Striga is a partial root parasite...here i m discussing about losses by striga i.e witchweed

1. Nazia Manzar
PGS12AGR5882

2. Introduction
Fungi, nematodes, bacteria, and viruses are probably the first things that come to mind
when thinking of plant pathogens.
Parasitic flowering plants are also important pathogens.More than 2500 species of
higher plants are known to live parasitically on other plants.
Parasitic plants as an angiosperm (flowering plant) that directly attaches to another
plant via a haustorium.

3. The families and the parasitic weeds of importance in
agricultural crops
Root parasite families Shoot-parasite families
Scrophulariaceae
(Striga sp. green hemiparasite)
Cuscutaceae
(earlier under Convolvulaceae;Cuscuta sp; a holo
parasite with twining yellow stems)
Orobanchaceae
(Orobancha sp; holoparasite)
Lauraceae
(Cassytha filiformis; a hemi-parasite
superficially resembles with cuscuta)
Santalaceae/sandalwood
family(Thesium; green parasite)
Loranthaceae ( Loranthus longiflorous,
Arceuthobium sp, Phoradendron sp, green
hemiparasite(mistletoes)
Balanophoraceae(Thonninga
sanguinea; a massive perennial root
parsite occasionally affects tree crops of
the humid crops)
Viscaceae ( Viscum sp; green hemi
parasite(Mistletoes)

4. Striga, deriving from Latin words meaning 'striate', 'harshly hairy', 'lean' or 'witch' .
Term 'witch' is especially expressive, reflecting the way the weed apparently be witches
the crop and causes damage even before the weed itself emerges above ground.
Striga is the biggest biological hindrance in grain and corn production.
Crop losses due to Striga are estimated to more than $ 7 billion adversely affecting
over 100 million people of West Africa alone.
Striga mainly affects vegetative growing stage, flowering stage, fruiting
stage, pre-emergence, and seedling stage of crops.

5. Rank Scientific Name and Common Name
Kingdom Plantae – Plants
Subkingdom Tracheobionta – Vascular plants
Super division Spermatophyta – Seed plants
Division Magnoliophyta – Flowering plants
Class Magnoliopsida – Dicotyledons
Subclass Asteridae
Order Scrophulariales
Family Scrophulariaceae – Figwort family
Genus Striga – witchweed
Taxonomy

6. Striga is a plant of the old world tropics and subtropics.
The hemi-parasite Striga is mainly distributed in tropical arid and semiarid zones
with 400 to 1000 mm of annual rain.
The genus Striga includes over 40 species, of which 11 species are parasitic on
agricultural crops .
Worldwide distribution of important Striga species

7. Striga hermonthica Sub-Saharan Africa
Striga aequinoctialis West Africa.
Striga angolensis Angola
Striga angustifolia East Africa, Asia, Indonesia
Striga asiatica(Asiatic witch
weed)
Africa, Arabian peninsula, India, Burma,
China, Indonesia, the Philippines, Malaysia,
New Guinea, Australia (Introduced), USA
(Introduced)
Striga aspera Africa
Striga bilabiata Africa
Striga gesnerioides(Cowpea
witch weed)
Africa, Arabian peninsula, India,
USA(Introduced)
Striga lutea Sudan, Ethiopia
Striga macrantha West Africa, Nigeria, Ivory Coast, Togo
Striga forbesii Africa, Madagascar
Worldwide distribution of important Striga species

8. S.asiatica
S.densiflora
S. forbesii
Different species of Striga

10. Striga problem in India has grown in magnitude after the introduction of new hybrid
CSH-1 which is highly susceptible to Striga.
S. asiatica, S. densiflora and S. gesnerioides occur in India .
S.densiflora is a recognized problem in the post-rainy season sorghum in parts of
Karnataka and Maharashtra states.
Striga is recognized as a serious problem in pearl millet in Gujarat and Rajasthan
states.
Striga also reported to cause damage to upland rice in Nellore district of Andhra
Pradesh.
Striga in India

11. Witchweed is a small, pretty plant. It has a bright green, slightly hairy stem and leaves.
The flowers are small and usually red or yellowish, or white.
A single plant may produce from 50,000 to 500,000 seeds. The root of witchweed is
white and round in cross section.
It has no root hairs, for it obtains all nutrients from the host plant through haustoria.
Morphological characters

12. Striga densiflora (Dense flower witch weed)
Striga densiflora occurs mainly in South Asia, especially India, eastwards to Indonesia
and China, but also in Oman.
The most important economic hosts range of S. densiflora are sorghum, maize,
sugarcane, finger millet and rice.
Striga densiflora is important in the Deccan rabi sorghum areas in India.

13. States Distribution Refferences
Gujarat Present Cooke, 1905
Karnataka Present Kumar, 1939
Madhya Pradesh Present Jain & Tripathi, 2002
Maharashtra Present Cooke, 1905
Rajasthan Present Luthra, 1939
Tamil Nadu Present Srinavasan, 1947
Uttar Pradesh Present Luthra, 1939
Distribution of Striga densiflora in India

14. The main host crops are sorghum, maize, millets, rice and sugarcane in both Africa and
Asia.
White flowered S. asiatica is reported from India, but the colours of flowers may vary
from red, pink, orange, yellow, white, or purple.
There are also reports of yellow-flowered types of S. asiatica in the malnad tract of
Karnataka state in India (Hosmani, 1975).
Overall losses in infested fields of Southern India were estimated to be about 21%.
Striga asiatica (red witch weed)

15. Andhra Pradesh Hosmani, 1978
Bihar Hosmani, 1978
Gujarat Kumar, 1939
Indian Punjab Hosmani, 1978
Karnataka Hosmani, 1978
Kerala Hosmani, 1978
Madhya Pradesh Ravi Upadhyay, 2004
Maharashtra Hosmani, 1978
Rajasthan Hosmani, 1978
Tamil Nadu Hosmani, 1978
West Bengal Cooke, 1905
Distribution of Striga asiatica in India

16. S. gesnerioides is a plant of the semi-arid tropics, the main economic host is cowpea,
tobacco and sweet potato.
Flower color in forms attacking cowpea is usually mauve but occasionally white,
reddish, purple or even yellow.
Striga gesnerioides have five races. Race 1 is found in Burkina Faso and Mali, race 2 in
Mali, race 3 in Nigeria and probably in Burkina Faso, race 4 in Benin and race 5 in
Burkina.
Striga gesnerioides (Cowpea Witch weed)

17. Maharashtra Common throughout
Karnataka Chikmagalur, Hassan,Shimoga.
Kerala Idukki,Kasargod, Kottayam, Kozhikode,
Malapuram.
Tamil Nadu Coimbatore, Dharmapuri, Kancheepuram,
Kanniyakumari.
Description of Striga gesnerioides in India

18. Striga species can cause severe disease symptoms including stunting, wilting,
veinal chlorosis, poor fruiting ,withering of foliage and bleaching of leaves.
When the crop is heavily infested no ears are formed.
Infected roots bear a large number of witch weed haustoria, which are attached to the
root and feed on it.
Symptoms
Interveinal chlorosis on Maize due to Striga spsStriga parasitizes the maize roots

19. Sorghum plants show drought like symptom
from severe infection by Striga hermonthica
Cowpea plants severely damaged by
Striga gesnerioides
Corn field heavily infested by witch weed

20. Segments of the host roots 3-5 mm long, each
infected with a primary haustorium, of Striga
A longitudinal section through the entire haustorium
reveals that the vessels fuse to form the `xylem disc ‘.
A pitted host vessel has been invaded by several Striga cells i.e called oscula.
Haustoria of Striga parasitizes the host plant

21. Several median cells of the haustorium enter the host
xylem element and form oscula completely filling the
lumen of the xylem element.
There is continuity between several oscula leading
directly to the haustorial xylem element.
Haustorial cells occlude the host vessel completely .
Newly formed fluffy material, which appears within
the host xylem elements surrounding the developing
osculum.

22. The parasite overwinters as seeds, most of which require a rest period of 15 to 18
months before germination.
Seeds close to host roots germinate and grow toward these roots, attracted by the
exudates of the host roots .
The chemical signals 2,6 dimethoxy-p-benzoquinone (2,6 DMBQ) as the product of
enzymatic degradation of the host root responsible for formation of haustorium.
The haustorium penetrates the host epidermis, cortex and endodermis finally, it reach
the vessels of the host roots and develops good connections with the host xylem.
Development of disease

23. After attachment the young parasite grows under the soil surface for about 4–6 weeks,
developing a short stem with achlorophyllous scale‐like leaves.
The parasite seedling draws all its water, mineral and sugar requirements from the
host.
Approximately half of the Striga life cycle is underground during which time much of
the damage to the crop host occurs.
Heavy infestations cause serious stunting, wilting and 'burning' of the foliage, nutrient
deficiency and almost total crop failure.
The disease spreads in the field in a circular pattern and it increases year after year as
the witch weed seeds spread in larger areas .

24. Disease cycle

25. Relatively high temperatures of 30-35°C are optimal for both conditioning and
germination of Striga sp.
Striga infestation is steadily increasing as a result of continuous cultivation of cereal
crops.
Pressure on land for continuous monocropping with high yielding cereal crops without
rotation favour Striga infestation in addition to soil moisture stress conditions.
Epidemiology and condition favouring for Striga growth

26. Seeds of Striga sp are sufficiently small that they are moved, along with soil, crop
seeds and other debris by high winds.
Flooding also transports or moves weed seeds available in the soil bank from one place
to another.
Farmers are unaware that farm tools, equipments (machinery) and man himself (shoes
or boots) can disseminate the Striga from one place to another causing infestation.
Striga sp. seeds intermixed
with seeds of cowpea, maize,
millet, and sorghum
Dispersal of Striga seeds

29. Hand weeding:
Hand weeding is an important part of controlling Striga especially with small
infestations. It is necessary to prevent seed production and reinfestation of the soil.
Mulching:
Mulches from Collophospermum mopane, Acacia karoo and Acacia nilotica reduced
the incidence of S. asiatica and delayed its emergence and flowering.
Burying of
Flowering Striga
Hand pullingWeeding Hand pulling

30. Soil Fertility Management:
Use fertilizers that have lots of nitrogen, such as manure and compost @ 120 kg/ha.
This keeps crops stronger and more resistant to attack against Striga.
The main effects of nitrogen are direct damage to Striga seeds and seedlings in soil, a
toxic effect of nitrogen on the developing Striga.

31. Crop rotation:
Crop rotation with non host /non susceptible crops like sunflower, cotton, groundnut,
field pea, cowpea, soybean, sesame, and lucerne can reduce the infestation of Striga.
Intercropping:
Using the perennial Desmodium uncinatum as the intercrop appears to have even
greater benefit, suppressing S. hermonthica almost completely.
Trap cropping:
Traps crop include cotton, cowpea, soybean, castor beans, sunflower which induce
Striga germination, but Striga radicle fails to make haustorium on them and die.

32. Chemical control:
Atrazine may be applied at 1.5 -2.0 kg as pre emergence in maize and sorghum reduces
Striga.
Pre planting soil incorporation of Fenac /Chlorfenac and 2,3,6-TBA are found
effective in controlling Striga in maize and sugarcane.
Suicidal Germination by Chemical induction:
Chemicals like Strigol, Ethylene, GR-27 and GR-24 helps in stimulating Striga to
germinate in absence of host and lead it to die.
GR 45, GR 7 @ 0.1 – 1.0 kg/ha as pre plant incorporation reduced over 50% Striga
seed population in sorghum in Nigeria and India.

33. Biological control:
Fungi species namely Fusarium nygamai, Fusarium semitectum var majnus have
been reported for biological control of Striga.
Fusarium nygamai and Fusarium semitectum require to be applied to soil before
planting crop and they can reduce Striga emergence by more than 90%.
PGPR bacteria Azospirillum brasilense strains: A. brasilense L2 and L4 completely
inhibited germination effect of Striga.
Untreated maize variety - control Bioherbicide combined with the maize
variety.

34. Integrated Striga Management:
One or few trap crop or catch crop if season /time permits + Striga resistant
variety+intercropping with cowpea or desmodium (push and pull strategy )+optimum
nitrogen fertilization + selective and effective pre emergence herbicide +hand
weeding / intercultural at 30-35 DAS significantly reduces Striga emergence.
Resistant variety:
Striga resistant sorghum varieties: SAR 16, SAR 35, S1511, S1561, S1477 , Yeju,
Abshir and Teshale.
Sugarcane varieties show resistance against Striga asiatica include Co-290, Co-281, CP-
33-224, CP-50-28, CP-53-19 and F-31-762 N-17, 52/219 and 75-F-2573 .

36. Transformed data are in parentheses. Within columns values with different letters are
significantly different; n.s. : not significant (P > 0:05); AM fungal inoculation: AM - no addition of
AM fungal inoculums, AM+ addition of AM fungal inoculums.

47. Striga resistant sorghum varieties : SAR 16, SAR 35, S1511, S1561, S1477 , Yeju,
Abshir, and Teshale.
Sugarcane varieties show resistance against Striga asiatica include Co-290, Co-281, CP-
33-224, CP-50-28, CP-53-19 and F-31-762 N-17, 52/219 and 75-F-2573 .
Striga resistant maize varieties: HR 2001, Gibe 1.
Resistant variety-

48. Mistletoes are partial stem parasites on branches of forest trees.
Mistletoe is the first plant pathogen to be recognized and the first pathogen for which a
cultural control (by pruning affected branches) was recommended, both by Albertus
Magnus around 1200 A.D.
Mistletoes are distributed all over the world but they are most abundant in the
tropical areas of the world.
Mistletoes infest the host vascular system, they can alter growth, reproduction and
physiology of the host, significantly reducing their performance .
Mistletoes and their menace

49. Loranthaceae is the largest family of mistletoe with 73 genera and over 900 species
Viscaceae includes seven genera of Old and New World mistletoes, and with over
540 species is second in size only to Loranthaceae.
Dendrophthoe falcata is the most common of all the mistletoes that occur in India.
Two of its varieties are widespread in India namely, var. falcata (Honey Suckled
Mistletoe) and var. coccinea (Red Honey Suckled Mistletoe).
Himalayan dwarf mistletoe (Arceuthobium minutissimum) is highly destructive to
blue pine (Pinus wallichiana) in North-West Himalayas.

50. Mistletoes Distribution Map

51. Taxonomy
Domain: Eukaryota
Kingdom: Plantae
Phylum: Spermatophyta
Subphylum: Angiospermae
Class: Dicotyledonae
Order: Santalales
Family: Viscaceae,Loranthacae
Genus: Arceuthobium,Loranthus,
Viscum

53. Most mistletoes produce relatively large aerial shoots, sometimes with large leaves
which are readily observed, while others may be squamate.
Mistletoes may have large, showy flowers that attract their bird pollinators, while
others have undergone extreme reduction in floral morphology, as in all Viscaceae
(Misodendraceae,)and some Loranthaceae .
Morphology

54. Dwarf mistletoes: Arceuthobium spp.
The dwarf mistletoe shoots may be simple or branched, and they are joined.
The leaves are inconspicuous, scale like, in opposite pairs, and of the same colour as
the stem.
Dwarf mistletoe plants also produce a complex system of haustoria.
The plants are either male or female and produce flowers when they are 4 to 6 years
old .

55. Fruits mature 5 to 16 months after pollination of the flowers.
The fruit at maturity is turgid and, on ripening, develops considerable internal
pressure.
When disturbed, the fruit expels the seed upward or obliquely at lateral distances up to
15 meters..
Dwarf mistletoe berriesMale (yellow) and female
(with fruit or seed capsules)
dwarf mistletoe plants
growing on a pine
Female Douglas-fir dwarf
mistletoe plant with
mature fruits.
male with ponderosa pine
dwarf mistletoe plants.

56. Mistletoe species Common Names Host Plant
Arceuthobium divaricatum Pinyon dwarf mistletoe Primary Host: Pinus
Arceuthobium douglasii Douglas-fir dwarf mistletoe Douglas-fir white fir,
subalpine fir, Engelmann
spruce, blue spruce
Arceuthobium americanum Lodge pole pine dwarf
mistletoe
Lodgepole pine, ponderosa
pine, whitebark pine
Arceuthobium cyanocarpum Limber pine dwarf mistletoe Limber pine ,
whitebark pine, bristlecone
pine
Arceuthobium vaginatum
subsp. cryptopodum
Southwest dwarf mistletoe Ponderosa pine
Phoradendron juniperinum Juniper mistletoe Rocky Mountain juniper,
Utah juniper.

57. Western spruce dwarf mistletoe. Piñon dwarf mistletoe.
Apache dwarf mistletoe Juniper mistletoe.

58. Symptoms of infection associated with mistletoes is a hypertrophy of the host branch
at the point of infection caused primarily by the disruption of normal tissue
development .
The common symptom of mistletoe infection is branch dieback. Over a period of time,
the branch distal to the mistletoe connection dies.
The large swelling on this pine branch
infected by dwarf mistletoe
Symptom
Branch dieback associated with
infection by south-western oak
mistletoe on Emory oak
Dwarf mistletoe plant parasitizing the
trunk of a conifer (larch) and causing it
to swell and, later, to possibly break at
the point of infection
Branch distortion due to
branch dieback

59. Trees severely infected with mistletoes often develop dead top.
Witches’-brooms are the most easily observed symptom of dwarf mistletoe infection
and serve as large nutrient sinks that contribute to the decline of host vigor and
growth and eventually causing premature death.
The effects of mistletoes on their hosts include reductions in growth, vigor, fruiting,
and seed production.
A dead top has developed on
this western larch severely
infected with dwarf mistletoe
Lodgepole pine with dead top and
dense dwarf mistletoe-induced
brooms on the lower stem.
Mortality of bristlecone pine associated with
severe infection by dwarf mistletoe. The many
witches’-brooms on the dead tree, demonstrating
that the tree was severely infected before it died.
Witches’ broom on spruce

60. Pine infected by Psittacanthus
angustifolius in Central America.
Large swellings on a host branch are associated with
profusely branched extraxylary absorptive structures
produced by mistletoes, such as with some species of
Phoradendron.
Witches' brooms -- dense,
multiple branches on lodgepole
pine infected with dwarf
mistletoe.
A large group of true
mistletoes growing on
many branches of a
hardwood tree.
Dense dark green brooms
on ponderosa pine
infected with lodgepole
pine dwarf mistletoe.

61. Dwarf mistletoe killed jack pine trees
Dead witch’s broom on a pine tree Opening in the forest caused by mistletoe

62. When a mistletoe seed lands on and becomes attached
to the bark of a twig or a young branch of susceptible
host, it germinates and produces a germ tube or radicle.
It produces a root-like haustorium that penetrates the
bark directly land reaches the phloem and the
cambium.
From this haustorium they absorb the nutrients from
the host needed for the development of the parasite.
Development of disease

63. After the entophytic system is well established and developed in the host, it produces
buds from which shoots develop the following year or several years later.
If witches’-brooms are produced on the affected area, the haustoria pervade all
branches and produce mistletoe shoots.
The parasite removes water, minerals, and photosynthates from the host and so
starves and kills the portion of the branch lying beyond the point of infection.
Furthermore, it causes excessive cell enlargement and division, with resulting swellings
and deformities of various shapes on the branches.

65. Mistletoes rating-
This method was originally designed for dwarf mistletoes (Arceuthobium spp.). In
this system, the live crown of each tree is visually divided into three parts.
Each third is rated according to the following scale: 0, no infection; 1, light mistletoe
infection (less than half of the branches infected); and 2, heavy mistletoe infections
(more than half of the branches infected). Bole infections were rated as 2 (Filip et al.,
2000).

66. The mistletoes is spread by dispersal of its seeds mostly through birds and some extent
by animals.
In southern India, Tickel's Flowerpecker is reported to facilitate seed dispersal of D.
falcata .
The dwarf mistletoes are primarily disseminated by an “explosive fruit” system
involving both hydrostatic and mechanical mechanisms .
The primary seed dispersers in Australia,
mistletoebirds (Dicaeum hirundinaceum)
Dwarf mistletoe seeds are expelled
from fruits at initial velocities of
about 24 m/s and may fly as far as 10
m
Tickel’s Flowerpecker
Dispersal Of Mistletoes seed

67. Management
Mechanical Control:
The most effective way to control mistletoe and prevent its spread is to prune out
infected branches, if possible, as soon as the parasite appears.
Infected branches need to be cut at least one foot below the point of mistletoe
attachment in order to completely remove embedded haustoria.

68. Some cases it is best to remove severely infested trees entirely because they are usually
a source of mistletoe seed.
Removal of mistletoe plants from infected branches does not kill the mistletoe, and
resprouting from the haustorial system often occurs. This has led to the application of
black plastic wraps around the infected portion of the branch to prevent resprouting
Prescribed fire can directly control dwarf mistletoes by scorch pruning lower infected
branches and brooms, killing severely infected trees,
The fire killed the mistletoe-infected branches
in the broom.
Underburns of sufficient intensity have a significant
controlling effect on ponderosa pine dwarf
mistletoe

69. Chemical control
The ethylene-releasing growth regulator, ethephon, may be used to control mistletoe
in dormant host trees which can cause abscission of the shoots and delay fresh seeding
for 2-4 years.
Injection of copper sulfate and 2,4-D into the affected branches has been found
effective against Dendrophthoe on many hosts.
A spray of Diesel oil emulsion in soap water is also effective in eradicating the
Dendrophthoe in mango trees.
Biological control :
Colletotrichum gloeosporioides is being developed as a biocontrol agent for use to
control A. americanum and A. tsugense .

70. Planting of Non host species:
Susceptible host seedlings should not be planted within about 50 feet of dwarf
mistletoe infection sources.
Planting non-host species in infected areas has often been recommended, and can be
a sound approach for increasing future productivity.
Deciduous trees and shrubs, such as birch, pea shrub, ash, aspen, cottonwoods, and
Gambel oak also can be planted in affected areas because dwarf and juniper mistletoe
do not attack these plants
radford flowering pear, Chinese pistachio, crape myrtle, eucalyptus, ginkgo, golden rain
tree, liquidambar, sycamore, and conifers such as redwood and cedar are resistant
against Broadleaf mistletoes.

73. Conclusion