lectures in: pests of crops (course # 494553) lectures in: pests of crops (course # 494553) prepared...

Lectures in: Lectures in:

Pests of CropsPests of Crops

(Course # 494553)(Course # 494553)

Prepared by

Prof. Yacoub Batta

Department of Plant Production & Protection Faculty of Agriculture An-Najah National University Nablus, West Bank, Palestine Issued on January, 2011

An-Najah National University Faculty of Graduate Studies Master program in plant Production and Protection

Course title and number Pests of Crops (494553)

Instructor(s) name(s) Prof. Yacoub BattaContact information (Email, office location, other information):

[email protected]; Khadouri (Tulkarm)

Semester/ academic year Spring semester 2010 /2011

Compulsory / Elective Elective course; 3 credit hours

Prerequisites -

Course Contents(description)

This course includes studying the different kinds of pests (e.g. animal, insect and mite pests) that can attack the different species of crops. It also includes studying classification of these pests, their hosts, damage, pest status, life history, distribution and control measures that could be undertaken against these pests.

mailto:[email protected]

Course Objectives To provide the student with required information regarding the common pests of crops in terms of their classification, hosts, damage, pest status, life history, distribution and control. To analyze & understand the research papers related to these pests

Intended learningOutcomes (ILO) andCompetences

At the end of this course, students should be able 1. to identify and describe the common pests of crops existing in the local environment, 2. to know the hosts that may be attacked by these insect pests 3. to know where these pests can survive during the cold winter or hot summer.4. to know the life history of pests especially their life stages and places of existence5. to define the environmental conditions that may be required for the development & growth of these pests6. to know the effective control measures that may be undertaken against these pests.7. to quantify & specify the damage caused by these pests8. to analyze and understand the research papers related to these pests

Textbook and References(Online Resources)

1.Text book: Hill, S. D. 2008. Pests of Crops in Warmer Climates and Their Control. Springer, Library of Congress. 704 Pages. 2. Reference: Richard J. Elzinga, 1997. Fundamentals of Entomology. 4th edition. Prentice Hall, Upper Saddle River, New Jersey. 475 Pages. 3. Periodicals & Scientific Journals 4. Other online resources

Assignment Criteria Activity Percent (%)

Midterm Exams (1st & 2nd exams)

2 X 20 = 40

Analysis of articles on pests of crops

15

Other criteria (Research, Discussion etc.)

5

Final Exam 40

Week

Subject

1 Introduction to pests of crops (pest control and pest damage). 2 Major groups of pests: I) Vertebrate pests like Higher animals, Rodents, Birds and

Other vertebrates + analysis of research paper related to these pests.3 II) Molluscous and Nematode pests + analysis of research paper related to these

pests.4 III) Insect pests (major group of pests): 1) Orthopterous insect pests + analysis of

research paper related to these pests.5 2) Isopterous insect pests + analysis of research paper related to these pests.6 3) Homopterous insect pests + analysis of research paper related to these pests.

7 MIDTERM EXAM 18 4) Heteropterous (Hemipterous) insect pests + analysis of research paper related to

these pests.9 5) Thysanopterous insect pests + analysis of research paper related to these pests.10 6) Cleopterous insect pests + analysis of research paper related to these pests.11 7) Dipterous insect pests + analysis of research paper related to these pests.12 8) Lepidopterous insect pests + analysis of research paper related to these pests.13 MIDTERM EXAM 214 9) Hymenopterous insect pests + analysis of research paper related to these pests15 IV) Pests of order Acarina + analysis of research paper related to these pests.

16 FINAL EXAM

Introduction to Pests of CropsIntroduction to Pests of Crops

I. The present status of pest management

*Integrated pest management (IPM) has been studied & discussed for > 20 years ago, but there has still been more discussion than action in regard to its implementation because of the:

#lack of a truly interdisciplinary approach to the basic research,

#reluctance of farmers to appreciate & accept the principles of IPM & thus to adopt this long-term approach to control pests. They usually still prefer frequent & repeated applications of insecticides.

*Enough IPM programs have been carried out in North America & Europe to demonstrate the effectiveness of this approach, and if an overall reduction in insecticide usage of 50% can be achieved, the future for IPM is surely bright.

*At present, it is desirable to adopt the best practice approach & to do the best that is possible using the existing knowledge. Of course in the hope that in the future more knowledge will be available to permit a complete IPM approach.

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Introduction to Pests of CropsIntroduction to Pests of Crops

II. Pest damage to crops

*Normally, the pest damage is easy to identify on damaged plants when both pest & its damage are visible on the attacked plant. For example, damage to crops by leaf-eating is the normal method of feeding of some mammals (rabbits & rodents), birds, molluscs (slugs & snails), most grasshoppers, locusts, caterpillars & some beetles.

*In some cases, the situation is more complicated. For example, the leaf miners may be larvae of Diptera (family Agromyzidae), or Lepidoptera (family Phyllocnistidae) or Coleoptera (family Chrysomelidae).

*Assessment of pest damage: if the pests are causing no crop loss, their presence on plants & the damage they cause may be ignored. However, most pest populations produce some damage of significance. For example, a single codling moth larva can effectively destroy a single apple tree & a relatively small number of larvae can ruin an entire crop. On the other hand, an

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Introduction to Pests of CropsIntroduction to Pests of Crops apple tree can accommodate a large number of foliage-

eating caterpillars or sap-sucking bugs with no discernible loss of yield.

*Results that can be collected on damage of a pest may be used to define economic injury level (EIL) for that pest on a certain crop then extended to other crops in different parts of the world.

*In summary, damage which can be ignored on one crop may be of considerable economic importance on another (even closely related) crop, so damage assessment is different for each crop grown. Read the two examples on crop damage assessment (Fig.15. A & B) pages 60 and 61.

*Types of pest damage: 1) damaged leaves (mostly by biting insects; Fig. 8 &9) pages 68 & 69.

2) damaged leaves (by sap-sucking insects and mites; Fig. 10) page 70.

3) damaged stems (Fig. 12) pages 74.

4) damaged fruits and seeds (Fig. 13) pages 76.

5) damaged roots, bulbs & tubers (Fig. 14) page 78.

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Major groups of PestsMajor groups of Pests

I. Vertebrata pests

This group of pests includes Man, Monkeys, Wild Pigs, Rodents, Tree Squirrels, Rats and Mice, Fruit Bats & Birds pages 115 to 132.

For classification, hosts, damage, pest status, life history, distribution & control of these pests, see pages 115-132.

II. Mollusca & Nematoda pests

This group of pests incudes mainly Snails & Root knot nematodes (see pages 133-136).

III. Insecta Pests This group of pests incudes:

1) Order Orthoptera such as Field Crickets (p.139), Mole Crickets (p.142), Red Locust (p.148), Desert Locust (p. 151) & Javanese Grasshopper (p. 152).

2) Order Isoptera such as Harvester Termite (p. 154) & Crater Termite (p.160). 9


3) Order Homoptera such as Indian Sugarcane Leafhopper (p. 165), Tobacco Whitefly (p. 170), Citrus Whitefly (p.171), Green Rice Leafhopper (p. 176), Cotton or Melon Aphid (p. 188), Green Peach Aphid (p. 189), Banana Aphid (p.190), Black Citrus Aphid (p. 192), Cottony Cushion Scale Insects (p. 199), Citrus Mealybug (p. 205), Helmet or Hemispherical Scale Insects (p. 217), Olive Black Scale Insects (p. 218), California Red Scale Insects (p. 220), Purple Scale Insects (p. 225) and Citrus Muscle Scale Insects (p. 227).

4) Order Heteroptera (Hemiptera) such as cotton Lygus (p. 235), Cotton Seed Bug (p. 236), Leaf-footed Plant Bug (Squash Bug) (p.239), Coconut Bugs (p. 241), Harlequin Bugs (p. 247) & Green Sting Bug (Green Vegetable Bug) (p. 249).

5) Order Thysanoptera such as Coffee Thrips (p. 258), Cotton Thrips (Flower Thrips) (p. 259), Banana Thrips (p. 261), Citrus Thrips (p. 262) & Onion Thrips (p. 265).

6) Order Coleoptera such as Chafer Grubs (p. 277), Citrus Bark

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Borer (p. 279), Dried Fruit Beetle (p. 283), Saw-toothed Grain Beetle (p. 284), Flour Beetles (Red & Confused) (p. 287), Lesser Grain Borer (p. 290), Pollen Beetles (p. 293), Bean Bruchid (p. 304), Rice Leaf Beetle (p. 308), Colorado Beetle (p. 310), Cabbage Flea Beetles (p. 315), Banana Weevil (p. 329), Alfalfa Weevil (p. 333), Red Palm Weevil (p. 339), Rice & Maize Weevils (p. 343).

7) Order Diptera such as Medfly (Mediterranean Fruit Fly) (p. 357), Melon Fly (p. 363), Olive Fruit Fly (p. 365) & Cereal Leaf Miner (p. 372).

8) Order Lepidoptera such as Citrus Leaf Miner (p. 388), Diamond-back Moth (p. 391), Codling Moth (p. 396), Potato Tuber Moth (p. 401), Warehouse Moth (p. 421), Asian Corn Borer (p. 428), Indian Meal Moth (p. 429), Small White Butterfly (p. 439), Black or Greasy Cutworm (p. 455), Cotton Bollworm (p. 464) & Cotton Leaf Worm (p. 475).

9) Order Hymenoptera such as Leaf-cutting Ants (p. 487+488),

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Harvester Ants (p. 491), Fire Ants (p. 493), Common Wasps (p. 495).

10) Order Acarina such as Oriental Mite (p. 502), Citrus Red Spider Mite (p. 504), Citrus Bud Mite (p. 508) & Citrus Rust Mite (p. 509).

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Vertebrata Pests

I) Class Mammalia: includes the following types of pests:

1) Man who becomes a pest in rural areas. High value field crops & fruits are especially vulnerable, as are grain stores. One result is that seed stores are kept in homes & many grain stores are dug in the floors of the huts.

2) Monkeys (fam. Cercopithecidae) are pests of edible crops crops. For hosts, damage, pest status, life history, distribution and control see p. 115.

3) Wild Pigs (fam. Suidae) are pests of root crops & tubers. For hosts, damage, pest status, life history, distribution and control see p. 116.

4) Tree Squirrels (fam. Sciuridae) are pests of fruit trees. For

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hosts, damage, pest status, life history, distribution and control see p. 118.

5) Common Mole Rats (fam. Muridae) are pests of crops by eating roots of different crops & their underground parts. For hosts, damage, pest status, life history, distribution and control see p. 119.

6) House Mouse (fam. Muridae) is common pest that can eat the same food as Man & is more domestic pest than field pest. For hosts, damage, pest status, life history, distribution and control see p. 124.

7) Fruit Bats (fam. Pteropidae) are pests of ripe fruits in tropical areas. Their natural food is basically ripe wild figs but they can eat other ripe cultivated fruits such as banana, papaya, avocado, guava etc. They roost commonly hanging upside down in the tree

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foliage during the day and forage for fruit at night. Prompt harvesting of ripe fruits will minimize the loss by fruit bats. See Fig. 9.16 p. 125 for the dog-faced fruit bat.

II) Class Aves (Birds): are damaging pests to growing crops as well as taking grain & pulses from produce stores. Many types of birds are considered pests like ducks, geese, sparrows & weavers, pigeons & doves, parrots & parakeets.

# Sparrows (fam. Ploceidae) are pests of small-grain crops when ripening (rice, wheat, sorghum, millets). For hosts, pest status, life history & distribution see p. 127 & 128.

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Mollusca & Nematoda pests I) Mollusca pests: Many species of snails are pests of

crops of which Rice snails and Giant African snail are the most common:

1) Rice snails: they belong to order Gastropoda (fam. Ampulla-riidae), a number of large round-boddied pulmonates are to be found in paddy fields, they are amphibious and air-breathing, so do not survive prolonged submergence. Because of their large size and shape, some referred to as Apple snails. About a dozen species are found worldwide such as the following species:

- Ampullaria sp. in S. America

- Globa sp. in S.E. Asia

- Lanistes spp. in Egypt, Central & Southern Africa

- Pomacea spp. in S. America

Damage: Extensive damage was registered to rice seedlings. Eggs of snails are laid in clusters sometimes stuck onto plant stems. In some regions, the snails are regarded as good food

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and have been introduced deliberately.

Control: is difficult to achieve, hand collection of the adults is effective and duck predation of egg masses and young snails is successful. Many molluscicides have been tried with mixed success.

2) Giant African Snail (Achetina fullonica, fam. Achatinidae): a very wide host range of plants throughout the old world tropics.

Damage: Foliage destruction by eating & small plants may be destroyed; large holes are made in the plant leaves. Their nocturnal grazing goes up to a height of 2 m. Tellate mucous trails & fecal stripes are left behind.

Life history: They are nocturnal feeders. Toothed radula is the feeding organ & scrapin actions is effective at grazing. Egg masses are laid in the leaf litter.

Distribution: Native to tropical Africa but introduced into tropical Asia & up to China & Pacific islands.

Control: seldom really needed but hand collection during night


can be effective since the snails are large in size. 2) Nematoda pests: are large group of crop pests, difficult to assess their economic damage especially the soil nematodes. The most important type is the root knote nematodes.

* Root knot nematodes (Meloidogyne spp., fam. Heterodidae): They sre totally polyphagous and contain half a dozen of species. They have large number of host plants including very wide range of crop plants.

Pest Status: very serious pests of a wide range of crop plants and infections result in a severe loss in yeild.

Damage: Above-ground symptoms are: loss of plant vigour, wilting, loss of yield, increased susceptibility to pathogens & sometimes death of the crop plant. Underground symptoms are galls of varying size (depending upon the host species). Inside the galls, there are swollen females (pear shape) with a gelatinous egg sac.

Life history: Infective 2nd stage larvae of the nematode penetrate

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the roots & settle in the tissue inside. They feed & develop into males or females. The female become very swollen in pear shape but the males remain vermiform. The egg sac (in a gelatinous capsule) protrudes through the wall of the roots into the soil. Number of eggs laid / female = 300-1000. 1st & 2nd stage larvae are free-living. Total life cycle = 2 months at 20 deg. C and 1 month at 27 deg. C.

Distribution: The genus Meloidogyne is worldwide in the warmer regions (including tropical regions). Some species of this genus are present in southern USA & southern Europe and may be found in greenhouses in northern Europe and Canada.

Control: by using the following methods:

1) Cultural methods: Crop rotation with non-susceptible crops can be very effective; Resistant varieties of crops; Hot water treatment will kill nematodes in seeds but it is not effective against root knot nematodes.

2) Chemical control: by soil fumigation using soil fumigants such

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as Methyl bromide, D-D and Ethylene dibromide (application by injection in the soil of greenhouses and seed beds). Also, by using non-volatile nematicides like Oxamyl and Aldicarb (granular forms)which can be applied through seed drill. Soil sterilization techniques using heat or fumigants will eradicate plant parasitic nematodes from nursery beds before planting.

Insecta Pests

For facilitating the study of insect pests, Entololgists have divided these pests according to their orders. More than 15 insect orders will be studied here:

I) Order Orthoptera: It contains the following pests of insect species:

1) Field Crickets (Acheta spp., fam. Gryllidae):

- Hosts: They live in the soil & attack many different herbaceous crops at night. They damage tea & coffee seedlings by eating

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their bark.

- Damage: They eat the foliage of young plants during the night & attack woody plants and eat their bark.

- Pest status: are considered general pests and sporadically attack many crops at the seedling stage causing occasionally economic damage to these plants.

- Life history: Adult insects have dark-brown to black color (body length = 2-3 cm). They have long cerci and long ovipositor (15-18 mm). Eggs (elongate, banana-shaped & yellow) are laid in the ground in batches (up to 30 eggs / batch & up to 2000 eggs / female). Eggs hatch within 10-12 days at 26 deg. C & develop-ment into nymphs takes 40-60 days. Adults live for 2-3 months. Total time for the whole development takes 50-80 days according to climate & diet. Four generations per year are produced in tropical regions.

- Distribution: The two-spotted cricket (A. bimaculata) is found throughout Africa, southern Europe & parts of Asia but the other

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species A. testaceus is found in south China & in south east Asia.

- Control: since they are occasional pests and damage is not sufficiently serious, the control is not necessary but if required, a poison baits consisting of wheat bran mixed with a powdered insecticide such as chlordane or Sefsan or chlorpyrifos are effective.

2) Mole crickets (Gryllotalpa spp., fam. Gryllotalpidae): For hosts, damage, pest status, life history, distribution & control----------- see p.142

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3) Red Locusts (Nomadacris septemfasciata; Fam.: Acrididae):

- Hosts: These locusts prefer grasses & graminaceous crops but they can attack other crops to a lesser degree.

- Damage: the leaves are eaten from the margins inward. In a heavy attack, the entire lamina is eaten away. Swarm damage can be devastating & result in complete crop defoliation.

- Pest status: sporadic serious pests in tropical Africa (South of Sahara) but outbreak may occur in certain areas of Tanzania, Zambia & Malawi.

- Life history: Eggs are laid in wet season (November to April) in pods containing 100 eggs each & 3-4 pods being laid /female. Eggs hatch within 30 days after laying. Nymphs have 6-7 stages (instar nymphs) to complete their development within 2-3 months. They take several colors (red, black & yellow). Adults when emerge have a yellow-brown body color. Prothorax with broad, yellow and red longitudinal bands. The tibia of hind legs are reddish & the base of the hind wings is characteristically red.

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Adults live for 9 months & only one generation is produced per year. Dimensions: 50-60 mm for males & 60-70 mm for females.

- Distribution: in Central & Southern Africa (from Angola to Somalia & Eeast Africa). The breeding areas of these locusts are in Tanzania, Zambia & Malawi.

- Control: # they can be killed with the use of poison baits (wheat bran + powdered insecticide such as BHC as dust or aldrin as W.P),

# ground spraying with Carbaryl, aldrin or dieldrin, parathion- methyl or diazinon to control crawling swarms,

# areal spraying with the above liquid insecticides to control flying swarms,

# barrier spraying with residual insecticides such as with dieldrin can be successful & effective.

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4) Desert Locusts (Schistocerca gregaria, Fam. Acrididae):

- Hosts: a very polyphagous pest, and all crops are at risk but some preference for cereals.

- Damage: these insects eat leaves & soft shoots of crops. Leaves were eaten from the margin inwards. Swarm damage result in complete defoliation of crops attacked.

- Pest status: Serious pests in Africa & India. When swarms occur, the damage can be devastating over a wide area. The outbreak area is very extensive and may extend from W. Africa through the sahara to Pakistan & India. Typically, it can breed in any desert- type area when there is sufficient rain.

- Life History: Eggs of these locusts are laid by the thrusting ovipositor in a hole (10 cm deep) made in the soil ( sandy & embedded in a frothy mass to form egg pod at hardening). Each egg is oval (1.2 X 0.7 mm). Each egg pod contains 70-100 eggs and 4-5 egg pods were laid/female. Egg incubation period = 2 weeks according to the temperature. Upon hatching, emerged

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nymphs pass in 5 nymphal instars over a period of several weeks. Young grasshoppers exist in 2 distinct phases: solitary & gregarious . Dimensions: 40-50 mm for males & 50-60 mm for females with pale-yellow or brownish in color. Several generations/year.

- Distribution: It occurs in Africa through the middle east to Pakistan & India. Another species S. cancellata is important in South America and S. piceifrons is important in Central America.

Control: as in red locusts.

5) Javanese grasshoppers (Valanga nigricornis; Fam.: Acrididae):

They are important in Malasia, Thailand & Philippines. Their damage resemble that of red locusts & desert locusts. For more information on Hosts, damage, Pest Status, Life History, Distribution & Control….. See p. 152.

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II) Order Isoptera: It contains the following pests of insect species:

1) Harvester Termite (Hodotermes mossambicus; Hodotermitidae):

- Hosts: main hosts are the different species of grasses whereas cotton & other crops are alternative hosts.

- Damage: Many conical earth mounds (10 cm high) are seen in the grass area. Adult termites (workers) cut the grass plants into pieces then transfer them into holes in the mound’s center. Many bare, grassless patches in the vicinity of the mounds.

- Pest status: a major pest of grassland below 1500 m of altitude in parts of Africa especially during periods of drought or following overgrazing.

- Life history: each colony of termite is consisting of many hives constructed under the soil surface (0.2 to 1 m). These hives are interconnected by underground passage. Each hive has a dome-shaped cavity (0.5 m diameter), some of these hives contain all stages of termite development whereas others are used for


storage of cut grasses. The hives are connected to the surface by tunnel passing through the center of conical mounds. If the foraging tunnels are not in use, they are sealed with mud. Only termite workers (14 mm long, gray-brown with large heads) are seen on the soil surface. They forage (cut & gather grass and wood pieces) at dawn & dusk and at other times in cool weather. The soldiers (have pale bodies & large dark heads with massive jaws) usually take up positions near the entrance of foraging tunnels to repel intruders.

- Distribution: in South & East Africa.

- Control: # spraying plants (grassland) with dieldrin

# application of granular insecticides (e.g. phorate, isofentos) down the tunnel is effective.

# nest destruction down the entrance / ventillation tunnel using a number of contact insecticides or fumigants (Dursban, Karate etc.).

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2) Crater termite (Odontotermes badius; Fam. Termitidae):

This species of termite attacks the seedlings of various crops & grasses. It is also found in the mulches used in coffee, tea and banana plantations. For damage, Pest status, Life history, Distribution & Control…… see p. 160.

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III) Order Homoptera: It contains the following pests of insect species:

1) Indian Sugarcane Leafhopper (Pyrilla perpusilla; Lophopidae):

- Hosts: Sugarcane as a main host; Millets, Wheat, Maize & other species of gramineae as alternate hosts.

- Damage: sap sucking from plants by the feeding of nymphs & adults of the insect and transmitting of virus diseases.

- Pest Status: Not a serious pest, but various leafhoppers are of a wide occurrence on crops in the tropics.

- Life history: eggs are white & oval. Dimensions: 1.0 x 0.5 mm. They are laid on the leaf in 2-4 irregular rows & covered with a white waxy secretions. Each batch contains 30-50 eggs. Nymphs disperse & begin to feed on the lower surfaces of leaves. Honey dew is excreted & many ants are usually in abundance & sooty mold are common. There are 5 nymphal instars taking 5-20 weeks for completion. Adults jump readily with 7-8 mm long, pale brown with conspicous veins in the forewings & scattered

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tiny dark spots. The complete life cycle takes 40-45 days & 3-4 generations per year are produced.

- Distribution: It is found in Pakistan, India, Sri Lanka, Afghanistan, Burma & Thailand. There are 2 species of Pyrilla found in India & Sri Lanka.

- Control: Seldom required but when numbers are high, it is recommended to use light traps (insects are attracted to light) and weed control will reduce leafhopper population. Use of insecticides at weekly intervals such as Carbaryl, Malathion, Azinphos-methyl that will reduce the population.

2) Tobacco whitefly (Bemisia tabaci; Aleyrodidae):

- Hosts: Main hosts are: cotton, tomato, tobacco, sweet potato and cassava. Alternative hosts are: many wild & cultivated plants.

- Damage: The immature stages are small white scale-like objects on the underside of the leaves & suck the plant sap.

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The adults suck the sap & transmit virus diseases to hosts such as tomato & cotton.

- Pest status: A minor pest of cotton in many parts of the world. Its damage is more severe during dry seasons but disappear rapidly with the onset of rain. Sporadically serious pest of tomato & tobacco. Viruses transmitted are Cassava mosaic virus, Cotton leaf curl virus, Tobacco leaf curl virus & Sweetpotato Virus B.

- Life History: Eggs are white when laid but become brown at hatching. It has pear shape with 0.2 mm long. It stands upright on the leaf by a pedicel inserted in the leaf. Incubation period of eggs = 7 days. When eggs hatch, larvae move for a short period then settle down to suck the plant sap and remain so until adult emergence . All immature stages (larvae + pupae) are greenish-white or yellowish & oval in shape, scale-like & sometimes spiny. Larval & pupal stages lasts 2-4 weeks according to temperature. The adult is small with 1 mm long & emerge through a slit in the pupal skin and covered with white waxy powder. The female lays 100-160 eggs. 32


- Distribution: Cosmopolitan occurring as far north as Europe & Japan.

- Control: Spraying infested plants with whiteflies with contact insecticides (synthetic pyrethroids) such as Kafil, Decis, Karate etc. The spray should be directed at the undersides of the leaves as far as possible.

3) Citrus whitefly (Dialeurodes citri ; Aleyrodidae):

- Hosts: Citrus spp. As the main hosts; Coffee, Gardenia and other ornamental trees & shrubs as alternative hosts.

- Damage: The direct damage is mainly the loss of sap caused by the feeding whiteflies and their immature stages. Excreted honey dew by these insects often leads to infection with sooty molds on both leaves & fruits.

- Pest status: Not a very serious pest on citrus trees but quite widely occurring & causing unsightly damage.

- Life History: Eggs are tiny, pale yellow & laid in groups on the

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undersides of young leaves. Each female lays 100-150 eggs. Incubation period = 8-24 days. The young larvae are active at first & move, but after that they settle the become firmly attached to the leaf. 20-30 days for completing the larval stages & pupal stage takes 14-300 days because of long period of quiescence before giving the adult. The adult are tiny white bug-like with white delicate wings (1.2 mm long). They live for 10 days. Total time for the life cycle = 35-330 days.

- Distribution: South France, India, Sri Lanka, Italy, USSR, Bangladesh, China, Vietnam, Japan, Thailand, USA (California), Mexico, Guatemala, Brazil, Chile, Peru & Argentina.

- Control: Ghemical control by spraying insecticides such as Azinphos-methyl, Tricholorophon, parathion-methyl will kill both larvae & adults effectively.

4) Cotton or Melon Aphid (Aphis gossypii ; Aphididae):

- Hosts: Cotton as main host; Hibiscus spp., Cucurbitacae, many

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legumes and other plants as alternative hosts.

- Damage: The leaves are curled & cupped or distorted with clusters of soft greenish or blackish aphids on young shoots & on undersides of young leaves. Drops of sticky honey-dew and/or patches of sooty mold on upper sides of leaves.

- Pest Status: outbreaks are common on young plants in short periods of dry weather alternates with long rainy periods. Plants may be become weak due to aphid attack but no evidence on seed reduction. It is a greenhouse pest in Europe especially on cucurbites. It is recorded as a vector of about 44 virus diseases.

- Life History: Only female adults are found (winged or wingless), they are blackish-green in color, with 1-2 mm long, antennae = half of body length, siphunculi usually black and cauda not often pale and the eyes are red. Adults may live 2-3 weeks & produce 2 or more generation /year.

- Distribution: Cosmopolitan but absent from colder parts of Asia and Canada.

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- Control: Chemical sprays are usually needed to be applied in case of aphid outbreak. Mixture of DDT and Carbaryl or Dimethoate are applied to keep the aphid population in check.

5) Green Peach Aphid (Myzus persicae ; Apgididae):

- Hosts: Polyphagous on many crop plants & weeds.

- Damage: Direct damage by sucking the plant sap causing distortion of young leaves & shoots (leaf curl). On many plants, these aphids transmit virus diseases to host plants, so symptoms of virus diseases may be seen on these plants.

- Pest status: very important pest on many crops around the world. It causes the damage by direct feeding & by virus transmission. It transmits 100 virus diseases of plants in about 30 different botanical families.

- Life history: The females are breeding by parthenogenesis & viviparity. Most individuals are apterous but winged forms are produced at times of dispersal of the species. Many physiological

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races of M.persicae have been discovered with no morphological differences but distinct host feeding preference. Adults have body length of 1.25-2.5 mm, green color with a darker prothorax. Antennae are 2/3 of the body, siphunculi are clavate.

- Distribution: Cosmopolitan, northwards up to South Scandinavia, North China & Canada.

- Control: Special attention should be paid to integrated control of this aphid without affecting its predators and parasites in addition to the alternative hosts & crop manipulation. Also, use of chemicals to prevent virus spread by controlling their aphid vectors (not generally successful) but chemicals are used to decrease the aphid numbers in case of outbreak. The selective aphicide used pirimicarb (pirimor) which do not kill the predators and parasites of aphids.

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6) Banana Aphid (Pentalonia nigronervosa; fam.: Aphididae):

- Hosts: Banana as the main host; many hosts as alternative hosts such as Alpina, Heliconia, Colocasia spp. & in greenhouse in Europe.

- Damage: slight damage may be caused directly to plants by sucking the sap but the main damage caused by this aphid is by transmitting the virus diseases to banana plants such as “Bunchy top virus disease”. This disease is widespread in Egypt, India, South East Asia & in Australia. Symptoms include dark green streaking on the leaves (midrib & petioles), progressive leaf dwarfing, marginal chlorosis & leaf curling. Fruit bunches are small & distorted. The fruits are not marketable.

- Pest status: Important as vector of Bunchy top virus disease which is serious in Asiatic banana-growing areas in addition to three other virus diseases.

- Life history: Adult has 1-2 mm long of body, brown in color with antennae as long as the body. The allate form has a very

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prominent dark wing venation; the siphunculi are slightly clavate and long. The aphids are found under the old leaf sheaths at the base of pseudostem near the ground level as colonies of brown shiny wingless aphids. Winged adults are produced after 7-10 generations of wingless aphids and these adults, when produced, migrate to other hosts.

- Distribution: in all areas of banana production of the world. Generally, it is pantotropical.

- Control: Effective control measure is done by chemical treatments accompanied by careful eradication of infested plants. Insecticides used are parathion, phosphamidon, pirimor etc. The treatment should be directed to the crown and pseudostem base, below soil level between the outer leaf sheath & stem and over the surrounding soil.

7) Black citrus aphid (Toxoptera aurantii, Fam. : Aphodidae):

- Hosts: Citrus spp. as the main hosts; Ficus spp., tea, coffee, cocoa & other plants (considered polyphagus).

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- Damage: Clusters of black aphids flush growth & under young leaves cause distortion of young leaves. Infestations with this aphid are often accompanied by sooty molds growing on the honey dew excreted.

- Pest status: usually present on citrus branches & occasionally severe outbeaks may occur especially in dry weather following a rainy season. It is recorded from 120 different host plants.

- Life history: The adults (1.2-1.8 mm body long) are shiny black in color & may be winged or apterous with relatively short antennae. Only females are found and produce dark brown living young (viviparous) at a rate of 5-7 per day (total = 50 / female). One generation takes 20 days at 15 deg. C, 6 days at 25 deg. C but the aphid population declines sharply at temperatures > 30 deg. C

- Distribution: it widely distributed throughout the warmer parts of the world including South Europe, Africa, Asia & Australia, Southern USA, Central & South America.

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- Control: Chemical control should be applied only at period of flush growth at the first sign of damage. The most successful treatment is often a full-cover spray of dimethoate or fenitrothion. Care must be taken to wet the flush leaves. Natural control measures can be encouraged by spray banding the bushes & tree trunks around the citrus orchards with dieldrin. Also a large number of predators & parasitoids have been recorded attacking this aphid.

8) Cottony cushion scale insects (Icerya purchasi; Margarodidae):

- Hosts: Citrus spp. as the main hosts; polyphagous attacking many other plants especially Mango, Guava & Forest tree seedlings.

- Damage: the twigs are usually attacked by this scale insects & infested leaves are often become yellow & fall prematurely. Heavily infested young shoots are killed, and in fact whole nursery trees can be killed. Copious quantities of honey dew are excreted.

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– Pest Status: Very widely distributed throughout the world in citrus growing areas. It was introduced into California in 1868 from Australia (native land of the pest) and it is now occurring in all areas of citrus growing areas.

- Life History: The adult female is a distinctive & large insect (35 mm long), sturdy with a brown body covered with a layer of wax. The most conspicuous part of the insect is the large, white, fluted egg-sac which is secreted by the female. The egg-sac usually contains > 100 oblong eggs. The hatching period = few days – 2 months according to climate. Three nymphal instars which are shiny & reddish and abundant along the midrib under the leaves. Males are seldom found.

- Distribution: Cosmopolitan through the warmer parts of the world. Only unrecorded from a few countries.

- Control: This done by biological control using Coccinellidae which have been introduced from Australia into most Citrus growing areas. Chemical control with azinphos-methyl or parathion may be practiced when the number is very high.

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9) Citrus mealybug (Planococcus citri ; Pseudococcida):

- Hosts: Citrus, Coffee & Cocoa as the main hosts; Cotton & various vines as alternative hosts

- Damage: the leaves wilt & turn yellow due to sucking the sap by the insects attacked by the insect. Roots may be infested with root mealybug & become often stunted & encased with fungal growth (Polyporus sp.). This insect can transmit virus diseases (virus vector) to host plants like swollen shoot disease of cocoa.

- Pest status: seedlings or occasional trees of coffee may be killed due to the infestation by the insect. It may occur in greenhouses in temperate climates.

- Life History: Eggs are laid in ovisac (150-300 eggs each). Incubation of eggs takes 3-5 days. Nymphal instars take 16-38 days. Reproduction is seasonal with sex ratio of 1:1. Root mealybug . Five or more generations per year.

- Distribution: It is completely pan-tropical & sub-tropical. It may attack crops in greenhouses of temperate zones.

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- Control: Infested trees with the insect should be treated carefully with insecticides. Sprays with malathion or parathion should be applied to infested trees. Mixing of these insecticides with the soil is necessary to control root mealybug.

10) Black scale (Olive scale) insects (Saissetia oleae; Coccidae):

- Hosts: Olive & Citrus trees as the main hosts; a very wide range of trees as alternative hosts.

- Damage: presence of blackish scales on the twigs & shoots. In heavy infestation, the leaves & shoots wilt & become chlorotic with heavy coatings of sooty mold. Development of leaves & fruits may be stopped.

- Pest status: These scale insects are polyphagous & spread all over the world in olive & citrus orchards.

- Life History: A single female can lay 1000-4000 eggs (average = 2000). Eggs are white turning brown at hatching that occurs 15-20 days after laying. 1st nymphal instar (crawlers) start feeding within few hours & prefer feeding on the tips new shoots & on

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the undersides of the leaves but adults prefer the shoots & twigs. Total time needed for nymphal development = 2-3 months and sometimes a period of diapause during the nymphal develo-pment is needed when environmental conditions are not favourable. If conditions are favorable, the life cycle takes 2-3 months. Winged males are occasionally found and reproduction takes place without fertilization.

- Distribution: Almost cosmopolitan but not recorded from West Africa. There are records from Japan and South France as the northmost countries.

- Control: Chemical control by spraying contact insecticides is directed towards the nymphs but not females. Mineral oil emulsions are effective against the females hidden under the scales.

11) California Red Scale (Aonidiella aurantii, Diaspididae):

- Hosts: Citrus spp. as the main hosts; a wide range of fruit trees & shrubs especially roses as alternative hosts.

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- Damage: presence of numerous small circular reddish-brown scales on the trunk, branches, leaves & fruits. Severe infestation may result in branch die back. When infest leaves, they are often surrounded by small pale chlorotic spots.

- Pest Status: it is considered a major pest of citrus in East Africa & in many other citrus growing areas of the world.

- Life History: Female produces small living young (2-3 per day) after mating with the winged male. They walk away from their mother before settling in a suitable feeding sites. They moult after settling twice before giving adult female that becomes covered with a scale. The immature males like the females, are scale-like and reddish-brown but their bodies are elongate with a size ¼ of the female adult’s size. Adult male is fragile with 2 wings & long filamentous antennae. The body of the female is flattened, crescent-shaped & reddish-brown . It is covered with a circular, transparent, waxy carapace (1-2 mm diameter) through which the body can be seen.

- Distribution: Cosmopolitan throughout the tropic & subtropics

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but with no record from West Africa.

- Control: If high quality fruit are to be produced, trees should be sprayed when 25% of the fruits are infested. Recommended sprays will be by white mineral oil emulsion + insecticide like Diazinon or malathion. A full-cover spray using as high a nozzle pressure as possible. The spraying process should be repeated after 2-3 weeks.

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lectures in: pests of crops (course # 494553) lectures in: pests of crops (course # 494553) prepared...

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