Economic threshold for the sunn pest, Eurygaster integriceps Put. (Hemiptera : Scutelleridae), on wheat in southeastern Turkey

The sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae), is the most important insect pest of wheat and barley in Turkey. To redefine an economic threshold (ET) for the sunn pest, we determined the yield loss as the result of white spike damage caused by overwintered adults and kernel damage by nymphs and new-generation adults in wheat fields. Studies conducted in 17 one-ha insecticide-free wheat fields showed that white spike damage occurred at low levels (0.1-1.7%). Regression analysis was used to assess the relationship between overwintered adult density and white spike damage and between percent kernel damage and sedimentation value. The relationship between overwintered adult density and white spike damage was not significant in bread and durum wheat. Mean kernel damage was 2.2% and 6.6% in bread wheat and 8.0% and 2.8% in durum wheat in 2002 and 2003, respectively. There was a positive relationship between nymph and new-generation adult density and kernel damage using regression analysis in bread and durum wheat. Sedimentation values were 18-82 and 7-89 in 2002 and 2003 in bread wheat, and 9-22 and 9-28 in 2002 and 2003 in durum wheat. No effect of sunn pest density on gluten strength up to 2.1% kernel damage in bread wheat or up to 0.9% kernel damage in durum wheat was detected, but kernel damages greater than these levels limited dough quality. When these limit values were used, economic thresholds were 8.1 and 9.2 nymphs/m(2) in bread and durum wheat. The current ET (10 nymphs/m(2)) may be lowered to 8-9 nymph/m(2) for some wheat varieties and regions, especially for low-yield levels (approximately 2000-2500 kg/ha) in bread wheat but may still be valid for durum wheat