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Title: Agronomy Notes
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Permanent Link: http://ufdc.ufl.edu/UF00066352/00113
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Title: Agronomy Notes
Physical Description: Serial
Creator: Agronomy Department
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date: June 2009
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Bibliographic ID: UF00066352
Volume ID: VID00113
Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: 000956365 - AlephBibNum


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IFAS Extension

Volume 33:6

Rubber gloves o,,.. t the
level ofpesticide
absorption on users as
found in a recent study on
farmers and their
families. (See page 4)
Photo: F. Fishel


June 2009


Late Corn Planting ..... .................... ... ..............................Page 2
Starter Fertilizer Placement Corn and Cotton ............... Page 3


Hay Field Day ........................................... Page 2
Pasture Caterpillars and Chemical Control ........................... Page 3

Weed Control

Farm Family Exposure to Glyphosate ........................................... Page 4
Bayer CropScience Insecticide Updates................................. Page 5
Dogfennel Control ........................................... Page 6


Fertilizer Blends vs. Homogenized Fertilizers.....................Page 2
Calendar .................................... Page 6

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Employment Opportunity-
Affirmative Action Employer authorized to provide research educational information and other
services only to individuals and institutions that function without regard to race, color, sex, age,
handicap or national origin. For information on obtaining other extension publications, contact your
county Cooperative Extension Office. Florida Cooperative Extension Service/Institute of Food and
Agricultural Sciences/University of Florida/Larry Arrington, Dean.

"Agronomy Notes" is prepared by: J.M. Bennett, Chairman and Yoana Newman, Extension Forage
Specialist ( !., i !1 ca il .i B. Sellers, Extension Agronomist (bsellers@ufl.edu); J. Ferrell, Extension
Weed Specialist (jferrell@ufl.edu); F.M. Fishel, Pesticide Coordinator (weeddr@ifas.ufl.edu); and D.
Wright, Extension Agronomist (wright@ufl.edu). Designed by Cynthia Hight (chight@ufl.edu.) The
use of trade names does not constitute a guarantee or warrant of products named and does not signify
approval to the exclusion of similar products.

Agronomy Notes

UF IFAS Extension presents...

Hay Field Day June 30

Mark Randell Farms, Welborn, FL
9:00 am 3 pm; Registration Fee $5.00
Registration: Call (386) 362-2771, Suwannee County Extension Office
CEU's and CCA 's will be available.

Commodity markets have fluctuated widely this spring while fertilizer prices have remained
high. Growers are still changing the crop mix for this year and some are planting corn after
small grain. There are very few corn hybrids that can be planted in June without major damage
from disease. Growing a Bt corn is critical for planting late. Even most Bt hybrids will
succumb to disease pressures of southern corn rust and corn leaf blight. There were good
tropical hybrids that are no longer available for late planting. However, some hybrids have
better disease resistance than others. Consult variety test information to make sure you are
planting the most disease resistant hybrids for late planting. If corn is to be planted after corn
Into green stubble or into green stubble or even weeds, a soil insecticide should be used. It
takes about 4 weeks, between crops or after being weed free, for the insect population to be
reduced enough that they will not damage the newly planted crop.

Dr. David Wright, Extension Agronomist
North Florida REC, Quincy, wright@ufl.edu

Fertilizer Blends vs. Homogenized Fertilizers

Farmers use soil tests to determine the amount of fertilizer that is needed to produce various crops. Soils
tests are a guide to efficiently produce a crop without inadequate or excessive use of fertilizer. When
fertilizer was cheap, growers would often use the same rate of material on an entire field. This practice
may not be the most effective method for crop production since there will be areas in the field that will
vary widely in nutrient content from other areas of the field. In many cases blends of 3 or more fertilizer
are mixed together in mixers and spread as dry material across the field. One problem with blends is that
they segregate after mixing in the spreader truck, or different materials are thrown different distances as
it is being spread.

Homogenized fertilizer is unique in that each granule has the same analysis. If it is spread from a
spreader truck that is spreading a uniform rate, nutrients should be uniform across the field. However,
the main limitation to homogeneous fertilizer material is that specific grades of fertilizer are not
produced to meet fertility needs for each field. In cases where fertilizer is banded and rates are reduced
by third or half from broadcast rates, homogenized fertilizer may be more appropriate since materials
mixed at the plant may be transferred 2 to 3 more times before they are put out at planting. Separation in
materials is likely to occur the more they are transferred from one cart to another.

Dr. David Wright, Extension Agronomist
North Florida REC, Quincy, wright@ufl.edu Agronomy NotesPa


Starter Fertilizer Placement Corn and Cotton

Corn and sometimes cotton have starter fertilizer placed near the seed. There are some companies that
sell materials to be placed with the seed. However, extreme caution at planting should be used when
placing any material in the furrow with the seed. Fertilizers such as urea and diammonium phosphate are
not recommended to be placed with the seed since free ammonia is very toxic to seedlings. The most
common placement is either 2"X2" to the side and below the seed or surface banding. In general, for
each 10 lbs/A of N in the starter, placement should be one inch further away from the seed in a surface
band. If 30 lbs/A of N are used in the starter fertilizer, it should be 3" away from the seed. Data at
Quincy (Rhoads) shows that triple super phosphate (TSP) is much more available than diammonium
phosphate (DAP) initially and has been noted by corn growers this year where corn is 6-8" taller from
banded applications of TSP in row as compared to DAP in the same field. This outcome may be due to
the effect of the ammonia acidifying the soil with DAP making P less available to plants.

Dr. David Wright, Extension Agronomist
North Florida REC, Quincy, wright@ufl.edu

Pasture Caterpillars and Chemical Control

With the change in weather conditions, caterpillars may start showing up in
pastures. If scouting during the day when there's still some morning dew, both
loopers and army worms tend to fall off the plants to the ground and rubber boots
(where they are easier to spot). Each looper pupates (stage the insect undergoes in
becoming a moth) by folding blades of grass to form a cocoon, whereas
armyworms pupate in the soil. You can see the tips of the leaves turned over where
the looper caterpillars pupate. The following is a refresher on the most common
insecticide treatments for pasture and hayfield caterpillars:

Product* Rate Restrictions (waiting time Maximum number of
prior to utilization) applications

Malathion 57% EC 2 pints per acre None No restrictions
Sevin XLR 1 to 1.5 quarts/ 14 days for hay or grazing Two (2) or less per year
Lannate LV 3/ to 3 7 days for grazing No more than 4 applica-
pints per acre 3 days for haying tions per year
Dimilin 2L 2 fl oz per acre/ No restrictions for grazing No more than 6 fl oz per
cutting 1 day for hay year. Cannot apply more
than 2 fl oz per acre/cutting
Tracer 1-3 fl oz/acre 3 days for hay or until it has
dried if grazing
*Thanks to the UF/Pesticide Information Office for their assistance on product update.

Dr. Yoana Newman
Extension Forage Specialist

Agronomy Notes Pa

The Farm Family Exposure Study, conducted in 2000, determined exposure of 48 farm-families to the commonly
applied herbicide, glyphosate. The purpose of the study was to quantify real-world pesticide exposures
immediately before, during, and after a pesticide application and to identify significant factors that influence
exposure. The study was funded through a research contract with the University of Minnesota and sponsored by
Bayer, Dow, DuPont, FMC, Monsanto, Syngenta, and the American Chemistry Council.

Farm families were recruited by randomly drawing licensed pesticide applicators from state listings in South
Carolina and Minnesota. Criteria for participation in the study included the following:

> The farmer, spouse, and at least one child 4 to 18 years of age had to live on the farm.
> The farmer had to farm at least 10 acres within 1 mile of the family residence.
> The farmer must plan to apply one of or a combination of the following: glyphosate, 2,4-D, or
chlorpyrifos. (Only glyphosate results are described in this article).
> Family members had to be willing to collect all urine voids for five consecutive days the day before
the pesticide application, the day of the application, and for three days after the application.
> The farmer and spouse had to be willing to fill out pre- and post-study questionnaires that detailed
family activities for the week before the study and the week of the study.
> The farmer and spouse had to agree to have their on-study pesticide application observed by trained
field staff.
Participating families were given a cash incentive of $300 and reimbursed for the pesticide used during the on-
study application to a maximum of $1,000. Laboratory analyses were used to determine urinary glyphosate

Of the 48 farmers, 10 reported never wearing gloves when working with pesticides, 14 had applied glyphosate
within a week before their scheduled on-study application, and the same number had made another application
within three days of their on-study application. Most of the farmers reported having tractors with enclosed cabs.

On the day of the on-study glyphosate application, a trained observer was present at each farm, documenting
practices and conditions that can influence exposure potential. Of the 48 farmers, 14 were not wearing gloves
during the application. According to the product label for the glyphosate used in this study, gloves were not
required to be worn. However, use of rubber gloves when handling pesticides reduces dermal contact and
absorption. All the farmers used tractors and boom sprayers, and most applied the Roundup Ultra formulation
over glyphosate-tolerant crops early in the growing season. Skin contact with glyphosate was observed for 15 of
the farmers and approximately 15 percent of farmers were observed to have had spills during mixing or
application. Thirteen repaired their equipment at some time during the application.

Urine concentrations of glyphosate for farmers ranged from less than 1 ppb to 233 ppb. Some farmers did not
have detectable glyphosate in their urine samples despite applications in excess of 100 acres. Overall, 29 farmers
participating in the study had detectable values on the application day, declining to 13 farmers by the third day
following the glyphosate application. The average concentration for farmers was 3.2 ppb on the application day,
and the concentration declined thereafter. Findings differed between South Carolina and Minnesota. On the
application day, 87 percent of the South Carolina farmers had detectable values, compared with 36 percent of the
Minnesota farmers. Mean values were 7.9 ppb in South Carolina and 1.4 ppb in Minnesota.

Of the farmers' spouses, two had detectable concentrations on the day of application. No spouse participated in
the glyphosate application. Nine of 78 children who provided samples had a detectable value on the day of
application. Of these nine children, all but one were reported by their parents to have been present for or assisted
with mixing or application activities.

Agronomy Notes Pag


Among the farmers who participated in the study, urinary concentrations were lower for those who were
observed to wear rubber gloves when mixing and loading glyphosate. The concentration for those wearing
rubber gloves was 1.5 ppb, versus 9.7 ppb for other farmers. Use of rubber gloves was much more common in
Minnesota than in South Carolina. The number of acres treated was not related with urinary glyphosate
concentration, but there was a trend between concentration and the number of times farmers mixed and loaded
the concentrated herbicide. Other factors positively associated with urinary concentration were using an open
cab tractor, observed skin contact with the glyphosate concentrate, and repairing equipment during the

Use of rubber gloves was a major influence on glyphosate

exposure as found in urine.

Use of rubber gloves was a major influence on glyphosate urinary concentrations. For farmers who did not wear
rubber gloves, the number of acres treated, the number of mixing operations, observed spills, and repairing
equipment were associated with large differences in urinary concentrations.

According to the EPA, the lowest no-effect level from glyphosate toxicology studies is considered to be 175
ppm. The reference dose, an estimate of the daily oral exposure to the human population, including children, that
is not likely to cause harmful effects during a lifetime, is 2 ppm per day. The urinary glyphosate concentrations
presented in the study were exponentially lower than these values in all instances.

In all of these pesticide-handling activities, rubber glove use minimized urinary concentrations of glyphosate.
Most pesticide product labels specify some type of protective gloves during handling activities. The study
provides emphasis for the importance of protective glove use. Although glyphosate is considered to be relatively
non-toxic and is not known to cause long-term human health effects, other more toxic pesticides are used by
growers and handled in a similar manner. Many pesticide labels directions provide flexibility in the type of glove
to be worn. The important message is that label directions should, at all times, be observed and followed.

Dr. Fred Fishel, Pesticide Information Director

Bayer CropScience Insecticide Updates

This past April, Bayer CropScience LP made the decision to exit the Di-Syston and Monitor insecticide
business in the United States. The active ingredients in Di-Syston and Monitor are disulfoton and
methamidophos, respectively. Effective immediately:

Monitor: Bayer CropScience's final production of Monitor will occur in 2009. Distributors will be
provided with an allocation based on previous purchase history.

Di-Syston 8 and Di-Syston 15G: Bayer CropScience's final production of these products will
occur in 2009. At this time, material will not be allocated and is available for purchase while
supplies last.

According to EPA's 1991 Existing Stock Policy, once purchased from Bayer CropScience, there is
no time limitation by which distributors are required to sell Di-Syston or Monitor to retailers or
growers. Once purchased from distributors or retailers, the EPA policy also allows growers to
use these products with no time limitation.

Agronomy No es Pc

Dr. Fred Fishel, Pesticide Information Director


Dogfennel Control


Dogfennel is the most common weed in Florida pastures. Unlike most states, dogfennel acts as a perennial in
Florida and sprouts off existing rootstock each spring. The perennial growth habit causes this weed to grow
very rapidly and be more difficult to control. Therefore, herbicide application timing and herbicide selection
are very important to achieve optimum

Dogfennel height Herbicide recommendation and cost dogfennel control.
0 to 24 inches Weedmaster (2 pt) $8/A
Control of dogfennel ranges very easy
24 to 36 inches Weedmaster (3 pt) $12/A to extremely difficult relative to its size
Cleanwave (1 pt) + 2,4-D (2 pt) $11/A at time of application. The smaller the
_________________________Pasturegard (2 pt) $12/A .
plants, the more easily and cheaply
36 to 48 inches Cleanwave (20 oz) + 2,4-D (2 pt) $14/A plantsthe moreeas and cheal
Pasturegard (3 pt) $18/A they can be controlled (see table on
>48 inches Pasturegard (3 pt) $18/A left.) But, delaying applications and
Cleanwave (20 oz) + Forefront (2 pt) $24/A spraying larger plants will require a
greater investment. In light of this, it is
advisable to develop a management strategy before the summer rain and heat cause rapid dogfennel growth.
Dr. Jason Ferrell, Extension Weed Specialist Dr. Brent Sellers, Extension Weed Specialist
jferrell@ufl.edu Range Cattle REC, Ona, sellersb@ufl.edu

June 5-9 American Society for Reproductive Immunology, Orlando

June 7-9 FSHS and SCSSF Meeting, Jacksonville

June 7-10 Meeting: In Vitro Biology, Charleston, SC

June 10 Pesticide Training CEU Day, Mid-Florida REC
Apopka, Register by June 5; $20; (407) 665-5554 rvt(@ufl.edu
For your CEU and Worker Protection Standards Training Needs

June 18 UF/UGA 2009 Corn-silage Field Day, Tifton, GA

June 30 Hay Field Day, Welbom (386) 362-2771

July 13-15 Short Course: Applications & Analyses of Mycorrhizal Associations
Information or registration call (352) 392-1951 email: aaag@ufl.edu

July 20-24 National Conference on Ecosystem Restoration (NCER)
Los Angeles, CA

July 22-23 Workshop: Breeding for Resistance to Whitefly-transmitted
Viruses, Orlando

August 1-2 Florida Small Farms & Alternative Enterprises Conference *
Kissimmee (Registration discount if received by June 1.)

September 22-24 Southwest Herbicide Applicator Conference, Panama City Beach

SAgro omy Notes Pa

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