Sampling of cotton and bracts were done twice a week throughout the growing season at Texas Tech (Lubbock), Texas A & M (College Station), Mississippi State (Starksville) and California State (Fresno). Cottons were studied separately for each of the sixteen sectors and the bracts were pooled, dried and shipped to our laboratory for endotoxin determinations by the limulus amebocyte lysate test.

Endotoxin content and gram negative bacilli (GNB) rapidly reached a high level and remained stable throughout most of the growing season. Correlations of endotoxin with GNB counts were better for cottons than for bracts. Samples from California were much better for cottons than endotoxin and GNB. The phylloplane microbial load is similar in microorganisms for all four sites, but significantly lower for California. One major factor my be lack of rain in California. A second study is underway.