Dodine management strategy

Black spot Diplocarpon rosae of rose

R.M. Beresford
Plant & Food Research, Private Bag 92169, Auckland 1142, New Zealand

(Revised November 2004)

A new fungicide resistance management strategy for apple black spot (Venturia inaequalis) has been put in place and supersedes the individual Mode of Action strategies shown elsewhere on this site for apple black spot in pipfruit.

The new strategy is available here.

Introduction

These guidelines are designed to avoid or delay the development of resistance to dodine fungicides in New Zealand. They have been developed from previously published information (Tate et al. 1996) in consultation with the New Zealand agricultural chemical industry (AGCARM) and are based on recommendations from the Fungicide Resistance Action Committee (FRAC) in Europe.

Dodine product perspective

Dodine is a guanidine derivative and acts predominantly as a protective fungicide, but also has a small degree of curative action. Its greatest use is in apples for the control of V. inaequalis (black spot or scab) and it is also used against a limited range of other diseases (Table 1). For apple black spot control it is applied early in the season, just after bud burst, and late in the season, before harvest. Its use when apple flowers or young fruit are present is avoided because it can induce fruit russet.

Four products containing dodine are currently marketed in New Zealand, Aklame, Dodine 400, Nuchem Dodine and Syllit Plus. All are suspension concentrate formulations.

**Table 1:** Pathogens and crops targeted by dodine fungicides.
Pathogen	Disease	Crops
Diplocarpon rosae	Black spot	Roses
Taphrina deformans	Leaf curl	Peaches and nectarines
Venturia inaequalis	Black spot	Apples
Venturia pirina	Black spot	Pears

Current status of dodine resistance

There is no known cross-resistance between dodine and the other fungicides used in the crops for which dodine is registered.

Resistance to dodine first developed in Venturia inaequalis in the United States and Canada during the 1960s and 1970s where it had been used as the only fungicide in spray programmes for 10 years or more (Jones 1981; Sholberg et al. 1989). Dodine resistance has also been reported from Europe and Australia. In New Zealand, dodine resistance was looked for in a field survey in 1994 (Bakker et al. 1995), but no resistant strains were detected. The maximum number of dodine applications that should be applied per season has recently been reduced from six to three as a result of ongoing international concerns about resistance development in Venturia inaequalis.

Resistance prevention strategy

Apply a maximum of three applications per season. Wherever practical, alternate each application of dodine with an application of a fungicide from a different cross-resistance group. Observe manufacturers' recommendations for application rate and timing. Exceeding the maximum number of applications per season will increase the risk of resistance development. Apply dodine preventatively when disease levels are low, but disease risk is high. Ensure that spraying equipment is accurately calibrated.

Implementation recommendations

Product labels for products that contain dodine should include an appropriate statement about resistance management. Most dodine products do not currently give resistance management statements on their labels.

References

Bakker GR, Butcher MR, Gaunt RE, 1995. Sensitivity of apple black spot to fenarimol, fluzilazol, myclobutanil, penconazole and dodine in New Zealand. Proceedings of the 48th New Zealand Plant Protection Conference: 7-11.

Jones AL 1981. Fungicide resistance: past experience with benomyl and dodine and future concerns with sterol inhibitors. Plant Disease 65: 990-992.

Sholberg PL, Yorston JM, Warnock D 1989. Resistance of Venturia inequalis to benomyl and dodine in British Columbia, Canada. Plant Disease 73: 667-669.

Tate G, Cliffe A, Manktelow D, Surman C 1996. Dodine resistance management strategy. In: Bourdôt GW, Suckling DM ed. Pesticide resistance: prevention and management. New Zealand Plant Protection Society, Rotorua, New Zealand. Pp. 144-145.