Walnut Blight Studies. (1) Material Efficacy screening - Air Blast Sprayer Trial

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Regina Stafford
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1 Walnut Blight Studies (1) Material Efficacy screening - Air Blast Sprayer Trial (2) Survey Fr The Incidence f Cpper Resistance Walnut Blight Bacteria 1990 Bill Olsn, Milt Schrth, Je Osgd ABSTRACT Champin prved t be a better prduct than Champ Flwable in terms f Walnut blight cntrl and reductin f buds being infested with blight bacteria. Phytticity was heavy regardless f treatment. Over half f the rchards surveyed revealed the presence f cpper resistant blight bacteria which crrelated well with the grwers incidence f walnut blight in OBJECTIVES A. Air Blast Sprayer Trial 1. Evaluate Champin and Champ Flwable fr walnut blight cntrl and leaf and nut phytticity in a replicated trial. 2. T determine the effect f Champin and Champ Flwable sprays n the ccurrence f Xanthmnas juqlandis n walnut buds. 3. T detect the presence f cpper resistant strains f ~ iuqlandis in Champin and Champ Flwable-treatedwalnut buds. B. Survey Fr The Incidence f Cpper Resistant Walnut Blight Bacteria. 1. Determine the incidence f cpper resistant Xanthmnas iuqlandis bacteria in drmant walnut buds. 2. See if there is any assciatin with the incidence f cpper resistant bacteria and the frequency r rate f cpper being applied

2 PROCEDURE A. Air Blast Sprayer Trial. 1. Establish plts and apply the fllwing treatments by air blast sprayer at th~ rate f 100 gallns per acre. (1) Champ Flwable 1 1/3 gal./a.; (2) Champ Flwable 1 2/3 gal./a; (3) Champin 8 lbs/a; (4) Champin 10 lbs/a; (5) Untreated. s were applied n 3/21, 3/28, 4/5, 4/13, 4/24, 5/7, and 5/21/ Cllect bud samples befre, during and after treatments were applied and evaluate fr the presence f walnut blight bacteria and the incidence f cpper resistance at 20ppm. 3. Evaluate nuts fr the incidence f walnut blight and nuts and leaves fr phytticity at the end f the trial. 1. Cllect drmant bud samples frm 20 rchards in Butte and Tehama Cunty and evaluate fr the incidence f cpper resistant walnut blight bacteria at 20ppm. 2. Questin grwers abut their histry f walnut blight cntrl effrts. RESULTS A. Air Blast Sprayer Trial Champin at 10 lbs/a was significantly better than ther treatments at the June evaluatin and, althugh there were n significant differences between spray treatments, Champin at 10 lbs/a had the least walnut blight present in July. All spray treatments were significantly better than the untreated at bth evaluatin dates. All spray treatments ehibited cnsiderable leaf and nut phytticity which was evaluated as the presence f burnt r brnzed areas n the leaflets r dark specks n the nuts. The 8 lb. rate f Champin had the least leaf phytticity but the mst nut phytticity. Champ Flwable at 1 2/3 GPA had the mst leaf phytticity and least nut phytticity amngst the spray treatments. These results are summarized in Table

3 Labratry prcedure prevented a statistical evaluatin f the ccurrence f Xanthmnas iuqlandis n the buds r the presence f cpper resistant X. iuqlandis. The data is summarized in Table 2. At the beginning f the trial, 80 t 100% f the drmant buds evaluated had walnut blight bacteria present. Twards the end f the trial 0 t 20% f the new buds were nt infested, with the 10 lb. rate f Champin shwing n bacteria present. At the end f the trial the tw Champin treatments had 40% f the buds infested. Champ Flwable at 1 2/3 GPA with 60% infestatin and Champ Flwable at 1 1/3 GPA with f the buds infested. The percentage f" the bacteria islates resistance t cpper generally increased during the trial. In June the 10 lb. rate f Champin treatment had 27% cpper resistance bacteria, Champin at 8 lbs. had 19%, Champ Flwable at 1 2/3 GPA had 18% and Champ Flwable at 1 1/2 GPA had 5% f the bacteria resistant t cpper. Twelve f the 20 rchards sampled revealed levels f cpper resistance ranging frm 4 t 92 % resistance. The survey questinnaire indicated that grwers wh have used cpper bactericides at high rates and fr the lngest time had the mst resistance. In general, cpper resistance culd accunt fr the pr walnut blight cntrl many f the grwers eperienced in 1989 (Fig.1). CONCLUSION A. Air Blast Sprayer Trial. This trial indicates that Champin is a better prduct than Champ Flwable in terms f reducing the incidence f blighted walnuts and in the reductin f infested buds which shuld impact the presence f blighted walnuts the fllwing year. Phytticity was very severe this year nt nly in this trial but in the walnut prducing area in general. Althugh there was sme statistical differences between spray treatments in this trial, it is dubtful that these differencesare real. The increased presence f cpper resistant bacteria at the end f this trail is alarming hwever its significance is nt knwn at this time. The results frm the survey indicate the imprtance f discvering new appraches t cntrlling walnut blight. They als help eplain why, in spite f gd effrts, sme grwers have cnsiderable difficulty cntrlling walnut blight. BILLRR

4 TABLE 1 Rate 1/ Percent Walnuts with Percent Phytticity Blight Lesins leaf nut 6/18/90 7/18/90 6/18/90 7/18/90 1. Champ Flw. 1 1/3 GPA 3.6 B 3.4 A 70.0 AB 80.0 B 2. Champ Flw. 1 2/3 GPA 4.4 B 3.4 A 73.2 A 65.6 C 3. Champin 8 lbs/a 2.4 AB 2.4 A 55.6 B 91.2 A 4. Champin 10 lbs/a 1.0 A 1.8 A 70.8 AB 85.6 AB 5. Untreated C 14.8 B 12.8 C 12.8 D 1/ means nt fllwed by a cmmn letter are significantly different at the 5% level accrding t LSD. Figure ; Percent Cpper Resistant Walnut Blight Bacteria 90 at 20ppm vs. 80! Incidence f Walnut Blight I 20 I I HIGH MED LOW 217

5 TABLE 2. Recvery f Xanthmnas campestris p.v. juqlandis frm walnut buds n BS Medium and CYE Medium + 20 ppm cpper at the 1990 Olsn/Agtrl plts, Chic, CA, fr three sampling dates. sampling Date #1: March 20, 1990 Percentage Infested Samples & Average BS CYE (20ppm Cu) Percent % Resistant Islates Champin 8# Champin Untreated 10# 100% (5/5) 1.5E+4 2.3E+4 3.5E+3 8.5E+3 7.0E+3 8% 2% 5% Sampling Date #2: May 19, 1990 BS CYE (20ppm Cu) Percent Percent Champin 8# Champin 10# 0% (0/5) 1. 2E+3 9.4E+3 9.7E+2 20% 2.4E+2 Sampling Date #3: June 11, 1990 BS CYE (20ppm Cu) Percent Percent Champin 8# Champin 10# 60% (3/5) 40% (2/5) 40% (2/5) 2.2E+4 3.3E+3 1.9E+3 5.1E+3 5% 18% 19% 27% 1. 2E+3 6.1E+2 3.6E E+3 averages are mean values fr 5 cmpsite bud samples (ie., 5 replicatins per treatment; 10 buds per replicatin) Cpper resistance fr Sampling Date #1 determined by subsulturing. Epnential ntatin read per fllwing eample: 2E+3 = Lwer detectin limit is apprimately 5 10 cfu per sample

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