Greenhouse studies were conducted on two southern Illinois star-of-Bethlehem populations to determine the influence of chilling and bulb chipping on plant growth and reproduction. Chilling was not required for leaf emergence of dormant bulbs, but an increase to 10 wk of chilling proportionally delayed leaf emergence by 41 and 42 d for the Murphysboro and the Marion populations, respectively. Bulb chipping did reduce plant height when compared to plants from nonchipped bulbs. Also, chipped bulbs produced a greater number of small daughter bulbs compared to nonchipped bulbs; however, total bulblet production was variable and dependent on population, mother bulb size, and chipping treatment. Overall, bulb chipping did not have any negative influence on star-of-Bethlehem and might promote increased daughter bulblet production. Therefore, field operations, such as tillage, that cut and chip bulbs might actually accentuate both the spread and density of star-of-Bethlehem infestations.

Field research was conducted to evaluate the efficacy of preplant herbicides commonly used in no-till corn and soybean production and to determine the efficacy of three application timings in the spring for star-of-Bethlehem bulb management. A single, preplant application of herbicide treatments that included flumioxazin, sulfentrazone, or paraquat resulted in 91 to 97% control of star-of-Bethlehem at 14 d after treatment (DAT). Star-of-Bethlehem control from atrazine and metribuzin was moderate (70 to 75%) at the Marion location but poor (< 20%) at Murphysboro. Regardless of the initial foliar control at 14 DAT from treatments included in the corn and soybean herbicide screen, only applications containing paraquat resulted in extensive control (75 to 86%) of star-of-Bethlehem foliar regrowth by 1 yr after treatment. Star-of-Bethlehem was most responsive to herbicide applications in mid-March in southern Illinois when compared with applications made March 1 and April 11. The mid-March application timing corresponded to the vegetative reproductive stage, approximately 3 wk prior to flowering. The average density of star-of-Bethlehem bulbs in nontreated plots occupied 7.9% of the field soil volume in the upper 7.6 cm of the soil profile. Spring applications of paraquat (repeated 2 yr consecutively) reduced bulb density in the soil by 88%, compared with 5% or less bulb reduction for consecutive applications of glyphosate or 2,4-D ester applied alone. Overall, paraquat and paraquat tank mixtures provided the most effective and consistent control of star-of-Bethlehem foliage and underground bulbs, which is paramount for long-term management of this invasive species.