RECEIVED

APR 0 7 1995 FINAL REPORT CSUF VERC

EVALUATION OF PONNAX ON IN THE SAN JOAQUIN VALLEY

RESEARCH COOPERATORS: Gwynn Sawyer Ostrom, Research Associate Carter D. Clary, Ph.D., Research Associate California State University, Fresno & Enology Research Center 2360 E. Barstow Avenue Fresno, CA 93740-0089 4 (209) 278-2089 Duke Wiley, Technical Service Rep. BASF Corporation P. O . B o x 2 1 9 8 Paradise, CA 95967 (916) 872-8006

The objectives of this research project were to:

1. Apply PONNAX at the manufacturer's recommended rate on three wine varieties at the CSU Fresno campus ;

2. Examine the effect of application on berry chemistries, yield, cluster size and number, and wine quality; and

3. Make recommendations concerning the use of PONNAX in wine grape vineyards.

RESULTS AND DISCUSSION:

Ponnax was applied at the rate of 1 pint per acre (0.25 lb ai^ac) on May 5, 1994 to French Colombard and grapes and May 11, 1994 to Thompson Seedless grapes. There was one treatment and one untreated control of six replications each, consisting of three vines per replication. The center vine was used for data collection, the other two vines to reduce spray drift between plots. Applications were made with a single row over-the-vine boom sprayer.

Cluster counts were taken on June 2, 1994. Berry chemistry data were collected weekly from until on July 19, July 26, August 3, and August 10, 1994. Yield, cluster weight, and berries per cluster were measured at harvest on 2

August 10, 1994. Grapes from the remaining 2 vines from each treated replication were discarded. Grapes harvested from the French Colombard plots were made into wine, and those were evaluated on February 16, 1995.

French Colombard.

Cluster counts (Table 1), yield (Table 2), and berry chemistries (Table 4) in Ponnax-treated plots were not significantly different from control plots. The average cluster weight and berries per cluster in control plots were significantly higher than in treated plots, indicating that there may be some shattering effect of Ponnax on French Colombard fruit (Table 3).

On a weekly basis, there were no significant differences in berry chemistries between the treated plots and the control plots. 100-berry weights were slightly larger in treated plots, sugar content was slightly higher in the control plots, and pH and T.A. were not significantly different in treated and control plots, over time. A lower sugar reading in the treated plots could indicate a delay of maturity. Without a corresponding lower pH and higher T.A., however, there would be no advantage to applying Ponnax to French Colombard. A delay in ripening would not necessarily be to a grower's advantage unless one gets an improved T.A. or pH. In fact, such a delay can mean trouble for a grower in regards to mid-September rains, and insect and disease pressure. Data is shown in Figures 1 through 4.

Grapes from the French Colombard trial only were processed into wine. All replicates were combined into two separate lots (control and treated) prior to processing. The wines were subjected to a triangle difference taste test by a trained panel. The data are shown in Table 5. A taste panel could significantly distinguish the wines (p<0.001); in 53 out of 75 presentations, panelists were able to choose the different wine. Comments from the tasters indicated that 6 preferred the treated wines, 6 preferred the control wines, and 3 had no preference f o r e i t h e r w i n e .

Malic acid, potassium levels, and anthocyanin pigments were measured in the French Colombard trial only. Malic acid levels ranged from 2.60 to 3.89 g/L. Potassium levels ranged from 456 ppm in the treated wines to 555 ppm in the control wines. Anthocyanins ranged from 0.77 mg/L in the Ponnax-treated wines to 1.24 mg/L in the control wines. All levels are within a normal range typically found in French Colombard wines grown in the San Joaquin Valley. 3

2Snfandel.

Cluster counts in treated plots were not significantly different than counts in control plots (Table 1). Yield was not significantly different between the treated and control plots (Table 2). The average cluster weight and berries per cluster were not significantly different between plots (Table 3). There were no significant differences in berry chemistries at harvest (Table 4).

On a weekly basis, there was no significant difference in berry chemistries between the treated and control plots. 100-berry weights in both plots were comparable at the start of data collection, then slightly increased in the control plots for the remainder of the sampling period. Both plots had nearly the same sugar content until 2 weeks before harvest, when the rate of sugar accumulation decreased in the treated plots. pH and T.A. were similar over time. The lower sugar in the treated plots would imply a delay of maturity. Again, there appears to be no advantage to applying Ponnax to Zinfandel, as was recommended for French Colombard. Data is shown in Figures 5 through 8.

Thampsan Seedless,

Cluster counts in treated plots were not significantly different than counts in control plots (Table 1). Yield was not significantly different between the treated and control plots (Table 2). Average cluster weight and berries per cluster were not significantly different (Table 3). There were no statistically significant differences between treatments for berry chemistries at harvest (Table 4).

Prior to harvest, lOO-berry weights were lower over time in the Ponnax-treated plots, until harvest, when the weights were slightly higher. Over time, sugar accumulated at the same rate in both treatments. pH levels were nearly identical over time, but there was a drop in the Ponnax treatment that caught up to the control by the next sampling date. T.A.S gradually declined over the season, and the levels were nearly identical. The data are shown graphically in Figures 9 through 12.

CONCLUSIONS:

Ponnax applied at bloom to French Colombard, Zinfandel and Thompson Seedless grapes does not have a signficant affect on berry chemistries, cluster counts, or yield. French Colombard cluster weight and berries per cluster were significantly higher in control plots than in treated plots. A taste panel could correctly identify the proper wine in a triangle difference taste test; because half the panel preferred 4 the treated wine and half preferred the untreated wine, it appears that this significant difference is important on a personal preference level only. It is recommended that future research be focused on additional applications during the season, or a specific variety such as Thompson Seedless be investigated in terms of raisin quality. T A B L E 1

CLUSTER COUNTS^ BASF PONNAX TRIAL, CSU FRESNO, 1994

Cluster Counts (#/vine)

French Colombard Zinfandel Thompson Seedless

Significance of F

^Average of 6 replications, taken from middle vine only T A B L E 2 YIELD (pounds per vine)^ BASF PONNAX TRIAL, CSU FRESNO, 1994

Yield (Ibg/vine)

French Colombard Zinfandel Thompson Seedless

51.77 29.50 18.34

51.90 27.70 19.94

Significance of F

^Average of 6 replications

TABLES CLUSTER WEIGHTS AND BERRIES PER CLUSTERS AT HARVEST BASF PONNAX TRIAL, CSU FRESNO, 1994

Treatment French Colombard Zinfandel Thompson Seedless C l u s t e r B e r r i e s C l u s t e r B e r r i e s C l u s t e r B e r r i e s Wt. (g) Per Cluster Wt. (g) Per Cluster Wt. (g) Per Cluster

Control 275.8 344.1 231.5 151.8

Ponnax 226.9 287.2 113.4 227.5 171.3

Significance 0.05 ofF

'Average of 6 replications. T A B L E 4

BERRY CHEMISTRIES AT HARVEST BASF PONNAX TRIAL, CSU FRESNO, 1994

TREATMENT

CONTROL P O N N A X S i g n .

FRENCH COLOMBARD % sugar

100-berry weight 176.0 181.6

ZINFANDEL % sugar

100-berry weight 137.4 129,6

THOMPSON SEEDLESS % sugar

100-berry weight TABLES

W I N E E V A L U A T I O N FRENCH COLOMBARD WINE BASF PONNAX TRIAL, CSU FRESNO, 1994

Poimax vs. Control 53 out of 75 detected difference, significance p<0.(X)l

Preference: Ponnax Control Neither

6 6 3

TA B L E 6

ANTHOCYANINS, MALIC ACID, POTASSIUM FRENCH COLOMBARD WINE BASF PONNAX TRIAL, CSU FRESNO, 1994

Treatment Anthocyanins Malic Acid Potassium ( m g / L ) ( g / L ) ( p p m )

Control 1.24 2.60 555

P o n n a x 0 . 7 7 3 . 8 9 4 5 6 Figure 2. Control vs. Ponncx sugar content, French Colombard, 1994. California State University, Fresno. Julian Date Fiqure 3. Control vs. Ponnox pH, French Colombord, Iy94. California State University. Fresno.

Julian Date Figure 4. Control vs. Ponnox titrotobie acidity, French Colombord. 1994. Colifornio Stote University, Fresno. — ^ — C o n t r o l O Ponnox (1pt a.i./oc)

21 Julian Date Figure 6. Control vs. Ponnox sugar content, Zinfondel. 1994. Coiifornic State University. Fresno — C o n t r o l

■Q— Ponnox (1pt o.i./ac)

Julian Date Figure 7. Control vs. Ponnox pH, Zinfondei. 1994 California State University, Fresno.

210 : Julian Date Figure 8. Control vs. Ponnox titrotabie acidity, Zinfondei, 1994. California State University, Frresno

^ C o n t r o l O Ponnox (1 pt a.i./oc) 1 1 1 1 1 200 205 210 215 220 Julian Dote Figure 11. Control vs. Ponnox pH, Thompson Seedless. 1994. Colifornlo State Univesity, Fresno.

0.5

•5 0-4 <

(U JD 0.3 o

E 0 . 2

Contro

211 Julian Date Figure 12. Control vs. Ponnox titrotoble acidity, Thompson Seedless, 1994. California State University, Fresno.