Effect of Glyphosate on Performance of Faba Bean Varieties Under Heavy Infestation of Orobanche crenata

Mahmoud M. Zeid and Mona M. Hemeid

Orobanche crenata is a devastating parasitic weed on faba bean with its effects not confined to the Mediterranean region anymore. This study investigated the effect of number of glyphosate sprays, at the rate of 86g a.i./ha, on the performance of a set of faba bean varieties varying in their resistance to the parasite under farmer’s field conditions. The main target was to find out whether faba bean resistance coupled with glyphosate application could be adopted as standard procedure for efficiently combating the parasite. Results indicated that, under current farmer’s field conditions, spraying resulted in a clear reduction in the number of emerged spikes from 18 to 49% and the amount of photo-assimilates accumulated by the parasite from 1 to 42%, depending on the variety and that was related to the number of sprays applied. There was no improvement in faba bean yield associated with the reduction in infestation under glyphosate sprays compared to the control, even with the most resistant faba bean varieties known in Egypt; namely Giza 843, Misr 1 and Misr 3. Considering its cost and impact on human health, glyphosate is not recommended for infested faba bean fields. In heavily infested fields, it is recommended to employ other integrated pest management protocols that aim at reducing the parasite seed bank per se before considering any winter pulses. This halt on winter pulses is essential to deplete the seed bank and prevent further spread of the parasite and should continue until a better technology to combat the parasite evolves. The new Misr 3 was seen here as a very promising variety that generally combines both good yield and low number of emerged spikes compared to older varieties Giza 843 and Misr 1.

KEY WORDS: hormesis; parasite; broomrape; resistance; Vicia faba.