A central hypothesis is given related to some alterations of cotton plant physiology treated with PHCA (Polyhydroxy carboxylic acids), specifically on the Phenyl-propanoid pathway within the Shikimic acid cycle to produce more lignin and probably a constant biosynthesis of phytoalexin-like compounds such as gossypol (even though this compound is synthesized via the Mevalonate pathway it requires also the reducing nucleotide molecule NADPH) to deter the feeding habit of the SPWF Bemisia tabaci Genn. type B, by increasing the cotton plant tissue strenght (cell wall integrity) and interfering in some way with whitefly pectolytic enzymes (synthesis inhibition?, blocking?, degrading?). To begin the testing of this hypothesis, an experiment on very late planted cotton cv. Delta Pine 80 was performed in 1991 in the Mexicali Valley BC, Mex. Results from this study on cotton corroborated previous works performed on different crop species. A line of five different PHCA compounds were applied from the beginning of the cotton plant squaring to the boll setting initiation on a randomized block experimental design with nine treatments and four replicates. A statistically significant difference was found on PHCA treatments particularly those with a combination of soil and foliar treatments versus UTC. The central variable "Damage by the excreta (honeydew)" on lint from open cotton bolls was less pronounced on PHCA treatments than UTC plots, the best recorded mean for the former was 5.8% against 64.3% for the latter, indicating a significantly lower number of SPWF active feeding stages on PHCA plots, whereas a big population from crawlers to adults was present on UTC plots.