AIR BLAST SPRAYER AND HAND-GUN TRIAL. Bill Olson, Milt Schroth

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1 ABSTRACT WALNUT BLIGHT CONTROL - MATERIAL EFFICACY SCREENING AIR BLAST SPRAYER AND HAND-GUN TRIAL Bill Olson, Milt Schroth 1989 Champ at 1 2/3 gal./acre and Kocide 101 at 8 lbs./acre were evaluated for their ability to control walnut blight in The materials were applied 5 times during April and May by an orchard sprayer. Incidence of walnut blight in the untreated trees was at 38% while both materials reduced the walnut blight level down to 3 percent. Both materials resulted in some but not serious phytotoxicity. In a handgun trial Kocide "xl"; Kocide "x2"; and yeast treatments provided the same level of control of walnut blight than did Kocide alone. OBJECTIVE 1. Evaluate Kocide 101 and Champ Flowable for walnut blight control in replicated trial. 2. To determine the effect of Kocide 101 and Champ Flowable sprays on the occurrence of Xanthomonas iuqlandis in walnut buds. 3. To detect the presence of copper resistant strains of ~ iuqlandis in Kocide- and Champ-treatedwalnut buds. B. Small Handgun Trial 1. Evaluate Kocide 101, Champ Flowable, "enhanced" Kocide 101 and a biological treatment for walnut blight control in a replicated trial. 2. To monitor the presence of Xanthomonas iuqlandis in untreated dormant vegetative walnut buds, expanding vegetative bud tissues, and newly-formed vegetative buds. 3. To determine the effect of fixed copper, enhanced fixed copper, and biological treatments on th~ occurrence of ~ iuqlandis in walnut buds. 4. To determine the prevalence of copper resistant strains of ~ iuqlandis in treated and untreated walnut buds. 5. To examine walnut buds for the presence of dominant

2 phenotypic groups of microorganisms that may be antagonistic to ~ ;uqlandis. PROCEDURE Establish a trial in an Ashley walnut orchard replicated 10 times and treated with one of two materials 5 times in April and May by air blast sprayer. The materials were Champ at 1 2/3 gal/acre or Kocide 101 at 8 lbs./acre. Evaluate treatments for walnut blight incidence and rate trees for phytotoxicity in June Nut blight evaluation was based on any blight strike on 50 nuts per replicate located about 6 feet off the ground and 50 nuts per replicate located 15 feet off the ground. Leaf phytotoxicity based on 50 leaves per replicate and categorized as being clean, bronzed or burnt. Bud evaluation: Ten shoot terminals were pruned on June 5, 1989 from each of five randomly selected trees in each sampling row. each shoot One newly-formed vegetative bud was excised from in the laboratory. Excised buds from each tree were combined to yield composite samples of 10 buds for each sampled tree. The composite samples were then individually weighed and macerated in 10 ml of sterile phosphate buffer solution. Ten-fold serial dilutions of the macerate were prepared and 0.1 ml aliquots of the 10-2 and 10-3 dilutions were plated onto Blue Starch medium. The plates were incubated for 4 days at 29 C, after which colonies of ~ juqlandis were counted. Three pathogen colonies from each positive sample were then transferred to medium containing 20 or 40 ppm copper sulfate, incubated again, and evaluated for growth. B. Small Handgun Trial Establish a 5 replicate hand-gun trial in an Ashley walnut orchard tested 4 times with Champ, Kocide, yeast, Kocide + xl' or Kocide + x2 and evaluate for incidence of walnut blight on nuts and leaves and phytotoxicity. Blighted nut evaluations based on all nuts per replicate with or without any blight strikes. Leaf blight and leaf phytotoxicity based on 25 leaves per replicate. Bud evaluation: Tissue samples were collected for assay on April 4 (prior to first spray), April 24 (after the first spray) and May 31 (after the third spray). Dormant vegetative buds were assayed at the first sampli~g date, expanding vegetative bud tissues on the second date, and newly-formed vegetative buds on the final sampling date. At each sampling, the terminal 6 inches of 10 randomly selected shoots were pruned from each replication (limb). Single buds from each shoot were selected for assay in the laboratory. Control bud samples were processed individually (50 buds per

3 sampling date), while buds from treated plots were combined for each replication (5 composite samples of 10 buds each for every treatment). Control buds were individually weighed and macerated in 5 ml phosphate buffer solution. Composite bud samples from treated plots were weighed and macerated in 10 ml of phosphate buffer. Ten-fold serial dilutions of the macerate were made and plated on Blue Starch (BS), Casetone Yeast Extract (), King's B (KB), and medium amended with 20 and 40 ppm copper sulfate. Medium Dilutions Plated BS KB + 20 ppm CuS ppm CuS04 The plates were incubated at 29 C for three to four days and colonies were counted. Bacterial or yeast colonies on KB and were also classed and quantified based on morphological features. Two or three x. iuqlandis colonies from each positive sample were transferred from BS to plus copper sulfate, incubated for 3 days and rated for growth to determine copper resistance. RESULTS Champ at 1 2/3 gal./acre and Kocide 101 at 8 lbs./acre gave good control of walnut blight with only slight phytotoxicity (See Table). Four of the five composite bud samples from the Kocidetreated block had detectable populations of ~ iuqlandis, while only two of five samples from the Champ-treated block tested positively for the pathogen. None of the ~ iuqlandis isolates grew on amended with 20 or 40 ppm copper sulfate, indicating X. iuqlandis was not resistant to copper. B. Small Hand-gun Trial Kocide + xl; Kocide + x2 and the yeast treatments gave equal control of walnut blight than did Kocide alone (See Table 1). Due to the unavailability of Champ at the first spray timing, it was only applied 3 times and this may ~xplain why it did not perform quite as well as the other materials. Bud evaluation: See following table

4 Number of individual control buds and composite (treated) bud samples with detectable populations of ~ iuqlandis from the 1989 Chico hand-sprayed trial.. Number Of Samples With ~ iuqlandis Sampling Date Previous Season Buds New Buds Treatment 4 Apr 24 Apr 31 May 1. Control 2/50* 2/50 16/50 (1/5)** (2/5) (5/5) 2. Kocide 101 0/5*** 1/5 3/5 3. Kocide Xl 1/5 1/5 0/5 4. Kocide X2 0/5 1/5 1/5 5. Yeast 0/5 3/5 1/5 6. Champ Flowable - - 2/5 *Number of individual control buds with detectable populations of ~ iuqlandis in a total of 50 buds **Number of control replications with detectable ~ iuqlandis populations ***Number of composite bud samples (replications) with detectable ~ iuqlandis populations in total of 5 samples per treatment Only three copper resistant (20 ppm) isolates of ~ juqlandis were detected during this trial. Two isolates were from the control plots and one from the yeast-treated plots. No copper tolerant strains were identified from the coppertreated plots. No phenotypic group or groups predominated among non-walnut blight organisms isolated on KB and. The buds appeared to be colonzied by a diverse group of bacteria and some yeasts. CONCLUSION Champ at the rate used was equal to Kocide 101 in the air blast spray trial. Different rates would be expected to give different results. The poorer control with Champ in the hand-gun trial was because it missed the first application. The handgun trial is preliminary, but encouraging data. Of interest is the fact that the yeast treatment gave equal control of walnut blight as did the copper treatments. It appeared that Kocide + enhancer and yeast had fewer infected new buds than did Kocide alone. Work in this area will continue in

5 Table 1 WALNUT BLIGHT CONTROL - AIR BLAST SPRAYER TRIAL TreatIrentllRate % Blighted % Blighted % Nuts-6 Ft. Nuts-15 Ft. Blighted Nuts High High Overall % Leaf Phytotoxicity Clean Bronze Burnt Chanp 1-2/3 5X galla 2.4 A 3.2 A 2.8 A Kocide 101-5X 8 lbs/a 2.8 A 4.0 A 3.4 A Untreated B 35.0 B 37.5 B / Applied 4j2 4/7 4/18 4/27 and 5/9/89 WALNUT BLIGHT CONTROL - HANDGUN TRIAL % Leaf TreatIrent..Y Rate % Blighted Nuts % Leaf Blight Phytotoxicity Charrp - 3X 15.2 mljgal 29.6 AB 29.6 A 20.0 B Kocide - 4X 9.1 gm/gal 25.6 A 30.4 A 19.0 B Kocide + Xl-4X 9.1 gm/gal + Xl 22.2 A 31.2 A 20.0 B Kocide + X2-4X 9.1 gm/gal + X A 28.0 A 23.0 B Yeast - 4X 1 plate/gal 25.2 A 30.4 A 5.0 A Untreated B 37.6 A 10.0 A!/ Applied 4/4 (except Chanp)~ 4/18~ 5/2~ and 5/22/