Amaryllis Herbicide Demonstration
I completed a short-term demonstration trial on amaryllis recently to determine a few safe preemergent-herbicides that might prove useful to prevent hand weeding since I couldn't find anything in the literature. Eight different herbicides were applied over the top of three pots and then on another set of three pots herbicide was applied under the canopy of the leaf blades to see if there were any differences. The rates were about twice the high labeled rate to make sure they would be relatively safe even with an over-application. Only above ground plants were evaluated. Herbicide injury could show up in slower growth rates, longer term growth, and root damage but these were not evaluated.
Here are the results three weeks after treatment application. Herbicides that look relatively safe were Corral, FreeHand, Tower, Snapshot. Ones that caused injury were OH2, O-O Herbicide, Jewel, Rout, and OHII. Almost all damage was in the axil of the leaves right at the base of the bulb (see red arrow in above picture). There was less injury when herbicides were applied under the canopy but nothing was 100% injury free if it caused damage in the overhead trial (see red arrow at bottom right picture above). It would be extremely difficult to apply these herbicides under canopy if there were any number of pots that would need to be applied and there would be no way to guarantee the application would be only to the soil. As a caveat with this information, this was done in a limited number of plants in April in West Central Florida with overhead irrigation. Data may be different with other environmental conditions, irrigation practices, media, etc. UF/IFAS Extension is not making any recommendations with this data, just showing the results of the small-scale demonstration. The use of trade names or registered products in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition. All chemicals should be used in accordance with directions on the manufacturer's label. Use pesticides safely. Read and follow direction on the manufacturer's label.