UC Small Farm Program Farm Advisor
Richard Molinar, Fresno County
In This Issue - September 2000
- Whiteflies - La Mosca Blanca
- The Early Bird Gets The Worm (Earliness)
- Eggplant Problems
- New or Updated Publications
- Winter Squashes
- Research activities: Ginseng,
Capers, Edamame, Long Beans, Lemongrass, Beans
- Bits and Pieces
Whiteflies - La Mosca Blanca
There are different species depending on the area
of California and specific crop or ornamental. Some
of the more important include the greenhouse
whitefly (of major concern for strawberry growers on
the coast), sweet potato whitefly, ash
whitefly, banded winged whitefly, iris
whitefly, giant whitefly, and the silverleaf
whitefly (our major vegetable problem in the Central
Valley).
Whitefly Lifecycle:
All whiteflies have a
similar lifecycle. They pass through four instars or stages
from egg to adult. Eggs are laid on the undersides of
the leaves. The first stage has legs and antennae, but
these are lost after the first molt and the flattened, oval
shaped larvae remain in one feeding spot until the adult stage.
Just before the adult stage the larvae stop feeding
and form a pupa where the larvae undergoes a transformation into an adult with wings. The
adults emerge from the pupae through a T-shaped slit and
soon mate and reproduce. There are many generations
each year. Whiteflies overwinter on weeds and
ornamentals (thousands on spotted spurge now through the fall.
Whitefly Damage:
Whiteflies can seriously
injure plants by sucking juices from them causing
wilting, stunting and even death. They also secrete a sticky
substance called honeydew which causes leaves to appear shiny and sticky. In addition, several
molds may grow on this sweet honeydew resulting in a
black color on the leaves. Ants are also attracted to
the honeydew.
Whitefly Population and Growth:
Whiteflies in-crease in numbers exponentially, that is 2 become 4,
4 become 8, 8 become 16 and so on. A single
female whitefly may lay 150 to 300 eggs during her lifetime.
During the warm summer months, they can develop from egg to adult in as little as 16 days. In 32
days, for example, 40,000 whiteflies would result from
one adult female which lays 200 eggs; then, each of
those 200 lay another 200 eggs. A harsh cold winter
helps to reduce numbers the following summer, but only
a few light frosts might mean a bad problem the
next year.
Whitefly Control:
Whiteflies are very difficult
to control. Their location underneath the leaf,
rapid reproduction potential, and resistance to
insecticides result in severe problems in all cucurbits
(cucumbers, melons, moqua, sinqua, squash) and bean (green
and long) crops in particular, along with 500 other
host plants. Biological control from parasites and
predators is of some benefit, but limited due to the
excessive honeydew production. Insecticides help, and the
best control seems to come from combinations of
several insecticides. In several trials conducted in
Fresno county, a combination of Thiodan" and
Lannate", or Thiodan" and Asana" gave the best control.
Summer oils and Trilogy" reduced numbers but
not as well as the combinations.
The Early Bird Gets The Worm - or The Early Crop Gets The Higher Price
Every year some growers try planting warm
season vegetables such as green beans, tomatoes, or
squash about February 15 in hopes of getting an earlier
crop and thus a better price. And three times out of
five they lose, and the plants are frosted back and killed.
Some construct tunnels with wire hoops, some try
bed tunnels ("poor-man" tunnels) and plant into a bed
ditch covered with plastic, and some try running water
down the furrow when temperatures start dropping
below freezing (some heat is produced from the
running water). All of the above can result in
warmer temperatures of one to several degrees.
A trial was conducted in Southern California to look
at bed orientation and angle. Keith Mayberry and Dr.
Tim Hartz found that beds running East to West and
sloping to the South with at least a 40 angle was best.
Using Dasher cucumbers planted on February 27 in
Riverside, a 2-3 temperature increase was observed over a
flat bed planting during mid-day. Although final yields
in all treatments were similar, there was a
substantial earliness advantage with sloped bed configurations.
Eggplant Problems??
Some growers are experiencing a problem in
eggplants which seems to be growing in the county and we
need your help. If you have parts of your field in
early summer where plants are stunted, yellow
(chlorotic), and the new growth results in leaves which
appear 'stringy' (like they have been chewed by
caterpillars) or deformed, then it may be starting. We have seen
the problem in Japanese, Chinese, and American
type eggplants. A laboratory found a virus several years
ago, however, nothing was found in 1999 or 2000. We
are looking at possible nutritional or insect causes.
If you have some of the above symptoms, please
call our office, and we will come out to inspect your field.
The more information we can gather about this
problem the faster we can hopefully find a solution call
(559) 456-7555.
New or Updated Publications:
UC Guide to Solving Garden and Landscape Problems
A simple to use CD for your computer. Answers questions on over 600 pests
of vegetables, fruits, and ornamentals.
Pests of the Garden and Small Farm: A Must for the Small Farmer
Covers pest problems and controls for many fruits and vegetables.
Organic Apple Production Manual
A 72-page reference which discusses pest management, soil fertility, post-harvest handling, marketing, and economic analysis.
Winter Squashes:
This type of squash gets its name from the fact that
the mature fruits can be stored into the winter months,
in contrast to the summer squashes such as
zucchini, scallop, and crookneck, which are harvested
immature and must be eaten very soon after harvest. The
price for some of the varieties can be quite good, but it
varies from year to year and month to month. Unlike
summer squash, winter squash will not get overripe if you
do not pick it right away.
Cucurbita pepo types such as acorn, spaghetti,
and delicata are suited for fall eating. These turn
orange inside (except spaghetti) and develop an orange
spot where the fruit touches the ground. Cucurbita
maxima types include buttercups, hubbards, banana,
and kabocha squash. These are best eaten in late
winter (December/January) and the sweetness
actually improves during storage. Cucurbita moschata
types can be stored the longest and the best known
example is butternut squash.
In the kitchen, substitutes for acorn squash
include buttercup (drier), butternut (nuttier flavor and easier
to peel raw), banana squash (larger), or turban
squash (sweeter). Buttercup is one of the more highly
regarded winter squashes with creamy pulp that tastes a bit
like sweet potatoes. Kabocha is sweeter and drier than
other winter squashes. In our own kitchen, given the
choice between butternut, kabocha, and spaghetti baked
fruits, the butternut won, hands-down. It was moister
and sweeter than the other two. A brown sugar glaze
makes it better yet. (From the September/October issue
of Organic Gardening magazine.)
Research:
Ginseng:
In the coming months we will be
reporting on results of research we are conducting with
these plants. Ginseng (species panax) has been
used medicinally for thousands of years for a wide range
of ills. Scientists are still largely in the dark about
its medicinal benefits, but its chemical properties
have been studied thoroughly. The plants active
ingredients are called 'ginsenocides' of which there are 13
types, along with volatile oils, sugar, fats, B
vitamins, minerals, and plant hormones.
There are at least three types of ginseng with
different propertiesPanax quinquefolius
(American ginseng) is on the endangered specie list because it has
been harvested so intensively as a cash crop; Panax
ginseng (Korean or Asian ginseng) is grown all over Asia;
Eleutherococcus senticosus (Siberian ginseng) is
not regarded a true ginseng.
(UC Berkeley Wellness Letter, July 2000)
Capers:
Currently, the best method for
propagation seems to be from cuttings. Seed germination
results following a 60-day stratification process gave
0% germination. Seed may have been too old.
Lemongrass:
Different planting methods (stem,
root, stem and root) as well as several different varieties
and species are being evaluated in a replicated trial.
Green Beans:
A planting of 11 different varieties
was established in the late summer for evaluation. It
will be repeated again in the spring of 2001.
Edamame:
Or edible soybean is valued for
its nutritional value as well as exceptional flavor.
Seeds are eaten green (not dried) and often sold in pods
and sometimes still attached to the plant. 10
different varieties are under evaluation.
Long Beans::
An observational trial was
established in late summer to look at 14 different varieties of
long beans. Yield, color, pod length, and virus
resistance will be evaluated.
Bits and Pieces
1. GMOs and biotechnology - two new
yellow summer squash varieties are now available
from Asgrow seed company with resistance to three viruses
- CMV (cucumber mosaic virus), WMV
(water-melon mosaic virus), and ZYMV (zucchini yellow
mosaic virus). The new varieties are Destiny III and
Liberator III. Genes were added to the squash plant to
improve the plant's defense against these three viruses.
There are 1-2 other viruses which can still attack the
squash plants in the Valley; however, with this resistance,
the problem is improved.
2. A 'Nitrate Quick Test' kit can save the grower
money by telling the grower whether nitrogen levels in
the soil are adequate. It can reduce over-fertilizing or
tell a grower that the soil is low in nitrogen. Check
with Richard or Michael about the availability of these
test kits.
3. Meetings
October 11, 2000
Field Day
Vegetable Pest Management and Specialty
Crops
UC Kearney Field Station in Parlier
8:00 a.m. - 12:00 noon
No charge (See insert)
October 31 - November 2
Marketing Conference: California Feeds the World
Modesto, California
Co-Sponsored by Cal Poly, USDA, and the Small Farm Center
November 17 - 19, 2000
California Farm Conference
Santa Rosa Junior College
$90.00 Pre-registration
www.californiafarmconference.com
December 12, 2000
'Plagas, Suelos, y Cultivos para
Agricultores'
A workshop in Spanish to discuss pests, soils, and crop culture in the Central Valley.
For More Information: Contact Richard Molinar or Michael Yang, UC Cooperative Extension, Fresno County, at (559) 456-7555.
Back to UC Small Farm Program Farm Advisors
