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Selectivity of Butachlor and Pendimethalin in Different Cultivars of Tomato (Lycopersicon Esculentum Mill.) and Cabbage (Brassica Oleracea L. Var. Capitata L.)
Dissertation Abstract:
The experiments were conducted to determine the tolerance of various cultivars of tomato and cabbage to butachlor and pendimethalin. The possibility of using activated carbon in protecting cabbages and tomatoes from pendimethalin and butachlor injury was also evaluated.
Tolerance of direct-seeded tomatoes to butchalor varied with cultivar and stage of seedling growth. However, no difference was observed among cultivars of cabbage.
Tomatoes and cabbages were not adversely affected by pre-emergence application of butchalor but were severely injured when the herbicide was applied at post-emergence. On the other hand, both direct-seeded crop species were very susceptible to pendimethalin regardless of cultivar or stage of herbicide application. Butchalor applied at 1.50 kg/ha and 1.0 kg/ha of pendimethalin had little or no effect on growth of both crop species when applied before transplanting. Post-transplanting application of butchalor cause severe foliage injury while pendimethalin inhibited growth and induced malformation of growing shoot.
Results confirmed that under laboratory conditions, both species were more sensitive to pendimethalin than butachlor. Continuous treatment of pendimethalin resulted in swelling of the hypocotyl. The swelling was the morphological manifestation of the enlargement of cells in the stele and cortex. Root thickening was due to the enlargement of cortical cells.
It can be concluded that the tolerance of tomatoes and cabbages to butachlor and pendimethalin was influenced by the concentration of herbicide, stage of seedling growth, depth of seeding, site and time of herbicide application, and type of cultivar.
Application of activated carbon on the soil surface directly over the seeds gave almost complete protection against pendimethalin phytotoxicity but was only slightly effective against butachlor phytotoxicity. Activated carbon applied at the seed level, however, failed to reduce phytotoxicity of either butachlor or pendimethalin. Dipping the root in 10 percent slurry of activated carbon before transplanting was effective in protecting cabbages from pre-transplanting application of either butachlor or pendimethalin but had no effect in transplanted tomatoes.