Genetic effects of foreign material in stripper harvested bur cotton were evaluated for 79 strains. Twenty plant, fiber and seed characters were examined for their effect on burs, sticks, and fine material in hand and machine harvested bur cotton. Multiple regression analysis was sued to determine effects of genetic characters on foreign material.

The genetic characters were able to predict 43 to 61% of the variation in hand harvested bur cotton while these factors accounted for 31 to 62% of the variations in machine harvested cotton. Sticks, fine material and total foreign material were closely associated with genetic characters. Bur content did not have as great a correlation as the other foreign material fractions. Sticks were positively associated with leaf hair density (bottom), plant height, maturity rating peduncle strength, 2.5% span length and micronair and negatively associated with puduncle diameter, boll size, bract hair density (bottom) and lint index. Fine material in bur cotton was positively associated with bract area, lint index, lock tenacity, plant height, micronaire and grade index.

Burs in machine harvested cotton was not closely associated with the genetic factors, but sticks and fine material were more closely associated. Boll angle, peduncle length, and plant height were positively associated with stick content of stripper harvested bur cotton, but leaf area, lint index, seed count, yield, and grade index were negatively associated. Fine Material was positively associated with number of bract teeth and maturity rating, while peduncle length, lint index, lock tenacity, plant height, verticillium rating and grade index were negatively associated. Fine material in the >8000 and 8000-1000 range had low coefficient of determinations for all three harvests, while the 100-90µ and 90µ had higher values in the range of 0.55 to 0.59.

It was also desired to determine if the genetic measured factors would affect weathering and harvesting of cotton. The change in bur, stick, and fine material content of by cotton between hand harvests on November 5, and December 15, 1980, had vary little correlation with the genetic factors. The difference in bur, sticks, and fine material content between the last had harvest and the machine harvest indicated the stick and fine material content could not be predicted by these factors by 57% of the stick variation was due to genetic factors measured. Percent change in stick due to genetic factors measured. Percent change in sticks due to harvesting was positively correlated with boll angle, peduncle length, and plant height and negatively associated with leaf area, yield and grade index.