parasitoid kills only one host in the course of its life cycle, but parasitoids are more specific in
the insects they attack than are predators.
Plant diversity in an agricultural setting generally adds stability to a system and helps
encourage the presence of beneficial insects. There are different options for providing plant
diversity depending on whether the main crops are annuals or perennials. Generally, crop
diversity can be achieved over a period of time or in a area of a field using crop mixtures, crop
rotations, border crops or windbreaks, or plants known to be attractive to beneficial insects.
Landscape diversity will generally favor populations of beneficial insects while lack of diversity
will generally increase insect pest outbreaks. Adding plant complexity to a system can be
achieved by providing sites which beneficial insects may use to obtain nectar or pollen, survive
on alternative insect pest species, find habitats in which to increase their numbers and/or as sites
in which to overwinter.
Flowering plants may provide nectar that can increase the life span of a beneficial species
and number of eggs it can produce. Such flowering plants can be used as part of the farm's
saleable crops as well as provide needed landscape diversification. In choosing which plants to
use to add diversity, a good rule of thumb would be to avoid plants in the same family as the
cash crop being grown since they may also serve as hosts for insects and diseases. Weeds may
also play a significant role in adding plant diversity. Flowering weeds in the families
Compositae (daisy), Labiatae (mint), and Umbelliferae (dill, Queen Anne's Lace) are often cited
in the literature as being able to support stable populations of natural enemies. Multiple
blooming sunflower varieties are also excellent for attracting beneficial insects.
We are in the process of developing a plan here at the North Florida Research and
Education Center Suwannee Valley farm to incorporate some of these practices to encourage
more beneficial insects in the future and use the farm to teach others these valuable IPM
principles.
Vegetarian Newsletter
A Horticultural Sciences Department Extension Publication
on Vegetable Crops
Eat your Veggies!!!!!
Issue No. 552 December 2009
Using solid oxygen fertilizers to alleviate flooding problems
in vegetable production
By: Guodong Liu, Post Doc Associate, Yuncong Li, Professor, Kati W. Migliaccio,
Assistant Professor, Tropical Research and Education Center
and
Teresa Olczyk, Extension Agent IV, Miami-Dade Extension Office-South
Flooding affects crop production
Vegetable plants uptake oxygen from the soil matrix. Under flooding conditions, plants may not
have enough oxygen to survive. Flooding has been a problem in Florida. Agriculture losses from
flooding as a result of the hurricane Irene in 1999 and a storm (13.9 in) in 2000 were estimated at
$77 and $13 million, respectively, in Miami-Dade County with nearly 19,000 acres of crop
damage.
Slow-release oxygen fertilizers
Slow-release oxygen fertilizers are eco-friendly compound fertilizers. They are insoluble and
inert if there is no water in the soil. In waterlogged or flooded soils, slow-release oxygen
fertilizer will gradually release oxygen for up to 6 months. Meanwhile, they also provide calcium
and/or magnesium nutrients.
Application of oxygen fertilizer
Application of slow-release solid oxygen fertilizers (e.g., magnesium peroxide plus additives)
can effectively increase oxygen bioavailability in flooded soils, alleviate the problem, and reduce
or exclude economic loss in vegetable production suffering from flooding. Application methods
include before and after planting or sowing. The method before planting can save labor but the
fertilizers may be wasted if there is no flooding. The other method requires more labor input
because manipulation in crop plants is time consuming but this method may save the fertilizers if
there is not a flooding problem during the growing season. We recommend applying the
fertilizers before planting or sowing for vegetable production.
Exemplification
We grew traditional Italian basil (cv. Genovese OG) in 6 inch-pots with ProMix growth medium
with (treatment) or without (the control) 1 g slow-release solid oxygen fertilizer incorporated
into the growth medium. The plants were not flooded or flooded for five days after they were all
20 cm tall. Their chlorophyll contents were determined using SPAD 502 Chlorophyll Meter
(Konica Minolta Holdings, Inc., Ramsey, New Jersey). The biomass was also measured after the
five-day flooding. The results showed that the chlorophyll contents and biomass of the flooded
plant with oxygen fertilization were both significantly greater than those of the control (Figure 1,
2 and 3).
Figure 1. The difference in growth of flooded basil plants with or without oxygen fertilization.
---'
r
SNo flooding Flooding
A A
30
20
10
0-
A B
No SOF
SOF
Figure 2. The chlorophyll contents of the basil plants without flooding were significantly
(p<0.05) greater than those with flooding but without oxygen fertilization. There was, however,
no difference in the chlorophyll contents of the plants without flooding and those with flooding
but also with oxygen fertilization.
* No flooding
SFlooding
A A
No SOF SOF
Figure 3. Biomass of the basil plants without flooding were significantly (p<0.05) greater than
those with flooding but without oxygen fertilization. There was, however, no difference in the
biomass of the plants without flooding and those with flooding but also with oxygen fertilization.
Summary and Conclusions
Slow release oxygen fertilizers are eco-friendly and affordable. They significantly increased
oxygen bioavailability in the flooded soil grown basil. Therefore, they significantly alleviated
reduction of chlorophyll contents and biomass of flooded basil plants and hence reduced
economic loss caused by flooding. Oxygen fertilization is promising to become a new approach
to minimize the negative impact of flooding on vegetable production in Florida.
A B
- 6000 -
-I
0
c 4000 -
E
0 2000 -
E
0
i-
I
Vegetarian Newsletter
A Horticultural Sciences Department Extension Publication
on Vegetable Crops
Eat your Veggies!!!!!
Issue No. 552 December 2009
Biography: Monica Ozores-Hampton, UF/IFAS, Vegetable
Specialist
By: Monica Ozores Hampton, Assistant Professor
Southwest Florida Research and Education Center, Immokalee, Florida
Since 1998, Dr. Ozores-Hampton has been a post-doctoral fellow at the Southwest Florida
Research Center, initially working to develop non-chemical alternatives to Methyl Bromide and
most recently evaluating the effects of nitrogen fertilization on tomatoes under commercial
growing conditions. She received her bachelor's degree in horticulture from the Universidad
Catolica de Chile, her master's degree in biological science from Florida International
University, and her Ph.D. in horticulture from the University of Florida.
As vegetable specialist, Dr. Ozores-Hampton provides statewide leadership and science-based
research and extension education programs on critical issues facing the vegetable industry in
Florida. Her focus areas include plant nutrition and fertilizer use efficiency to demonstrate
updated nitrogen recommended rates and facilitate the adoption of nutrient best management
practices by the vegetable industry. Additionally, she conducts Tomato Yellow Leaf Curl Virus
and pepper variety evaluation.
Dr. Ozores-Hampton's twelve-month, tenure-accruing position is a split appointment between
extension (60 percent) and research (40 percent). Her primary clientele groups are county
extension agents, commodity groups, regulatory agencies, and vegetable growers. She is a
member of the American Society for Horticultural Science, the Florida State Horticultural
Society, and the United States Composting Council.
Dr. Ozores-Hampton's office is located at the Southwest Florida Research and Education Center,
Immokalee, Florida. She can be reached at (239) 658-3400 or by e-mail at ozores@ufl.edu.
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