VegNet Vol. 13,
No. 9.
On the WEB at: http://vegnet.osu.edu
If experiencing problems receiving this
fax, Call 614-292-3857
In This Issue
1. Late Blight Reported on Tomatoes in
2. Maximizing Yield by Understanding Vine Crop Pollination
3. Spray Drift Management
Late Blight Reported on
Tomatoes in
Late blight was confirmed June 16 in tomatoes in one field in
Symptoms of late blight in tomatoes are shown below. Late blight is favored by cool, rainy
conditions. If prolonged cool, rainy
weather persists or threatens, or the relative humidity is greater than 90% for
20 hours or more, tomatoes and potatoes should be scouted intensively and
treated with protectant fungicides. If late blight occurs in the area, growers
can consider applying additional fungicides such as Quadris,
Cabrio, Gavel or Ranman
tank mixed with protectant fungicides. Be sure to follow label instructions.
If you believe you have late blight in tomatoes or potatoes,
samples can be sent for diagnosis to Sally Miller or Melanie Ivey, Department
of Plant Pathology, The Ohio State University, OARDC,
A.
B
C
D
E
A) leaf
lesion; B)microscopic view of mycelia and sporangia of Phytophthora infestans;
C) petiole
blight; D) stem lesions; E) blighted fruit.
MAXIMIZING
YIELD BY UNDERSTANDING VINE CROP POLLINATION
H. Chris Wien,
From:Vegetable IPM
News, Cornell Cooperative Extension Vol. 11
Number 3 Mid June, 2006, _ By John Mishanec, Area
Vegetable IPM Educator, Albany, New York 12207
Most of the commercially important vine crops have separate male
and female flowers, and thus require pollinators to transfer the pollen. To
successfully form the fruit, we must understand something about the behavior of
the pollinating insect, as well as the biology of the plant. Fortunately, a lot of work has been done in
this area in recent years, so our understanding is good.
The most common pollinating insects are honeybees, which can be either wild, nesting in trees, old unused buildings, etc. or
raised in commercial hives. Bumblebees
are active and important cucurbit crop pollinators as well. Both the above species are generalist
pollinators, and will visit the flowers of the full range of cucurbit crops, as
well as other flowers in the vicinity of the hive. For crops of the genus Cucurbita,
which includes summer and winter squash, pumpkins and ornamental gourds, the
specialist pollinator the squash bee has been recognized as important. Although the same size as the honeybee, this
species is solitary and nests in tunnels they dig in the ground near or in
fields. Both male and female squash bees
visit the flowers of squash and pumpkin, and they are often there early in the
morning, long before the honeybee becomes active. Squash bees are numerous and widespread
throughout the pumpkin growing areas of the Northeast, and appear from our
studies to be the main species pollinating these crops.
So if there is such an abundance of pollinating insects for
pumpkin and squash, there should not be a need to introduce hives of bees into
fields. Some recent research in
The ability of the cucurbit plant to produce flowers is also an
important factor in determining the success of pollination and fruitset. Again, to
use pumpkin as an example, under summer field conditions, in moderate
temperatures, the plant produces first male, then female flowers on the main
stem. Farther up the plant, female
flowers are produced at about every fifth node.
If the weather gets hot, and/or the plants are crowded in the field, the
frequency of open female flowers can be decreased to such an extent that fruit
set and yield are significantly reduced.
The flowering habits of the other vine crops,
and their methods of pollination are sufficiently different from that of
pumpkins and squash that they need separate explanations below:
Cucumber: Traditional cucumber varieties have a
flowering habit similar to that of pumpkin explained above. In the 1960’s plant breeders discovered new
lines that produced only female flowers, and no males. These so-called gynoecious
lines were used to develop new varieties that have a high frequency of female
flowers that produce high early yields.
Although most of these field-grown cucumber varieties produce some male
flowers, seed companies mix in a small percentage of traditional cucumber to
make sure that there will be enough pollen available for adequate fruitset. The
European greenhouse cucumber, on the other hand, is all-female in its
flowering, producing no male flowers.
These plants have another special trait; they set fruit without the need
for pollination, so male flowers are not needed in this case.
Watermelon: This crop has a flowering pattern similar to
pumpkin, and requires pollinators. In
recent years, seedless fruits have become popular. For these, pollination is still required,
even though no viable seed is formed in the fruit. The pollen must come from a standard variety
that is capable of forming seeds.
Generally, the recommendation is to plant one row of this pollinator
variety for every three or four seedless rows. More recently, seed companies
have developed special pollinator lines that can be mixed in with the seedless
variety, and whose fruits are easily distinguishable, and kept separate.
Muskmelon: Plants of this species develop male flowers
first, followed by perfect flowers. The
latter contain both male and female parts, but the pollen is sticky, and still
requires pollinators to transfer pollen.
As with all these crops, the fact that the first nodes have male flowers
implies that the plant is able to grow to adequate size before it becomes
stressed by the developing fruit. Since
we pay particular attention to melon fruits that have adequate size and sugar
content, having sufficient leaf area on the plant to produce high quality fruit
is of great importance.
SPRAY DRIFT MANAGEMENT
Andrew Landers,
From:Vegetable IPM
News, Cornell Cooperative Extension Vol. 11
Number 3 Mid June, 2006, _ By John Mishanec, Area
Vegetable IPM Educator, Albany, New York 12207
Spray drift of pesticides is an important and costly problem
facing pesticide applicators. Drift results in damage to
susceptible off target crops, environmental contamination to water courses and
a lower than intended rate to the target crop, thus reducing the effectiveness
of the pesticide. Pesticide drift also affects neighboring properties,
often leading to concern and debate. There are two types of drift, airborne
drift which is often very noticeable and vapor drift. The amount of vapor drift
will depend upon atmospheric conditions such as humidity and temperature, and
the product being applied and can occur days after an application is made.
Management strategies to reduce drift:
Before spraying:
- Select the correct nozzle for the target:
Fine droplets for fungicides and insecticides
Medium droplets for herbicides. The higher the operating the pressure, the
smaller the droplet; too large a droplet will bounce off the target. Air blast
sprayers give the greatest cause for concern as they produce many small
droplets which are often off-target.
- Use nozzles with as large a hole as possible to produce a
coarser droplet.
- Consider spray additives to reduce drift.
- Only spray when conditions are ideal, a 2-4 mph wind.
- Calibrate the sprayer with water to ensure that everything is
working correctly.
Avoid spraying when:
warm and sunny days with less
than 2 mph winds are greater than 4 mph.
These conditions are favorable for atmospheric inversion
During spraying:
- Stay alert: ensure the spray is not allowed to drift on to
non-target areas and watch for changes in wind speed and direction.
- Keep spray pressure as
low as possible and ensure an accurate gauge is used.
- Keep the boom as close to the target as possible, ensure good
boom suspension.
- Maintain a constant speed and pressure, if an automatic
regulator is fitted, remember, small increases in speed result in large
increases in pressure.
- Avoid spraying near sensitive crops or water courses; use at least
a 50 to 100 feet buffer zone This is
especially important when using Quadrus
fungicide. Do not use
anywhere near Macintosh apples as leaf drop will be induced.