Fungicide resistance management

SBI s Rally Viticure Elite Vintage Bayleton Strobilurin s Sovran Flint Abound Quinoline s Quintec Combination s Pristine Adament Inspire Super

Benlate*benomyl DuPont systemic (local) Topsin-M thiophanate-methylcerexagri systemic (local)*label withdrawn Mode of action: FRAC1 Group 1; single-site inhibitors that interferes with nuclear division. Resistance risk: high; levels of resistant populations do not decline in absence of fungicide use Growth effects: inhibits mycelial growth Sporulation: inhibits

Sulfur Dust Micronized df- Kumulus JMS Stylet Oil Purespray Green Oil Serenade (Bacillus subtillus)- Biocontrol Sonata (Bacillus pumilus)- Biocontrol Elexa (chitosan) SAR Messenger (Harpin Protein) SAR Trilogy (Neem Oil) Copper materials-champ 50wp(Nufarm) Milstop Milsana Kaligreen Physpe Vigor Cal, Vigor K Prevam Valero

Bayleton triadimefontriazole systemic (local) Elite tebuconazoletriazole Bayer CropScience systemic (local) Mettle tetraconazole Triazole Sipcam Agro USA systemic (local) Indar fenbuconazole Triazole Dow Agrosciences systemic (local) Orbit propiconazoletriazole Syngentasystemic (local) Bumper*propiconazole Triazole Makhteshim-Agan systemic (local) Procure triflumizole Imidazole Chemtura systemic (local) Rally (Laredo) myclobutanil Triazole Dow Agrosciences systemic (local) Rubigan fenarimol Pyrimidine Gowan systemic (local) Inspire difenconazoletriazole Syngenta systemic (local)* Registration pending Mode of action: FRAC1 Group 3; single-site inhibitors; inhibit demethylation and other processes in sterol biosynthesis; locally systemic; have little effect on spore germination, but interfere with other early developmental processes; all inhibit mycelial growth and may stop lesions from sporulating; Resistance risk: high Growth effects: inhibit mycelial growth Sporulation: suppresses

Quintec quinoxyfen Company Dow AgroSciences Activity contact Mode of action: FRAC Group 13; probably single-site inhibitor; disrupts early cell signaling events. Resistance risk: medium Growth effects: suppresses spore germination, early germ tube development and/or appressorium formation Sporulation: no effect

Abound azoxystrobin Syngent acontact and systemic Cabrio pyraclostrobin BASFcontact and systemic Evito*fluoyxstrobin Arysta contact and systemic Flint trifloxystrobin Bayer CropScience contact and systemic Pristine pyraclostrobin + boscalid BASFcontact and systemic Sovran kresoxim methyl BASFcontact and systemic Mode of action: FRAC1 Group 11; single-site; blocks respiration by interfering with cytochrome b. Resistance risk: high Growth effects: inhibits spore germination and mycelial growth Sporulation: no effect

Pristine pyraclostrobin/boscalid BASF Mode of action: Activity contact and systemic FRAC1 Groups 11 and 7; see above for strobilurin; unknown for carboxyanilide. Resistance risk: low-med (combination of different chemistries) Growth effects: see above for strobilurin; unknown for carboxyanilide Sporulation: see above for strobilurin; unknown for carboxyanilide

SUCCINATE DEHYDROGENASE INHIBITORS (SDHIs) Endura boscalid BASF contact (DPX-LEM17)* penthiopyrad DuPont contact Luna Privilege (USF-2015)* fluopyram Bayer CropScience contact Resistance risk probably high

Relatively easy to find field or lab mutants resistant to DMI fungicides Suggests that rapid resistance would develop in the field and have in fact occurred Was assumed that resistance would be less problematic Resistant isolates generally less fit than wildtype Not true Management strategies in place

Population sampled in 1990 To compare directly the overall and regional subpopulations surveyed

Early Findings Occurrence of resistance in Erysiphe necator to triadimefon, myclobutanil, and fenarimol in California grapevines Gubler, W. D., Ypema, H. L., Ouimette, D. G., Bettiga, L. J. 1996 Plant Disease 80(8): 902-909 Notable regional variation in sensitivities to DMI fungicides recorded. Environmental influence on generation time Prevalence of cliestothecial stage in disease cycle

Resistance Management Aim- Reduce Selection pressure to prevent further buildup of resistant strains. Use mixes or alternate use of fungicides with different modes of action i.e. DMI s and Strobilurin s, Quinoxyfen, Boscalid etc. Should not use within class chemistry for mixes or alternations. Make sure spray coverage is not an issue

Conclusions There was no shift towards reduced sensitivity in the absence of fungicide selection pressure. In vineyards where Bayleton was used in the absence of sulfur, there was a significant shift in sensitivity to Bayleton and Myclobutanil and a lesser shift towards Fenarimol. Resistance was shown to be maintained in the population in overwintering ascospores Disease control is achievable when growers know what the disease pressure is at any given time.

Conclusions Resistance to triadimefon and other triazoles increased over 14 yrs statewide in the absence of triadimefon use. Resistant isolates have remained fit with continuous selection pressure and functioning of sexual stage. Resistance increase the result of use of other DMI fungicides with the same mode of action. DMI fungicides can still be used effectively but rotation with other fungicide classes is very important.

Conclusions Risk of resistance development to single site of action fungicides high regardless of where used. Could probably have delayed resistance onset by using tank mixes and alternations with other chemistry classes.

Historical Triadimefon introduced to vines in California in 1982. Resistance to DMI triadimefon was suspected in 1985. Control failures in field, most severe along coast, 1985 and 1986. Demonstrated high EC 50 value isolates able to infect seedlings 7-17 days earlier than isolates with lower EC 50 values.

Historical 1989 and 1990 large scale losses at field level. Poor field performance ascribed to coverage problems, rate problems, fast tractor speeds; not resistance. 1987 and 1988 higher than normal temperature years; only control problems along coast.

Early Findings Resistance of Uncinula necator to DMI fungicides in California vines Gubler, W. D., Ypema, H. L., Ouimette, D. G., Bettiga, L. J. 1994 in Fungicide Resistance, British Crop Protection Council Monograph No 60, pp 19-25 Environmental conditions influence latent period, therefore number of generations exposed to selection pressure. 5 days at optimum temperature conditions (20-30 C) 15 days @ 33-35 C lethality is only a few hours @ 37 C

Early Findings Resistance overwinters in ascospore populations, increases over course of season in conidial populations. Areas of higher chassmothecia production include cool coastal areas, Delta area, southernmost San Joaquin Valley. These areas often have 2 viable ascospore crops per season; the overwintered spores in spring, and a second crop in late summer or fall.

Early Findings 1990 monitoring study applications of Bayleton 50DF @ 285g/ha (= 4 oz/acre, i.e. 2 oz/acre triadimefon or roughly 80-200ppm @ nozzel tip (label is 2-6 oz in vines). Steady increase over season in mean EC 50 values of sensitivity to triadimefon BUT ALSO FENARIMOL AND MYCLOBUTANIL.