Table 1.

Frequency of HR-like necrosis induced by Pieris eggs in different B. nigra populations.

B. nigra population	Pieris species	N plants	% HR
Peloponnese, Greece	P. brassicae	74	47.3
	P. rapae	38	31.6
South-Wageningen (Steenfabriek), The Netherlands	P. brassicae	76	51.3
	P. rapae	79	46.8
North-Wageningen (Radix), The Netherlands	P. brassicae	15	46.7
Rhenen (Blauwe Kamer), The Netherlands	P. brassicae	15	26.7
West Sacramento, CA, USA	P. brassicae	11	63.6
	P. rapae	15	26.7