Parasitic Plants in Agriculture and Management

*Pervin Erdogan*

### **Abstract**

Parasitic plants are among the most problematic pests of agricultural crops worldwide. They are found worldwide in all plant communities except aquatic. Parasitic plants are the organisms that settle in the host plant by means of the special organs they have developed and penetrate the vascular tissues of the hosts and meet their nutritional, water and mineral needs from the host plant. This particular body they have is called a haustorium. The discovery and investigation of the haustorium structures led to the evaluation of many heterotrophic plant species previously defined as parasitic plants in different groups. Host organisms are very important in completing the life cycle of parasitic plants. In general, the parasite weakens the host, so it produces fewer flowers and viable seeds or the value of the timber is reduced. However, some parasites, mostly annual root parasites belonging to the Orobanchaceae, can kill the host and cause significant economic damage while attacking monocultures in agriculture, and much effort is put into controlling these harmful parasites. Parasitic weeds are difficult to control because there are few resources for crop resistance and it is difficult to apply sufficiently selective control methods to kill weeds without physically and biochemically damaging the crop to which they are attached.

**Keywords:** Plants, Parasitic, Species, Agriculture

#### **1. Introduction**

Parasitic plants are among the most problematic pests of agricultural crops worldwide. About 4000 parasitic plants exploit another plant vascular system to fulfill their nutrient requirements. The majority, about 90% of these species are hemiparasites retaining photosynthetic capacity while the rest, 390 species are holoparasites with obligate dependence on the host to obtain all their nutrients [1, 2]. They are extremely morphologically diverse and range from diminutive herbaceous plants to large trees, as well as highly reduced parasites that grow embedded in their host and lack leaves and roots. Parasitic plants can be divided according to whether they are photosynthetically active (hemiparasites) or lack of photosynthetic activity, and whether they are completely attached to a host for carbon (holoparasites), whether they are optional or obligate parasites, and whether they are attached to the roots or stem of the host. In natural ecosystems, parasitic plants form a component of the plant community and contribute to the overall community balance of parasitism. Conversely, when parasitic plants are established in low biodiverse agroecosystems, their persistence causes enormous yield losses and renders agricultural land inoperable. It has been determined that many features from seed germination

to haustorium formation, from feeding patterns to host selection are based on the relationships between the host and the parasite [3].

Parasitic plants change in host dependence of and the rate at which they can attach. Facultative hemiparasites complete their life cycle without the need for a host. Also, obligate parasites (can be hemi- or holoparasites) need host to survive and reproduce. Most of facultative parasites have a broad range of hosts. For example, *Rhinanthus* attach to more than fifty species of herbaceous plants and grasses. Obligate parasites (especially holoparasites) more likely to specialize in a single host plant species or a narrow host range, and host shifts can be included speciation. Parasitic plants should synchronize their life cycle with the host for maximum fitness. Tiny seeds of obligate root parasites such as *Striga* germinate only after a conditioning period at the appropriate temperature, then are exposed to host-derived chemical signals such as strigalactones that are extruded by the host's roots to signal symbiotic arbuscular mycorrhiza in the soil [4].

Holoparasities and hemiparasites develop haustoria. There are two types of houstria. Primary haustorium develops directly from the primary root apex. It is the only haustorium to function during the parasite's lifetime. When only the primary haustorium is present, the parasite is considered evolutionarily more advanced. The development of primary haustorim made holoparasitism possible because holoparasites with small seeds usually require water, and nutrients from a host immediately after germination [5].

Parasitism appeared several times independently during angiosperm evolution, and the lifestyles of parasitic plants vary widely between taxa [1]. Some species are optional parasites that can survive in the absence of a host, others are necessarily parasitic and cannot develop independently. A distinction can be made between hemiparasitic herbs containing chlorophyll and can produce some of the essential nutrients through photosynthesis, and holoparasitic plants that do not contain chlorophyll and are completely dependent on host sources, but this distinction is not always clear [6, 7]. They pose a tremendous threat to the world economy because they are virtually uncontrollable at the moment [8, 9]. They belong to a variety of plant families and are attached to host roots, shoots or branches. The mistletoes like *Viscum* and *Arceuthoubium* that parasities trees, climbers like *Cuscuta* that parasitise shoots, and parasites like Striga and *Orobanche* that connect to host roots [3].

#### **1.1 Parasitic plants**

Weed parasites, usually unique to the host, do their greatest damage before they emerge; therefore, most crop yield loss may occur before infection is diagnosed. Despite intense efforts in the twentieth century, effective ways to selectively control various parasitic weed species are still scary or absent. While all agricultural weeds compete with crops for the field to obtain water, nutrients and light, parasitic weeds are also particularly harmful as they extract valuable water and nutrients directly from the host plant. To extract nutrients from host plants, parasitic weeds have developed a unique multicellular structure called the haustorium that invades the host, connects with the host vascular system and draws the water and nutrients it needs [10, 11]. A successful haustorial connection to the host causes permanent damage to a large part of the crop's life cycle, lowering the harvested yield, lowering the crop value, and contaminating it with parasitic seeds. Parasitic weed infection strongly reduces crop harvest by disrupting crop orchestration of resource allocation by altering dry matter partitioning between crop organs that prioritize those adjacent to the [12].

*Parasitic Plants in Agriculture and Management DOI: http://dx.doi.org/10.5772/intechopen.98760*

#### *1.1.1 Mistletoe*

Mistletoe (*Viscum album* L.), (Viscaceae) whose distribution areas are widening in the world, is a semi-parasitic plant that lives by sucking the sap of the host plants it lives in, thus harming its host. It has small bushes, leaves and is an evergreen plant. "Zodiac sign" and are also known by the names of "chekem". Rosaceae like apple and pear (Rosaceae) family trees semi parasitic lives on its branches. It can also be found in other trees. The plant can withstand several seasons leathery leaves, narrow and is long. The flowers, the seats of the shoots and yellowish-green is colored. The end of autumn and the beginning of winter the size of a pea. It was white and bright (**Figure 1**). Mistletoe lives as a semi-parasite on nearly 200 plant species, including fruit and forest trees and ornamental plant. This plant can cause losses in many economically important crops. Pear, plum, apricot, apple, almond, pear, walnut, chestnut is some of them. Along with these, the wood quality of trees such as willow, poplar and oak decreases [15].

The way mistletoe spreads are quite interesting, with all leaves, flowers monogamous and sticky, juicy and soft fruit. Thanks to its sticky structure, the seeds that stick to the beaks and feet of the birds or the birds that eat the fruits, especially the junipers, leave their feces on the trees they put on, and the seeds continue to grow by germinating on the tree they are transported. The germinated mistletoe seeds pierce the bark of the tree and reach their suckers down to the wood pipes and share the water and mineral substances of the host. Yield losses of up to 50 percent can be seen in sensitive fruits due to mistletoe Mistletoe provides its food by inserting its

#### **Figure 1***.*

*a) Entry of triple suckers from* Viscum album *seed to plant tissue, b)* Viscum album *L., [13], c) swelling in the branch of the Ankara pear of* V. album.*, [14], d) damage of the* V. album *damage (*trwikipedia.org*).*

#### *Parasitic Plants*

suckers into the trunks and branches of fruit, park and forest trees. Swelling is seen in these parts. It weakens the host tree, decreases the yield, and sometimes causes the old trees to dry. The fruits are spherical and the abundant viscin substance in the fruit flesh provides the stickiness of the fruit and the seed [16]. The stem of the plant lives dependent on the host, if it cannot find a host, it cannot survive. Seed need to attach to the host in germination the duration is known to be 3–5 weeks. By moving the jab body end counterclockwise hugs the host he reaches. Of the held body parasitic plant from the host facing surface, it dips suckers to his host and these suckers connects with its host phloem and xylem. They typically exhibiting broad host ranges, and inflict serious damage to many crops, including forage legumes (alfalfa, clover, lespedeza), potato, carrot, sugar beets, chickpea, onion, cranberry, blueberry, and citrus [17].
