西北农林升枚大学 NORTHWEST A&F U时VERSITY ◆ Greenbug causes severe damage during wheat seedling stage;English grain aphid,after earring; Oat bird-cherry aphid can be found at all wheat stages. 88880 Greenbug causes severe damage during wheat seedling stage; English grain aphid, after earring; Oat bird-cherry aphid can be found at all wheat stages.