Effect of Phosphonic Acid and Other Fungicides on Fungal

Diseases of Green Peas

Drs. Lyndon Porter and Debra Inglis, USDA-ARS and Washington State University

Rolling vs. Non-rolling Non-treated vs. Treated seed

Cultivar type

Photo Courtesy NDSU Carrington Reseach Extension Center

Aerial and Columbian

Phostrol(phosphorous acid)

Columbian

Aerial

Cultivar Type

Foliar applications

Soilborne Pathogens of Peas

Pythium and Aphanomyces

Phosphonic acid

Objective of Research

• Identify phosphorus foliar treatments to manage seed and root rot of fresh and dry peas caused by Aphanomyces root rot and Pythium.

Why look at foliar phosphorous acid applications to manage root

rots in peas?

Pink rot

Phytophthora erythroseptica

Late Blight of Potato

Phytophthora infestans

Phosphorous Acid

Not for Organic Use

Application rates of Product• Phostrol at 2.5 or 4 pints/acre/application

– Mono- and dibasic sodium, potassium and ammonium phophites (53.6%)

– Other ingredients (46.4%)– Contains 6.69 pounds/gallon of the active

ingredients– Equivalent to 4.32 pounds phosphorous acid

per gallon (35.6% by weight).

0100000200000300000400000500000600000700000800000900000

Nontrea

ted

Captan/A

llegianc

e

T-22 Plan

ter Box

GB-34Head

s Up 1

Heads U

p 2Kod

iakMicr

o 108

Serena

de ASO

Phostr

ol infur

row

Phostr

ol infur

row/emerge

nce

Seed Treatment

Emer

genc

e (P

lant

s/ac

re)

2004 Mount Vernon 2005 Mount Vernon 2005 Prosser

*

* * ** * *

* = Significantly different from nontreatedcontrol

* **

Yield

0100020003000400050006000700080009000

10000

Nontre

ated

Captan/Alle

giance

T-22 Planter B

oxGB-34

Heads U

p 1Hea

ds Up 2

Kodiak

Micro 1

08Seren

ade ASO

Phostro

l infurro

w

Phostro

l infurro

w/emer...

Phostro

l emerge

nce/14 .

..

Treatment

lb/a

cre

2004 Mount Vernon (Fresh)

2005 Mount Vernon (Fresh)

2005 Prosser (Dry)

* = Significantly different from the nontreated control

** **

Greenhouse tests

Non-treated

Wet seed treatment

1 Foliar3 Foliar

2 Foliar

Foliar dry weight and plant height

Impact of applications of phosphorous acid on dry root weight

Significantly increased(56.97% or 0.5 g)

Present

May or may not significantly increase(2 out of 10 foliar sig. increased)

Absent

Dry root weightDisease Pressure

Impact of applications of phosphorous acid on foliar dry weight

Always significantly increased (23.3% or 2.4 g)

Present

Not significantly increased (1 exception)

Absent

Foliar dry weightDisease Pressure

Impact of applications of phosphorous acid on plant height

Significantly increasedwith foliar applications (16.9% or 2.4 cm)

Present

Did not significantly increase (3 of 4 trials)

Absent

Plant heightDisease Pressure

2006 Field test in Mount Vernon, WA

• Planting density 355 lbs/acre

• Variety = Charo

• Phosphorous acid and Phosphoric acid

• Foliar applications at 35 gallons/acre using backpack sprayer

• Applications made at emergence and 14 days later

Phosphorous Acid

Cost = $18/gallon

Insert Picture of PhytoplusPhosphoric Acid

$7.60 in Oregon and Washington

Cost per gallon:

Application rates of Product• Phostrol at 2.5 pints/acre per application.

– Mono- and dibasic sodium, potassium and ammonium phophites (53.6%)

– Other ingredients (46.4%)– Contains 6.69 pounds/gallon of the active

ingredients– Equivalent to 4.32 pounds phosphorous acid

per gallon (35.6% by weight).

Application rates of Product• Phytoplus 12% Phosphorus• 8.87 pints/acre per application.

– 2.0% ammonical nitrogen– 1.0% Urea nitrogen– Available phosphoric acid (P2O5) 12%– Derived from urea, ammonium phosphate,

phosphoric acid and potassium phosphate.

Yield in pounds/acre

01000200030004000500060007000

NTS

Phosp

horo

us (P

S)

Phosp

horic

(PC)

Captan

/Alle

gianc

eC/A

+ PSC/A

+ PC

c c

bc abab

a

Total income in $/acre

0100200300400500600700

NTS

Phosp

horo

us (P

S)

Phosp

horic

(PC)

Captan

/Alle

gianc

eC/A

+ PSC/A

+ PC

$349 $352$437

$484 $530$603

Economics• Tenderometer = 100

– Fresh peas sold for $184/ton in 2006• Costs per acre

– Captan/Allegiance seed treatment • $10.31

– Phosphoric acid = $ 16.84– Phosphorous acid = $11.25 – Application costs = ?

Net income in $/Acre

0100200300400500600

NTS

Phosp

horo

us (P

S)

Phosp

horic

(PC)

Captan

/Alle

gianc

eCA +

PSCA +

PC

$349 $341$421

$473$509

$576

Average plant height/cm

02468

10121416

NTS

Phosp

horo

us (P

S)

Phosp

horic

(PC)

Captan

/Alle

gianc

eC/A

+ PSC/A

+ PC

b b b

a aa

Conclusions• Phosphorous and phosphoric acid can be

used to manage Aphanomyces root rot on peas based on greenhouse tests.

• Phosphoric acid performed the best in field tests in Mt. Vernon, WA.

• Use of phosphorus-based products appears to be economical.

Does Phosphorous acid work for dry land production of peas?

Economics• Cost of the seed treatment = $5.50/acre• Cost of 2.5 pints of Phostrol per acre =

$5.63/acre (At $18.00/gallon)• Phosphorous acid tank-mixed with insecticide

Yield (lb/acre)

219 lbDifference in

Yield

122 lbDifference in

Yield

333 lbDifference in

Yield

122 lbDifference in

Yield

$6.75/cwt -$5.63

$7.00/cwt-$5.63

$6.75/cwt -$5.63

$7.00/cwt-$5.63

Net Profit$9.15/acre

Net Profit$2.91/acre

Net Profit$16.85/acre

Net Profit$2.91/acre

Standard867

Standard1075

Standard491

Standard781

R/TS/2.5P1086**

R/TS/2.5P1197

NR/TS/2.5P824*

1.NR/TS/2.5P903

Moscow, IDAerial

Moscow, IDColumbian

Kendrick, IDAerial

Kendrick, IDColumbian

We’ve got a good shot…..

Acknowledgements

• Ginny Coffman• Mike Nielsen• Nufarm America

The End

Conclusions• Phosphorous acid appears to have a big impact on

yield of semi-leafless dry pea varieties and their susceptibility to root pathogens.

• Phosphorous acid significantly increased plant height of both Columbian and Aerial cultivars.

• Phosphorous acid may be important to enhancing the ease of harvesting semi-leafless types with a wheat bar.