QUALITY EVALUATIONS OF WALNUT VARIETIES IN SAN BENITO COUNTY 2004

Transcription

1 QUALITY EVALUATIONS OF WALNUT VARIETIES IN SAN BENITO COUNTY 2004 William W. Coates ABSTRACT: Walnut varieties sometimes have different tree and nut characteristics in the cool Central Coast climate of San Benito County when compared to the same varieties in the warmer Central Valley climate. Evaluations of both older, well-tested varieties and some newer established varieties were conducted. Tulare had the highest nut weight while Pedro had the lowest. Tulare had the highest edible yield followed by Serr while Hartley had the lowest. Serr had the highest Relative Light Index rating followed closely by Chandler while and Payne had the lowest. Serr had the highest Relative Value followed by Chandler and Tulare while Hartley had the lowest Relative Value followed by Payne and Overall, Tulare, Serr and Chandler performed very well. Howard was less competitive with the best varieties compared to previous years. Pedro performed better than in the past. Hartley, Payne and gave sub-par performances. Chandler is the recommended variety for organic production. OBJECTIVES: The objective of this project was to evaluate established standard as well as some newer varieties from several locations in San Benito County with different management practices and microclimates. The performance of some varieties may differ when grown in a cooler climate than found in the Central Valley where most of the evaluation of new varieties is conducted. PROCEDURES: Samples of walnuts were collected at random during the normal harvest timing from various commercial orchards including variety trials. Samples were dried in mesh bags in a laboratory drying oven with a maximum temperature of 110 F. These were then transported to Diamond (Walnut) of California, Stockton, CA who provided the crackout information listed in Table One. RESULTS AND DISCUSSION: The 2004 growing season was one dominated by mild weather throughout the season except for one heat wave in early September (which resulted in sunburn) and greatly increased walnut husk fly damage throughout the district. Samples 902, 903, 906, 909, 910, 917, 922 and 928 were from organic orchards. The following results were derived from 1000 g samples of in-shell dried walnuts. Nut weight was relatively uniform across both variety and location versus previous years. Tulare and had the largest nuts overall as determined by percent large and percent large sound nuts (Table 1). Most of the stained shells and adhering hulls were due to walnut husk fly damage. In nearly half of the samples there was no internal insect damage which refers to codling moth and navel orangeworm damage (Table 2). Mold was mostly low except

2 for one Hartley sample. Percent edible yield was relatively low especially in some early varieties such as Payne. The lowest and highest percent edible yield samples were both Tulare although sample 922 with 36.7 percent kernel was specially selected for 100 percent walnut husk fly damage. Overall, Tulare had the highest percent edible yield (minus sample 922) of all varieties (Table 3). There was a high percent of kernels with light amber and amber color in many samples probably related to the late season hot weather. Payne averaged only 5% light and extra-light kernels. Even some Chandler samples had a relatively low percentage of light colored kernels and a low relative light index (RLI) versus previous years. RLI is an objective color rating derived from bouncing light off of a given sample a higher rating is desirable. The average RLI for each variety is shown in Table 3. The highest RLI was for Serr this was the first year any variety other than Chandler held this position in my tests. Relative value (RV) values also varied from previous years in the summary table (Table 3). RV is now determined by the formula Edible Yield X RLI X.0364 which sets the value of a sample with a 50% yield and a RLI of 55 equal to an RV of An overall relative value rating of 1.00 or higher generally indicates very high quality nuts. This is different than previous years so the data is not comparable. The highest RV was Serr followed closely by Chandler and Tulare. As with RLI, this is the first year in my testing that Chandler did not have the highest RV. Hartley had the lowest RV for cracking purposes, as expected. All three Serr samples, two out of three Tulare samples (excluding 922), and four out of seven Chandler samples exceeded a RV of The three lowest RV ratings (excluding 922) were one sample each of Payne, Howard and Hartley. Howard in general in 2004 was less competitive with Chandler, Serr and Tulare in quality than in previous years. Pedro performed better than in previous years. CONCLUSIONS Payne : This variety was not competitive for size, % edible yield, color or relative value. When combined with its high susceptibility to blackline, codling moth, walnut husk fly, walnut blight, and sunburn, it would be difficult to recommend based upon this year s data. Serr : This variety has always excelled in % edible yield although actually this was down this year. However, Serr did excel in RLI and RV versus previous years making it the top variety this year. However, this is not consistent over several years and this variety is noted for low and variable yield. Howard : Nut weight and % edible yield were low this year. Howard was in the middle of the pack as far as RLI and RV. This was a comparatively poor year for Howard. This variety has had some grower concerns involving weak tree growth and kernel spotting. Tulare : Nut weight, % edible yield, RLI and RV were all outstanding this year. This has not always been true in previous years but tree vigor is better than Howard and harvest date is earlier than Chandler which are pluses when considering a replacement variety. One grower reported a poor shell seal problem this year.

3 Pedro : This variety is rarely planted anymore but was very competitive this year except for nut size. In previous years, this has been one of the lowest value varieties : This is a local variety that was never released by the University of California. It has very distinctive, large nuts that are pointed at both ends (dirigible-shaped). It performed about with Payne this year except for larger nut size. It can have a lot of blanks some years. Chandler : The recognized standard for kernel quality based upon color, Chandler actually had some color problems this year that have not been observed in the past. It was still outstanding in most characteristics. Its greatest fault is late harvest which was a problem this year with rainfall in mid and late October. This is the recommended variety for organic production due to the low incidence of codling moth, walnut husk fly and walnut blight.

4 TABLE 1: WALNUT VARIETY EVALUATION, SAN BENITO CO NUT SIZE, EXTERNAL DEFECTS Mean Stained Broken Adh. External Sample # Variety Nut Wt (g) Large % Large Sound% Shell % Shell Hull % Hull% Damage% 901 Payne Payne Payne Payne Serr Serr Serr Howard Howard Howard Howard Howard Howard Tulare Tulare Tulare Tulare Hartley Hartley Hartley Pedro Tulare WHF Chandler Chandler Chandler Chandler Chandler Chandler Chandler

5 TABLE 2: WALNUT VARIETY EVALUATION, SAN BENITO CO INTERNAL DEFECTS, QUALITY, VALUE Edible Extra Light Sample # %Insect %Mold %Shrivel Yield% Lt% Lt% Amb% Amb% RLI Value

6 TABLE 3: WALNUT VARIETY EVALUATION, SAN BENITO CO SUMMARY TABLE No. of Mean Nut Large Large Edible Insect Mold Shrivel Light & Variety Samples Wt (g) (%) (%) Sound (%) Yield(%) (%) (%) (%) Ex. Lt. (%) RLI RV Payne Serr Howard Tulare Hartley Pedro Chandler RLI = Relative Light Index: A measure of overall kernel color (higher is better) RV= Relative Value: A measure of overall value (higher is better)