This document discusses the importance of alternate hosts in crop pest management. It notes that alternate hosts can act as reservoirs for crop pests by providing food, shelter, and oviposition sites. Specific examples are given of weed species that serve as alternate hosts for pests of various crops like rice, cotton, horticultural crops, and more. Alternate hosts can also function as trap crops, natural refugia for Bt crops, and providers of food and shelter for beneficial natural enemies. While alternate hosts play several beneficial roles, their removal is not always advisable as it could also drive pests to infest crops. Careful management of alternate hosts is important for integrated pest management.

1. STATUS AND SCOPE OF ALTERNATE HOSTS IN
CROP PEST MANAGEMENT
BY
P.MANIKANDAN
1st Ph.D Entomology
Chairman
Dr.V.Selvanarayanan
Professor in Entomology

2. FEEDING BEHAVIOUR
Monophagous
Stenophagous
Polyphagous
2

3. HOST ALTERNATE HOST
3

4. IMPORTANCE OF ALTERNATE HOSTS IN CROP PEST
MANAGEMENT
1. Alternate hosts as reservoir for crop pests
2. Scope of alternate hosts as trap crops
3. Alternate hosts as natural refugia for B.t.
transgenic plants
4. Alternate hosts as food and shelter for
natural enemies
5. Alternate hosts as dead end hosts
Norris and kogan , 2005 4

5. 1.Alternate hosts as reservoir for crop
pests
• Weed as a hosts for different insect and mite
pests
• Weeds-primary producers
• Weeds-alternative hosts for crop pests when the
crop is absent or is not in a phenological state
suitable for the pest.
• Weed used as alternative hosts are located in the
crop field, adjacent noncropped land or even
within the ecoregion, distant from the crop field.
Norris and kogan , 2005 5

6. • weeds can enhance or hinder arthropod fitness
within the crop field.
• Weed presence or absence may affect arthropod
survival- Crop canopy is suboptimal for the
arthropods.
• Weeds- Faster spreading of pest.
Norris and kogan , 2005 6

7. Alternate
host as
reservoir for
crop pest
Food
Oviposition
substrate
Shelter
7

8. Alternate host as food
Alternate hosts of field crop pests
8

9. Kandu Jigi Hulu,( 2008).
Rice Thrips Eichnocloa crusgali
Rice water weevil Fimbrisylis tenera
9

10. Paspalladium geminatum Rice Gall midge
Paspalum scrobiculatum
Ischaeum ciliare
Panicum spp
Cynadon dactylon
Eleusine indica
10

11. Kandu Jigi Hulu,( 2008).
Cynadon dactylon
Eichnocloa crusgali Fimbrisylis tenera
Rice Whorl maggot
11

12. Kandu Jigi Hulu (2008)
Rice Blue beetle Ammania sp
Imperata spRice Green horned caterpillar
12

13. Kandu Jigi Hulu,( 2008).
Rice case worm
Brachiaria mutica Cyperus rotundusPaspalum scrobiculatum
13

14. Razzaque and Karim, 1989
Eichnocloa crusgalli
Rice leaf folder
Leersia hexandravena sp Leptochloa chinensis
Setaria itlalica.
14

15. Rice gundhi bugs
Paspalum scrobiculatum
P. repensEichnocloa crusgalli
15

16. Rice Yellow stem borer
(Zaheruddeen and Prakasa Rao, 1983)
Leptochloa panicoids
16

17. (Zaheruddeen and Prakasa Rao, 1983)
Rumex dentatusChenopodium album
Cyperus difformis
Echinochloa colona
Rice-root nematode Hirschmanniella oryzae
17

18. (Zaheruddeen and Prakasa Rao, 1983)
Chilo partellus Pennisetum purpureumm Echinochloa pyramidalis
18

19. Spotted pod borer: Maruca testulalis
Blue butterfly: Lampides boeticus Gliricidia sepium
Sesbania pachycarpa
Krutti chyya, 2012
19

20. Narrow-leaved vetch,
Vicia sativas
Cowpea curculio
purple cudweed,
Gnaphalium purpureum
Moss verbena, Verbena tenuisecta.
20

21. Red hairy caterpillar
Aproaerema modicella
Psoralea corylifolia
Pennisetum sp
Okello et al., 2016 21

22. Helicoverpa armigera,
Sonchus oleraceus
Leaf webber,
Antigastra catalaunalis Pedalium murex
Sphinx moth-Acherontia styx Clerodendrum phlomidis
Gu and Walter, 1999 22

23. Tridax procumbensSemilooper, Achaea janata
Cotton mealybug
Xanthium strumarium
Portulaca grandiflora
23

24. Cotton stem weevil
Abutilon indicum
Hibiscus rosa sinensus
Corchours olitorius
Sida spp
24

25. Pink bollworm
Pink bollworm
Thespesia
Hollyhock,
Dusky cotton bug
Abutilon indicum 25

26. Alternate hosts of Horticultural crop
pests
26

27. Brinjal shoot and fruit borerBrinjal spotted leaf beetle
S. Indicum
Solanum xanthocarpum
Solanum nigrum
S.torvum
Rai et al., 2014 27

28. Cucurbit fruit fly
Coccinia
Radish flea beetle
Gynaudropsis pentaphylla
Colorado potato beetle
Solanum carolinenese 28

29. Thlaspi arvense
Cabbage diamond back moth
Gynaudropsis pentaphylla
Cabbage aphid
Capsella bursa-pastoris
Gabrys and Pawluk, 1999 29

30. Tomato thrips
Amaranthus hybridus
S. nigrum
Tagetes minuta
Daturastramonium
30

31. Banana aphid
Colocasia antiquorum
Citrus butterfly Psoralea corylifolia
Amomum subulatum
31

32. Citrus fruit sucking moth
Cocculus pendulus
C. hirsutus
Tinospora cardifolia 32

33. Trianthema portulacastrum
Chenopodium albumPortulaca oleracea
Beet webworm
33

34. Oxalis sp
Datura stramonium,
Sonchus sp.,
Tagetes sp
Serpentine leaf miner
Shepard and Johnson, 2000
34

35. Synedrella nodiflora,Erechtites hieraciifolia
Deeringia amarantoides Ipomoea aquatica Basella alba
Vegetable leaf miner
Shepard and Johnson, 2000
35

36. Southern beet
webworm moth
S. indicum
Purslane
Portulaca oleracea
Chenopodium album
Solanum nigrum
36

37. Alternate hosts as Oviposition Substrates
37

38. common chickweed- Stellaria mediaHenbit -Lamium amplexicaule
Alfalfa weevil-Hypera postica
BenSaad and Bishop,1969 38

39. Black cutworms-Agrotis ipsilon
Yellow rocket
Curly dock-Rumex crispus
Busching and Turpin, 1976 39

40. Amaranthus retroflexusSpodoptera exigua
western corn rootworm-Diabrotica virgifera Setaria spp
Greenberg et al., 2002
Kirk and Calkins., 1968 40

41. Giant foxtail -Setaria faberii
Quackgrass -Elytrigia repens
The stalk borer-Papaipema nebris
Levine et al., 1975 41

42. Alternate host as on Shelter
Rice water weevil Dallisgrass -Paspalum dilatatum
Blueberry maggot -Rhagoletis mendax
Palrang et al.,1994
Geddes et al.,1992 42

43. Nematodes
(Sunil et al., 2010)
weeds-slender amaranth old world diamond flower Tropic ageratum
sickle pod
balsam apple
little ironweed ivy gourd cut leaf ground cherry
43

44. (Leo, 1998).
Digitaria sanguinalis
Cassava infested with Meloidogyne
Potato infested with Meloidogyne incognita
44

45. Role of weeds in crop ecosystems
• Lead to increased pest populations
• Japanese beetles (Popillia japonica) in Soybean field(10 fold).
• Diabrotica barberi and D. virgifera virgifera in corn
• Flower thrips (Megalurothrips sjosdti) populations in cowpeas
(Vigna sinensis)
Hammond and Stinner., 1987
45

46. Scope of weed hosts as trap crops
shepherd’s purse
Capsella bursa-pastorisTwin cress-Coronopus didymus
Hedge mustard-
Sisymbrium officinale
Cameron et al., 2017
46

47. grasshoppers
Digitaria ciliaris
Coop and Croft .,1993
47

48. Army worm
Colocasia esculenta
Zhou et al., 2010
48

49. Army cutworm - Euxoa auxiliaris
John, 2014
Tansy mustard - Descurainia pinnata
49

50. Sesame webworm,
Antigastra catalaunalis Pedalium murex
Saravanaraman et al.,2016
50

51. western corn rootwormCommon ragweed – Ambrosia artemiisifolia
Alternate hosts as natural refugia for
B.t crops
Losey et al., 2001
51

52. Sesbania pachycarpa Maruca vitrata
Ibrahim Baoua et al.,2011 52

53. Alternate Hosts for
Beneficial Arthropods
Pollen and
nectar provider
Host provider
53

54. • Weed plants those are growing naturally such
as Tridax procumbens, Ageratum sp,
Alternanthera sp., etc. which act as nectar
source for natural enemies.
Tridax procumbens Alternanthera sp
Pollen and Nectar provider
54

55. • Pollen feeding by the predacious mite Euseius
(Amblyseius) finlandicus on poppy (Papaver
rhoeas) was reported by Broufas & Koveos
(2000)
Euseius finlandicus Poppy-Papaver rhoeas
55

56. • Weeds differed in their ability to provide
additional food for Diadegma insulare, a
parasitoid of the Plutella xylostella ; wild mustard
(Brassica kaber), yellow rocket (Barbarea
vulgaris), and wild carrot (Daucus carota) were as
effective as honey-water mixture.
Daucus carotaYellow rocket
Idrius and graphius, 1995 56

57. • Lambsquarters (Chenopodium album) and
common sowthistle did not provide nectar,
but the parasitoid used honeydew from
aphids feeding on the weeds.
Norris and kogan, 2005
57
Chenopodium album

58. As host provider
• Several native parasitoids are developed from
host larvae that live on smooth pigweed
(Amaranthus hybridus).
Tingle et al.,1978
58
Spodoptera spp Amaranthus hybridus

59. • Parasitoids of Lygus spp. were found from
bugs living on several weeds.
Graham et al.,1986
59

60. • The mymarid Anagrus epos, which uses the
blackberry leafhopper (Dikrella californica)
when the grape leafhopper (Erythoneura
elegantula) is not present.
Doutt and Nakata, 1973.
60
Anagrus epos Dikrella californicablackberry

61. Alternate host as Dead-End crops
• Yellowrocket, Barbarea vulgaris var. arcuata,
works as a dead-end trap crop for the
diamondback moth, Plutella xylostella.
Shelton et al., 2004
61

62. • Sunn hemp, Crotalaria juncea, has also been
suggested as a dead-end trap crop for the
bean pod borer, Maruca testulalis .
62
Crotalaria juncea Maruca testulalis

63. Constraints
63

64. Removal of weeds: Boon or Bane?
• Removing spiny amaranth (Amaranthus
spinosus)-beans (Phaseolus sp.) by cutworms.
Genung.,1959
64
Amaranthus spinosus

65. • Reducing London rocket (Sisymbrium irio), and
other weeds, drove false chinchbug (Nysius
raphanus) to grapes (Vitis vinifera)
Barnes.,1970 65
London rocket false chinchbug

66. • Burning weeds resulted in the migration of
blueberry maggot adults to production
blueberry fields.
Geddes.,1992
66

67. Natural enemies efficiency
• Prey eggs present in weed hosts may not be
recognised by parasitoids as like primary hosts
which results in fewer parasitized eggs.
• Percentage parasitization of the rice bug
(Leptocorisa oratorius) eggs laid on weeds
such as goosegrass (Eleusine indica) and jungle
rice (Echinochloa colona) was less than half
that of eggs laid on rice (Oryza sativa) plants .
Morrils and Almazon, 1990
67

68. • Redstem filaree (Erodium cicutarium) and desert plantain
(Plantago ovata) are suitable hosts for the beet
leafhopper (Circulifer tenellus), but its mymarid egg
parasitoid does not function well on these species, with
the result that inundative biocontrol releases do not work
well when these two species represent much of the
vegetation.
Al-Wahaibi and Walker, 2000.
68
Redstem filaree Desert plantain

69. • Interactions between soybeans and weeds
such as showy crotalaria (Crotalaria
spectabilis), sicklepod (Cassia obtusifolia), and
Florida beggarweed (Desmodium tortuosum)
resulted in reduced rates of attack on prey by
Geocoris punctipes.
• Carabid beetles were caught in herbicide-
treated than in untreated weedy plots,
although there were more carabid and
staphylinid larvae in the weedy plots .
69
Norris and Kogan, 2005

70. • Problem in using as trap crop over population
development leads to field infestation.
• Using as dead-end crops is limited because of
lack of knowledge on more number of dead
end crops.
70

71. Conclusion
• Destruction of alternate hosts
• Trap crops
• Refugia
• Natural enemies conservation
• Dead end crops
• Two edged sword
71

72. Thank you
72