Protect Thy Beans
     

     
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Now is the time to scout for soybean insects.

Soybean aphids, bean leaf beetles, and grasshoppers are showing up
in soybean fields throughout South Dakota. Insect infestations at this
time of year can result in serious yield losses because soybeans are
now in the pod-fill stages.

Soybean plants are the most sensitive to injuries right now.

Bean leaf beetles:  Bean leaf beetles can be very destructive pests
of soybeans because they feed directly on the pods and developing
seeds. Whole pods may also fall to the ground as a result of pod
clipping by the beetles.

SDSU research in 2002 on a grower’s field near White has shown that
spraying for the bean leaf beetle during R5 (beginning seed) stage in
early August can improve yield by 2-9 bushels (7-27 percent) per acre
depending on the insecticide and rate used.

Insecticides labeled for use on bean leaf beetles in soybeans are:

Asana XL (5.8-9.6 fluid ounces per acre);
Baythroid 2 (1.6-2.8 fluid ounces per acre);
Chlorpyrifos 4E AG (1-2 pints per acre);
Dimethoate 400 (1 pint per acre);
Lorsban 4E (1-2 pints per acre);
Mustang (3.0-4.3 fluid ounces per acre);
Mustang MAX (2.8-4.0 fluid ounces per acre);
Nufos 4E (1-2 pints per acre);
Penncap-M (2-3 pints per acre);
Pounce 3.2 EC (2-4 fluid ounces per acre);
Sevin XLR PLUS (1-2 pints per acre); and
Warrior (1.92-3.20 fluid ounces per acre).

On the Internet:  Bean Leaf Beetle Management in SD
 

Soybean aphids: An average of 200 soybean aphids per plant is currently
considered economically damaging. Soybean aphids are tended by ants
which "farm" the aphids for their honeydew. Scout for them by watching
for ants along the borders of soybean fields as one sign that aphids may
be present.

A new pest to South Dakota since 2001, soybean aphids are very small
but can be seen with the naked eye. They are about one-sixteenth of an
inch long and yellowish to yellowish-green in color. A magnifying lens will
also reveal that they have a pair of black “tail pipes” on the rear. They're
found on the growing points, stems, and on the underside of leaves.

SDSU research in 2002 at the Southeast Research Farm near Beresford
has shown that spraying for the soybean aphids during R5 (beginning seed)
stage in early August can improve yield by 2-11 bushels (8-27 percent) per
acre depending on the insecticide and rate used.

Insecticides labeled for the soybean aphid on soybean and their
recommended rates and pre-harvest intervals (PHI) are as follows:

Asana XL (5.8-9.6 fluid ounces per acre, 21 day PHI);
Dimate (0.50-0.75 fluid ounces per acre, 21 day PHI);
Furadan 4F (0.5 pint per acre, 21 day PHI);
Lorsban 4E (1 to 2 pints per acre, 28 day PHI);
Mustang (3.0-4.3 fluid ounces per acre, 21 day PHI);
Mustang MAX (2.8-4.0 fluid ounces per acre, 21 day PHI),
Penncap-M (1 to 3 pints per acre, 20 day PHI);
Pounce 3.2EC (4-8 fluid ounces per acre, 60 day PHI); and
Warrior (1.92-3.20 fluid ounces per acre, 45 day PHI).
Always read and follow label directions. Consult the label for
restricted entry intervals (REI).

On the Internet:  Soybean Aphid in SD
 

Grasshoppers: The economic threshold at which it pays to spray
for grasshoppers is defoliation, or leaf loss, of 20 percent. Twenty
percent leaf loss means that 20 out of 100 of similar-sized soybean
leaves completely eaten by the insects.

SDSU research in 2001 conducted by graduate student Dave Mills
at the Southeast Research Farm near Beresford indicated that a
50 percent defoliation at full pod stage soybean can result in
8 bushels per acre (15 percent) yield loss.

Insecticides labeled for use on grasshoppers in soybean are:

Asana XL (5.8-9.6 fluid ounces per acre);
Baythroid (2.1-2.8 fluid ounces per acre);
Dimethoate 400 (1 pint per acre);
Dimilin 2L (2 fluid ounces per acre);
Furadan 4F (0.25-0.50 pint per acre);
Lorsban 4E (0.5-1.0 pints per acre);
Mustang (3.4-4.3 fluid ounces per acre);
Mustang MAX (3.2-4.0 fluid ounces per acre);
Nufos 4E (0.5-1.0 pint per acre);
Penncap-M (2-3 pints per acre);
Sevin XLR PLUS (1-3 pints per acre); and
Warrior (3.20-3.84 fluid ounces per acre).

On the Internet:  How Tough is the Soybean Plant?
 

Thy Sunflowers Too
   
   
   
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 Producers should inspect oilseed and confection sunflowers
for insects when the plants are starting to show yellow petals.

Insects showing up at this time are red sunflower seed weevils
and head moths. Larvae of these insects may feed on
developing seeds, hurting yield and quality.

The economic threshold of the red sunflower seed weevil
on oilseed sunflower depends on the cost of control,
sunflower market value, and plant population per acre.

For example, at $10 per acre cost for chemical-plus-
application, an oilseed market value of $9.45 per hundred
pounds, and 20,000 plants per acre population, growers
should consider spraying with an insecticide if an average
of six weevils per flower are present on the field.

For confection sunflowers, just one seed weevil per flower
is enough to trigger spraying of the field.

In scouting for the small orange-colored seed weevils --
the pests are about one-eighth inch long -- use an insect
repellent containing DEET to flush the weevils hiding
between the florets in a sunflower head.

To effectively control the red sunflower seed weevil,
insecticides must be applied on or before 40 percent
of the florets (within a sunflower head) have shed pollen
in three out of 10 sunflowers. This is to prevent the female
seed weevils from laying eggs on the developing seeds.

Insecticides labeled for adult sunflower seed weevils
include Asana XL (5.8 to 9.6 fluid ounces per acre),
Baythroid (1.6 to 2.8 fluid ounces per acre),
Furadan 4F (1 pint per acre),
Lorsban 4E (1 to 1.5 pints per acre),
Scout X-tra (2 to 2.33 fluid ounces per acre), and
Warrior (2.56 to 3.84 fluid ounces per acre).
Always read and follow label directions.

Two moths also are attracted to blooming sunflowers –
the sunflower moth (gray in color, three-quarters on an
inch long) and the banded sunflower moth (yellow in color
with a dark band, one-half inch long). Scouting must be
done at dusk or early morning when moths are most active.

The economic thresholds on oilseed sunflower are
two moths per five plants for the sunflower moth, and
one moth per two plants for the banded sunflower moth.

The insecticides, rates, and timing of insecticide
application mentioned above for the sunflower
seed weevil also apply for the sunflower moth
and banded sunflower moth.

On the Internet:  Sunflower Seed Weevil Management


I'll be baack.  Hasta la vista.
 

 Last Updated on Thursday, August 14, 2003 by Mike Catangui.