Chemical control and herbicide resistance of hairy fleabane (Erigeron bonariensis L.) in Jordan.

The effect of paraquat, oxadiazon and oxyfluorfen herbicides was tested on two populations of hairy fleabane (Erigeron bonariensis L.), collected from a date palm orchard at Tal al-Ramil (Central Jordan Valley) and al-Twal (Northern Jordan Valley) sites using the recommended rates (0.5, 1.25 and 0.792kg a.i ha-1 for each herbicide, respectively) and 10-fold (5, 12.50 and 7.92 kg a.i. ha-1, respectively) under glasshouse conditions. Results showed that the date palm weed population was resistant to the three herbicides at both application rates and al-Twal site population was highly susceptible. Two field experiments were conducted to evaluate the effectiveness of 12 herbicides in controlling the weed in the date palm orchard during the spring of 2017, revealed that E. bonariensis resists paraquat (0.5, 1.0 and 1.5 kg a.i. ha-1), oxadiazon (1.25 kg a.i. ha-1) and oxyfluorfen (0.792 kg a.i. ha-1) herbicides. None of the three herbicides was effective against the weed and treated plants continued to grow normally similar to those of untreated control. Ten-fold higher rates of these herbicides failed to control the weed. The effect of other tested herbicides was variable with bromoxynil plus MCPA (buctril®M), 2,4-D- iso-octyl ester, glyphosate, glyphosate trimesium and triclopyr being the most effective and completely controlling the weed at recommended rates of application. It is concluded that the tested populations of E. bonariensis developed resistance to paraquat, oxadiazon and oxyfluorfen but control of the weed was possible using other herbicides with different mechanisms of action. Herbicide rotation or other nonchemical weed control methods have been suggested to prevent or reduce the buildup and spread of resistant populations of this weed. These results represent the first report of herbicide resistance of E. bonariensis in Jordan.

Ephedra alte (joint pine): an invasive, problematic weedy species in forestry and fruit tree orchards in Jordan.

A field survey was carried out to record plant species climbed by Ephedra alte in certain parts of Jordan during 2008-2010. Forty species of shrubs, ornamental, fruit, and forest trees belonging to 24 plant families suffered from the climbing habit of E. alte. Growth of host plants was adversely affected by E. alte growth that extended over their vegetation. In addition to its possible competition for water and nutrients, the extensive growth it forms over host species prevents photosynthesis, smothers growth and makes plants die underneath the extensive cover. However, E. alte did not climb all plant species, indicating a host preference range. Damaged fruit trees included Amygdalus communis, Citrus aurantifolia, Ficus carica, Olea europaea, Opuntia ficus-indica, and Punica granatum. Forestry species that were adversely affected included Acacia cyanophylla, Ceratonia siliqua, Crataegus azarolus, Cupressus sempervirens, Pinus halepensis, Pistacia atlantica, Pistacia palaestina, Quercus coccifera, Quercus infectoria, Retama raetam, Rhamnus palaestina, Rhus tripartita, and Zizyphus spina-christi. Woody ornamentals attacked were Ailanthus altissima, Hedera helix, Jasminum fruticans, Jasminum grandiflorum, Nerium oleander, and Pyracantha coccinea. Results indicated that E. alte is a strong competitive for light and can completely smother plants supporting its growth. A. communis, F. carica, R. palaestina, and C. azarolus were most frequently attacked.