breeding for insect resistance in cucurbits

1. BREEDING FOR INSECT
RESISTANCE IN CUCURBITS
Manohar Lal Meghwal
PhD I year
Dept. of Pomology and flori.

2. Insect pests of cucurbits
Major insect pests
• Red Pumpkin Beetle, Aulacophora foveicollis
(Coleoptera: Chrysomelidae)
• Cucurbits Stink Bug, Cordius janus (Hemiptera:
Pentatomidae)
• Pumpkin Fruit Fly, Bactrocera curcubitae (Diptera:
Tephritidae)
• Spotted Beetle, Epilachna vigintioctopunctata / E.
Pussillanima (Coleoptera: Coccinellidae)

3. Red pumpkin beetle Cucurbit stink bug
Spotted beetle, Epilachna beetle Cucurbit fruit fly

4. Minor insect pests
• Cutworm, Agrotis segetum/A. ipsilon (Lepidoptera: Noctuidae)
• Flea Beetle, Phyllotreta crucifera (Coleoptera: Chrysomelidae)
• Aphids, Aphis gossypii/ Myzus persicae (Homoptera: Aphididae)
• Whitefly, Bemisia tabaci (Homoptera: Aleyrodidae)
• Soybean Hairy Caterpillar, Spilarctia casigneta (Lepidoptera:
Arctiidae)
• Banded Blister Beetle, Mylabris orientalis (Coleoptera: Meloidae)
• Semilooper, Anadividia (Phytometra) peponis (Lepidoptera:
Noctuidae)
• Stem Boring Beetle, Apomecyna saltator (Coleoptera: Cerambicidae)

5. Cutworm ` Flea
beetle
White fly Peach aphid Banded blister beetle
Stem boring beetle

6. MYZUS PERSICAE (PEACH-POTATO APHID)
APHID COLONYALATE FORM APTEROUS

7. Soybean hairy catterpillar

10. Red Pumpkin Beetle,
Aulacophora foveicollis
(Coleoptera: Chrysomelidae)
• Red pumpkin is serious pest of cucurbits which is widely distributed in
Asia, Australia, southern Europe and Africa.
• Damage is caused by grubs as well as by beetles.
• The grubs lead a subterranean(underground) life and, full grown grub
measure about 12 mm in length and 3.5 mm across the mesothorax.
• They are creamy white, with a slightly darker oval shield at the back.
• The beetles feed on above the ground plant parts. They are oblong
and 5-8mm long.
• Their dorsal body surface is brilliant orange red & ventral surface is
black being clothed in short white hair.

11. Life cycle:
• The beetles are found concealed in groups under dry weeds, bushes
& plant remains or in the cervices of soil.
• They resume activity as soon as the season warms up
• In life span of 60-85 days, lay about 300 oval yellow eggs singly or in
batches of 8-9 in moist soil, near the base of the plants.
• The eggs hatch in 6-15 days and the grubs remain below the soil surface
feeding on roots, underground stems of creepers and on fruits
laying in contact with the soil.
• They are full grown in 13-25 days and pupate in thick walled earthen
chambers in the soil, at a depth of about 20-25 cm.
• The pupal stage lasts 7-17 days and the beetles, on emergence, begin to
feed and breed.
• The life cycle is completed in 26-37 days and the pest breeds five times
from March to October.

12. Damage:
• The beetles are very destructive to
cucurbitaceous vegetables, particularly during
March-April when the creepers are very young.
• The grubs damage the plants by boring into the
roots, underground stems & sometimes into the
fruits touching the soil.
• The beetles injure the cotyledons, flowers and
foliage by biting holes into them.
• The early sown cucurbits are to severely damage.

13. Management:
• Infested fields plough deep to kill the grubs in the soil.
• Flooding irrigation in the field.
• Sow the crop in November to avoid damage by this pest
• Apply 7Kg of carbofuran 3G per ha 3-4 cm deep in the
soil near the base of the plants just after germination
and irrigate.
• Spray 375g of Carbaryl 50WP in 250 liters of water per
ha

14. Cucurbits Stink Bug,
Cordius janus
(Hemiptera: Pentatomidae)
• The cucurbits stink bugs attack all
members of the cucurbits.
• Adults are winged and grayish brown.
• The edges of the abdomen and underside of the insect
have orange to orange brown stripes.
• Feeding by piercing and sucking mouthparts occurs
primarily on the plant foliage and tender stems.
• Sometimes, cucurbits stink bugs may also damage on
fruits.
• The associated damage symptoms include wilting of
leaves and ultimately result black or dry out.

15. Life Cycle:
• Cucurbits stink bug egg are 1/16 inch long & laid in
clusters of 15-40 on the undersides of leaves or stems.
• Eggs are bronze to brick red in color and hatch in 1 to
2 weeks.
• The colour of nymph ranges from mottled white to
greenish gray, which have black legs.
• Later on, they turn dark brown & resemble with
adults.
• The nymphs have partial development of wings, whereas
the adults have full-grown wings.
• The nymph become adult in 4 weeks.
• The total life cycle completes within 4-5 weeks.

16. Management:
• Collect and destroy the different stages of bug.
• Field sanitation, removal of weed hosts and other
overwintering sites of bugs.
• Parasitiod like a Tachinid fly (attack nymph and
adult) and some wasps (Hymenoptera: Encyrtidae
and Scelionidae are egg parasition) can be used
for management.
• Spray 1 liter of malathion 50EC in 250 liters of
water per ha.
• Spray Rogor (dimethoate) 30 EC @1ml/liter of
water.

17. Pumpkin Fruit Fly, Bactrocera
curcubitae (Diptera: Tephritidae)
• This is the most destructive pest of cucurbits.
• Only the maggot cause damage by feeding on near
ripe fruits, riddling (piercing ) them and polluting the
pulp.
• The maggots are legless and appear as headless, dirty
white wriggling creatures, thicker at one end and
tapering to a point at the other.
• A full grown maggot is 9-10 mm long & 2 mm broad
in the middle.
• The adult flies are reddish brown with lemon yellow
markings on the thorax and have fuscous areas on the
outer margin of their wings.

18. Life cycle
• This pest is active throughout the year, but the life cycle is prolonged during
winter.
• The adult flies emerge form pupae in the morning hours and mate at dusk.
• It takes a few days for the eggs to mature inside the body of female which
starts laying them within 14 days.
• During winter, the pre-oviposition period is prolonged.
• They oviposit in comparatively soft fruits avoiding those with hard rind.
• The selection of a suitable sites and the actual laying of eggs take about 6-8
minutes.
• A cavity is made by sharp ovipositor and about a dozen white cylindrical egg
are laid, mostly in the evening hours.
• After laying the eggs, the female releases a gummy secretion which cements
the tissues surrounding the pucture and makes the entrance water proof.
• The female, on an average lay 58-95 eggs in 14-54 days.

21. Life cycle contd.
• The egg hatch in 1-9 days and the maggots bore into the pulp forming
galleries.
• The attacked fruits decay because of secondary bacterial infection.
• The larva are full grown in 3 days during summer & 3 weeks during winter.
• The mature larvae come out of the rotten fruits and move away in jumps of
12-20 cm.
• These are made possible by folding & unfolding the two ends of the
elongated body.
• After reaching a suitable place, they bury themselves about 5 mm deep in
the soil and pupate.
• The pupae are barrel shaped, light brown & they transform themselves into
winged adults in 6-9 days in the rainy season and 3-4 weeks in the winter.
• There are several generations in a year.

22. Damage:
• The maggot pollute and destroy fruits by
feeding on the pulp.
• The damage caused by this fruit fly is most
serious in cucurbits
• After the first shower of the monsoon, the
infestation often reaches up to 100 percent.
• . resistance to fruitfly is reported in C.
callosus.

23. Management:
• The regular removal & destruction of the infested fruits
• Frequent raking of the soil under the vine/ ploughing the infested field
after crop harvested can help in killing the pupae.
• Install Cue lure trap (3 traps per ropani)
• Foliar spray of malathion 50%EC @ 2ml/liter @2g jaggery/liter of
malation solution.
• Treat root zone soil of plants with Malation 5% Dust@ 20 kg/ha to kill
hibernating pupa
• Use protein bait spray (Malathion+hydrolysed protein+ water at few
spots in a field. Both male and female are attracted to ammonia generated
by protein sources.
• Use food lure@ 1kg pumpkin and & 100 gm of jaggery and 10 ml
malathion.
• Apply bait spray containing 50ml malation 50EC +0.5kg of sugar in 50
liters of water per ha. Repeat the spray if problem is serious.

24. Spotted Beetle, Epilachna vigintioctopunctata /
E. dodecastigma (Coleoptera: Coccinellidae)
• 2 species of spotted beetle Epilachna dodecastigma, E. vigintioctopunctata
attacked different cucurbits and also solanaceous crops like brinjal, tomtato and
potato.
• Another species E. demurili, attacks cucurbitaceous vegetable exclusively.
• Damage is caused by the beetles as well as the grubs.
• Beetles of all the three species are about 8-9 mm in length & 5-6 mm in width.
• E. viginitioctopunctata beetles are deep red and usually have 7-14 black spot on
the each elytron whose tip is somewhat pointed.
• Beetles of E. dodecastigma are deep copper- coloured and have six black spot on
each elytron whose tip is rounded.
• E. demurili beetles have a dull appearances and are light copper coloured. Each
of their elytron bears six black spots surrounded by yellowish rings.
• Grubs of all the three species are about 6 mm long, yellowish in colour and have
six rows of long branched spines.

25. Life cycle
• The life cycle & mode of damage of the three species of spotted beetle are very similar.
• Considering their abundance, E. vigintioctopunctata is the most important.
• It passes the winter as a hibernating adult among heaps of dry plants or in cracks & cervices in the
soil.
• It resumes activity during March- April & lays yellow cigar shaped eggs, mostly on the underside of
leaves, in batches of 5-40 each.
• A single female can lay up to 400 eggs in her lifetime. The egg hatch in 2.9-5 days at 35-25 °C.
• The grubs feed on the lower epidermis of leaves and are full grown in 7-17 days at 35-25 °C
• The pupae are darker and are found fixed on the leaves, stems and most commonly, at the base of plants.
• The pupal stage lasts from 5- 13 days at 35-25 °C.
• The pest passes through several breeds from March to October and its population maximum at the end of
April or in early May.
• During the hot and dry months, the number declines greatly but the population again builds up in
August.

27. Damage:
• Both the adults and grub cause damage by feeding
on the lower and upper surface of leaves.
• They eat up regular areas of the leaf tissue,
leaving parallel band of uneaten tissue in
between.
• The leaves become a lace like appearances.
• They turn brown, dry up and fall off and
completely skeletonize the plants.

28. Management
• Field sanitation
• Collect and destroy the infested leaves along
with insect in initial stages
• Spray 625ml of malathion 50EC in 325 litres
of water per ha at 10 days intervals as soon as
the pest appears.

29. Mechanism of Insect
Resistance

30. • Mechanisms of defense in plants against pests Plants exhibit a
wide variety of strategies and mechanisms of defense against
pathogens and insects pest that may be classified into three major
groups – avoidance, resistance, and tolerance.
• KM. Painter (1951)classified mechanisms of resistance into 3 main
categories
• Avoidance Also described as escape, avoidance is a mechanism that
reduces the probability of contact between insect pests and the plant
Antixenosis is mechanism employed by the plant to reduce
colonization by insects. Plants that exhibit antixenotic resistance
should have a reduced initial number of colonies early in the
season..
• Resistance The mechanism of resistance manifests after a host has
been attacked by a insect pest. The mechanism operates to curtail
the invasion or to reduce the growth and/or development of the
Insect. Antibiosis operates after the insect have colonized and have
started utilizing the plant.

31. • Tolerance Unlike avoidance and resistance
mechanisms that operate to reduce the levels of
infestation by the pest, tolerance operates to
reduce the extent of damage inflicted. The
afflicted host attempts to perform normally
inspite of the biotic stress.
• Tolerance of the plant does not affect the rate of
population increase of the target pest but does
raise the threshold level.

32. Antixenosis to oviposition
Resistance to oviposition may come from plant characteristics
that either fall to provide appropriate oviposition-inducing
stimuli or provide ovipositional inhibiting stimuli.
Oviposition preference is discussed on two bases of the plant’s
1. biophysical and
2. biochemical traits

33. Biophysical factors
• Plant pubescence
• Frego bract
• Visual factors

34. Plant pubescence
Insects with piercing and sucking mouth parts are deterred from
feeding on hairy plants or vascular bundles.
Breeding of hairy cottons in Africa and Asia to combat the Jassids
Empoasca spp. constitutes the foremost host plant resistance (HPR).
Pargell et al., (1949) demonstrated that greater hairiness to both
upland cotton (Gossypium hirsutum) and Egyptian cotton (G.
barbadense) mm related to jassid resistance.
Soybean varieties with a dense hairiness of foliage can manifest both
antixenosis to oviposition and feeding deterrence against leafhoppers,
The simple trichomes deter oviposition and feeding by preventing; the
insect’s ovipositor or proboscis from reaching the plant epidermis(Lee
1983)

35. Frego bract
• Other morphological features of plants, such as frego bract in cotton,
help reduce the number of eggs laid and subsequent damage by boll
weevils Anthonomus grandis (Jenkins and Parrot 1971).
• In field experiments, frego-bract cotton showed 50% less damage
from oviposition than normal cottons did. The role of the frego bract
in reducing damage by the boll weevil appears to be due to some
adverse effect on insect behavior.
• Frego bract is associated with hypersensitivity to the plant bugs Lygus
spp. and cotton fleahopper Pseudatomoscelis seriatus (Jenkins et al
1973).

36. Visual factors
• The colour and shape of plants remotely affect host selection
behaviour of phytophagous insects and have been associated with
some resistance.
• Yellow colour is preferred by aphids
• Green and blue green is preferred by cabbage butterfly
• Dark green preferred by rice leaf folder

37. Biochemical factors
• Chemical cues are involved in all the three phases of host
selection behavior; orientation, oviposition and feeding. Many
factors play a role in the process of opposition by different
insects, but long-range orientation of many insects to their host
plants is known to be guided by volatile, compounds
emanating from plants. Volatile hydrocarbons and other
secondary compounds act as oviposition deterrents
• Onion volatile diallyl disulfide is antagonistic to onion fly
Delia antiqua..

38. Antixenosis to feeding
• Insects respond to various feeding stimuli when selecting their host plants.
The absence of such stimuli and the presence of deterrent compounds
presumably contribute to antixeniosis types of resistance. The plant surface
is embedded with physical and chemical factors responsible for antixenosis
to feeding insects (Southwood 1986).
• number of phytophagous insect species shows that before feeding on a
plant they make some land of sensory exploration of the plant surface as a
prelude to biting. The leaf surface acts as the crucial interface between the
insect's battery of chemoreceptors and the plant (Southwood 1986

39. Antixenosis to feeding
• Non-glandular trichomes
• Glandular trichomes
• Leaf surface waxes
• Thickness of cell well
• Nutrient deficiency

40. Non-glandular trichomes
• Trichomes affect locomotion, attachment, shelter, feeding,
digestion and oviposition of insect and the effect depends on
density, length and shape of trichomes. Long hairs not only impede
movement, but also prevent the insect from reaching the leaf
surface to feed on.
• Trichomes have basically three types of effects on insect behavior
over the leaf surface:
(1) simple impedance
(2) physical trapping by hooked hairs
(3) stickiness caused by exudates from the glandular
trichomes.

41. • Smith et al (1975) showed that the rate of travel by the
first-instar larvae of the pink bollworm Pectinophora
gossypiella was more than six times faster on smooth
leaves the an on those with pubescence. Because of this
lack of movement, the larvae were deterred from the plant
substrate.
• Hooked trichomes in French bean offer resistance, to
aphid, Aphis craccivora

42. Glandular trichomes are widely distributed in vascular plants that exude
gummy, sticky, or polymerizing chemical mixtures that severely impede
the insect's ability to move, feed, and/or survive.
A number of plants of the Solanum lycopersicon, Nicotiana and Medicago
spp, are particularly adept in producing sticky leaf exudates.
Polyphenoloxidase and peroxidase activities are exhibited by the
glandular trichomes of S. berthaultii for oxidation of the phenolic
compounds in glandular exudates (Ryan et al 1982).
GLANDULAR TRICHOMES

43. Leaf surface waxes
Plant epicuticular waxes affect the feeding behavior of insects
particularly the settling of probing insects, acting as
phagostimulants or feeding deterrents. They also effect
colonisation and oviposition.
Ex: Wax bloom on leaves of crucifers deter feeding by
diamond back moth.
 In onion glossy foliage provide more resistance to thrips.

44. Thickness of cell well
Cell walls thickening affect the feeding behavior of
insects.
Examples:
• Rice varieties containing thicker hypodermal layers
offer resistance to stem borer.
• Stem density of pith and node tissues in wheat resists
damage by the wheat stem fly
• Sorgham varieties resistant to shootfly due to the
thickness of the cell walls

45. Nutrient deficiency
• The deficiency to the level of solids and
nitrogenous compounds in Canby an aphid
resistant raspberry showed delayed development,
significantly reduced size, lower fecundity, and
extensive mortality in the aphids Amphorophora
agathonica (Hottes)

46. Biochemical factors
• Several chemical constituents of plants that serve as
olfactory and gustatory stimuli, these may be
nutrients, sugars, amino acids, phospholipids, etc, or
non-nutritive constituents, i. e., glycosides, alkaloids,
terpenoids, etc. Such stimuli are specific and are
crucial in evoking the behavioral response of insects
(preference/antixenosis) to plants.

47. Repellents
Plant defense compounds that prevent or reduce
contact between the insect and the substrate are
known as repellents.
• The exudates from the glandular trichomes of
Solanum spp contain volatile substances Including
sesquiterpenes. These volatiles repel the aphid Myzus
persicae

48. Antibiosis
• Adverse effect of the host plant on the biology (survival,
development and reproduction) of the insects and their
progeny due to the biochemical and biophysical factors
present in it.
• Manifested by larval death, abnormal larval growth, etc.
• Antibiosis may be due to
- Presence of toxic substances
- Absence of sufficient amount of essential nutrients
- Nutrient imbalance/improper utilization of nutrients

49. Symptoms of insects affected by antibiosis
include
• Death of young immature at stages
• Reduced growth rate
• Increased mortality in pupal stage
• Small adults with reduced fecundity
• Shortened adult life span
• Morphological malformations
• Restlessness and other abnormal behaviour

50. Presence of toxins:
Presence of toxic metabolites such as alkaloids and
glueosides play an important role in resistance to insects.
1. DIMBOA (Dihydroxy methyl benzoxazin)- Against
European corn borer, Ostrinia nubilalis
2. Gossypol (Polyphenol) -Helicoverpa armigera (American
bollworm)
3. Sinigrin - Aphids-Myzus persicae
4. Cucurbitacin -Cucurbit against fruit flies.
5. Salicylic acid -Rice stem borer

51. Presence of growth inhibitors
• Steriodal glycosides in potato and saponins in alfalfa
offer resistance to insects
• Gossypol, the yellow polyphenolic pigment found in
the pigment glands of the genus Gossypium, is insect-
growth inhibitor that has resistant to the bollworm,
tobacco budworm, pink boll worm, and other tissue
borers.

52. Nutritional imbalance
Reduction in the sugar content of the plant at the critical stages
of insect growth may adversely affect the insect.
• Ex: larvae of the European, corn borer require glucose up to the
fourth instar and are capable of differentiating between varying
sugar concentrations to the, host plant tissues.
Structural factors can serve as defense mechanisms for plants when herbivores
come in contact with them. The most common contact factors that impart
antibiosis resistance are
Plant-tissue toughness, Cell-wall composition
Proliferation of wounded tissues
Structural factors

53. • Melon
Whitefly :C. asper, C. denteri, C. dipsaceus, C. sagittatus.
Fruitfly : C. callosus
Sources of resistance

54. Plant-tissue toughness
Toughness may reduce the suitability of leaves as a food source
for herbivores in several ways:
• Indigestible polymers such as cellulose and lignin in secondary
tissues may reduce the rate of leaf consumption by herbivores.
• Indigestible materials in tough leaves may be less suitable for
herbivore growth, development, and/or survival.
• Nutrients such as proteins and carbohydrates may be less
available in tough leaves because of the hydrogen bonding
between these compounds.
Ex: Tough leaves of Salix babylonica and S. alba that can resist
tearing, erode the cutting surface of the incisors of the leaf beetle
Plagiodera versicolora

55. Cell-wall composition
• The presence of neutral detergent fiber (NDF), lignin, and biogenic
silica in cell walls of plants can affect insect feeding at both
nutritional and physical level. Plants high cell wall structural
components are not desirable for herbivores (Scnber and Sansky
1981 ).
• Elevated levels of indigestible fiber and silica may Increase the
bulk density of the diet to the extent that insect are
unable to ingest sufficient quantities of nutrients and water.
Ex: Silica in the rice leaves affect the feeding of stem borer

56. Proliferation of wounded tissues
• Involve the proliferation of cells triggered by injury or
increased secretion 0f plant substances known to
cause the death of eggs or young larvae inside of
damaged plant
• Ex: larvae of young pink bollworms were crushed or
downed by proliferating cells of the injured tissues in
certain corn line.
• In mustard – necrotized zone around the base of the
egg of cabbage worm causing them desiccate.

57. Tolerance
• Tolerance refers to the ability of the host plant to with stand an
insect population sufficient to damage severely the susceptible
plants.
• Tolerance is a plant response to an insect pest. Whereas, antibiosis
and antixenosis resistance cause an insect response when the
insect attempts to use the resistant plant for food, oviposition, or
shelter.
• This form of resistance include general vigour, compensatory
growth in individual plants and or the plant population, wound
healing, mechanical support in tissues and organs and changes in
photosynthate partitioning.

58. Advantages and limitations of tolerance
Advantages
• Tolerant varieties have higher ETL
• They prevent development of biotypes
• They increase yield stability
Limitations
• Insect populations are allowed to sustain epidemics in an area, causing
problems in other crops
• It is more strongly affected by environmental extremes than other
forms of resistance

59. Conclusion
• The mechanism of resistance has three main
components that check the pest population from
orientation, feeding and oviposition. These
components are responsible for the development
of resistance against various insect pest in
cucurbits.
• These resistance does not end with a generation of
the insect pest, but lasts against successive
generations.
• These are eco-friendly and does not cause any
pollution in component of the environment nor
does it have any deleterious effect on man or wild
life.