Off-season Weed and Sting Nematode Management for Organic Strawberry

In designing a cropping system for the production of organic strawberry, some of the factors that should be considered include: cropping system diversity, resilience to pests, soil fertility, and soil health. To this end, sunn hemp (Crotalaria juncea L.) and hairy indigo (Indigofera hirsuta L.) cover crops were evaluated at four locations in north-central Florida during the summer off-season for the potential to suppress weeds in comparison with a weedy control. Sesame (Sesamum indicum L.) and a four-way legume mix of American jointvetch (Aeschynomene americana L.), hairy indigo, short-flower rattlebox (C. breviflora DC.), and sunn hemp were also evaluated at one of the locations. The susceptibility of different accessions of Crotalaria species including sunn hemp to the sting nematode (Belonolaimus longicaudatus Rau) – a key soilborne pest of strawberry in Florida – was also assessed in greenhouse experiments. Sunn hemp shoot biomass production exceeded that of hairy indigo at three of the four locations. Sesame shoot biomass was higher than hairy indigo but not significantly different from biomass obtained with sunn hemp and the four-way legume mix. Total weed biomass with sunn hemp and hairy indigo was suppressed in a similar manner at the three locations where sunn hemp biomass exceeded that of hairy indigo. Total weed biomass with sesame and the four-way mix also was significantly lower than in the weedy control. Of the eleven sunn hemp accessions evaluated, all exhibited lower susceptibility to sting nematodes than corn, which was used as a susceptible control. However, sunn hemp accessions differed in their susceptibility with no nematodes recovered from six accessions, whereas 12.8 nematodes per 100 cm³ were recovered from the most susceptible accession. Although the single C. breviflora variety proved to not be significantly different from corn in susceptibility to sting nematodes, all four accessions of C. ochroleuca were either nonhosts or poor hosts. Of the nine C. spectabilis accessions evaluated, two were nonhosts and two were as susceptible as corn. Based on these results, in future evaluations of a four-way legume mix, C. breviflora will be replaced with C. ochroleuca.