R H Smith Institute of Plant Sciences and Genetics, Faculty of Agriculture, Food and the Environment Robert H. Smith, Hebrew University of Jerusalem, Rehovot, Israel
Ambrosia confertiflora DC. (Bur ragweed) and Parthenium hysterophorus L. (Santa Maria feverfew) are known as the greatest aggressive and allergenic weeds in the world. Ambrosia confertiflora is a hard to kill perennial weed, especially when the plant already formed many root rhizomes, A. confertiflora is enormously spread in several regions of Israel, infesting agricultural lands, natural ecosystems, rights of ways, and populated living districts. Ambrosia confertiflora was introduced to the Hefer valley (the coastal plain of Israel) along the Alexander river banks during the late 1990s and since then, it has continued spreading to other country sites. Parthenium hysterophorus was found in Bet She’an valley in a fishpond bank during the late 1980s. Both species were introduced to Israel via importation of animal feeding grains from the USA. While the dispersal of A. confertiflora is extremely fast, P. hysterophorus was found to be in slow dispersion for almost 25 years, and only in the last 5 years it began to invade out of its original establishment area. Field experiments that were carried out during the last 15 years in order to limit the distribution of A. confertiflora, showed that the repeated applications of glyphosate products and herbicides that contain 2,4-D failed in controlling the plant and only caused temporary injury. Mature plants of A. confertiflora that have more than 150 shoots/m2, requests better systemic ability in order to get maximal efficacy. We showed previously that Shotgun® (Imazapyr) succeeds to eradicate A. confertiflora plants while leaving lasting residues in the soil. Considering the recent ban of Imazapyr by the EU authorities and the public debate over the use of glyphosate, we considered the use of other herbicides. Aminopyralid is the active ingredient (ai) in the herbicide Milestone® registered and marketed in the USA and produced by Corteva Agriscience™. It is a member of pyridines acid (pyridine carboxylic acid) group of chemicals mainly used for the control of broadleaf (annual and perennial) species. Aminopyralid is a highly systemic herbicide, intended for selective post emergence weed control application.
In order to improve the control of both species, several experiments with Milestone® have been carried out across different sites in Israel. Aminopyralid is very efficient in controlling herbaceous and woody deciduous plants. Milestone® is not toxic to mammals, birds, aquatics and other living in the marine environment. Milestone® is used in the USA EPA’s action plan of programs that allows reducing the risk to the environment, by using such “eco” herbicides. In experiments performed with aminopyralid as part of a research project of the Min of Agriculture’s Chief Scientist, we found that using Milestone®, either by spraying on top of developed plants or by very low concentrations of the diluted substance applied as moistening of 2 individual leaves of a plant, caused aboveground wilting as well as underground rhizomes control. P. hysterophorus is a noxious annual infesting field crops, subtropical orchards (avocado), dates and rights of ways in the inland worm areas. The weed was controlled effectively in date palm infested heavily with Milestone® causing no damage to the palm trees in Bet She’an region.