Margaret G. Lloyd

lloydMy research explores non-chemical management strategies under the overarching effort to develop alternatives to methyl bromide.  Since the 1950′s, methyl bromide has very successfully minimized common soil pests including nematodes, weeds and soil borne diseases like Verticillium wilt, Fusarium wilt and black root rot. International efforts to reduce pollutants causing ozone depletion, methyl bromide was banned in the 1998 Montreal Protocol.  Complete phase-out was scheduled for 2005 in developed nations and 2015 in developing nations.  California strawberries received exemptions from complete phase out and have been given allotments of methyl bromide by county.  While this has allowed methyl bromide to be available, the allotments have been continually decreasing and complete phase out is expected in the next year or two.

To this end, developing strategies to effectively manage soil borne diseases has become more urgent.  In my PhD research, I have undertaken two aspects of soil borne disease management.  First, I’m exploring the potential of biological control effected by compost to suppress pathogens.  I work with four commercial composting companies found in the central coast to test the effect of each compost on disease suppression and strawberry root health, canopy development and productivity.

Second, I’m evaluating the potential of 10 legume cover crops in supporting the development of Verticillium dahliae, causal agent of Verticillium wilt. In the absence of known hosts, cryptic infection may contribute to the persistence of V.dahliae in the soil. Fava beans, bell beans, Austrian field pea, Vetch (hairy, lana woolypod, common and purple), black eyed peas, crotolaria sunn hemp, and sesbania are evaluated based on root infection, systemic stem colonization and density of microsclerotia formation.