Three years' experience is described involving 35 experiments using our system of techniques to inoculate first instar larvae of Heliothis virescens onto cotton terminals to develop uniform infestation levels of the insect in field plots in host plant resistance research. Correlations of data for the check cultivar in each experiment over years indicated good utility of the technique.

Data show the techniques can measure different levels of resistance when yield in inoculated and protected plots is used as the measure. A group of 13 strains was considered in detail for 2 years. The system of techniques yielded information on resistance to H. virescens that was not available when the lines were evaluated only under insect protected conditions. Differences between 'Stoneville 825' and 'Stoneville 506' were significant with the latter being more resistant than the former.

This system of techniques can be used by cotton breeders to obtain useful information on cotton lines relative to resistance to H. virescens. The system is continuing to be refined; however, it is useful in its present form. We suggest that breeders should use our system to develop uniform infestation levels of H. virescens on groups of their own strains and if different levels of resistance are present they should be detected. We have found different levels of resistance to H. virescens in most groups of lines we have examined.