Top Crop Manager

Features Agronomy Insect Pests
Seed piece savvy

Master effective control with new application technology.


November 14, 2007
By Top Crop Manager

Topics

24aA seed piece treatment for insect control is a great way to provide cost effective
early season protection in potatoes. But it has to be done right.

Compared to a foliar application, a seed piece treatment of Admire offers a
number of benefits, including better control, reduced risk of drift, less need
for in-crop scouting, fewer sprayer trips across the field and reduced risk
of resistance development.

Do it right
"The effectiveness of a seed piece treatment depends largely on the uniformity
of application and accuracy of rate," says Andrew Dornan, horticulture
field development representative with Bayer CropScience. "For growers who
have never used seed piece treatment before, there's a bit of a learning curve.
They need to know how to do the job properly so that control is never compromised."

Each seed piece must be thoroughly covered with an adequate dose of Admire.
Calibrate the spray delivery system to determine the exact nozzle output. Determine
the seed piece conveyor speed. Then calculate the rate of Admire you will be
using, keeping in mind the highest rate is best for full season varieties.

Adequate water volumes are critical to achieving good coverage. This is an
example calculation to determine how much water should be used.

  • Nozzle(s) output = 221mL/minute.
  • Seed piece movement rate: 4.2cwt/minute.
  • Rate of Admire: 18mL/cwt.
  • Rate of Admire required per minute: 18 X 4.2 = 75.6mL/minute.
  • Rate of water required per minute = 221 – 75.6 = 145.4mL of water/minute.
  • Dilution ratio = 145.4/75.6 giving you a ratio of 1.93.
  • Water to add for each cwt to be treated: 1.93 X 18 = 34.7mL.

Once treated, plant seed pieces promptly. Exposure to sunlight will reduce
the effectiveness of Admire and could also reduce root and shoot development
of the seed piece.

In-field experience
Ron Pitblado, a potato researcher with the University of Guelph, has worked
with Admire seed piece treatment and agrees it is a cost effective way of applying
an insecticide for early season insects, such as Colorado potato beetle (CPB).
"It does a super job on early season CPB and because there's less material
applied than other methods, it can provide a definite cost benefit to growers
in terms of cost per acre," says Pitblado. "However, the material
does run out and as a result, some growers have had to apply a foliar insecticide
application later in the season."

Pitblado believes that is not much of a hardship, but some growers have commented
that they thought they had completed their insecticide application. "The
product is weaker (than an in-furrow application of Admire) in any case on leafhopper
and because the rate is lower, growers need to be aware they may have to spray
for late season CPB or leafhopper."

The bottom line: If you use a seed piece treatment, scouting later in the season
to monitor for a break in control is a good idea.

When to use a seed piece treatment
For maximum peace of mind all season long, in-furrow is still the best. For
short season varieties or varieties that require low seeding rates such as Russet
Burbanks, a seed piece treatment may be the most cost effective. Calculate the
cost of treatment based on seeding rate and compare to an in-furrow application.
Then consider if the savings are worth the risk based on how long your crop
might be unprotected prior to maturity.

Next, consider treatment equipment. Do you have a closed system for seed piece
treatment? If not, it is best to stay with in-furrow. And finally, consider
when imidacloprid was last used on that field? Admire is a Group 4 insecticide
and should be rotated with different chemistries that control the same pests
in a field. If resistance development is a major concern on your farm, use in-furrow.
It is the only application method that consistently provides a lethal dose to
insects all season long.

Effective resistance management
Resistance development is less likely with either seed piece treatment or soil
application than with foliar applications because insects never have a chance
to become established. Foliar insecticide applications bring the highest risk
of resistance development because, after every application, the concentration
of the insecticide in the foliage diminishes over time. The insect population
is potentially exposed to non-lethal doses several times throughout the spray
season.

"With a seed piece treatment, the seed absorbs the insecticide and translocates
it to roots, shoots and foliage," says Dornan. "Once exposed, feeding
insects die." They never have an opportunity to reproduce and potentially
transfer some level of tolerance to the next generation.

To avoid resistance development, use the highest label rate. If in-season foliar
applications are required for control of insects other than Colorado potato
beetle, do not use a Group 4 insecticide in crops treated with Admire. Be sure
to use an insecticide with an entirely different mode of action (see Top
Crop Manager's
Potato Pest Control Guide supplement).

Safety first
For applicator safety, use a spray hood to reduce applicator exposure. Make
sure the spray system is completely contained to avoid losing any of the liquid
insecticide. Apply in areas with proper ventilation and ensure those handling
treated seed pieces or the application equipment wear appropriate protective
clothing. -30-