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1 Evaluation and omparison of iofungiides and fungiides for the ontrol of post harvest potato tuer diseases. E. Gahango, W. W. Kirk, P. S. Wharton, R. Shafer and P. Tumalam. Department of Plant Pathology, Mihigan State University, East Lansing, MI Summary Potatoes are suseptile to a variety of storage pathogens, inluding late light (Phytophthora infestans), Fusarium dry rot (Fusarium samuinum), Pythium leak (Pythium ultimum) and silver surf (Helminthosporium solani). Current reommendations for potato storage diseases inlude sanitation and exlusion as the primary ontrols for these pathogens in storage failities. Few fungiides are registered for diret appliation to tuers for ontrol of these important pathogens and few ompounds are availale for potato tuer treatment in storage, inluding hlorine-ased disinfetants suh as, sodium hypohlorite, alium hypohlorite and hlorine dioxide. In reent years several new iofungiides ased on the ioontrol ateria Baillus sutilis (Serenade) and B. pumilis (Sonata) have een registered or are awaiting EPA approval for use on potato, and have shown promise in the ontrol of seed and soil orne diseases suh as late light, lak surf and pink rot. These produts have een evaluated for the ontrol of pathogens under post-harvest potato tuer storage onditions. Thus, studies were initiated to evaluate the effiay of these iofungiides for the ontrol of potato storage pathogens under post-harvest onditions. For a omparison, several ommerial storage produts Phostrol (sodium, potassium and ammonium phosphates), and Oxidate (hydrogen dioxide) and experimental treatments suh as Quadris (azoxystroin) and mixtures of azoxystroin and fludioxinil (Maxim) at different rates + thiaendazole (Mertet) and more reently difenoonazole were evaluated for their effetiveness under storage onditions. Preliminary results show that in general the onventional fungiides (azoxystroin, fludioxinil and difenoonazole) provided the most effetive disease ontrol. The iofungiides provided moderate ontrol. The ojetive of these trials was to ontinue the evaluation of fungiides and iofungiides against the most ommon storage disease enountered in Mihigan potato prodution. Materials and Methods Experiments were arried out in Novemer 2009 with potato ultivars FL1879, and Dark Red Norland. The tests were arried out at two storage temperatures used in the potato industry; 10 o C (49 o F), hip proessing and 4 o C (39 o F), tale stok and seed. The ultivars used in the 10 o C test were v. FL1879 a hip proessing ultivar; v. Dark Red Norland at 4 o C a red skinned tale-stok ultivar. Potatoes free from visile diseases [exept v. Dark Red Norland that was uniformly infeted with H. solani (Hs, silver surf, 20% of surfae area affeted) at the time of appliation] were seleted for the trials from tuers harvested in Otoer Tuers were prepared for inoulation with Phytophthora infestans (Pi), P. erythroseptia (Pe), Pythium ultimum (Py), and Fusarium samuinum (Fs) y grazing with a single light stroke with a wire rush, suffiient to arade the skin of the tuers to a depth of 0.01 mm. Solutions (1 x 10 3 /ml ) of sporangia/zoosporangia of Pi (late light), oospores/sporangia of Pe (pink rot), oospores of Py (Pythium leak), and maroonidia of Fs (dry rot) were prepared from ultures of the pathogens previously isolated from potato tuers in Mihigan. All pathogens were

2 grown in Potato Dextrose Nutrient Broth for 20 days prior to preparation of inoulum solutions. Two non-treated ontrols, either inoulated with one of the pathogens or noninoulated were inluded in the trial. Inoulated and damaged/inoulated tuers, (50/repliate/treatment; total 200 tuers/treatment) were sprayed with 10 ml of pathogen suspension, for a final dosage of aout 0.25 ml per tuer. Tuers were stored for 2-d after inoulation at 20 C efore treatment. Fungiides were applied as liquid treatments in a water suspension with a single R&D XR11003VS spray nozzle at a rate of 1L/ton at 50 psi onto the tuer surfaes, with the entire tuer surfae eing oated. After inoulation, tuers were inuated in the dark in plasti oxes at 10 C or 4 o C (depending on ultivar and disease omination) for 90 (oomyete pathogens and dry rot) to xxx days. The oomyete diseases were evaluated as the perent inidene of tuers with any signs or symptoms of the pathogen. Tuers with surfae sporulation, disoloration of the skin or lakened/dead sprouts were onsidered infeted. The remaining tuers were ut open and the numer of tuers with symptoms or signs of the individual pathogens were ounted to determine inidene of disease. Dry rot was and silver surf disease severity was assessed using a disease severity index. Disease severity lasses were determined as lass 0 = 0%; 1 = 1-10%; 2 = 11-20%; 3 = 21-50; 4 > % internal area of tuer tissue with disease (dry rot) or surfae area affeted (silver surf). The disease severity index was then alulated as the numer in eah lass multiplied y the lass numer and summed. The sum was then multiplied y a onstant to express severity on a sale. Data were analyzed y two-way ANOVA using ARM software (Version 7, Gylling Data Management) and mean separation alulated using Fisher s proteted least signifiant differene (LSD) test at P= Results and Conlusions In the late light test at 10 o C, late light developed in several treatments and the inoulated hek had 58.8% inidene (Tale 1). No late light developed in the noninoulated hek. Treatments with less than 58.8% inidene of late light were signifiantly different from the inoulated hek. Treatments with greater than 10.0% inidene of late light were signifiantly different from the non-inoulated hek. In the pink rot test at 10 o C, pink rot developed in several treatments and the inoulated hek had 65.0% inidene (Tale 2). No pink rot developed in the non-inoulated hek. Treatments with less than 65.0% inidene of pink rot were signifiantly different from the inoulated hek. Treatments with greater than 7.5% inidene of pink rot were signifiantly different from the non-inoulated hek. In the pythium leak test at 10 o C, pythium developed in several treatments and the inoulated hek had 60.0% inidene (Tale 3). No pythium developed in the noninoulated hek. Treatments with less than 60.0% inidene of pythium were signifiantly different from the inoulated hek. Treatments with greater than 6.3% inidene of pythium were signifiantly different from the non-inoulated hek.

3 In the Fusarium dry rot studies at 10 o C Fusarium dry rot developed in several treatments and the inoulated hek had 70% inidene and 31.9-severity index (Tale 4). The noninoulated hek had signifiantly less dry rot inidene and severity than the inoulated hek. Treatments with less than 56.3% inidene of dry rot were signifiantly different from the inoulated hek. Treatments with greater than 13.8% dry rot inidene were signifiantly different from the non-inoulated hek. Treatments with less than 24.1 dry rot severity index were signifiantly different from the inoulated hek. Treatments with greater than 5.9 dry rot severity index were signifiantly different from the noninoulated hek. In the silver surf leak test at 4 o C on Dark Red Norland, severe silver surf developed in several treatments and the inoulated hek had 93.1% inidene of silver surf (perentage of tuers in lass 0) and 55.6% severity index (Tale 5). Although the perentage inidene and severity were relatively high in all treatments, they were all signifiantly lower than the untreated hek. In this study, the oomyetes were not all ontrolled equally y the same programs. For example, Ranman 400SC 0.25 fl oz gave exellent ontrol of late light and pythium leak ut was moderately effetive against pink rot. GWN-4700 alone and in mixture was effetive against all three oomyetes and not signifiantly different from the standard program, Phostrol. Late light was well ontrolled y many produts inluding WE1042-1, whih was possily related to the inoulation tehnique in that the pathogen had not fully penetrated the lentiels y the time the fungiides/iofungiides were applied. This was also true of the Pythium study ut the rate of growth and penetration of Phytophthora erythroseptia may have een at a rate great enough for the infetion to our and estalish prior to the appliation of the produts. The iologial ontrols were generally les effetive than the est hemial ontrols ut still provide some useful redution in the estalishment of the oomyetes. For example, BUPots-4 in the Pythium trial and the late light trial and BuPots-1 in the pink rot trial. In the dry rot trial, the three-way mixtures of fludioxinil, azoxystroin and difenoonazole produed exellent ontrol and at all rates of the fungiides (espeially at the highest mixture rate of difenoonazole). While treatment with fludioxinil and azoxystroin together or difenoonazole alone provided effetive ut numerially less dry rot ontrol than the three-way mixtures although in terms of severity there was no signifiant differene among treatments. The iologial ontrol produts in some ases provided a moderate redution in inidene and severity of dry rot. In the silver surf trial, azoxystroin plus fludioxinil and all rates of difenoonazole in the three-way mixtures of fludioxinil, azoxystroin and difenoonazole produed the est ontrol ut only suppressed the development of silver surf. WE DS and the iologial ontrol produts provided a moderate redution in inidene and severity of silver surf.

4 Tale 1. Inidene of tuers with potato late light stored at 10 o C for 90 days after treatment with fungiides/iofungiides. Treatments and rate of appliation per wt of tuers Late light inidene (%) a Non-inoulated hek 0.0 l Inoulated hek 58.8 a Ranman 400SC fl oz f-k Ranman 400SC 0.05 fl oz. 7.5 h-l Ranman 400SC fl oz g-l Ranman 400SC 0.25 fl oz. 0.0 l Phostrol 53.6SC 1.28 fl oz 3.8 jkl Oxidate 27SC fl oz i-l GWN WP 0.14 oz 12.5 f-j GWN WP 0.14 oz + Phostrol 53.6SC 1.28 fl oz e-i GWN WP 0.14 oz + Phostrol 53.6SC 1.28 fl oz 6.3 i-l GWN WP 0.14 oz + A FS d 0.03 fl oz 7.5 h-l GWN WP 0.14 oz + A SC d 0.03 fl oz 3.8 jkl GWN WP 0.14 oz + A FS 0.03 fl oz + A SC 0.03 fl oz 1.3 kl 09 BuPots-1 100L 0.2 fl oz d-g 09 BuPots-2 100WS 1.52 oz d-h 09 BuPots-3 100WS 1.52 oz de 09 BuPots-4 100LS 0.2 fl oz. 7.5 h-l 09 BuPots-5 100LS 0.3 fl oz e-j WE DS 1 l 3.8 jkl ME A 100D 1 l 26.3 d ME A 100D 1 l 23.8 de W103-5B 100D 1 l ND04-1A 100D 1 l def Vermiulite 100D 1 l LSD a Late light inidene (%); tuers with any symptoms and signs of Phytophthora infestans. Values followed y the same letter are not signifiantly different at P = 0.05 level aording to Fisher s proteted least signifiant differene (LSD) test. Applied in 4 pt H 2O/ton tuers. d A8574D= difenoonazole; A9859= fludioxinil.

5 Tale 2. Inidene of tuers with pink rot stored at 10 o C for 90 days after treatment with fungiides/iofungiides. Treatments and rate of appliation per wt of tuers Pink Rot inidene (%) a Non-inoulated hek 0.0 k Inoulated hek 65.0 a Ranman 400SC fl oz f-i Ranman 400SC 0.05 fl oz efg Ranman 400SC fl oz ef Ranman 400SC 0.25 fl oz ef Phostrol 53.6SC 1.28 fl oz 10.0 hij Oxidate 27SC fl oz jk GWN WP 0.14 oz 8.8 ij GWN WP 0.14 oz + Phostrol 53.6SC 1.28 fl oz. 7.5 ijk GWN WP 0.14 oz + Phostrol 53.6SC 1.28 fl oz 11.3 g-j GWN WP 0.14 oz + A FS d 0.03 fl oz 10.0 hij GWN WP 0.14 oz + A SC d 0.03 fl oz 8.8 ij GWN WP 0.14 oz + A FS 0.03 fl oz + A SC 0.03 fl oz 8.8 ij 09 BuPots-1 100L 0.2 fl oz ijk 09 BuPots-2 100WS 1.52 oz hij 09 BuPots-3 100WS 1.52 oz def 09 BuPots-4 100LS 0.2 fl oz de 09 BuPots-5 100LS 0.3 fl oz e-h WE DS 1 l 21.3 def ME A 100D 1 l 8.8 ij ME A 100D 1 l 28.8 d W103-5B 100D 1 l ND04-1A 100D 1 l d Vermiulite 100D 1 l Vermiulite 100D 1 l 53.8 LSD a Late light inidene (%); tuers with any symptoms and signs of Phytophthora infestans. Values followed y the same letter are not signifiantly different at P = 0.05 level aording to Fisher s proteted least signifiant differene (LSD) test. Applied in 4 pt H 2O/ton tuers. d A8574D= difenoonazole; A9859= fludioxinil.

6 Tale 3. Inidene of tuers with pythium leak stored at 10 o C for 90 days after treatment with fungiides/iofungiides. Treatments and rate of appliation per wt of tuers Pink Rot inidene (%) a Non-inoulated hek 0.0 k Inoulated hek 60.0 a Ranman 400SC fl oz g-j Ranman 400SC 0.05 fl oz e-h Ranman 400SC fl oz g-j Ranman 400SC 0.25 fl oz. 6.3 ijk Phostrol 53.6SC 1.28 fl oz 3.8 jk Oxidate 27SC fl oz ijk GWN WP 0.14 oz 7.5 hij GWN WP 0.14 oz + Phostrol 53.6SC 1.28 fl oz. 6.3 ijk GWN WP 0.14 oz + Phostrol 53.6SC 1.28 fl oz 3.8 jk GWN WP 0.14 oz + A FS d 0.03 fl oz 6.3 ijk GWN WP 0.14 oz + A SC d 0.03 fl oz 6.3 ijk GWN WP 0.14 oz + A FS 0.03 fl oz + A SC 0.03 fl oz 6.3 ijk 09 BuPots-1 100L 0.2 fl oz d-g 09 BuPots-2 100WS 1.52 oz e-h 09 BuPots-3 100WS 1.52 oz d-g 09 BuPots-4 100LS 0.2 fl oz f-i 09 BuPots-5 100LS 0.3 fl oz def WE DS 1 l 6.3 ijk ME A 100D 1 l 18.8 de ME A 100D 1 l 20.0 de W103-5B 100D 1 l ND04-1A 100D 1 l d Vermiulite 100D 1 l LSD a Late light inidene (%); tuers with any symptoms and signs of Phytophthora infestans. Values followed y the same letter are not signifiantly different at P = 0.05 level aording to Fisher s proteted least signifiant differene (LSD) test. Applied in 4 pt H 2O/ton tuers. d A8574D= difenoonazole; A9859= fludioxinil.

7 Tale 4. Severity and inidene of tuers with Fusarium dry rot 90 days after treatment with fungiides/iofungiides at 10 o C. Treatments and rate of appliation per wt of tuers Dry rot Inidene (%) Dry rot Severity index a Non-inoulated hek 2.5 f 0.6 f Inoulated hek 70.0 a 30.6 a A SC 0.03 fl oz + A SC 0.03 fl oz d 5.9 f A8574D 360FS fl oz de 5.0 f A12705P 250SC 0.03 fl oz + A8574D 360FS fl oz + A SC 0.03 fl oz def 4.4 f A12705P 250SC 0.03 fl oz + A8574D 360FS fl oz + A SC 0.03 fl oz. 7.5 ef 2.2 f A12705P 250SC 0.03 fl oz + A8574D 360FS fl oz + A SC 0.03 fl oz. 8.8 def 2.8 f A12705P 250SC 0.03 fl oz + A8574D 360FS 0.03 fl oz + A SC 0.03 fl oz. 3.8 f 0.9 f 09 BuPots-1 100L 0.2 fl oz 62.5 a 29.1 a 09 BuPots-2 100WS 1.52 oz a 26.9 a-e 09 BuPots-3 100WS 1.52 oz de 09 BuPots-4 100LS 0.2 fl oz de 09 BuPots-5 100LS 0.3 fl oz a 31.9 a WE DS 1 l e ME A 100D 1 l de ME A 100D 1 l de W103-5B 100D 1 l a 24.1 a-e ND04-1A 100D 1 l e Vermiulite 100D 1 l a 28.1 a-d LSD a Severity lasses were determined as lass 0 = 0%; 1 = 1-10%; 2 = 11-20%; 3 = 21-50; 4 > % internal area of tuer tissue with disease and inidene is perentage of tuers in lass 1-4. Values followed y the same letter are not signifiantly different at P = 0.05 level aording to Fisher s proteted least signifiant differene (LSD) test. A12705= azoxystroin; A8574D= difenoonazole; A9859= fludioxinil.

8 Tale 5. Severity and inidene of tuers with silver surf 101 days after treatment with fungiides/iofungiides at 4 o C. Silver surf Severity index a (%) Silver surf Treatments and rate of appliation per wt of tuers inidene (%) Non-inoulated hek 93.1 a 55.6 a A SC 0.03 fl oz + A SC 0.03 fl oz de A8574D 360FS fl oz gh 32.2 h A12705P 250SC 0.03 fl oz + A8574D 360FS fl oz + A SC 0.03 fl oz fg 32.3 gh A12705P 250SC 0.03 fl oz + A8574D 360FS fl oz + A SC 0.03 fl oz d 36.6 fg A12705P 250SC 0.03 fl oz + A8574D 360FS fl oz + A SC 0.03 fl oz de 36.9 f A12705P 250SC 0.03 fl oz + A8574D 360FS 0.03 fl oz + A SC 0.03 fl oz h 33.0 fgh 09 BuPots-1 100L 0.2 fl oz e 09 BuPots-2 100WS 1.52 oz BuPots-3 100WS 1.52 oz ef 44.5 de 09 BuPots-4 100LS 0.2 fl oz BuPots-5 100LS 0.3 fl oz de 42.4 e WE DS 1 l d 47.5 d LSD 0.05 a Severity lasses were determined as lass 0 = 0%; 1 = 1-10%; 2 = 11-20%; 3 = 21-50; 4 > % internal area of tuer tissue with disease and inidene is perentage of tuers in lass 1-4. Values followed y the same letter are not signifiantly different at P = 0.05 level aording to Fisher s proteted least signifiant differene (LSD) test. A12705= azoxystroin; A8574D= difenoonazole; A9859= fludioxinil.

Evaluation and comparison of biofungicides and fungicides for the control of post harvest potato tuber diseases ( ).

Evaluation and comparison of biofungicides and fungicides for the control of post harvest potato tuber diseases (2008-2009). E. Gachango, W. W. Kirk, R. Schafer and P. Tumbalam. Department of Plant Pathology,