Paraquat

On all Pacific Northwest grapes, paraquat was applied to 8,356 acres (7,503 base acres) for control of annual broadleaves and grasses. This included 3,017 acres (2,761 base acres) on juice grapes, 245 acres (90 base acres) on Idaho wine grapes, 1,810 acres (1,445 base acres) on Oregon wine grapes, and 3,284 acres (3,207 base acres) on Washington wine grapes. If paraquat were unavailable, glyphosate applications would replace 70% of the acre treatments of paraquat; mechanical cultivation would replace 20% of the acre treatments; and glufosinate would replace 10% of the acre treatments.

The number of glyphosate and glufosinate applications would be the same as for paraquat, but mechanical cultivation would be required four times per season to replace paraquat. Glyphosate would be an imperfect substitute, because growers normally use paraquat during the summer. It is risky to spray glyphosate near vines during the growing season when suckers are present on the trunks, so glyphosate would be applied before budbreak and in the fall.

More weed competition would occur on acres where glyphosate is used, causing a slight yield loss (1%). Because cultivation is difficult between vines, mechanical cultivation also would lead to increased weed competition and a 1% yield loss on mechanically cultivated acres.

No yield loss would occur on acres where glufosinate replaces paraquat. Use of glufosinate would probably increase over time as growers become more familiar with it.

The overall cost (replacement compounds, increased applications, and yield loss) of replacing paraquat with glyphosate, glufosinate, and mechanical cultivation would be $729,000 ($96 per base acre) on all Pacific Northwest grapes. Cost would be $238,000 ($86 per base acre) on juice grapes, $5,000 ($57 per base acre) on Idaho wine grapes, $126,000 ($87 per base acre) on Oregon wine grapes, and $360,000 ($112 per base acre) on Washington wine grapes. See also Table 15.

Table 15. Economic assessment for paraquat on Pacific Northwest wine and juice grapes.
Active ingredient	Target pest	Acres treated	Base acres	Rate lb ai/A	Treatments per year	Cost/A/ application	Alternatives	Rate lb ai/A	Cost/A/ application1	Æ2 Control costs (1000$)	ÆYield %	Æ Yield ($)	Total impact3 (1000$)	Impact/A4 ($)
Idaho wine grapes
paraquat	annual weeds	245	90	1.25	2.7	$18.00	glyphosate glufosinate cultivation	1.00 2.00 6 x	$13.75 24.38 8.50	4	0-1	1	5	57
Oregon wine grapes
paraquat	annual weeds	1,810	1,445	1.25	1.3	$18.69	glyphosate glufosinate cultivation	1.00 2.00 6 x	$13.37 28.88 8.50	94	0-1	32	125	87
Washington wine grapes
paraquat	annual weeds	3,284	3,207	1.25	1	$19.47	glyphosate glufosinate cultivation	1.00 2.00 6x	$12.91 32.50 8.50	258	0-1	102	360	112
Juice grapes
paraquat	annual weeds	3,017	2,761	1.25	1.1	$19.47	glyphosate glufosinate cultivation	1.00 2.00 6x	$12.91 32.50 8.50	190	0-1	48	238	86
Pacific Northwest totals	annual weeds	8,356	7,503		1.1					545	0-1	184	729	96
1Costs shown are for the pesticides only. Labor and equipment costs are about $6 per acre for each application. 2 Æ is a symbol that means "change in." 3Total impact is total cost to the growers, figured by adding Æ control costs and monetary Æ yield. A positive number is the cost to the grower. A negative number indicates a positive impact to growers. 4Total impact per base acre is the change in cost per acre to acres that have the pest problem and require use of the current pesticide."

Simazine

On all Pacific Northwest grapes, simazine was applied to 7,573 acres (7,519 base acres) in the fall and spring for control of annual broadleaves and grasses (mainly broadleaves). This includes 3,454 acres (3,443 base acres) on juice grapes, 1,884 acres (1,884 base acres) on Oregon wine grapes, and 2,206 acres (2,163 base acres) on Washington wine grapes.

If simazine were unavailable, diuron applications would replace 30% of the acre treatments of simazine. Norflurazon, glyphosate, and mechanical cultivation would each replace 15% of the acre treatments; oryzalin and oxyfluorfen would each replace 10% of the acre treatments; and paraquat would replace 5% of the acre treatments.

Diuron and norflurazon control a spectrum of weeds similar to those controlled by simazine; no yield loss would occur on acres where diuron and norflurazon replace simazine. Oxyfluorfen and oryzalin control different spectrums of weeds; replacement of simazine with these compounds would cause a slight yield loss (1%) due to increased weed competition.

Glyphosate and paraquat, which are contact herbicides, are not good substitutes for simazine; their use in place of simazine would result in a 1% yield loss from increased weed competition. Two applications of glyphosate would be needed to replace simazine, and three applications of paraquat would be needed.

Use of mechanical cultivation would also result in a 1% yield loss due to increased weed competition, because cultivation is difficult between vines. Cultivation would be required six times per season to replace simazine. The overall cost (replacement compounds, increased applications, and yield loss) of replacing simazine with diuron, norflurazon, glyphosate, oryzalin, oxyfluorfen, paraquat, and mechanical cultivation would be $692,000 ($92 per base acre) on all Pacific Northwest grapes. Cost would be $260,000 ($76 per base acre) on juice grapes, $137,000 ($73 per base acre) on Oregon wine grapes, and $295,000 ($136 per base acre) on Washington wine grapes. See also Table 16.

Table 16. Economic assessment for simazine on Pacific Northwest wine and juice grapes.
Active ingredient	Target pest	Acres treated	Base acres	Rate lb ai/A	Treatments per year	Cost/A/ application	Alternatives	Rate lb ai/A	Cost/A/ application1	Æ2 Control costs (1000$)	ÆYield %	Æ Yield ($)	Total impact3 (1000$)	Impact/A4 ($)
Oregon wine grapes
simazine	annual weeds	1884	1884	2.0	1	$8.71	diuron norflurazon glyphosate cultivation oryzalin oxyfluorfen paraquat	2.40 2.36 1.00 6x 2.0 2.0 1.25	$10.50 46.84 13.50 8.50 35.99 92.50 18.69	112	0-1	25	137	73
Washington wine grapes
simazine	annual weeds	2206	2163	2.0	1	$9.34	diuron norflurazon glyphosate cultivation oryzalin oxyfluorfen paraquat	2.40 2.36 1.00 6x 2.0 2.0 1.25	$19.20 55.49 12.91 8.50 40.37 81.10 19.47	253	0-1	42	295	136
Juice grapes
simazine	annual weeds	3454	3443	2.0	1	$9.34	diuron norflurazon glyphosate cultivation oryzalin oxyfluorfen paraquat	2.40 2.36 1.00 6x 2.0 2.0 1.25	$19.20 55.49 12.91 8.50 40.37 81.10 19.47	223	0-1	36	260	76
Pacific Northwest totals		7573	7,519		1					588	0-1	104	692	92
1Costs shown are for the pesticides only. Labor and equipment costs are about $6 per acre for each application. 2 Æ is a symbol that means "change in." 3Total impact is total cost to the growers, figured by adding Æ control costs and monetary Æ yield. A positive number is the cost to the grower. A negative number indicates a positive impact to growers. 4Total impact per base acre is the change in cost per acre to acres that have the pest problem and require use of the current pesticide."

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