Biofumigation, although a well-known method, is still controversially debated as a management strategy for plant-parasitic nematodes (PPN). Its controlling effect is attributed to the production of isothiocyanates (ITCs) following the action of myrosinase on glucosinolates (GSLs). Different ITCs are formed from different GSLs, depending on the plant species. To better understand the potential of ITCs, eight cultivars from three Brassicaceae species were investigated as biofumigation crops to control the root knot nematode Meloidogyne hapla. Since results were inconsistent, the nematicidal effect of selected ITCs were further evaluated in vitro. Based on its nematicidal potential, allyl ITC (AITC) was specifically investigated under different soil:sand compositions. A significantly lower nematicidal activity was observed in soil compared to sand. AITC was also evaluated as an additive to the biofumigation in a greenhouse trial. Its supplementation to the biofumigation process with Brassica juncea cv. Terrafit controlled M. hapla, while no control was observed using Raphanus sativus cv. Defender. Thus, the success of biofumigation seems to be strongly dependent on the soil characteristics and the ITC produced during the biofumigation process. Therefore, the supplementation of AITC in combination with the right cover crop can improve the biofumigation process to control M. hapla.

Reduced nutrient mineralization rates under minimum tillage are usually compensated by mineral fertilizer application. These, however, cannot be applied in organic farming systems. We hypothesized that an organic minimum tillage system based on frequent cover cropping and application of dead mulch would improve soil fertility and compensate for the potential negative effects of minimum tillage. Two long-term field experiments were set up in 2010 and 2011 to compare plowing versus minimum tillage including the application of transferred mulch. A second factor, the application of compost versus mineral potassium and phosphorus, was also compared. In 2019, soils were analyzed for soil pH, organic carbon, macro- and micronutrients, microbial biomass, microbial activity, and total nematode abundance. In addition, performance of pea in the same soils was determined under greenhouse conditions. Across both experiments, macronutrients (+52%), micronutrients (+11%), microbial biomass (+51%), microbial activity (+86%), and bacterivorous nematodes (+112%) increased in minimum tillage compared to the plow-based system. In the greenhouse, pea biomass was 45% higher in the soil that had been subjected to minimum tillage compared to the plow. In conclusion, soil fertility can be improved in organic minimum tillage systems, which include intensive cover cropping and the application of dead mulch, over plow-based systems.

Root-knot nematodes cause global economic losses in a wide range of crops. We investigated the potential of seed coatings of the cover cropPhacelia tanacetifolia(Boraginaceae) when inoculated with the nematophagous fungusPochonia chlamydosporia(Hypocreales: Clavicipitaceae) to protect subsequently grown tomato plants from root galling caused by the root-knot nematodeMeloidogyne hapla(Tylenchida: Meloidogynidae). Therefore, seeds ofP. tanacetifoliawere coated withP. chlamydosporiablastospores and planted inM. hapla-infested pots. After 50 days of growth in infested soil,M. haplaeggs were extracted fromP. tanacetifoliaroots and quantified. Tomato plants grown in the remaining soil served as bioindicator ofM. haplainfestation as expressed by the gall index. Results showed that seed coating ofP. tanacetifoliawithP. chlamydosporia(290 ± 51 CFU per seed) reduced the number ofM. haplaeggs up to 95.6% in comparison to untreated controls.Pochonia chlamydosporiaas blastospore suspension (5·10⁸blastospores per 600 ml soil) reduced the number ofM. haplaeggs by up to 75.5%. Additionally, tomato plants grown for 50 days in substrates previously planted withP. tanacetifoliaseeds coated withP. chlamydosporiashowed a significantly lower gall index than plants grown in untreated pots. In conclusion, biological enhancement ofP. tanacetifoliaby seed coating withP. chlamydosporiasuccessfully reducedM. haplaand thus provides an additional tool in the management of this nematode. The method still has potential for further improvement such as increasing blastospore viability within the seed coating by optimized formulation technology.

The development from growing plants in field soil to soil-less culture systems has not resulted in the elimination of problems caused by plant-parasitic nematodes. Species of Meloidogyne and Radopholus have been reported to occur in soil-less culture systems, such as flower crops. The reasons for initial nematode infestation are numerous but the primary reason is likely to be infested plant material. Since nematodes are not expected in soil-less systems, they are often overlooked. However, extension specialists report an increasing occurrence of plant-parasitic nematodes in soil-less culture systems and nematodes seem to be more prevalent than is often thought likely. In an attempt to increase the awareness of the prevalence of plant-parasitic nematodes in soil-less culture systems, this short paper summarises incidences of nematode detections and reviews methods for their detection and strategies for their control.