Management Strategies for Lettuce Drop in Arizona and California. Barry Pryor Department of Plant Pathology University of Arizona

Transcription

1 Management Strategies for Lettuce Drop in Arizona and California Barry Pryor Department of Plant Pathology University of Arizona

2 Lettuce Drop

3 The Pathogens: Sclerotinia minor and sclerotiorum S. and S. over 1500 recorded hosts cottony rot, white mold, watery rot on fruits, flowers, leaves, stems, and roots growth is favored by moist conditions both species produce long-lived lived resting structures known as sclerotia

4 S. sclerotiorum S. minor

5 Lettuce drop disease cycle

6 Eruptive Germination S. sclerotiorum S. minor

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8 Lettuce drop disease cycle

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10 Apothecium discharging ascospores

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12 Integrated disease management of lettuce drop host resistance cultural practices chemical control biocontrol

13 Host Resistance No commercially acceptable cultivar exist Most breeding programs have focused on S. minor - slow-dying phenotypes have been described Little progress has been made on resistance to S. sclerotiorum

14 Cultural Practices Crop rotation -broccoli rotation for control of S. minor -fallow rotation for control of S. sclerotiorum Irrigation water management is key to reduced disease -furrow sprinkler subsurface drip

15 Chemical control of lettuce drop iprodione (Rovral) vinclozolin (Ronilan) dicloran (Botran) boscolid (Endura)

16 2003 Yuma Fungicide Trials Rate Treatment lb a.i./a S. minor S. slerotiorum Rovral 4F Ronilan 50DF Endura 70WG Serenade AS Pristine 38WG Botran 5F Endura 70WG Pristine 38WG Botran 5F Switch 62.5WG Endura 70WG Switch 62.5WG Contans Contans Non-treated control qt prod lb prod. 2.0 lb prod *each plot contained approx. 55 plants

17 Benefits of biocontrol strategies complement other disease management strategies development of resistance unlikely cost effective few restrictions on use worker and environmental safety development of specialty markets

18 Objectives evaluate the efficacy of commercially available biocontrol agents for the control of lettuce drop evaluate the survival of biocontrol agents in the field evaluate the sensitivity of biocontrol agents to Botran, Rovral,, and Ronilan

19 Evaluate the efficacy of commercially available biocontrol agents for the control of lettuce drop Contans - Coniothyrium minitans Soilgard - Gliocladium virens Trichodex, Supresivit,, TRI Trichoderma harzianum Companion Bacillus subtilis Sporidesmium sclerotivorum

20 Evaluate the efficacy of commercially available biocontrol agents for the control of lettuce drop RCBD with 4 blocks biocontrol treatments plus one fungicide treatment plus control two trials - high and low density of sclerotia- S. minor and S. sclerotiorum two application schedules - pre-plant plant application and pre-plant plant plus side application

21 Evaluate the efficacy of commercially available biocontrol agents for the control of lettuce drop record incidence of lettuce drop record number and weight of marketable lettuce heads

22 Yuma S. Sclerotiorum Trial 2003 Yuma S. Minor Trial healthy heads/ 50' bed 0 blank control rovral contans plantshield supresevit soilguard companion control rovral contans plantshield supresevit soilguard companion blank Yuma S. sclerotiorum trial 2002 Yuma S. minor trial Blank Control Rovral Contans Plantshield Supresevit Rootshield Tusal Trichodex Soilgard Companion healthy heads/ 50' bed Healthy heads/50' bed Rovral Contans Plantshield Rootshield Tusal Trichodex Soilgard Companion Supresevit Control Blank Yuma Biocontrol Trials healthy heads/50' bed

23 Imperial Valley Biocontrol Trials Holtville S. sclerotiorum trial 2003 Holtville S. minor trial blank control rovral contans plantshield companion blank control rovral contans plantshield companion healthy heads/50' bed healthy heads/50' bed

24 Blank Untreated control Rovral Contans

25 Blank Untreated control Rovral Contans

26 Long-term Objective To develop biocontrol strategies for desert winter lettuce production that are compatible with chemical and cultural management strategies

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