Orobanche Aegyptiaca - Management

Management

Three main types of control exist for Orobanche aegyptiaca: chemical, cultural, and biological.

Chemical control can be achieved via soil fumigation with methyl bromide. This method is effective yet is rarely used because only a shallow layer of the soil is affected, it is a costly treatment, and methyl bromide poses environmental concerns. Another form of chemical control is soil solarization which is a solar heating of the soil by placing clear polyethylene sheets over moist soil. This kills the majority of seeds that are viable and induces secondary dormancy in the rest. Lastly, sulfonylurea and imidazolinone herbicides have been shown in many studies to be an effective form of chemical control for O. aegyptiaca with the efficacy depending on the method of application, the species of crop, and the timing of the application. One study has shown application times between 14 and 42 days after planting to be ideal for controlling Egyptian Broomrape.

Some forms of cultural control of Orobanche aegyptiaca include sanitation efforts to help prevent the movement of seeds, individual picking of weeds by hand, and avoidance by changing the sowing time or not growing a host plant. Reducing spread of infected soil via farm machinery, avoidance of grazing on infected plants, and staying away from the use of hay produced from "Orobanche"-infested plants are all methods to help prevent the movement of seeds. The individual picking of weeds by hand is very important as the plant is able continue living as only a stem and produce a flower that can spread seeds even while not connected to the host. Any avoidance strategy must be carried out with a plant that cannot be parasitized by "Orobanche aegyptiaca" and could take up to 15–20 years to complete, as this is how long the plant's seeds can remain viable in the soil. Also, because seeds can safely pass through an animal digestive system, it’s important to ensure manure is not contaminated. Another option for cultural control is the use of trap crops or catch crops. Trap crops promote the germination of O. aegyptiaca seeds but will not allow parasitism; these include flax, mung bean, maize, and sorghum. Catch crops allow parasitism but are destroyed before the parasitic plant flowers, so the broomrape seeds cannot be produced and dispersed. Finally, there has been some success with host plant resistance in sunflower, fafa bean, lentil, and tomato but it has been very limited. Resistant cultivars of sunflower were bred in Russia and Spain but quickly lost their host-plant resistance due to selection towards more aggressive biotypes of the plant that had adapted to the new cultivars. In the resistant sunflower cultivars, germination was still induced but the plant's germ tube never develops after penetration by the haustorium. Because has been shown that macromolecules are transferred from the host to the parasite, one method for resistance is the introduction of anti-microbial gene from the flesh fly into the host genome. This allows for its protein product to transferred to the parasite and work as a means of control.

Most forms of biological control are still being developed and studied although studies have shown three species to be potential forms of control: Fusarium oxysporum, Fusarium solani, and Sclerotinia sclerotiorum. Fusarium oxysporum has been shown to successfully control Orobanche aegyptica in sunflower and tobacco while Sclerotinia sclerotiorum has been shown to cause wet rot in the plant without having any negative impact on the host. Field experiments carried out in Hungary showed promise for control with some "Fusarium solani" isolates. The "Fusarium" species usually work through phytotoxins that help them to conquer Orobanche aegyptica 's defenses and establish themselves.