Allelopathic Effects of Lantana (Lantana camara) on Blackjack (Bidens pilosa) and Pearl Millet (Pennisetum glaucum)

Lantana camara L. (Verbanaceae) is an invasive plant widely distributed in Zimbabwe and is toxic to livestock and humans. Greenhouse and laboratory experiments were done at the Crop Science Department, University of Zimbabwe to assess the allelopathic effects of L. camara on Bidens pilosa and pearl millet. First, L. camara biomass was evaluated for its impact on the emergence and growth of B. pilosa and pearl millet, after the addition of 0, 10, 30, 40 and 50 g per pot (18 cm diameter x 17 cm depth each), under glasshouse conditions and adequate moisture conditions. Second, L. camara leaf extracts at 0, 10, 20, 30, 40 and 50 % concentrations were screened for their effects on the germination of B. pilosa and pearl millet under laboratory conditions. Randomized complete block designs, with 6 treatments replicated 4 times were used in both experiments. Lantana camara leaf biomass significantly (p<0.05) reduced the emergence and growth of B. pilosa, when it was added to the soil under glasshouse conditions. In contrast, pearl millet emergence and growth was not affected by L. camara. However, L. camara leaf extracts reduced the germination percentage, radicle length and plumule length of pearl millet under laboratory conditions.