LITERATURE REVIEW Biology and Management of Cuscuta in Crops W.T. Lanini1 and M. Kogan2 1Department of Plant Science University of California, Davis One Shields Ave, Davis, CA 95616 2Facultad de Agronomía e Ingeniería Forestal Pontificia Universidad Católica de Chile Casilla 306-22, Santiago, Chile Abstract W.T. Lanini and M. Kogan. Biology and management of Cuscuta in crops. Cuscuta is a stem and leaf parasite that infects many broadleaf crops, ornamentals and weeds and a few monocot crops. It lives entirely on the host plant, thus reducing the growth and yield of the host. Preventing infestations by planting crop seed free of Cuscuta seed, rotating to non-host crops, delaying crop planting until fall for sugarbeet (Beta vulgaris), use of resistant varieties or large transplants, and preemergence herbicides have all been shown to be successful in certain crops. Once Cuscuta attaches to a crop, some yield loss will occur, regardless of the method of control, and selective control becomes very difficult. Post attachment control often requires killing or severely injuring the host plant to avoid spread of Cuscuta to surrounding plants. However, several herbicides have been shown to selectively suppress attached Cuscuta, but complete control is rarely obtained. Cuscuta attached to genetically modified, herbicide resistant crops, have not been successfully killed by treatment with herbicide in all cases, indicating that these crops will only be a partial solution to the problem. Cuscuta control will require an integrated approach conducted over a period of many years. Key Words: Cuscuta, dodder, parasitic plant, resistance, weed management. Cien. Inv. Agr. 32(3): 127-141. 2005 INTRODUCCTION as important in Chilean crops. Dodder is a nonspecific parasite that attacks, sometimes The genera Cuscuta (known as dodder) are simultaneously a wide range of host species obligate parasitic plants with approximately including many cultivated plant species and 170 different species distributed throughout dicotyledonous weeds, but not grasses or the world (Holm et al., 1997). Most of the monocotyledonous weeds (Table 1; Dawson 170 species are found primarily in the et al., 1994). Similarly, the same crop may Americas from Canada to Chile of which 7 serve as a host of several dodder species or 8 are known in Chile (Navas, 1979). (Cudney and Lanini, 2000). The dodder Kogan (1992) recognized C. chilensis, C. seedling coils around the host stem and racemosa var. chiliana and C. campestris leaves, penetrates their tissue and vascular Received on 16 March 2005; Accepted on 29 April 2005 1 Corresponding author: W.T. Lanini,[email protected] 128 CIENCIA E INVESTIGACION AGRARIA system via haustoria, and exploits the host throughout the warm seasons. In addition, by withdrawing photosynthates and water the nature of attachment and association (Figure 1). Thus, the vigor of the host is between host and parasite requires a highly lowered and crop production is dramatically selective herbicide to destroy the parasite reduced. Once a seedbank is established, without crop damage (Fer, 1984). This article control is extremely difficult, as dodder seeds reviews the life cycle, distribution and the can remain viable in soil for 20 years or control measures currently used for control more, and continue to germinate and emerge of dodder in crops. A B C Figure 1. Dodder, Cuscuta sp, common obligate parasitic plants. A. Onion field heavily infested with dodder; B. Dodder haustoria (arrow) penetrating tomato stems; C. Dodder wraping (arrow) arrow around tomato stems. VOL 32 N°3 SEPTEMBER - DECEMBER 2005. 129 Table 1. Crops, ornamental plants, and common weeds susceptible to dodder (Cuscuta spp.) infestation. Latin name Common name Crops Monocotyledonous Allium cepa Onion Allium sativum Garlic Dicotyledonous Asparagus officinalis Asparagus Beta vulgaris Sugarbeet Capsicum annuum Pepper Carthamus tinctorius Safflower Citrus spp. Citrus Cucumis melo Melon Cucumis sativus Cucumber Daucus carota Carrot Ipomoea batatas Sweet potato Lycopersicon esculentum Tomato Punica granatum Pomegranate Solanum melongena Eggplant Solanum tuberosum Potato Ornamental Monocotyledonous Impatiens spp. Impatiens Chrysanthemum spp. Chrysanthemum Ipomoea spp. Morningglory Dicotyledonous Satureja hortensis Summer savory Coleus blumei Coleus Geranium spp. Geranium Dahlia merckii Dahlia Parthenocissus quinquefolia Virginia-creeper Campsis radicans Trumpet-vine Hedera helix English ivy Petunia inflata Petunia Foeniculum vulgare Fennel Mentha spp. Mint Origanum majorana Marjoram Catharanthus roseus Periwinkle Weeds Monocotyledonous Solanum nigrum Black nightshade Portulaca oleracea Common purslane Amaranthus blitoides Prostrate pigweed Dicotyledonous Bilderdykia convolvulus Wild buckwheat Convolvulus arvensis Field bindweed Salsola tragus Russian thistle Chenopodium album Lambsquarters DODDER LIFE CYCLE 1987). Favorable soil temperatures for dodder germination and emergence are in Cuscuta seeds germinate independently the range of 15 to 38°C, with an optimum of the presence of host plants (Dawson, around 30°C (Hutchison and Ashton, 130 CIENCIA E INVESTIGACION AGRARIA 1979), which corresponds with the disappear completely (Wolswinkel, 1984). prevailing temperatures during the spring As the dodder plants grow, support is and summer. Because of the seed size (1 maintained by continually reattaching to to 2 mm in diameter), emergence is limited the host. Dodder plants grow about 7 cm to the upper 1 to 1.5 cm of soil. Germi- per day and one plant can cover 3 m2 in a nating seeds will emerge as rootless and growing season. When other suitable hosts long yellow-orange thread-like leafless are nearby, dodder extends and attaches stems, which can grow to 2.5 to 7 cm in to their stems, spreading from one host to height. After germination, the dodder another, often forming a dense vegetative seedling circumnutates in a counter mat of intertwined stems. Flowering can clockwise direction in search of a host occur from late spring through fall, stem or other objects to wind around. It is depending on the species and date of possible that light or humidity may emergence, however seed set is highest in influence growth toward a host plant. the late summer and fall. In a field study These rootless seedlings will generally of dodder (C. pentagona) developing on only attach to hosts that are within a processing tomato, the first dodder flowers distance of 2.5 to 5 cm. Cuscuta seedlings were observed at 51 days after initial possess a rudimentary autotrophic system, attachment and the first viable seeds were containing only a small amount of observed at 60 days after attachment. First chlorophyll (Table 2) and other accessory flowering of dodder was observed to pigments (Dinelli et al., 1993). However, initiate near the point of initial attachment the autotropic system is insufficient to and later flowering progressed out away support growth. Thus, if no suitable host from this point. Once seeds are shed to is found within 3 to 5 days, the seedling the soil they can remain dormant, yet will die. Soon after the connection between viable, in the soil for 10 to 30 or more the parasite and host is established, the years, depending on the species and dodder seedling loses its soil connection environmental conditions. and lives entirely from photosynthates and water extracted from the host plant (Parker Table 2. Content of chlorophyll a and b in and Riches, 1993). Dodder adheres to the Cuscuta campestris, Convolvulus arvensis and host with a cementing layer of pectin and Beta vulgaris. develops haustoria within a few days due Species Organ Chlorophyll a + b to thigmotropic responses and chemical (mg·g-1)1 recognition of the host plants (Press et al., B. vulgaris Leaves 3.91 ± 0.31 1990). The haustoria, single-cell hyphae, C. arvensis Leaves 2.54 ± 0.21 elongates within the host tissue and meets C. campestris Stems 0.28 ± 0.02 the vascular bundles, where they From: Dinelli et al., 1993. differentiate into xylem and phloem 1Based on dry matter measurements. ±Standard elements. This highly efficient absorption deviation system allows the parasite to divert resources - water, amino acids and Economical Importance and geographical assimilates - from the host into the parasite distribution (Dorr, 1987). It has been shown that when The wide geographical distribution of Cuscuta and developing seeds from the dodders (Table 3) and their wide range of host plant fruit compete for assimilates, hosts, make them amongst the most the sink activity of dodder is much stronger damaging parasites worldwide (Parker and while the sink activity of the fruit can Riches, 1993). Studies have shown that VOL 32 N°3 SEPTEMBER - DECEMBER 2005. 131 field dodder (C. pentagona) infestation production by more that 50% (Cudney et reduced tomato (Lycopersicumal., 1992). Where present in harvested esculentum) yield by 50 to 75% (Table 4; alfalfa, its moist stems will not allow the Lanini, 2004). It was shown that field hay to cure properly resulting in moldy, dodder infestation reduced carrot (Daucus unmarketable hay. Other legume crops carota) yield by 70 to 90% (Bewick et al., vary in their sensitivity to dodders. Bean 1988). Dodder is also considered a (Phaseolus spp.) was reported as resistant troublesome weed in onion (Allium cepa). to China dodder (C. chinensis) (Rao and Rubin (1990) stated that onion fields Reddy, 1987) and to field dodder in India heavily infested with dodder should be (Nemli, 1987), but sensitive to C. destroyed, as there is no selective herbicide lupuliformis in France (Liu et al., 1991). to control it available for this crop. In On the other hand, China dodder is a carrots or onions infested with dodder, the noxious weed in soybean (Glycine max) roots or bulbs, respectively, fail to reach in China (Li, 1987). Ornamental shrubs, a marketable size. When multiple dodder trees and groundcovers are often infested plants attack the same host (tomato) plant, with dodder (Table 1). Dodder infestations death of the host often occurs. Alfalfa are readily apparent along roadsides in (Medicago sativa) and clover (Trifolium weeds, shrubs and trees. Host plants are pratense) are the most common crops rarely killed by dodder infestation.