evaluation of quality damage of sugarcane whitefly, neomaskellia andropogonis (hom., aleyrodidae) on sugarcane in khuzestan province

the sugarcane whitefly, n. andropogonis, sucks severely the sap of plant and produces a lot of honey-dew. this study was conducted to quantify the relationships between whitefly damage and sugar quality in order to estimate the monetary loss occurring at different levels of damage at harvest time. during this trial, the number of infected leaves was expressed as an index. the investigation was conducted as a split-block design with five replications. three commercial cultivars, sp70-1143, cp57-614 and cp69-1062, were compared together based on the estimated damage and the sugar quality. stalks were divided into seven groups: control (without damage), one to five and more than five-infected leaves per stalk. analysis of the data showed that brix, pol, juice purity and refined sugar were inversely and significantly correlated with infected leaves. comparison of means by a lsd test revealed that sugar quality of stalks with one-infected leaf and control stalks were similar but stalks with more than two infected leaves were significantly different. especially in stalks with more than four-infected leaves, damage was severe. for example, stalks with five-infected leaves had 9.2, 10.3, 1.5 and 11.2 reduced percent brix, pol, juice purity and refined sugar, respectively. also, the results showed that whiteflies damage in the cultivars was different and it was possible to group cultivars into two categories. whitefly damage in two cultivars sp70-1143 and cp57-614 was higher than in the cp69-1062 cultivar. sp70-1143 and cp57-614 are early mature cultivars, and so based on quality damage, early mature cultivars are susceptible to whitefly damage.