Cuscuta spp. (Dodder):

cA Literature RevieW" of Its Biology and Control

Division of Agricultural Sciences BULLETIN UNIVERSITY OF CALIFORNIA 1880 P RINTED AUGUST 1976 This review cites and summarizes lite.rature published for the last 25 years on Cuscuta spp. (dodder) - parasitic plants that attack many commercial crops in California, as well as other plant pests in themselves hard to control. Following the introduction, the review is organized topically in the following sequence: taxonomy, host species, disease transmission, flower and seed formations, dormancy and germination, anatomy and cytology, biology, chemical com­ position, metabolism, translocation, growth and development, chemical control, biological control, and cultural control.

2 Cuscuta spp. (Dodder): A LITERATURE REVIEW OF ITS BIOLOGY AND CONTROL

A single dodder plant may cover mum) or swamp dodder (C. gro­ INTRODUCTION several square feet and produce novii), and largeseed dodder (C. thousands of "hard" seeds, the indecora). primary method of reproduction. Cuscuta (dodder) are parasitic Some seeds germinate the season This review summarizes the liter­ plants with slender thread-like, after they are produced, but many ature on dodder that has been yellow-to-orange, twining stems, will remain dormant in the soil for published since Gaertner's (1950) and inconspicuous flowers that coil years. Therefore, once a field publication, "Studies of Germina­ about and fasten to their host plants becomes infested with dodder seed, tion, Seed Identification, and Host with wart-like attachments called it may be a problem for several Realtionships in Dodder, Cuscuta haustoria. About 170 species of this years - even though no additional spp." Occasionally, it is necessary to genus occur; Munz (1963) lists 16 in seed are produced. In the labor­ cite some of the older literature in California. atory, "hard-seed" dormancy of order to put the subject in prospec­ dodder seed can be broken by soak­ tive. Well over a thousand publi­ Tomatoes and alfalfa are the pri­ ing the seeds in concentrated cations have been written in at mary commercial crops parasi­ sulfuric acid or by scarification. Cer­ least a dozen languages since 1950. tized by dodder in California. tain species have been reported to Tomatoes are usually attacked by overwinter in the stems of some Following the introduction, this Cuscuta campestris, but in San Joa­ woody plants, although dodder is review has been topically organized quin County C. californica has also usually an annual. in the following sequence: tax­ been a problem. Alfalfa has been onomy, host species, disease reported to be attacked by C. In the field, dodder seeds germinate transmission, flower and seed for­ campestris, C. indecora, C. epi­ in the soil and are dependent initial­ mations, dormancy and germina­ thymum, C. planiflora, and C. ly upon the food stored within the tion, anatomy and cytology, biol­ racemosa. The first two species are seed. The dodder plant will die if it ogy, chemical corporation, metab­ probably the most serious. Aspar­ does not attach to a suitable host olism, translocation, growth and agus, clovers, cucurbits, and plant within several days after ger­ development, chemical control, bio­ onions are also parasitized by dod­ mination, since it cannot produce logical control, and cultural con­ der; C. campestris and/or C. the food necessary to sustain its trol. californica and perhaps other dod­ growth. Once a dodder plant has at­ der species are involved. Citrus tached attached to a host plant, orchards and citrus nursery stock the part of the dodder stem between TAXONOMY plantings have been invaded by C. the point of attachment and the soil subinclusa. This species has also dies. Then the dodder plant is total­ Gaertner (1950) reviewed the tax­ been found in a number of naturally ly dependent on the host plant for onomic history of Cuscuta. The occuring woody species including its food, inorganic salts, and water. genus Cuscuta was first established Ceanothus, Rhus, Prunus, Sal'ix, Consequently, the host plant has by Tournefort in 1700 and has since Aesculus, Sambucus, Eriogonum, less food for its own growth and been monographed four times, most and Quercus. Many common her­ yields of crop plants are reduced. recently by Yuncker (1932). Be­ baceous annual and perennial cause of the ecotylendonous na­ weedy species also are hosts for cer­ Some of the common names used for ture of the embryo, Cuscitta was tain dodder species; i.e., C. Cuscuta, besides dodder, are tangle first believed to be a monocot. campestris has been found in gut, love vine, strangle gut, devil's However, taxonomist now consider knotweed, pigweed, lambsquarters, gut, witch's shoelaces, and angel's Cuscuta to be a member of the field bindweed, cheeseweed, mal­ hair. In general, we have used the · Dicotyledoneae. low, and alkali mallow. The fact scientific names given by the that many of the hosts of dodder authors for these species. However; Although there is some controversy species that are problems to for a few species that are mentioned on whether the genus belongs in the agriculture are also parasitic on frequently, we have used the com­ Convolvulaceae or in the Cus­ naturally occuring plants makes mon names - field dodder ( C. cutaceae, most taxonomists place eradication impossible and control campestris ), flax dodder (C. ep­ it in the Cuscutaceae. Munz and most difficult. ilinum), clover dodder (C. epithy-. Keck (1959) place heavy taxonomic

3 emphasis on cuscuta's parasitic reduction before developing new of three groups: (1) as a good food habit and considers the Cuscutaceae adaptations peculiar to its peculiar provider for dodder; (2) as a host on to be composed of the single genus, parasitic habit (Searcy, 1970; Sear­ which dodder can survive; (3) as a Cuscuta. cy and Macinnis, 1970). plant serving only to support dod­ der. Gaertner also praises Dean Yuncker's (1965) final contribution The possibility of polyploidy as an (1934, 1935) for his species-host list to the study was published post­ influence in the development of this of the United States. Although humously and is the only signifi­ genus is an intriguing question in Yuncker's (1932) monograph is an cant recent publication on the need of additional study. Moreover, excellent taxonomic addition, it con­ taxonomy of Cuscuta. Most of the as indicated in other sections of this tains no new relevant data on host information reviewed here is de­ review, data from field observations species. rived from Yuncker's two publica­ of floral biology, host relationship, tions. and general biology will no doubt in­ The results of Gaertner's study are fluence taxonomic judgements. compiled into two lists. The names The genus Cuscuta has a sub­ of 609 species parasitized by dodder cosmopolitan distribution. Al­ are presented by family in the first though some species are found in list. There is some experimental Africa, Australia, New Zealand, HOST SPECIES data for 55 of the 609 species. The Polynesia, Asia, and Europe; most names of 118 species immune to of the 170 species are found primari­ dodder are presented in a second ly in the Americas from Canada to list. Argentina. The seeds of some spe­ Since Gaertner's review of the lit­ erature in 1950, few publications cies, such as C. campestris, C. suaveolens, C. epilinum, C. epi­ have expanded our knowledge on From her literature review and ex­ thymum and C. approximata are host species of dodder; further­ periments, Gaertner concludes believed to have been accidently more, her suggested lines of in­ that: vestigation have not been fol­ dispersed along with the seeds of (1) Data on species parasitized their economic hosts. lowed. Gaertner (1950) has re­ viewed the literature on host by and species immune to species. With her 1950 review, she dodder are generally lacking; Taxonomic characters are primarily presented data from her exper­ (2) According to preliminary in­ limited to the flowers and in­ iments using material from the vestigation using nine po­ florescence. Moreover, on the following species: Cuscuta camp­ tential hosts, no species of basis of style and stigma characters, es tris, C. epilinum, C. epi­ dodder is limited to one host the genus is divided into three thymum, C. epithymum var. alba, species; subgenera. Gram mica has the C. glomerata, C. europaea, C. (3) Succulents are frequently widest distribution and is believed gronovii, C. lupuliformis, C. pen­ parasitized by dodder; to have given rise to the two other tagona, and C. suaveolens. (4) The age of the host as it af­ subgenera, Cuscuta and Monogyna. fects its growth may pro­ However, all native American spe­ According to Gaertner, problems in vide mechanical obstruc­ cies are members of the subgenera rearing both the parasite and poten­ tion to parasitism; Gram mica. tial host reduced the amount of (5) Survival and reproductive new experimental data she could capacities of the parasite are Although chromosome numbers for present. Field dodder ( Cuscuta dependent on the physio­ a few species have been reported, campestris), for example, was found logical condition of the neither of Yuncker's publications at various times to be thriving or host. (1932, 1965) contained this data. dying on tomato (Lycopersicon Three of the sixteen Californian esculentum). In this example, she cuscutas have chromosome numbers suggested that the varying results Host-parasite Relationship of 2N = 50 and 2N = 60 (Munz and were due to imbalances in the age of Keck, 1959). These numbers are the parasite and potential host. Olifirenko (1961) has compiled a list similar to the chromosome numbers Hence, Gaertner's conclusions re­ of 68 host species parasitized by first reported by Gaertner (1950) in lied heavily on reports in the Cuscuta arvensis. He is one of the her review of Cuscuta taxonomy. literature with supplements of her few individuals who has made field Gaertner suggested that the basic own research. She also implied the observations, noting that some chromosome number for the genus need to be aware that many prev­ plants (sunflower, timothy grass, is X = 7. She also raised the pros­ ious reports may be fraught with and black poplar) are only weakly pect that some species with high inaccuracies. Such reports should be affected by C. arvensis. chromosome numbers may be the verified. result of polyploidy. Table 1 shows the host species Gaertner recognizes Krohn (1934) to parasitized by six dodder species Finally, speculation based on ex­ be the first botanist to report that from collections made by various in­ perimental DNA hybridization not all plants are susceptible to di vid ua ls in California during studies, indicate that Cuscuta may parasitism from dodder. Krohn 1973. A total of 54 specimens were have originally undergone a genome classified all potential hosts into one identified.

4 TABLE 1. DODDER SPECIES FOUND IN CALIFORNIA AND HOST PLANTS1

Cuscuta spp. Host plant

campestris tomato knot weed pigweed lambsquarters field bindweed cheeseweed sugar beet alfalfa asparagus mallow alkali mallow honeydew melon

californica tomato onions ivy suksdorfi var. subpedicellata Eriogonum Fig. 1. Flowers of C. campestris. Left, 42.5 X; right 100 X. Scanning electron indecora alfalfa photomicrographs by Richard H. Falk. Sa/sofa Chenopodium

salina var. major Sa/icornia

subinc/usa elderberry Cuscuta europaea were not affected when carrying toma to-aspermie FLOWER AND SEED 1 Ashton, F. M. and J. McCaskill (unpublished data). virus from host plant to test plant. However, both the test plant and FORMATION dodder were severely deformed DISEASE when attempting to transfer a virus called GMV. Only a limited amount of research TRANSMISSION has been conducted on flower induc­ In other experiments, dodder has tion and seed formation in dodder. been used successfully to transfer a In general, information on the floral Plant pathologists have often used virus from plant to plant without be­ biology, including pollination, is one of the following methods to ing deformed by the pathogen. needed. Meanwhile, however, transfer a virus or fungus from one Greber (1966) reported that Cuscuta Gaertner (1950) reviewed the host to another: (1) grafting a virus­ austra/,is was successfully employed literature and confirmed some infected host onto the test plant; in transferring yellow crinkle earlier observations on flower and (2) using sucking insects to transfer disease from papaw to tomato, seed formation. Cuscuta suave­ viruses; and (3) training dodder, white clover, and Datura stra­ olens, parasitizing aquatic plants parasitizing a host infected with a monium. The virus causing yellow such as Alternanthera philoxroi,d,a virus, onto a test plant. crinkle disease in papaw brought on and vasturtium officinale, were big bud symptoms in tomato. When observed by early botanists and by The main purpose of the research the virus causing bud symtoms in Gaertner not only to develop vig­ reviewed here was to characterize tomato was transferred to papaw, orously but to flower profusely, the effects of known virus stocks on yellow crinkle disease symptoms oc­ even when both host and parasite different hosts. curred in papaw. are submerged underwater for several days. Aside from an incidental report that Marchoux, Lechlant, and Giannotti a species of dodder could not be (1970) successfully transferred Gaertner also noted that host used to transfer a fungal disease yellow strain virus of Convolvulus physiology not only affects parasite termed frenching (Mandryk, 1969), arvensis to Vinca rosea and other survival, but that flower and seed most of the dodder disease­ solanaceous plants via field dodder production are affected as well. transmission literature involves and C. subinclusa. The purpose of Mor_eover, if vegetative growth of virus transmission from host plant the experiment was to compare the host was near completion when to test plant via dodder. stolbur of tomato to the yellow . becoming parasitized by dodder, strain virus. Symptoms in the then flowers and seeds were not In some cases, the pathogen de­ solanaceous plants brought on by produced by the parasite. She also forms dodder as well as the test the yellow strain virus were observed that some dodder species plant. Schmelzer (1957) for exam­ reported to be comparable to stol­ flowered wh·en the host did, ple, reported that field dodder and bur. regardless of day length.

5 Fig. 2. Emergence of rad ical from germinating C. Campestris seed. Upper left, 6 hours, 40 X; upper right, 9 hours, 40 X; lower . left, 12 hours, 25 X; lower right, 24 hours, 20 X. Scanning electron photomicrographs by James Hutchison and F. D. Hess.

6 Two recent investigations on floral transmitted from the noninduced induction of Cuscuta reflexa using in member to the induced member via vitro material were conducted in the dodder "bridge." California and in East Germany. Baldev (1962) reported that stem Plants parasitized by dodder but tips of C. reflexa flowered when otherwise healthy have been re­ they were maintained in continuous ported to produce fewer flowers darkness or in a light-dark regime of than unparasitized plants. Ac­ 10 and 14 hours, respectively. He cording to Resende (1953), Kal­ proposed that C. refl,exa is a short­ anchoe blossJel.dvana var. feuer­ day plant. Moreover, he suggest­ blute flowers less when parasi­ ed that the bud itself is sensitive tized by flax dodder. to photoinduction, and that no flower-forming substance is trans­ All species of dodder appear to have mitted from one plant to another. the polygonum type of embryo sac Jacob (1966) also working with development except Cuscuta re­ saprophytic cultures of C. reflexa fl,exa, which has the allium type of reported that a maximal flower re­ embryo sac development (J ohri and sponse occurred after a single in­ Tiagi, 1952). ductive period of at least 120 to 140 hours of darkness. He agreed that C. refl,exa is a short-day plant. However, he found that floral induc­ DORMANCY AND tion takes place in isolated buds GERMINATION and that no flowering hormone is transmitted from an induced bud to a non-induced bud. Information on the natural germina­ tion of dodder seed is relatively The results of experiments con­ meager. Gaertner (1950), however, ducted by Fratianne (1965) some­ studied seed germination of swamp what contradict the results re­ dodder, field dodder, Cuscuta ce­ ported by Baldev (1962) and Jacob phal,anthi and C. obtusiflora in the (1966). Fratianne reported field greenhouse. She concluded that: (1) dodder parasitizing Xanthium pen­ Given favorable conditions, dodder sylvanicum (short-day plant) and seed can readily germinate even Glycine max var. biwxi (long-day while still in the fruit. (2) Seed dor­ plant) flowers only when its host is mancy is at least partly due to the in flower. Unlike Resende's (1953) seed coat drying out and becoming observation, Fratianne reported impermeable. (3) Dormancy can be that flowering in the host plant is broken if the seed are subjected to unaffected by parasitism of field concentrated sulfuric acid (a method Fig. 3. Apex of germinating C. campestris dodder. In an experiment conducted originating with Kinzel,1901) for a seedl ing. Upper, 500 X; lower, 20 X. Scanning by Fratianne, leaves from the host predetermined time. (4) The lon­ electron photomicrographs by James Hutchi­ son and F. D. Hess (soybean) were removed. The pre­ gevity of dormancy varies for each viously nonflowering dodder be­ species; for example, the seed of gan to flower. These results sug­ swamp dodder can remain viable for gested that during non-inductive at least 30 years, and the seed of C. photoperiods, the host may produce cuspidata as long as 61 years. a substance that inhibits dodder from flowering. To test this hy­ pothesis, Fratianne used pairs of Dormancy soybean plants linked together only by a living intact dodder plant. One Menke (1954) reported that under member of each soybean pair was field conditions dodder seed can re­ According to Gaertner, some spe­ kept on non-inductive long photo­ main dormant for as long as ten cies such as flax dodder (Cuscuta periods while the other member years. Dormancy may be promoted epithymum] are self pollinated, was kept on inductive short by a water-soluble inhibitor (located while other species such as field photoperiods. The results indicated in the seed coat) however, the dodder, swamp dodder (C. grono­ that no flower hormone is transmit­ nature of the inhibitor is unknown vii), and C. obtusiflora, need to be ted from the induced to the non­ (Tronchet, 1961). Dormancy can be cross-pollinated by insects of the induced soybean partner. How­ used to an advantage in research, Sphegidae to produce seed. Only a ever, since the induced partner since the stratified seeds can be few seed were produced by hand showed a "definite weaker flower­ dried and stored for long periods pollination of the flowers of C. ing," pattern, it was suggested (Gaertner, 1956) and later studied suaveolens and C. subinclusa. that a flower-hormone inhibitor was at a more convenient time. 7 Fig . 4. Seeds of C. campestris. Upper left, untreated, 50 X; upper right, untreated, 1200 X; center left, scarified with sand paper, 50 X ; center right, scarified with sand paper, 1200 X ; lower left, concentrated sulfuric acid (60 minutes), 50 X; lower right , concentrated sulfuric acid (60 minutes), 1200 X. Scanning electron photomicrographs by James Hutchison and Robert Bowman.

8 Germination Induced by Chemicals days later, large-seeded dodder ger­ TABLE 2. SIZES OF Cuscuta SEED 1 minated at 51 °F, and field dodder Seed of clover dodder (Bertossi, began to germinate 2 or 4 days after Cuscuta spp. Seed size (mm) : 1957), Cuscuta approximata (Tingey large-seed dodder. Very few seeds Range Average and Allred, 1961), and C. chinensis of C. approxi'mata germinated after, (Hassawy, 1973) have been success­ mid-May, but seeds of the latter two epilinum 0.86 - 1.46 1.25 fully germinated using the con­ continued to germinate throughout plaiflora 0.86 - 1.07 0.99 centrated sulfuric acid method. the summer. In Yugoslavia, the epithymum 0.80 - 1.10 0.90 Excess water has also been found seed of C. trifoli"i, C. prodani and C. glomerata 1.50 - 2.06 1.70 useful for germinating the seeds of tinei germinated best at 20°C campestris 1.12 - 1.50 1.34 cephalanthi 1.67 - 2.32 1.90 clover dodder (Bertossi, 1957) and (68°F), while seed of field dodder, obtusiflora 1.37 - 1.85 1.50 swamp dodder (Tronchet, 1962); C. pentagona, C. lupuliformis, and gronovii 1.07 -1.93 1.55 however, Bertossi noted that "abun­ C. monogyna germinated best be­ indecora 1.20 - 1.89 1.42 dant moisture has an inhibitory ef­ tween 30 to 33°C (86 to 91 °F) (Sto­ 1 fect on seed germination." While janovic and Mijatovic, 1973). Anal yzed by Gaertner (1950) . testing the effects of herbicides on Olifirenko (1959) observed the ger­ field and largeseed dodder, Dawson mination of dodder seed in the Stem Anatomy (1967) noted that diphenitrile pro­ field and found that germination oc­ moted seed germination of these curred at 14.2°C (56.6°F). Stem anatomy of dodder, aside from species. Attempts to germinate the haustorium, has not received dodder seed with other chemicals the careful scrutiny that stem such as B-complex vitamins and anatomy of autotrophic plants has auxin have not been successful (Ber­ received. However, there are a few tossi, 1957). reports, two experimental and ANATOMY AND three descriptive, that are of in­ CYTOLOGY terest. Germination Induced by Tronchet (1960) studied the effects Mechanical Means of colchicine and an inhibitor on Seed Anatomy stem structure. The inhibitor was Scarification of the seed coat has extracted from the seed of swamp proved useful for some dodder A brief review of dodder seed dodder. These materials produced species. Walzel (1952b) found that anatomy is given by Gaertner tumors in seedlings of swamp dod­ abrasion of the seeds of swamp dod­ (1950). The species studied by der. der with glass dust in almost total Gaertner are listed in table 2. On darkness resulted in quick and equal the basis of seed size, species of dod­ Libbert and Urban (1967) reported germination. In our laboratory, rub­ der are often grouped into one or that Cuscuta lupuliformis, unlike bing seeds between fine sand two categories: (1) species with most dodder, possesses remainders paper gave almost 100 percent ger­ seeds 1. 3 mm or more in diameter of a fascicular cambium. They found mination of field dodder, and, in are termed largeseeded dodder; (2) that the fascicular cambium activity general, this method was easier species with seed 1 mm or smaller in can be increased by applying IAA than the sulfuric acid treatment. In diameter are termed small-seeded (3-indol acetic acid). Attempts to tests comparing scarification versus dodder. These terms are sometimes simulate the activity of the sulfuric acid treatment for C. ap­ useful, but they, do not provide cer­ fascicular cambium with IAA ap­ proxima ta, Tingey and Allred tain identification of species. Seed plications on the host (Coleus), or (1961) found that scarification was color varies from gray to brown by applying kinetin, or by making the less effective of the two. depending on cuticle thickness. Sur­ incisions on dodder were not suc­ face reticulation of the seed coat is cessful. due to the collapse of the outer tangential wall of the seed coat. MacLeod (1961, 1962) studied stem Other Factors Influencing Moreover, the seed coat is com­ anatomy and physiology of Cusuta Germination posed of four layers of cells; the reflexa and field dodder. He ob­ outer three-cell layers are species served that the dodder stem forms Ambient and soil temperatures can specific, while the inner layer of a tight coil, the haustorial coil, influence the germination of dodder cells of the seed coat are often around the host. The haustorium is seed. Allred and Tingey (1964) de­ disrupted during seed formation a specialized structure that pene­ termined that seeds of large-seed and are thus taxonomically value­ trates the host opposite its vas­ dodder, field dodder, and Cuscuta less. The ecotyledonous embryo cular bundle. Hyphae extend from approximata germinated best at may be either twisted, double the tip of the haustorium into the 60°F and above in greenhouse ex­ spiral, or spiral in one plane. Using host and are believed to be at­ periments. From field experi­ the preceding set of characteristics, tracted to the host vascular bun­ ments, they found that seeds of C. Gaertner devised a dichotomous key dles. The hyphae have well de­ approximata germinated first at a for use in identifying the ten species fined sieve-like areas that corres­ soil temperature of 39°F; 7 to 10 she studied. pond to the sieve plate of sieve

9 elements in higher plants. Doerr was recorded in field dodder and C. it may lie dormant from 4 to 5 weeks (1967) and Kollmann and Doerr reflexa, although chloroplasts were before dying (Lee and Timmons, (1969) investigated the hyphae of not found in field dodder. To ac­ 1958). If a suitable host is parasi­ Cuscuta odorata parasitizing count for the absence of chlor­ tized, the seedling terminates its Pel,argonium zonal,e and Primul,a ob­ oplast, MacLeod suggested the connections with the soil. conica. According to these two presence of chlorophyll in orange reports, a hypha changes in struc­ plastids or chromoplast. After seedlings of Cuscuta arvensis ture and content from the time it become attached to a host by the penetrates the host tissue until it haustoria, the stem changes from begins to conduct food to the ex­ yellow to orange. It then begins to ternal dodder plant parts. The tip BIOLOGY lengthen beyond the haustorial coil of the penetrating hyphae always and branch (Bezrutchenko, 1947). A retains its cell wall and is rich in single seedling can grow and finally organelles as it grows between host Life History cover 10 to 15 square feet of alfalfa cells and into the lumen of a phloem (Loveridge, 1966). cell. The hyphal wall becomes lig­ Our knowledge of dodder life nified from the internal region of history is based on studies of a few the hypha back to the haustorium, taxa that are serious pests of as food material begins to pass economically important plants. Reproductive Biology through plasmadesma to the para­ site. By this time, hyphae have Seed germination involves develop­ Dodder can produce new individuals surrounded the host sieve tubes and ment of the embryo. Tronchet by seed or by asexual means. The vessels with many finger like projec­ (1961) reported that seed germina­ sexual means of reproduction were tions; the tonoplast and the nu­ tion of swamp dodder terminates 5 discussed previously in "Flower and cleus are no longer detectable at days after the proximal or "radi­ Seed Formation." the tip of the hypha. cular" end penetrates through the integument and curves in an op­ New individuals can be generated Loo (1946) reported the successful posite direction to the curvature from scraps broken off from an in­ in vitro culture of field dodder stem of the coiled, resting embryo. tact active parent (Olifirenko, tips. These in vitro stem tips could 1959). Exactly what portions of the be kept for periods of 5 months Seven days after germination is plant will regenerate new growth is through many transfers. Lateral completed, the individual seedling uncertain. Cuscuta trifolii and C. ap­ buds and flowers were produced emerges from the soil (Olifirenko, proximata can overwinter in the from the excised tips without forma­ 1959). The seedlings of some species crowns of legumes or weeds in the tion of leaves or roots. Ma­ such as Cuscuta lupuliformis and C. European areas that are subject to heshwari and Baldev (1961) cul­ monogyna of Yugoslavia and the frost. Furthermore, Dean (1954) has tured adventive embryos from North American species have been successfully demonstrated that dodder embryos and ovules. The observed to emerge from as deep as haustorial tissue can overwinter in adventive embryos share many 10 cm. below the surface of the soil dodder-induced galls. similar stages of development with (Dawson, 1965; Stojanovic and Mi­ normal dodder embryos. However, jatovic, 1973). The source of nour­ most adventive embryos eventually ishment for the emerging seedling became callused. This callus was is the food stored in the seed. There Dispersal capable of producing a fresh crop of are some claims that some species adventive embryos. have roots (Loveridge, 1966). How­ Dodder seed and plant fragments ever, dodder is generally believed were no doubt transported across to have only rudimentary roots and great distances before the enforce­ Plastids leaves. ment of strict govermental regu­ lations. The amount and exact MacLeod (1962) has studied the Once above ground, growth of the method of dodder transportation distribution and association of seedling is in a circumnutative pat­ under cultivation and natural condi­ chlorophyll in various types of tern until it contacts a possible tions is difficult to determine. plastids presents in Cuscuta reflexa host. Bezrutchenko (1947) has and field dodder. Depending on the observed seedlings of Cuscuta In agricultural areas, dodder seeds species, "chlorophyll" green color arvensis making contact with a host are thought to be transported by: has been observed in the pith, as early as 2 and as late as 6 days (1) water, (2) the sowing of fields vascular bundles, cortex, and after germination in the field. Other with contaminated seed, (3) animal flowers of both species. Under poor species of dodder are known to movement and later dropping in­ growing conditions, field dodder make contact with a host as late as gested seed, or (4) farm equip­ stems change colors from orange to the ninth day after germination ment. Stem fragments may also yellow or green. This color change is (Olifirenko, 1959). However, if a be transported to new areas, where, thought to be due to a change in the dodder seedling does not contact a if they remain viable, they can in­ plastid complement. Photosynthesis suitable host soon after emergence, fect a new host (Urton, 1945).

10 the control plants. Although no function for the phenolics could be CHEMICAL found, it was suggested that phen­ METABOLISM COMPOSITION olics do not appear to impart to the host a resistance or susceptibili­ ty to parasite infection. Contrary to popular belief, photo­ Mature Plant synthesis has been confirmed in a In the section Chemical Control of number of dodder species. How­ Although the general chemical com­ this paper, the effect of shading on ever, since the rate of photosyn­ position of mature dodder plants is the growth of some dodder species thesis is relatively low, dodder is discussed in some papers (and the was discussed. Setty and Krishnan still dependent on the host for suffi­ literature is limited) most studies (1970) investigated the effects of cient food to complete its life cy­ have been concerned with pig­ shading on field dodder, largeseed cle. Although some enzyme activi­ mented compounds such as chlor­ dodder, and Cuscuta refkxa, and ties have been detected in some ophyll and carotenoids. Walzel the host plant (alfalfa). As the light species of ·dodder, most essential (1952a) investigated chlorphyll and intensity decreased, the content of steps in intermediary metabolism vitamin C content of stems of dry solids, protein, and total phos­ have not been demonstrated. swamp dodder. She found that the phorus also decreased in all four Therefore, much additional re­ amount of vitamin C and green pig­ species. However, these effects search is necessary before the m en ta tion increased in the stem were less pronounced in the host true interdependence of the host­ from the haustorium to the stem tip. than in the parasites. par a site relationship can be MacLeod (1961; 1963) reported the understood. presence of low concentrations of A compound similar in biological ac­ chlorophyll a and b in field dodder; tivity to kinetin was isolated from the ratio of chlorophyll a and b was Cuscuta refkxa (Abou-Mandour, Photosynthesis similar to the ratio found in auto­ Volk, and Reinhard, 1968). This trophic plants. He speculated that compound stimulated the growth of MacLeod (1961, 1962) was one of the the reason that some species of dod­ tobacco stem tissue, inhibited first to report that dodder (Cuscuta der do not appear green is that the chlorophyll dissimilation, and in­ campestris and C. reflexa) can fix high concentrations of carotenoids creased the transport of 14C­ CO2 (table 3). Since then, light­ mask the chlorophyll color. It has glycine. It is possible that this com­ stimulated CO2 fixation has been been suggested that the carotenoid pound promotes the transport of confirmed in seedlings and detached pigments are the photoreceptor food from the host to the parasite. stem filaments of flax dodder sites for accepting light waves that (Ciferri and Poma, 1963a, b) and in influence growth processes (Piz­ seedlings, stems, and flowers of C. zolongo, 1966). In largeseed dod­ Seeds australis (Baccarini, 1966). Light der, light stimulates the formation and dark fixation of 14CO2 occurs in of chlorophyll (Lane, Baker, and Rahman and Krisnan (1971) found C. pentagona (Kerstetter and Hull, Danielson, 1965). that the seeds of field dodder con­ 1970) and in an insect (Smicronyx ) tained high amounts of starch, induced galls of C. australis (Laudi Pigments other than chlorophyll polyfructosan, and phospholipids. and Albertini, 1965). Using radioac­ and carotenoids have also been They also found that phytic acid and tive 14CO2 and manometri1~ reported. A preliminary investiga­ acid-insoluble polyphosphate con­ methods, Pattee, Allred, and tion by Denliev, Meshcheryakov, stitituted the reserve forms of Wiebe, (1965) has shown that a and Orazkuliev (1969) was con­ phosphorus in the seed. Moreover, small amount of photosynthesis oc­ ducted to determine the presence the occurance of large quanities of curs in seedlings of field dodder, or absence of flowers and alkaloids nucleotides, hexoses, and dicarbox­ largeseed dodder, and C. approx­ in a number of totally unrelated ylic amino acids suggested a ready imata but diminishes as the plant species of the Turkish flora. They potential for metabolic activity. becomes parasitic. C. pentagona has found flavones in Cuscuta lehman­ been grown as an autotroph on a ni.ana and recommended addition­ Ikan, Rapaport, and Bergmann, sterile agar medium (Zimmermann, al study of this and other species. (1968) examined the seeds of 1962). various species of lpomoea, Con­ In a preliminary biochemical exam­ volvulus, and Cuscuta and found Extracts made of plants that have ination of three angiosperm para­ that only the seeds of Cuscuta assimilated 14CO2 and analyzed by sites, Khanna, et aL, (1968) com­ monogyna contained agroclavine, a chromatographic methods have pared the phenolics of Cuscuta, pharmacologically active alkaloid. given somewhat different results. Orobanche aegyptia, and Den­ Kawasaki, Tsukawaki, and Okabe, In light-assimilated 14CO2 extracts, doroph thoe falcata. In general, (1965) apparently responding to radioactivity was detected in areas they found that all parasites ex­ earlier suggestions, reported that corresponding to dark fixation pro­ amined contained a high concen­ the seeds of Cuscuta japonica con­ ducts (organic and amino acids) tration of phenolics. Furthermore, tains no resinous glycosides ana­ rather that photosynthetic products the combined phenolics of host and logous to pharbitin and convol­ (3-phosphoglycerate, sugar phos­ parasite exceeded the phenolics in vulin. phates, or sugars) (Ciferri and

11 TABLE 3. PHOTOSYNTHESIS BY TWO SPECIES OF DODDER AND A LEAF OF Pe/argoniumsp. (ADAPTED FROM MACLEOD, 1961) GROWTH AND

Exposure Photosynthesis by: DEVELOPMENT 14 to co 2 C. gronovii C. campestris Pelargonium

1 Growth and development includes minutes counts/min./gm fresh weight the entire life cycle of a plant. 15 12 19 172 However, in dodder most research 30 27 40 276 has been directed to the seedling 60 43 63 288 stage of the life cycle before or just 120 101 81 587 after attachment to the host. How­ 180 150 108 1228 ever, a number of biotic and a bi­ 240 200 175 2576 otic factors influence the early Dark control 12 10 89 stages of growth. The major abiotic Boiled control 1 2 5 factors are temperature, moisture,

190 percent ethanol soluble fraction counted. and light. A natural plant hormone is the only biotic factor affecting growth that will be reviewed in this Poma, 1963a, b ). However, Kerstet­ host and Cuscuta refl,exa and field text. ter and Hull (1970) reported that dodder as the parasites, MacLeod assimilated 14CO2 occurs mainly in (1962) studied the distribution of Gaertner (1950) attempted to study glucose of C. pentagona seedlings, erythrosin (a dye) from host to host-parasite relationships by grow­ and MacLeod (1961) found radioac­ parasite. He was able to determine ing dodder and a potential host in tivity only in sucrose in field and that only one vascular bundle in a a cotton-plugged flask. However, swamp dodder. haustorial coil is responsible for flask conditions were unfavorable transport of the "xylem sap." Dye for such a study, since the dodder movement in the haustorial coil seedlings tended to grow up the Intermediary Metabolism moves equally in both directions to walls of the flask and away from the the apex and away from the apex host. To determine why dodder In a general study of the factors beyond the haustorial attachment. seedlings responded unfavorably, related to parasitism, MacLeod Furthermore, by cutting the stem various conditions such as the (1963) demonstrated the presence of below the dye surface, it was deter­ growth medium and temperature transaminases in field dodder and mined that the dodder plant is were altered. Since stem rotation Cuscuta refl.exa. He suggested that under a state of negative pressure. was stimulated at the low tem­ these findings indicate that dodder perature of 15°C, it was suggested may not require amino acids from By radioautographic techniques us­ that dodder movement could be cor­ the host to carry out protein ing 14CO2, a number of com­ related to temperature. synthesis. However, even though pounds originating in the host they may be able to synthesize their have been detected and identified in own amino acids, the precursors of dodder. For example, Salageanu Abiotic Factors these amino acids (organic acids and and Fabian-Galan (1968) found that inorganic nitrogen) must be re­ the first compounds translocated Since Gaertner's(1950) study, the ceived from the host. from Rubus i,daeus to Cuscuta are effects of moisture and temperature aspartic and glutamic acids. Su­ fluctuations on dodder growth have crose, glucose, fructose, as well as been studied. Tronchet (1958b) succinic, malic, and citric acids are reported that preliminary evidence TRANSLOCA TION translocated secondly. indicated that unattached swamp dodder seedlings grown with an in­ In studies using alfalfa as the host, sufficient water supply exhibited a some materials were translocated positive hydrotropism toward water Translocation is the movement of from dodder to the host. However, or wet objects. materials within the plant. In dod­ most material is translocated from der, food, inorganic salts, and the host to dodder even when Tronchet (1958b) also found two water are translocated from the metabolic activities in the host are stages of development of swamp host plant to the parasite. Research limited (Allred, 1966; Littlefield, dodder seedlings. In the first stage, conducted by Moss (1928) and Koll­ Pattee, and Allred, 1966). Com­ the proximal or "radicular" end mann and Doerr (1969) indicate pounds harmful to other orga­ emerges through the integument that materials translocated from the nisms apparently have no detri­ and curves in a direction opposite to host to the parasite originate in the mental effects on dodder. Poisons, the direction of the coiled embryo. xylem and phloem. such as the cardiac poisons of During the first stage, the proximal Digitalis, are translocated until high end shows no tropism. However, In experiments using Impatiens sul­ concentrations are attained (Grim­ during the second stage the proxi­ tani¥ and a Bulbine species as the mer et al., 1958). mal end shows a positive hydro-

12 tropism and no geotropism. After two photo-reactions act synergis­ Chemicals which have been contacting water, the proximal area tically to promote hook opening reported to control dodder. gorges itself with water and the and antagonistically in twining. coiled embryo emerges from the Hence, it appears that specific wave seed. Thereafter, growth of the lenghts of light are highly important seedling takes place below the U­ for normal growth responses of dod­ Amitrole Dinoseb curved distal tip of the stem. der seedlings. BCPC Diphenamid Biotic Factor Light is a third abiotic factor BP-2 Diquat thought to be important in the Although only a cytokinin-like hor­ growth of dodder seedlings. For ex­ mone has been reported for dod­ BP-3 DMPA ample, twining is believed to be der (Abou-Mandour, Volk, and dependent on the action of light Reinhard, 1968) it appears likely BP-4 DNOC (Lane, Baker, and Danielson, 1965). that other plant hormones such as Various interpretations are possible auxin, gibberellins, and abscisic acid BP-7 Ferrous sulfate from results of studies on the effect are required to control the growth of different wave-lengths of light of the species of this genus. BP-12 Fluometuron on different species. Zimmermann (1962), found that far-red radiation BP-18 GS-14260 induced haustorial initiation and CHEMICAL CONTROL inter-twining, while red radiation CDAA KN3 inhibited these in Cuscuta pen­ tagona. Danielson and Gentner CDEC Lenacil ( 1966) have reported that cir­ cumnutation of largeseed dodder This will summerize reports on in­ CEPC Metham is counter-clockwise, and that twin­ vestigations of those herbicides ing around a peg (an artifical host) showing a high degree of control of Chloramiben N-3446 will occur only after it has been ex­ dodder on some of the world's most posed to far-red radiation. Piz­ important cultivated plants. Chlorbufam NC-8438 zolongo (1966) studied the behavior of C. pentagona seedlings Gaertner's (1950) review noted that Chlorpropham Nitraphen grown in darkness, daylight, and common laboratory chemicals, such monochromatic light. Twining, hau­ as, ammonium nitrate, formalin, Chlorthal OCS-21693 storial emission, and parasitism and monochloracetic acid effectively occured in white light but did not oc­ controlled dodder seed germination CP-31675 PCP cur with seedlings grown in dark­ in the soil. However, these were not ness. Furthermore, after bright economically feasible. Since that CP-45592 Pronamide light had stimulated twining and time, the techniques and materials haustorial initiation, they continued for chemical weed (including dod­ CPPC Propham after the plants were moved to der) control have increased greatly. darkness. In contradiction to earlier Although dodder is known to be Cycloate RP-11755 reports, he found that blue light parasitic on a number of native and (413-480mµ) was the most effective cultivated species most reports of 2, 4-D RP-11561 in promoting twining, haustoria, chemical control of dodder concern and thus parasitism. Radiation with either alfalfa (Medicago sativa L.) or 2, 4-DEP Sodium arsenite longer wave lengths reversed the clover (Trifolium pratense L.) as the effects of blue light. Carotenoids, in host. The following list shows many Dazomet TH-073-H the terminal portion of the stem of the chemicals that have been were suggested by Pizzolongo to be evaluated in both field and green­ DCPA TH-306-H the photoreceptors in this "high house studies for the control of dod­ energy reaction" system. Other ex­ der by various investigators on a Dichlobenil Trifluralin periments indicated that at least variety of host species. The effec­ two photoreaction systems acting in tiveness of the herbicides found in sequence may control hook opening this list was reported by the various and twining in large-seed dodder authors to be good, satisfactory; or seedlings (Lane and Kasperbaver, excellent, and, in some cases, high 1965). One photoreaction system re­ percentages of control were re­ quires high irradiation in the blue ported. For some of the herbicides, Greenhouse Experiments and far-red spectral regions, and there are contradictory reports, but the other is controlled by low this is to be expected, since a her­ Two general greenhouse studies amounts of red and far-red irradia­ bicide may require narrow param­ were conducted to determine what tion. The latter is reversible. The eters to be effective. herbicides have any controlling ef-

13 feet on dodder seedling attach­ TABLE 4. HERBICIDES (OF 100 TESTED) THAT GAVE 99 TO 100 PERCENT CONTROL ment to the host . Table 4 lists OF DODDER-SEEDLING ATTACHMENT TO HOST (DAWSON, 1967) thirty-two of one hundred her­ bicides tested by Dawson (1967) Herbicide (common that were found to be 99-100 per­ name or designation) Rate Formulation Application depth cent effective in preventing dod­ der seedlings from attaching to Ch lor prop ham 3 20% granular surface alfalfa. Many of these herbicides Propham 12 20 % granular surface have been field tested and will be Chlorbufam 6 technical 0.2 BP-2 6 2 lb/gal 0.5 discussed later in this text. BP -3 12 2 lb/gal 0.5 BP-4 6 1 lb/gal 0.5 Dawson (1969) tested the longevity BCPC 6 1 lb/gal 0.5 of: (a) twenty-seven herbicides, BP-7 12 1 lb/gal 0.5 found earlier to have a controlling CEPC 6 1 lb/gal 0.1 effect on dodder seedling attach­ CPPC 6 1 lb/gal 0.1 ment (Dawson, 1967); and (b) BP-18 6 1 lb/gal 0.1 chlorpropham with a PCMC (micro­ PPG 6 technical 0.1 bial enzyme inhibitor) additive. BP-12 6 1 lb/gal 0.1 Dawson considered a herbicide ef­ RP-11561 2 2.5 lb/gal 0.1 RP-11755 3 2.5 lb/gal 0.1 fective if it prevented seedling at­ CDEC 6 20 % granular surface tachment to the host. According Fluometuron 3 t echnical 0.1 to Dawson, the following three tests DCPA 10 t echnical 0.1 were used to determine if a seedling OCS-21693 4 2 lb/gal 0.1 was attached to a host: (a) an in­ CDAA 6 20 % granular surface crease in dodder stem diameter; CP-31675 2 65 % W .P. 0.1 (b) change in dodder stem color CP-45592 2 4 lb/gal 0.1 from pale yellow to gold; and (c) Trifluralin 4 4 lb/gal 0.1 N-3446 12 t echnical 0.2 stem elongation on the host. Nine of Dichlobenil 2 4% granular 3.0 the 27 herbicides (table 5) effective­ TH-073-H 2 50% W .P. 0.1 ly controlled dodder for periods T H-306-H 2 50 % W .P. 0.1 equal to or longer than chlor­ DMPA 5 3 lb/gal 0.1 propham, a herbicide commomly KN 3 200 technical 1.0 used for dodder control. Also, the Chloramiben 6 2 lb/gal 0.2 controlling period of PCMC-added DNBP 4 3 lb/gal 0.1 chlorpropham was doubled from an 2, 4-D E P 6 4 lb/gal 0.1 average of 5½ to 11 weeks. Some of the her_bicides fluctuated in degree of control. For example, RP-11755 (at 2 lb. / acre) had a 100 percent con­ TABLE 5. HERBICIDES THAT CONTROLLED DODDER FOR PERIODS EQUAL trol on seedling attachment for the TO OR LONGER THAN CHLORPROPHAM (ADAPTED FROM DAWSON, 1969) first twelve weeks, then 90 to 100 percent control for one week, fol­ Herbicide (common Control beyond chlor­ lowed by 80 to 90 percent control name or designation) Rate propham treatment 1 for one week, and finally a return to 100 percent control for 4 weeks lb/acre weeks2 before termination of the experi­ ment. No discussion of these seed­ RP-11755 2 12 + ling response fluctuations is given 4 12 + by Dawson, even though an under­ 6 12 + RP-11561 2 2 standing of the factors promoting 4 5 such fluctuation might prove mean­ 6 6 ingful. Tr ifluralin 6 4 DCPA 10 7 BIPC 6 6 Field Investigations D inoseb 4 5 8 6+ Alfalfa 12 8+ CP-31675 2 2 Most investigations and reports of Dichlobenil 2 2 chemical control of dodder in North TH-073-H 2 1 Chlorpropham + PCMC 6 + 0.5 4 America concern irrigated alfalfa crops as the host. Detailed methods 1Chlorpropham at 6 lb ./acre controll ed dodder spec ies for the controls of both small and from 3 to 5 weeks. widespread infestations of dodder 2Th e plus sign in dicates herbicide stil l control ling on alfalfa in the United States have dodder when the experiment was terminated . 14 been reported by Lee and Timmons Torell (1967) reported that dodder sprayed with sodium arsenite (4 (1958) and Dawson (1965). Chemical remains attached to alfalfa stubble percent solution) (Govorkova, control of small patches involves cut for hay. This stubble-attached 1959). Less effective than sodium spraying with aromatic weed oils or dodder plus new dodder seedling arsenite was a 4 percent solution of with fuel oils fortified with dinoseb. further weaken the host and thus ammonium dinoseb. Later experi­ Control of widespread infestations reduce alfalfa seed yields. Torell ments revealed that a 2.67 percent of dodder involve cultivation (dis­ found that propane flaming and solution of sodium PCP was effec­ cussed in detail in another section) dinoseb gave nearly 100 percent tive and could replace sodium and the use of herbicides such as control of stubble-attached dodder. arsenite. chlorpropham and CDEC. These and other herbicides will be dis­ Dichlobenil. Dawson (1970) has Walls (1962) and Loveridge (1966) cussed in greater detail in the found that application of dichlobenil reported dodder infesting alfalfa following paragraphs. (2 lb/ acre), before irrigation or after crops grown in New South Wales, the soil was moistened, controlled New Zealand, and both recom­ Torell (1968) has reported reason­ dodder seedlings and other weeds mended the use of diquat, sodium ably satisfactory control of dodder from four to six weeks without chlorate, kerosene, 2,4-D, or on alfalfa using variations of ten significantly affecting established amitrole to destroy small isolated recommended treatments. Ac­ alfalfa plants. Subsurface applica­ patches of dodder. They also re­ cording to Torell the following tions of dichlobenil increased the ported that chemical control of ex­ four questions must be answered herbicidal effect on dodder, but it tensive dodder infestations was not before any one of the recommended caused alfalfa injury. practical at that time. treatments can be used: (1) Is the alfalfa crop to be used for seed or Chlorpropham. Investigations were animal feed? (2) How large is the conducted with alfalfa in Utah (Lee Clover dodder infestation? (3) Is frequent and Timmons, 1954; 1955; 1958), cultivation feasible? and (4) What Wyoming (Lee and Timmons, 1958) Clover was reported 98 to 99 per­ are the field characteristics, such as Washington (Dawson, 1966a, 1971a, cent free of dodder at two sepa­ slope, soil, and drainage? 1972), Idaho (Torell, 1967, 1968)and rate test sites when sprayed with California (McNeely et al., 1966). sodium pentachlorophenate and tri­ Several chemicals, including the fol­ Chlorpropham (6 lb/ acre) has often ethanolamine salt of dinoseb (3-4 lowing, have been found to give been used as a standard when com­ percent solutions) (Konik and Safra, satisfactory results in control of paring the efficiency of other 1957). At a third test site, excess of dodder: (1) DCP A, (2) RP-11735, (3) chemicals for the control of dodder. 98 percent control of dodder in­ dinoseb (4) dichlobenil, (5) chlor­ One of the first field experiments festing clover stubble in its third propham, and (6) diquat. with chlorpropham was conducted year was reported using ferrous by Lee and Timmons (1954); they sulfate (25 percent solution), dino­ DCPA. Bayer (1965) found that reported that chlorpropham could seb (6 percent or 25 percent solu­ preemergence applications of DCP A be expected to give ". . . efficient tion) and DNOC (3-4 percent or 25 in March, controlled largeseed dod­ and economical control of dodder." percent solution). Sodium arsenite der (Cuscuta indecora) seedlings Later, Dawson (1966a) concluded (25 percent solution) was also tested throughout the season under Cali­ that 20 percent granular chlor­ at this thfrd test site, but poor fornia conditions. However, De­ propham (6 lb/ acre) gave 95 to 100 results were obtained. cember applications gave only early percent control for 3 to 6 weeks season control. McNeeley, et al. when applied uniformly to a moist (1966) also found that DCPA (7.5 soil surface before dodder seedlings Clover and alfalfa lb/ acre) controlled dodder germina­ wrapped themselves around the tion but that no systemic control host plant. The shading effect from Red clover and alfalfa infested with could be expected using DCP A. the maturing host and a drying soil dodder in the U.S.S.R. was con­ prolonged the control of dodder tJ:olled by applying DNOC, nitra­ seed germination beyond the ex­ phen or PCP-sodium to 2 or Dinoseb and RP-11755. Dawson pected soil life of the herbicide. 3-day-old stubble' (Beilin, 1969). (1971a) field-tested both RP-11755 Subsequently Slater et al (1969) From Yugoslavia, Stojanovic and and dinoseb to determine their abili­ determined that chlorpropham kills Mijatovic (1973) reported efficient ty to control largeseeded and emerging as well as emerged dod­ control of dodders of the subgenera field dodder seedlings for longer der seedlings. Dawson (1972) sug­ Cuscuta and Grammica on alfalfa periods than was currently available gested that chlorpropham activity and red clover using dinoseb acetate from chlorpropham (6 lb/ acre), a can be prolonged by adding PCMC and diquat. common dodder herbicide. Dinoseb (P-chlorophenyl N-methyl-carba­ was found equal to or less effective mate), a microbial enzyme inhibitor. Finally, Sarpe, Halazau, and Guta than chlorpropham. However, dino­ (1973) tested three herbicides and seb and chlorpropham vaporize Gemesi (1966a, 1966b) tested twen­ and have a short soil life, whereas Other chemicals. Alfalfa infested ty herbicides; both concluded that RP-11755 does not vaporize - ac­ with field dodder and Cuscuta ap­ diquat was the most efficient and counting, perhaps, for its longer pro xima ta was effectively con­ economical herbicide tested. Diquat activity. trolled 15 to 17 days after being (0.1 percent at 1 liter/ sq. m) hand

15 sprayed on dodder patches, no Fungicides the simultaneous use of Alternari.a larger than 0.5 to 1.0 sq. m before (5 cuscutacidae spores and secondary to 7 days) and after (5 to 10 days) Murdmtsev and Agivistikova (1970) invaders such as Cladosporium, cutting alfalfa or red clover gave 100 have compared the effects of a Fusarium, Rhi.zoctonia, Trichoder­ percent control. Gemesi listed the number of fungicides on seedlings of ma, Penicillium, or bacteria, the following advantages for using di­ field dodder and Cuscuta monogyna. effectiveness of A. cuscutacidae was quat: (a) no damage to the host at Trichothecin, decaffentin, brestan, improved. Curvalaria, also a the recommended concentration, if karathane, maneb, MC-1520, primary pathogen, has been found diquat is sprayed before the dodder dichlone, tuzed, dodine, ruston, to be even more agressive than A. weakens the host so much that the gransan, blastcidin S and cyclohex­ cuscutacidae (Wilson,1970). host succumbs to the herbicide; (b) imide were tested and the latter rapid eradication of dodder and the two proved to be the most effective. carpet-like dodder web; (c) no damage to crops planted later; and CULTURAL CONTROL (d) activity independent of tem­ perature, thus can be used any BIOLOGICAL CONTROL time during the year. Dodder parasitizing cultivated plants can be removed or controlled by hand weeding; however, it is not Phytophagous Insects economical on extensive infesta­ Tobacco seed beds tions. In row crops, dodder plants Five species of insects were ob­ between the crop rows can be re­ This crop often can be infested by served inflicting heavy damage on moved by cultivation; but, in the dodder according to a report dodder that was parasitizing her­ row, cultivation is not effective. (Anon., 1969). Chemical control of baceous and woody plants in West Within the crop row they are also dodder in the beds can be obtained Pakistan (Baloch, Din, and Ghani, more likely to attach to the crop using metham or dazomet. Heavy 1967). Table 6 gives their scientific plant. watering of the bed before planting names, families, stages of develop­ tobacco seeds removes the her­ ment injurious to dodder, and na­ bicides; they are also toxic to ture of damage. Three of the five Seed or Seedling tobacco seeds. species of insects (Eupoecilia ambiguella, Smicronyx cuscuta, Seeds of dodder can be accidently Mel,anagromyza cuscutae) were re­ harvested, transported, and planted corded only on Cuscuta. Mel­ with crop seed. This is especially Raspberries anagromyza cuscutae has su bse­ true with alfalfa because the seed of quently been shown to be a alfalfa and dodder are similar in According to Natal'ina (1963), rasp­ specific herbivore of Cuscuta reflexa size. berries did not require the deep stems and flowers (Baloch, Mohyud­ pruning for dodder control in areas din, and Ghani, 1967). However, dodder can be removed where frost occurs, since dodder did from several legume seeds with the not over-winter on raspberries. In West Pakistan, thick-vined dod­ dodder cleaner. Seed coats of dod­ Chemical control with sodium pen­ der parasitize shrubs and trees der are rough and pitted and stick tachloroph ena te (4 kg/ ha) or and thin-vined dodder parasitize to felt cloth; legume seeds are DNOC (6 to 8 kg/ ha) applied at the small areas of field crops. Mel­ smooth and waxy and do not. Ad­ time of dodder seedling emergence anagromyza cuscutae has been ob­ joining, felt-covered rollers rotate was effective for dodder control. served attacking only dodders in opposite directions, and seeds Beilin (1969) also recommended that parasitize shrubs and trees. pass between them. Dodder seeds sodium-pentachlorophenate (4-6 Although M. cuscutae is subject to are carried to the outside, while kg/ ha) for control of Cuscuta heavy parasitism, it may prove legume seeds remain between the lupuliformis infesting raspberries useful as a biological control agent rollers. Rollers are slanted so that and other soft fruits. Beilin also in areas where its natural enemies legume seeds slide out at the lower recommended sodium chlorate and do not live. ends. DNOC for control of clover dodder (C . epithymum). Matos (1946) and Crow (1958) have Fungal Agents reported on methods to reduce con­ tamination of dodder seed that oc­ Research in the Soviet Union has cur in alfalfa seed. According to Sugar beets shown that dodder parasitizing al­ Crow, dodder, and other weed seed, falfa has been effectively con­ can be separated from alfalfa or red This crop, infested with field dodder trolled (90 percent) by using clover seed by applying an electrical (Cuscuta campestris) was effective­ fungal spores of Alternari.a species. charge. The amount of electrical ly treated with trifluralin, NC- This same technique proved less charge depends on the seed species 8458, cycloate, or cycloate com­ successful in controlling dodder and then varying capacities to hold bined with lenacil (Stojanovic and parasitizing sugar beets (Rudakov, the charge. In some cases, several Mijatovic, 1973). 1963; Wilson, 1970). However, by thousand volts are required.

16 TABLE 6. INSECTS THAT INFLICT HEAVY DAMAGE ON CUSCUTA SP . IN WEST PAKISTAN (BALOGH, MOHYUDDIN, AND GHAN! , 1967)

Family Species Damaging stage Nature of damage

Olethreutidae Acroclita sp. all stages boring vines L obesia serangodes all stages boring vines Phaloniidae E upocilia ambiguella all stages boring vines Curculionidae Smicronyx cuscuta eggs, grubs, adults grubs cause vine galls A gromyzidae Melanagromyza cuscutae all stages boring vines and flowers

In soil contaminated with dodder The Mature Parasitic Plant patches or crop residues suspected seed, other cultural control methods to be infes ting it. Plowing the soil have been attempted. Natal'ina and allowing it to lay fallow for a (1963) reported that early spring Baker (1950) suggested the pruning season or changing to crops resis­ plowing or irrigation stimulated of California native shrubs to tant to parasitism by dodder such dodder seed germination in straw­ remove dodder. However, most re­ as the cereals, corn, or soy beans berries in the absence of an in­ ports on the cultural control of has also been suggested (Macrae, termediate host. In the state of mature dodder involve legumes 1952; Loveridge, 1966). Washington, Dawson (1971a) found such as alfalfa. According to Lee that by postponement of alfalfa and Timmons (1958), the cultural seeding from before August 1 to control of dodder is effective only August 15 or later, the crop escaped where small patches occur in alfalfa. injury from field and largeseeded Some of the measures suggested by ACKNOWLEDGMENTS dodder and became well established Lee and Timmons for controlling before winter. In the following isolated patches of dodder are burn­ spring a preemergence herbicide ing, cutting or other mean~ of con­ (chloropropham or DCP A) was ap­ tinually killing any new vegeta­ The support of the California plied. Ninety-eight to 100 percent tion. Menke (1954), Walls (1962), Tomato Growers through their control was thus achieved by shif­ Torell (1967; 1968), and Beilin (1969) Processing Tomato Advisory Board ting the crop seedling date and have also suggested the burning for the preparation of this literature later applying an herbicide. technique on either isolated dodder review is gratefully acknowledged.

17 LITERATURE CITED

Abou-Mandour, A. A., 0. H. Volk, and E . Reinhard. 1968. On the existence of the cytokinin-like factor in Cuscuta reflexa. Planta 82:153-63. Allred, K. R. 1966. Translocation of radioactive substances in the Medicago-Cuscuta complex after expose to C14O2. Advancing Frontiers Plant Sci. 16:1-9. Allred, K. R., and D. C. Tingey. 1964. Germination and spring emergence of dodder as influenced by temperature. Weeds 12:45-48. Anonymous. 1969. Herbicides and tobacco. Pans (Pest Articles and News Summaries) 15:100. Baccarini, A. 1966. Antotrophic incorporation of C14O2 in Cuscuta australis in relation to its parasitism. Experientia 22:46-47 Baker, K. F. 1950. Perennation in relation to control of dodders on native shrubs in southern California. Phytopath. 40:213-14. Baldev, B. 1962. In vitro studies of floral induction on stem apices of Cuscuta reflexa Roxb. A short-day plant. Ann. Bot. 26:173-80. Baloch, G. M., I. M. Din, and M. A. Ghani. 1967. Biological control of Cuscuta spp. I. Cuscuta spp. and insects associated with these in W. Pakistan. Commonwealth Institute of Biological Control. Tech. Bull. 8:149-58. Baloch, G.M., A. I. Mohyuddin, and M.A. Ghani. 1967. Biological control of Cuscuta spp. II. Biology and host-plant range of Melanagromyza cuscutea Hering (Diptera Agromyzidae). En­ tomophaga 12:481-89. Bayer,D.E. 1965. DCPA in host-parasite relations of alfalfa and dodder. Weeds 13:92-95. Beilin, I.G. 1969. Control of dodder and broomrape in the USSR. Pans [Pest Articles and News Summaries] 15:603-04. Bertossi, F. 1957. Research on the physiology of Cuscuta epithymum. 1. Culture in vitro. Atti 1st. Bot. Univ. Lab. Crittogam. Pavia Ser. 5 14:174-92 Bezrutchenko, N.Z. 1947. The biology of Cuscuta arvensis Beyr. Var. calycina Engeim. Sovietskaia Botanika [Moscow] 15:212-17. Ciferri, 0., and G. Poma. 1963a. Fixation of carbon dioxide by Cuscuta epithymum. Life Sci. 3:158-62. 1963b. CO2 fixation by Cuscuta epithymum. G. Bot. Ital. 70:345-46. Crow, J. W. 1958. Electronic separator does the tough jobs. Western Feed and Seed 13:31, 64. Danielson, L.L., and W.A. Gentner. 1966. Chemical mediation of growth movements in dodder. Weed Society of America. (Abst.), p. 67. Dawson, J.H. 1965. Prolonged emergence of field dodder. Weeds 13:373-74. 1966a. Factors affecting dodder (Cuscuta spp.) Control with granular CIPC. Weeds 14:255-59. 1966b.Response of field dodder to shade. Weeds 14:4-5. 1967. Soil-applied herbicides for dodder (Cuscuta) control; initial greenhouse evaluation. Wash. Agr. Exp. Sta Bull. 691. 1969. Longevity of dodder control by soil-applied herbicides in the greenhouse. Weed Sci. 17:295-98. 1970. Dodder control in alfalfa with dichlobenil. Weed Sci. 18:225-30. 1971a. Establishing alfalfa on dodder-infested soil. Weed Sci. 19:222-25. 1971b. Dodder control in alfala with dinoseb and D(-) (3-chlorophenylcarbamoyloxy)-2N-isopropylpropionamide. Weed Sci. 19:551-54. 1972. Inhibitor of microbial enzyme prolongs dodder control with chloropropham. Weed Sci. 20:465-67. Dawson, J. H., W. 0. Lee, and F. L. Timmons. 1965 Controlling dodder in alfalfa. U .S.D.A. Farmers Bull. 2211, 16 pp. Dean, H. L. 1934. Host plants of Cuscuta gronovii. Rhodora 47:371-74. Dean, H.L. 1935. Host plants of Cuscuta glomerata. Proc. Iowa Acad. Sci. 42:45-47. 1954. Dodder overwintering as haustorial tissues within Cuscuta-induced galls. Proc. Iowa Acad. Sci. 61:99-106. Denliev, P. D., A. A. Meshcheryakov, and I. Orazkuliev. 1969. The search for biologically active compounds in plants of the flora of the Turkmenian SSR. lzv Akad Nauk Turkm SSR Ser Biol Nauk. 1:81-84. Doerr, I. 1967 On the hyphal fine structure in Cuscuta odorata and their connection to the sieve tubes of their host plants [Pelargonium zonale, Primula obconica]. Naturwissenschaften 54:474. Frantianne, D.G. 1965 The interrelationship between the flowering of dodder and the flowering of some long and short day plants. Amer. Jour. Bot. 52:556-62. Gaertner, E. E. 1950. Studies of seed germination, seed indentification, and host relationships in dodders, Cuscuta spp. N. Y. Agr. Expt. Sta. Memoir 294, 56 pp. 1956. Dormancy in the seeds of Cuscuta eurO'pea. Ecology 37:389.

18 Gemesi, A. 1966a. Selective control of dodder {Cuscuta spp.) in clover and lucerne. Weed Res. 6:81-83. 1966b. Dodder (Cuscuta) eradication with reglone. Outlook Agr. 5:28-34. Govorkova, 0. I. 1959 . The results of trials of toxic chemicals for controlling dodder. Tr. lolotansk. Selektsionnoi Sta. 1:149-55. Greber, R. S. 1967. Identification of the virus causing papaw (Garica papaya (yellow crinkle with tomato big bud virus by transmission tests. Queensland Jour. Agr. Anim. Sci. 23:147 -53. Grimmer, G. , H. Machleidt, F. Schwanitz, and R. Tschesche. 1958 . Selective absorption of Digitalis glucosides by Cuscuta species. Zeitschr. Naturforsch. 13:672-77. Hassawy, G.S. 1973 . Cuscuta species in Iraq: Their hosts and seed germination. Proc. Eur. Weed Res. Coun. Symp. Parasitic Weeds 282-89. Ikan, R., E., Rapaport, and E. D. Bergmann. 1968. The presence of agroclavine in Cuscuta monogyna seeds. Isr. Jour. Chem. 6:65-7. Jacob, F. 1966. The release of the flowering process in the short day plant Cuscuta reflexa Rox b. Flora Alig Bot . Zeitung 156:558-72. Johri, B. M., and and B. Tiagi. 1952. Floral morphology and seed formation in Cuscuta reflexa Roxb. Phytomorphology 2:162-80. Kawasaki, T., H. Tsukawaki, and H. Okabe. 1965. Constituent of the seeds of Cuscutajaponica Choisy. Syoyakugaku Zasshi 19:36-38. Kerstetter, R. E., and R. J. Hull. 1970. Autotrophic incoporation of 14CO2 in Cuscuta pentagona in relation to its parasitism. Advan. Front. Plant. Sci. 25:83-91. Khanna, S. I. , P. N. Viswanathan, C.P. Tewari, P. S. Krishnan, and G.G. Sanwal. 1968. Biochemical aspects of parasitism by the angiosperm parasites: Phenolics in parasites and hosts. Physiol. Plant. 21:949-59. Kinzel, W. 1901. Die Keimung der Gattung Cuscuta. Landw. Vers. Stal. 55:255-66 . Kollmann, R., and I. Doerr. 1969. Structural basis of intercellular material transport. Ber. Deut. Bot. Ges. 82:415-25. Konik, B. T., and R. A. Safra. 1957. For better control of dodder. Zashchita Rast. ot Vredit. i Boleznei 1957:45-48. Krohn, V. 1934. Kurzer Bericht uber Cuscuta halophyta Fries. Phytopath. Zeitschr. 7:505-14. Lane, H.C., amd M: J. Kasperbaver. 1965. Photomorphogenic responses of dodder seedlings. Plant Physiol. 40:109-16. Lane, H. C., J . E. Baker, and L. L. Danielson. 1965. Effect of diuron on photosynthesis and photomorphogensis of dodder (Cuscuta indecora) seedlings. Weeds 13:371-72 . Laudi, G., and A. Albertini. 1965 Fixation of carbon dioxide by galls of Cuscuta austra/,is. G. Bot. Ital. 72:351-54. Lee, W. 0 ., and F. L. Timmons. 1954 CIPC gives promise of controlling dodder in alfalfa Farm. & Home Sci. 15:3, 20. 1955. Control of dodder {Cuscuta) in alfalfa seed crops with pre-emergence application of CIPC. Agron.47:77. 1958. Dodder and its control. U.S.D.A. Farmers' Bull. 2117, 20 pp. Libbert, E., and I. Urban. 1967. Morphological and anatomical effects of indole-3-acetic acid on parasitizing and in vitro growing Cuscuta lupuliformis. Flora. Allig. Bot. Ztg. 157:454-66. Littlefield, N.A., H.E. Pattee, and K. R. Allred. 1966. Movement of sugars in the alfalfa-dodder association. Weeds 14:52-54. Loo, S-W. 1946. Cultivation of excised stem tips of dodder in vitro. Amer. Jour. Bot. 33:294-300. Loveridge, J. A. 1966 . Ridding lucerne of dodder. Power Farmer Australia New Zeal. Better Farming Dig. 25:31. MacLeod, D. G. 1961. Photosynthesis in Cuscuta. Experentia 17, 542 1962 Some anatomical and physiological observations on two species of Cuscuta. Trans. and Proc. Bot. Soc. Edinburgh 39:302-15 . 1963. The parasitism of Cuscuta. New Phytol. 62:257-63 . Macrae, J. W. 1952. The increase of dodder and suggestions for its control. Canada. Natl. Weed. Cont. East Sect. Proc. 5:80-81. Maheshwari, P., and B. Baldev. 1961. Artificial production of buds from the embryos of Cuscuta reflexa. Nature 191:197-98. Mandryk, M. 1969. Frenching of tobacco in Australian soils and in soil leach ates. Aust. Jour. Agr. Res. 20:709-17. Marchoux, G., F. Lechlant, and J. Giannotti. 1970. Transmission and symptomatology of bindweed yellows in relation to stolbur of tomato. Ann. Phytopathol. 2:429-41. Matos, H.P. de. 1946. Bo!. Soc. Brasileira Agron. 9:263-68. McNeely, G.H., E.C. Hoffman, D. E. Bayer, and C. L. Foy 1966. Control of dodder in alfalfa with DCPA. Calif. Agr. 20:14-15. Menke, H.F. 1954. Dodder infestation can halt certified seed production. Western Feed and Seed 9:24, 36, 37. Moss, E. M. 1928. The haustorium of Cuscuta gronovii. (Abstr .) Phytopath. 18:478.

19 Munz, P. A. and D. D. Keck. 1959. A California flora. Berkeley: University of California Press. 1681 pp. Murdmtsev, G. S., and V. N. Agivistikova. 1970. Suppressing the growth of dodder seedlings with synthetic and biosynthetic fungicides. Pans (Pest Articles and New Summaries) 16:354-56. Natal'ina, 0. B. 1963. Dodder control on raspberries. Zashch rast Vred Boleznei 8:34-35. Olifirenko, V. I. 1959. Some observations on dodder (Cuscuta). Bot. Zhur. 44:1664-65. 1961. Notes on field dodder (Cuscuta arvensis). Tr. Nauchn.-Issled. Inst. Zashchity Rast. Kazakhsk. Akad. Sel'skokhoz. Nauk 6:341-43. Pattee, H. E., K. R. Allred, and H. H. Wiebe. 1965. Photosynthesis in dodder. Weeds 13:193-95. Pizzolongo, P. 1966. On the behavior of plantlets of Cuscuta pentagona Engel. in monochromatic light and in darkness. Ann. Fae. Sci. Agr. Univ. Stud. Napoli. Portici 1:116-25. Rahman, Q., and P. S. Krishnan. 1971. Phosphorus, nitrogen and carbohydrate composition of seeds of Cuscuta. Phytochemistry 10:1751-57. Resende, F. 1953 . Parasites which inhibit flowering of their host. Bo\. Soc. Portuguesa Cienc. Nat. 4:243-47. Rudakov, 0. L. 1963. The first results in the biological control of Cuscuta spp. Zashchita Rast ot Vreditelei i Boleznei 8:25-26. Salageanu, N. and G. Fabian-Galan. 1968. Studies on the nutrition of Cuscuta sp. Rev. Roum. Biol. Ser. Bot. 13:321-24. Sarpe, N., D. Halazau, and M. Guta 1973. Research on the chemical control of dodder in lucerne and red clover. Symp. Parasitic Weeds, Malta. Eur. Weed Res. Coun., Wageningen, Netherlands, pp. 289-95. Schmelzer, K. 1957. Versuche zur Ubertragung des Tomaten aspermie-Virus.Phytopath. Z. 30:449-52. Setty, P. N., and P. S. Krishnan. 1970. Influence of shading on the gross composition of Cuscuta species on Medicago sativa. Physiol. Plant. 23:1017-23. Searcy, D. G. 1970 . Measurements by DNA hybridization in vitro of the genetic basis of parasitic reduction. Evolution 24:207-19. Searcy, D. G., and A. J. Macinnis. 1970. Measurements by DNA renaturation of the genetic basis of parasitic reduction. Evolution 24:796-806. Slater, C.H., J. H. Dawson, W.R. Furtick, and A. P. Appleby. 1969. Effects of chlorpropham vapors on dodder seedlings. Weed Sci. 17:238-41. Stojanovic, D., and K. Mijatovic. 1973. Distribution, biology and control of Cuscutaspp. in Yugoslavia. Proc. Eur. Weed. Res. Coun. Symp. Parasitic Weeds, 269-79. Timmons, F.L., W. D. Lee, and L. W. Weldon. 1958. For high alfalfa seed yields control dodder. Farm & Home Sci. (Utah Sta.) 19:7-9, 21, 27-28. Tingey, D. C., and K. R. Allred. 1961. Breaking dormancy in seeds of Cuscuta approximata Weeds 9:429-36. Torell, P. J. 1967. Dodder control in alfalfa grown for seed. Idaho Univ. Ext. Idaho Curr. Inform. Ser. 39,3 pp. 1968. 10 treatments for controlling dodder in alfalfa seed fields. Idaho Univ. Ext. Idaho. Curr. Inform. Ser. 75, 4 pp. Tronchet, J . 1958a. Responses of plantlets of Cuscuta gronovii Willd. to 2, 4-D at 0.2%. Ann. Sci. Univ. Besancon Bot. 10:23-49. 1958b. New results on the first stages of development of Cuscuta gronovii Willd. Ann. Sci. Univ. Besancon Bot. 10:51-64. 1958c. Growth of plantlets of Cuscuta gronovii Willd. at 24°C in continuous light. Ann. Sci. Univ. Besancon B. 10:65-72. 1960. Tumorisation des plantules de Cuscuta gronovii. Acad. Des. Sci. Compt. Rend. 8:1546-48. 1961. Contribution to the study of growth and movement in Cuscuta gronovii Willd. seedlings. Ann. Sci. Univ. Besancon. Bot.16:1-206. 1962. Physiological effects of coumarin on Cuscuta seedlings. Bull. Soc. Hist. Natur. Doubs. 64:65-67. Urton, N. R. 1945. Dodders and lucerne in South Africa. S. African Jour. Sci. 41:231-37. Walls, F. 1962. Dodder-serious parasitic weed. Agric. Gez. N. S. Wales 73:133-35. Walzel, G. 1952a. Colchicine-treated Cuscuta. Phyton. Ann. Rei. Bot. 4:137-43. 1952b. Vitamin C in Cuscuta. Protoplasma 41:260-62. Wilson, C. L. 1970 . Use of plant pathogens in weed control: Dodder. Pans [Pest Articles and News Summaries) 16:484. Yuncker, T. G. 1932. The genus Cuscuta. Torrey Bot. Club Mem. 18:113-331. 1965. Cuscuta. N. Amer. Flora 4;1-51. Zimmermann, C. E. 1962. Autotrophic development of dodder (Cuscuta pentagona Englm.) in vitro. Crop Sci. 2:449-50. Zimmerman, M. 1963. Dodder [Cuscuta]. Oreg. State U. Ext. FS 38, 1 p.

20 .. ' PLANT PESTICIDE USE WARNING - READ THE LABEL ~ Pesticides are poisonous and must be used cedures for rinsing and disposing of empty POSTING TREATED FIELDS: When worker with caution. READ the label CAREFULLY contain ers. Do not transport pesticides in safety reentry intervals are establi shed be sure BEFORE opening a container. Precautions and vehicles wit h foods, feeds, clothing, or other to keep workers out and post t he treated directions MUST be followed exactly. Spe­ materials, and never in a closed cab with areas with signs when required indicating t he cial protectiv e equipment as indicated must be t he vehi cle driver. safe reentry date. used. RESPONSIBILITY: T he grower is legall y res­ PERMIT REQUIREMENTS: Many pesticides STORAGE: Keep all pesticides in original ponsible for proper us e of pesticides including require a permit from the County Agricu ltural containers onl y. Store separately in a locked drift to other crops or properties, and for Commissioner before possession or use. Such shed or area. Keep all pesticides out of the excessive residues. Pesticides should not be compounds mentioned in thi s publication arP reach of children, unauthorize d personnel, applied over streams, rivers, ponds, lakes, marked with an asterisk (*\. pets and livestock. DO NOT STORE with run-off irrigation or other aquatic areas except foods, feeds or fertilizers. Post warning signs where specifi c use for that purpose is intended. PLANT INJURY: Certain chemi ca ls ma y on pesticide storage areas. ca use injury or give less t han optimum pest BENEFICIAL INSECTS: Many pesticides are control if used: at t he wrong stage of plant USE: The suggestions giv en in this publica­ hi ghl y toxic to honey bees and other benefi­ development; in cer tain soil types; wh en tem­ tion are based upon best current information. cial in sects. The farmer , the beekeeper and peratures are too hi gh or too low ; the wrong Foll ow directions: measure accurately to the pest control industry should cooperate formu lation is used: and excessive rates or in ­ avoid residu es exceeding tolerances, use exact closely to keep losses of beneficial species to compatible materials are used. amounts as indicated on t he label or lesser a minimum. amounts given in this publication. Use a pesti­ PERSONAL SAFETY: Foll ow label dirPctions cide on ly on crops, plants or animals shown PROCESSED CROPS: Some processors will exactl y. Avoid splashing, spilling, leaks, spray on the label. not accept a crop treated with certain chem- drift or clothing contamin ation. Do NOT eat. icals. If your crop is going to a processor, smoke. drink, or chew whil e using pesticides. CONTAINER DISPOSAL: Co nsult your County be sure to check with the processor before Provide for emergency medical care in advance. Agricultural Commissioner for correct pro- making a pesticide application.

22 COOPERATIVE EXTENSION UNIVERSITY OF CALIFORNIA Thi s information is prov id ed by Cooperat ive Extensi on, on educational agency of th e University of California and the Unite d States Deportment of Agriculture. Support for Cooperative Extension is supplied by federal, state, and county governments . Cooperative Ext ension provides the people of California with the latest scientific information in agriculture and fom i ly con sumer sc iences. It also sponsors the 4-H Youth Program, Cooperative Extension representatives, serving 56 counties in Ca liforn ia, ore known as form, home o r youth advisors. Their offices usual ly are located in the county seat. They wi II be happy to provide you with information in their fields of work.

Floyd M. Ashton is Professor ofBotanyandBotanist in the AgriculturalExperiment Station, Davis. DonaldSantanaisResearchAssistant, Department ofBotany, Davis.

Th e University of California's Cooperative Extension programs are avail abl e to all , withou t regil rcl to race, color, or national origin . Issued i n furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation w ith the Unite d States Deportment of Agriculture. James B. Kendr ick, Jr., Director, Cooperative Extension, Univers ity of C alifornia .

... COOPERATIVE EXTENSION U S DEPARTMENT OF AGRICULTURE POSTAGE AND FEES PAID UNI V ER SITY OF CALIFORNIA U.S. DEPARTMENT OF Berk eley, California 94720 AGRICULTURE AGR 10 l U.S.MAIL O FFI CIAL BU SINESS Pe na lt y for Pr iv ate U!>e $300 THIRD CLASS

'