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Factors affecting biofumigation success against potato cyst nematodes

Watts, W.D.J. (2018) Factors affecting biofumigation success against potato cyst nematodes. Doctoral thesis, Harper Adams University.

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Abstract

Potato cyst nematodes (PCN), Globodera rostochiensis and Globodera pallida, cause in excess of £25M in losses to the UK potato industry per annum. Nematicides are used by potato growers to manage PCN, and protect yield. However, increasingly restrictive legislation within the European Union (EU), could instigate the retraction of nematicides from the region in the near future. Alternative management strategies, such as biofumigation, are therefore being evaluated for their potential to replace nematicides. Biofumigation involves the incorporation of glucosinolate (GSL) rich plant residues into soil for pest management. Upon tissue disruption, GSL’s are liberated from biofumigant plant cells, and are subsequently enzymatically hydrolysed to form toxic volatile organic compounds (VOC’s). The VOC’s are chemically similar to the synthetic fumigant nematicide currently used for PCN management within the EU, and have been found to consistently reduce field populations of PCN by c.40-50% in previous studies. However, biofumigation efficacy is dependent on a number of agronomic factors, many of which are poorly understood. This project investigated the effect of soil moisture conditions at biofumigant incorporation on biofumigation efficacy against PCN. Commercially available maceration and incorporation implements were also sourced and evaluated for their effectiveness in generating, and placing PCN suppressive biofumigant material into soil. Soil moisture investigations in the glasshouse found Brassica juncea biofumigation to reduce Globodera pallida viability by between 17-43%, and that efficacy could be improved by up to 14.3 % under certain soil moisture conditions. Soil moisture of 50% of field capacity was found to be more effective for biofumigation than 0, 25, 75 and 100% of field capacity, and water saturated soil. This could be due to an optimal water to air ratio within soil pores for VOC diffusion, and retention within soil. However, evidence is also presented which could suggest, that the optimal soil moisture condition for biofumigation, may be dependent upon the quantity of biofumigant biomass incorporated into soil, and the depth of biofumigant incorporation. Further work is required. In-vitro studies were then carried out which investigated the effect of water films surrounding PCN cysts, on the efficacy of biofumigant VOC’s. There was no evidence that water films might act as a barrier to biofumigant VOC contact with encysted PCN eggs. Maceration and incorporation implements, and combinations of implements, were investigated in field experiments for their effect on biofumigation efficacy against PCN. Biofumigation efficacy ranged between 27-34% for three geographically separated sites, over two years. A flail topper was found to improve biofumigation efficacy against G. pallida by 7% when compared to a roll conditioner. However, further investigation of haulm topper tines and shear-plate positioning provided no evidence that the implement set-up of topping implements, might influence biofumigation efficacy against PCN. Incorporation implements; spader, plough and rotavator, facilitated no extra efficacy against PCN when analysed in isolation to the effects of maceration implement, despite incorporating biofumigant material to diverse working depths, and despite producing contrasting soil structure. However, a separate analysis showed a flail-spader implement combination to produce a c.8% more effective biofumigation of G. pallida than a roll conditioner-rotavator combination. Further work is therefore required. Biofumigant biomass ranged between 14-48 t ha-1 fresh weight for field studies, and equivalent to 0-100 t ha-1 for glasshouse studies. Glucosinolate contents ranged between 3-12 μmol g-1 dry weight between studies, with 2-propenyl (sinigrin) being the dominant GSL. Clearly, biofumigation could have an important role to play in the future management of PCN

Item Type: Thesis (Doctoral)
Divisions: Crop and Environment Sciences
Depositing User: Ms Kath Osborn
Date Deposited: 16 Nov 2018 12:00
Last Modified: 16 Nov 2018 12:00
URI: http://hau.collections.crest.ac.uk/id/eprint/17347

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