Cabbage Integrated Pest Management : An Ecological Guide.

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Major Natural Enemies of Cabbage Insect Pestsfrom the caterpillar after some time to spin their silken cocoons on or very nearto the host caterpillar. The cocoons are usually found in an irregular mass nextto the dead caterpillar.Adults of Cotesia plutellae are also small black wasps. Females live only ashort time: about 10 days, depending on environmental conditions. Total lifecycle from egg to adult takes about 25 days.Cotesiaplutellae adultCotesia plutellae lays its egg inside a DBM larva. The parasitoid larva developsinside the DBM caterpillar. When fully grown, the parasitoid larva emergesfrom the side of the DBM body and it spins a silken cocoon for pupation. Thecocoons are white and can usually be found attached to the under surface ofthe leaves.larvae develop in caterpillarfemale lays egg in caterpillarpupae in silken cocoonsadults emerge(from Hoffmann et al, 1993)EffectivenessCotesia glomerata is reported to be a very effective control agent of cabbage butterflies Pieris sp. In theU.S.A., more than 80% of the caterpillars may be parasitized in fields unsprayed by chemical insecticides(ref. www16).Cotesia plutellae can give effective control of diamondback moth. In studies (1995) in the highland area ofDalat, Vietnam, Cotesia was found soon after DBM occurred, and reached parasitism levels up to 90%.In the lowlands of Hanoi area (1994-1995), parasitism was not more than 22% on average. (FAO -Updates on Vietnam national IPM programme in vegetables, 1999)Studies show that Cotesia plutellae can reach high parasitation levels when pest populations are alreadyhigh, but is less effective at lower pest densities (FAO Dalat report (V.Justo), 1998).Cotesia can be naturally present in fields. Several Cotesia parasitoids are commercially available, forexample in the U.S.A. Mass-rearing houses have also been established in Philippines (FAO Dalat report(V.Justo), 1998) and will be established in Vietnam. In Lao PDR, Cotesia is being reared and releasedwith assistance of the AVRDC.In addition, C. glomerata may be a vector in the transmission of a granulosis virus in cabbageworm,Pieris rapae (ref. www16).123 Cabbage Ecological Guide - 2000
Major Natural Enemies of Cabbage Insect PestsConservationLike almost all other predators and parasitoids, Cotesia sp. are quickly eliminated when spraying chemicalinsecticides. When Cotesia is active in the field, avoid using insecticides when possible. Insecticideapplication may actually lead to an increase of pest insect populations because the natural enemies arekilled (see section 4.11.11 and box in section 5.1).6.2.4 Diadromus collarisHost: pupae of diamondback moth (DBM).The wasp Diadromus collaris belongs to the family of Ichneumonidae.Adult females are about 6 mm long with an obvious ovipositor.This DBM parasitoid was originally from Europe and came to Asia via Australia. It was introduced toVietnam in 1997. It is reared and has been released in the field in Dalat, a highland area in Vietnam. Therelease in Dalat is being carried out in conduction with monitoring and ecological studies by Farmer FieldSchools and farmer study groups (FAO progress report ’96 – ‘99). Initial results, however, show a lowparasitism percentage.In other studies, parasitism of pupae of 1 to 12% has been recorded (Hoffmann, 1993).Diadromus collaris complements the action of the larval parasitoid, Diadegma semiclausum. Togetherwith D. semiclausum, Diadromus collaris helps keep diamondback moth populations low, especiallywhen there is low (or no) use of chemical insecticides.6.3 PathogensPathogens are bacteria, viruses, fungi, and nematodes. Insects, like humansand plants, can be infected with pathogens which cause diseases. Insectpathogens generally kill, reduce reproduction, slow the growth or shorten thelife of a pest insect. Under certain conditions, such as high humidity or highpest populations, these pathogens can cause disease outbreaks that reducean insect population. This is why such pathogens can be considered naturalenemies of insects. Most insect pathogens are specific to certain groups ofinsects and certain life stages of the insect. Some microbial insecticides mustbe eaten by the target pest to be effective, others work when in contact with thetarget pest.Unlike chemical insecticides, microbial insecticides usually take longer to kill or weaken the target pest.J Most insect pathogens are not harmful for other beneficial insects, Jand none are toxic to humans.Pathogens are most effective when pest populations are very high. Pathogens are difficult to managebecause their presence and effectiveness strongly depends on factors like temperature and humidity.During the dry season for example, you will almost never see aphids killed by a fungus because thatfungus needs a high humidity for survival and spread.Cabbage Ecological Guide - 2000124
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Why this guide?About this guideThis
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Introduction1.4 Cabbage: a bit of h
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Cabbage Crop DevelopmentPresently t
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Cabbage Crop Development2.2 Suscept
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Major Agronomic Practices3MAJOR AGR
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Major Agronomic Practices3.2.3 Seed
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Major Agronomic PracticesUse protec
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Major Agronomic Practices3.4.2 Soil
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Major Agronomic Practicesthan 7, th
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Major Agronomic Practices3.4.7 Soil
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Major Agronomic PracticesSome of th
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Major Agronomic PracticeslllCreates
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Major Agronomic PracticesWhen a com
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Major Agronomic PracticesIn additio
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Major Agronomic PracticesSome farme
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Major Agronomic PracticesEffects of
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Major Agronomic PracticesAn example
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Major Agronomic Practicesseed beds,
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Major Agronomic Practicesthis layer
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Major Agronomic PracticesPotting se
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Major Agronomic PracticesTransplant
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Major Agronomic Practices3.9 Water
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Major Agronomic PracticesHowever, w
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Major Agronomic PracticesSome examp
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Ecology of Insect Pests and Natural
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Page 73 and 74: Ecology of Insect Pests and Natural
Page 75 and 76: Major Cabbage Insect Pests5MAJOR CA
Page 78 and 79: Major Cabbage Insect PestsDiadegma
Page 80 and 81: Major Cabbage Insect PestsTrap crop
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Page 98 and 99: Major Cabbage Insect PestsThe adult
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Page 138 and 139: Disease Ecology7.1 Plant diseases a
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Page 142 and 143: Disease EcologyThe disease triangle
Page 144 and 145: Disease Ecologygrowth malformations
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Page 150 and 151: Disease EcologyTrichoderma species
Page 152 and 153: Major Diseases of Cabbage8MAJORDISE
Page 154 and 155: Major Diseases of CabbageRole of en
Page 156 and 157: Major Diseases of CabbageOnce there
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Page 168 and 169: Major Diseases of Cabbage8.7 Downy
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Page 172 and 173: Major Diseases of CabbageNitrogen (
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Weed Management9WEEDMANAGEMENTSUMMA
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Weed ManagementBroadleaf weeds or g
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Weed Managementcompost or it may be
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Weed Management· Check details of
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Weed ManagementTherefore, to date,
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Rodent ManagementRats are a common
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Rodent Management10.4 Rat managemen
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Rodent Management10.4.4 Biological
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Key to Some Common Cabbage Insect P
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Literature and Internet Reference L
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PESTS & DISEASES COMMON TO CABBAGEP
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Plate 3Fig. 13 : Advanced symptoms
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deficiency symptoms ---------------
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chemical --------------------------
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