Submitted to: Pest Management Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/26/2004
Publication Date: 2/15/2005
Citation: Abbas, H.K., Johnson, B.J., Pantone, D.J., Wax, L., Hines, R. 2005. Response of multiple seeded cocklebur and other cocklebur types to herbicide treatment. Pest Management Science 61:643-648. 2005. Interpretive Summary: Multiple seeded cocklebur (MSC) is a new type of the common weed cocklebur that has more seeds, up to 25 per bur, and produces up to 9 seedlings. These factors may make this weed more invasive and more difficult to control. Because of this, the study tested the biological control agent, the fungus Alternaria helianthi, as well as common herbicides against MSC. Results showed that MSC can be controlled with both A. helianthi and the herbicides more easily than normal common cocklebur. Therefore, the same strategies used to control the normal weed should be effective to control MSC. This information should be useful for the herbicide industry as well as farmers.
Technical Abstract: Multiple seeded cocklebur (MSC) was found in the last decade in Texas and described as a biotype that has up to 25 seeds per bur, usually producing up to nine seedlings. Alternaria helianthi was highly effective and shown to cause severe damage and mortality on 8 to 12 leaf stage plants, with 8 hr dew period. At 1 x 105 conidia/ml 0.2% Silwet L-77 of A. helianthi caused mortality of 100% on 8 to 12 leaf stage of MSC, 50% in 6 to 8 leaf stage of both normal common cockleburs from Arkansas (NCC-AR) and from Illinois (NCC-ILL), and 100% in 6 to 8 leaf stage of normal common cockleburs from Mississippi (NCC-MS#1, NCC-MS#2), and from Texas (NCC-TX). Mortality was 100% in MSC 8 to 12 leaf stage and in NCC-TX at 6 to 8 leaf stage when sprayed with herbicides chlorimuron (6 g/A), imazaquin (12 g/A), MSMA (113 g/A) and imazethapyr (16 g/A). Whereas, 0 to100% mortality was observed in NCC-AR, NCC-IL, NCC-MS#1 and NCC-MS#2 at 6 to 8 leaf stage when sprayed with the same above herbicides at the same rates. These results showed that MSC was the most susceptible to the biological agent A. helianthi and conventional herbicides used in these studies.