红铃虫为害青铃对棉花产量和单价的影响

红铃虫Pectinophora!gossypiella(Saunders)的为害可分为直接取食为害和间接诱发病害。两年来每隔5天左右系统剥查吐絮棉铃,分析结果表明,受害棉籽产量损失平均为60.92克籽棉/千粒,每头幼虫平均为害2.03粒棉籽。根据单铃幼虫数估计的每条幼虫为害造成的产量损失是籽棉0.24克,皮棉0.101克,其中直接为害分别是0.133克和0.0467克,间接为害分别是0.11克和0.0543克。棉籽受害后皮棉等级降低4级,单价降低31.6%。百斤皮棉单价损失是9.383元/条/铃,其中直接为害5.559元/条,间接为害3.824元/条。应用皮棉产量损失0.101克/条和百斤皮棉单价损失9.383元/条/铃,推导了估计产值损失的公式,可以在生长期的不同阶段估计当时红铃虫所造成的产值损失。

THE LOSS OF YIELD AND PRICE OF LINT COTTON DUE TO BOLL DAMAGE BY PINK BOLLWORM

This study was carred out during 1981-1982 in which newly opened boll were collected at about five-day intervals. The bolls then dissected to determine number of larvae per boll and the seed cotton from the bolls having same number of larvae was put together. The seed cotton was weighted, ginned and the lint cotton weighted, a quality index was given and the price determined. The regression. analysis was used to analyse the re-lationship between number of larvae per boll and yield and price.The damage of cotton boll by pink bollworm can be distinguished into direct and inderect,which were caused by larvae feeding and inducing disease respectively. A attempt was made to estimate these losses in monetary terms. The estimated loss by feeding and disease induced in lint yield was 0.046714g and 0.054366g per larvae, and in price was 5.559 yuan and 3.624 yuan per 50kg lint cotton with one larvae per boll.A formula for estimating the pink bollworm damage in monetary term on mu basis was given as:loss in value (yuan/mu)=number of bolls per plant×number of larvae per boll×number of plants per mu×5.7087×10^-4.The parameter 5,7087×10^-4 is suitable for Shanghai area.