The document discusses the development of biologically-based strategies for managing apple replant disease. Specifically, it summarizes that (1) management of soil biology can lead to disease suppression, (2) research has identified a complex of pathogens that cause apple replant disease, and (3) formulations of Brassica seed meals can provide fumigant-level control of the disease and enhance soil resilience in an organic system.

1. The Development of Biologically-Based Strategies for
the Management of Apple Replant Disease
Mark Mazzola
USDA-ARS, Tree Fruit Research Lab, Wenatchee, Washington, USA

2. Biologically-based strategies
• Management of the resident orchard soil
biology in a manner that leads to
disease suppression.
• The development of disease control
methods based upon the causal
pathogen/parasite complex

3. Control of Apple Replant Disease
Historically (USA): Soil Fumigation primary means of control
Cost effective
Readily available
Requires no knowledge of the causal biology
Motivation for change:
Loss of fumigants (methyl bromide)
Potential loss of additional fumigant chemistries
Restrictions in use of registered fumigants

4. Barriers to development of biology-based control methods
Development of effective non-fumigant controls requires knowledge:
What are the biological targets?
How do they interact to cause disease?
Progress hindered by perception/approach:
Etiology is biologically too complex
Cause varies dramatically from orchard to orchard (?)
Certain studies used one-dimensional approach yielding ID of unlikely
causal agents

5. Apple Replant Disease Etiology
Causal Pathogen Complex:
Control Pre-plant Fum
Cylindrocarpon
(destructans, olidium)
Phytophthora
(cactorum, syringae, cambivora, megasperma)
Pythium
(at least 15 species)
Rhizoctonia (solani AG 5, 6 binuc. AG’s G, I, Q)
Pratylenchus penetrans (lesion nematode)
Mazzola, 1997; 1998; Mazzola et al., 2002
Paulitz et al., 2003, Allain-Boulé et al., 2004

6. Strategies evaluated for management of replant disease
Manipulation of resident soil Establishing new orchard
microbial antagonists In old orchad aisle
Solarization
Soil excavation
Rootstock tolerance

7. Control of Soilborne Diseases with
Brassica Seed Meal Formulations

8. Brassica residue amendment for disease/pest control
“Biofumigation”: the chemistry-based paradigm
Brassica residue
Myrosinase
Glucosinolate Isothiocyanates
Pest Suppression
Fungi
Oomycetes
Nematodes
Weeds

9. Brassica seed meal amendments for soilborne disease control
Current model:
Multiple mechanisms of action
Operative mechanism can change over time
Functional mechanism varies with target pest
Resident soil biology is often instrumental
Mazzola et al., 2001; 2007; 2009
Cohen & Mazzola 2005; 2006
Weerakoon et al. 2012

10. Outcomes that imply biological mechanism:
Level of disease suppression increased for weeks after active chemistry
lost from the soil system (Lewis and Papavizas, 1971; Warton et al., 2003; Weerakoon et al.,
2012)
Pathogen or parasite suppression was obtained irrespective of seed
meal (Brassica napus) glucosinolate content (Mazzola, 2001).
Disease suppression only functions in a biologically intact soil system
(Cohen & Mazzola, 2006).

11. Application of Brassica SM amendments for control of apple replant disease
Ten trials General conclusions:
Six orchard locations Individual seed meals used independently always fail
Failure can be traced back to causal biology
Trial duration 3-6 years

12. Individual seed meals always fail:
CV orchard trial
2004-2009
Treatments
B. juncea (BjSM; yellow mustard)
B. napus (BnSM); canola)
S. alba (SaSM, white mustard))
Mefenoxam (Ridomil)
Telone-C17 c
b
ab
a a
a
Mazzola & Brown 2010 Plant Disease

13. Individual seed meals always fail; however…
CV orchard trial
2004-2009
Treatments
B. juncea+mef
B. napus+mef
S. alba+mef
Mefenoxam c
c bc c
Telone-C17
ab
a
Mazzola & Brown 2010 Plant Disease

14. Why did independent use of seed meal fail?
Pythium
Phytopthora cambivora and Phytophthora cactorum incidence
of root infection increased dramatically in B. juncea amended soil

15. Brassicaceae SM formulations for disease control in organic systems
STM commercial organic orchard trial
B. juncea/S. alba seed meal formulation applied 6 April 2010
Planted to Jonagold/G11 12 May 2010

16. Brassica SM formulation for replant disease control in organic systems
Jonagold/G11 yield data 2012
B. juncea/S. alba seed meal

17. Brassica SM treated soils biologically more robust:
Pratylenchus penetrans

18. Nematode pathogens and parasites elevated in seed meal treated soils
Arthrobotrys
(nematode trapping)
Aporcelaimellus
(predatory nematode)
Plectosphaerella cucumerina
(parasitic fungus)

19. Brassica SM formulation for replant disease control
Sunrise organic orchard trial
Seed meal formulations: B. juncea/S. alba or B. juncea/B. napus
Application date: Sept. 9, 2009 (autumn prior to planting) or
April 6, 2010 (spring of planting)
Cultivar/rootstock: Gala/M9 or Gala/G11
Planting date: May 13, 2010

20. Effect of Brassica SM formulation on fruit yield
Gala/M9 yield data 2012 Gala/G11 yield data 2012
BjSa = B. juncea+S. alba Au = application autumn Sp = application spring of
prior to planting planting
BjBn = B. juncea+B. napus

21. Effect of Brassica SM formulation on Pratylenchus penetrans root densities
Gala/M9 2012 Gala/G11 2012
BjSa = B. juncea+S. alba Au = application autumn Sp = application spring of
prior to planting planting
BjBn = B. juncea+B. napus

22. Pyrosequencing Analyses of Rhizosphere Microbial Communities
NMDS plot of Bacterial Phyla
In seed meal treated soil yield performance
and microbial community composition was
rootstock dependent
In fumigated soil yield performance and
microbial community composition similar
among rootstock genotypes

23. Summary:
• Development of non-fumigant measures for replant disease control is a
knowledge-based process
• Biologically-based methods for control of replant disease are attainable
• Brassicaceae seed meal formulations can yield fumigant levels of
replant disease control and enhance system resilience
• Degree of efficacy and persistence of biological effects may be
rootstock-dependent
Acknowledgments:
Personnel
Sarah Strauss
Xiaowen Zhao
Michael Cohen
Jack Brown, Univ. of Idaho
Gennaro Fazio, USDA-ARS, Geneva, NY