Overall versus band application of the nematode Phasmarhabditis hermaphrodita with and without incorporation into soil, for biological control of slugs in winter wheat

In two concurrent field experiments the effects of three types of soil cult ivation and two patterns of nematode application were studied in order to i nvestigate their effects on damage to winter wheat by slugs (assessed at Za doks Growth Stage 12). In experiment I, infective juveniles (IJs) of the ne matode Phasmarhabditis hermaphrodita were applied to soil as an overall spr ay or as a band spl ay (8-cm wide), centred on the drill rows (16.7-cm apar t). Nematodes were either left undisturbed on the soil surface or hai rowed into the soil immediately after application. The control provided by nemat odes was compared with that provided by metaldehyde and methiocarb pellets broadcast at the recommended rare immediately after drilling. In this exper iment, winter wheat on plots treated with IJs showed significantly less slu g damage than on wheat plots treated with metaldehyde or methiocarb pellets or untreated plots. There was no significant difference in plant damage be tween plots treated with band and overall spray applications of IJs, nor wa s there any significant difference between plots with and without harrowing . There was also no significant difference between untreated plots and plot s treated with metaldehyde or methiocarb pellets, probably because rainfall shortly after treatment rendered the pellets ineffective. In experiment 2, nematodes were applied as an overall spray or plots were not treated with nematodes before soil was cultivated,vith tines, Roterra or Dutzi cultivato r. Nematode application before soil cultivation using tines or Roterra redu ced the number of plants damaged significantly However; nematodes applied b efore Dutzi cultivation appeared to be rendered ineffective. Damage to wint er wheat was lowest in plots that had been sprayed with nematodes and subse quently cultivated with tines or Roterra.