Morpholine (Amine) [Group 5] resistance management strategy
Morpholine fungicides may be used to control powdery mildew
(Erysiphe cichoracearum) on cucurbits
(Photo: David Mitchel, www.nifg.org.uk)
Introduction
The purpose of this guideline is to help maximise the useful life of fungicides in the Fungicide Resistance Action Committee (FRAC) Group 5 for controlling plant diseases in New Zealand by providing relevant information about the nature of pathogen resistance to this group and guidance on practices that may prevent or reduce the development of resistance.
Disclaimer:
The fungicide and bactericide resistance information in the mode of action group table, the mode of action-based strategies and the crop-based strategies is intended to help manage the effects of pesticide resistance on plant disease control by agrochemicals in New Zealand. The New Zealand Committee on Pesticide Resistance (NZCPR) is a subcommittee of the New Zealand Plant Protection Society (NZPPS). The following parties: NZCPR, NZPPS, any people named in the strategies and any organisation the people may be affiliated with, do not guarantee that the resistance information is complete, consistent, accurate or up-to-date, or that resistance will not develop, or that the degree of resistance will decrease, as a result of the resistance information being used, and the parties accept no liability for loss or damage arising from the use of the resistance information contained in these strategies.
Morpholine product perspective
Morpholine fungicides have protective and systemic activity and a site-specific mode of action that inhibits sterol biosynthesis. The mode of action is different from that of the demethylation inhibitor (DMI) fungicides, which are also sterol biosynthesis inhibitors. Morpholines are useful for controlling powdery mildew diseases on a wide range of crops and for controlling a range of cereal foliar diseases (Table 1). Morpholines were first introduced internationally in the late 1960s. The morpholine active ingredients, fenpropimorph and tridemorph, which were previously available in New Zealand, are no longer available but spiroxamine (Impulse, etc), is registered in New Zealand.
Current status of morpholine resistance
There are no records of morpholine resistance in New Zealand, and evidence from overseas suggests that, although resistance can be selected in the laboratory, this group is low to medium risk from resistance development (Fungicide Resistance Action Committee; FRAC). Morpholines have been used for many years for barley powdery mildew control overseas and there are no reports of loss of efficacy in the field (Hollomon 1994). For wheat powdery mildew, there is evidence of a decrease in sensitivity to fenpropimorph in Europe, but no reported disease control problems (Readshaw & Heaney 1994). Tridemorph is used for control of black sigatoka disease (Mycosphaerella fijiensis) in bananas, but a survey found no evidence of sensitivity changes in South and Central America (Cronshaw et al. 1994).
| Pathogen | Disease | Crops |
|---|---|---|
| Horticultural crops | ||
| Erysiphe cichoracearum | Powdery mildew | Cucurbits |
| Sphaerotheca fuliginea | Powdery mildew | Cucurbits |
| Uncinula necator | Powdery mildew | Grape |
| Cereal Crops | ||
| Blumeria graminis | Powdery mildew | Wheat, barley |
| Leptosphaeria nodorum | Glume blotch | Wheat, barley |
| Mycosphaerella graminicola | Speckled leaf blotch | Wheat |
| Puccinia coronata | Crown rust | Oat, ryegrass seed crops |
| Puccinia hordei | leaf rust | Barley |
| Puccinia graminis | Stem rust | Wheat, oat, ryegrass seed crops |
| Puccinia recondita | Leaf rust | Wheat |
| Puccinia striiformis | Stripe rust | Wheat |
| Pyrenophora teres | Net blotch | Barley |
| Rhynchosporium secalis | Scald | Barley |
Resistance prevention strategy
There is no specific limit on the number of morpholine fungicide applications per year, but it is recommended to avoid excessive use. Adhere to manufacturers' recommendations for application rate and timing for specific products. Reduced-rate applications should be avoided. Apply morpholines preventatively when disease levels are low.
Implementation recommendations
Product labels should include a statement indicating that there is a risk of resistance development if excessive numbers of morpholine applications are made.
Acknowledgements
This strategy includes information from The Fungicide Resistance Action Committee (FRAC) about mode of action groups, the occurrence of resistance worldwide and resistance management recommendations.
References
Cronshaw K, Lorenz G, Mappes D, 1994. Monitoring results of Mycosphaerella fijiensis to tridemorph. In: Heany S, Slawson D, Holloman DW, Smith M, Russell PE, Parry DW ed. Fungicide Resistance. British Crop Protection Council Monograph No. 60. Pp. 315-321.
Hollomon DW 1994. Do morpholine fungicides select for resistance? In: Heany S, Slawson D, Hollomon DW, Smith M, Russell PE, Parry DW ed. Fungicide Resistance. British Crop Protection Council Monograph No. 60. Pp. 281-289.
Readshaw AE, Heaney SP 1994. Fenpropimorph sensitivity in Erysiphe graminis f.sp. tritici, survey of northern France 1991-1993. In: Heany S, Slawson D, Holloman DW, Smith M, Russell PE, Parry DW ed. Fungicide Resistance. British Crop Protection Council Monograph No. 60. Pp. 297-302.
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