Trials with western flower thrips confined on growing safflower buds for 34 days demonstrated that the buds are able to tolerate numbers of nymphal thrips averaging as high as 75 per bud (when cages were initially injected with 10 adults per bud) without any significant drop in seed production. However, infestations that had started with 20 or 40 adults per bud did significantly decrease the number of good seed heads produced, the number of seeds per head, and the total yield. Trials with lygus bugs, Lygus hesperus Knight, indicated that the threshold of economic damage to the safflower crop was exceeded when the ratio of bugs to buds exceeded 1-to-8. Significant decreases in yield criteria were obtained when the bug-to-bud ratios were adjusted to 140–4 or higher. A new stripe, or thin-hulled, variety appeared to be more susceptible to injury by lygus bugs than the variety U. S. 10.

These studies were conducted under project 1565 with the assistance of John Campbell, Nurseryman at the Davis campus.