Cabbage Integrated Pest Management : An Ecological Guide.

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Major Cabbage Insect PestsPlant damage and plant compensationThe first signs of attack are small bleached areas on the leaves of infested plants. The leaves then turnyellow and become crumpled. The aphid colonies are protected inside the crumpled leaves. The effectsof infestation are worst on seedlings and young plants. They can be stunted and may die in unfavorableweather. Early damage to the growing point of a cabbage plant distorts the head. Even when youngplants are infested only lightly, the leaves of the plants when they are mature continue to show signs ofthe original attack. Infestations on larger plants may reduce yield and also spoil the plants by contaminatingthem with wax, cast skins and honeydew. Honeydew is the excretion of aphids. It is slightly sweet andis excreted from the syphons. Honeydew can make the leaves sticky and several fungi species grow onthe honeydew producing black marks on the surface of the cabbage. This lowers the quality. Wheninfestation is large, the aphids sometimes penetrate the heart of the cabbage.Aphids tend to be very localized: they usually colonize just a few plants but can be very abundant oneach plant.In addition to the direct crop damage, cabbage aphids also transmit the cauliflower mosaic virus and theturnip mosaic virus to cruciferous crops. Good crop hygiene (uprooting and destroying the virus infectedplants), rather than trying to kill the aphids, is the only way of reducing the impact of these viruses as thetime taken by virus-carrying aphids to infect new crops is often less than one minute. This is too short tokill the aphids by any control practices.Aphids as milk cows for ants...?!Ants are attracted to aphid colonies because the aphids produce honeydew whenthey are disturbed. Ants like to eat the sweet honeydew. The ants keep and sometimeseven protect the aphid colonies. They “milk” the aphids to get the honeydew.Although ants can be natural enemies of some pest insects, in this case, ants cannot beconsidered as natural enemies of aphids because they do not kill aphids but may in fact protectthem.Natural enemiesThe weather is a major natural agent restricting the build-up of cabbage aphid infestation in cold, temperateregions and mountainous areas. In dry, warm seasons the aphids can often produce extremely largeinfestations whereas in wet, cool seasons the aphid population remains small. In a period of frequentrain, aphid populations will be very low if not absent.Predators such as lady beetles and hover flies (Syrphids) and parasitoids like the wasp Diaeretiella rapaeare important natural enemies of the cabbage aphid.In wet seasons, outbreaks of fungi that killaphids may occur. This often coincides withperiod of high humidity and rain. Dead aphidsmay be seen covered with white coloredfungus growth on the body. These fungi canspread quickly to reduce aphid populations.See chapter 6 for details on these naturalenemies.LarvaeLady beetle : an important predator of aphidsAdult83 Cabbage Ecological Guide - 2000
Major Cabbage Insect PestsManagement and control practicesPrevention activities:· Healthy, quickly growing plants are the best way of preventing many pests and diseases. Aphidinfestation often occurs when plant condition is slightly poor, for example just after transplanting,or when too much or too little fertilization is added or when the soil structure is poor.· Host plant resistance: There is little chance of producing a cabbage variety with a durable resistanceto cabbage aphids. This is because there are many biotypes (individuals with slightly differentcharacteristics) of aphids present in the field and new biotypes can form regularly. It is very difficultto produce a variety that has a resistance against all these biotypes.· Cultural control: Cruciferous plants that remain in the field after harvest are largely responsible forlarge numbers of eggs and/or adults staying over. Therefore, the most effective prevention andcontrol measure is to eliminate as many of these sources of infestation as possible to prevent theaphids from spreading to the new crop. The crop left-overs can be buried into the soil, fed to farmanimals, added to a compost pile or collected, slightly dried and burnt. Removing crop left-overs isalso very valuable for disease prevention.· Undersowing with clover may help to reduce aphid infestation. In a study where cabbage wasundersown with white clover, cabbage aphid population was reduced with 90%! (Finch, 1996). Seesection 3.5.3.4 on organic mulch.Once aphids are present in the field:· Monitor the field regularly to check population growth. Cabbage aphid population build up rapidlybut locally. It is important to examine plants regularly, both in seedbeds and in the field. Whenaphids are found but the number of infested plants is low and at the same time there are naturalenemies like lady beetles present, no additional control measures are necessary.· On a small scale, aphids can be washed off the plants with water or rubbed by hand.· Small populations can also be removed by removing the infested leaves by hand and destroyingthese.· When large populations of aphids are present in the field at an early stage (newly transplanted oryoung plants) and the weather is warm and dry, chances are that the aphid population will expandvery quickly and causes damage to the growing points of the plants. Monitor the field carefully forpresence of natural enemies (particularly note lady beetles and aphid “mummies” (see sections6.1.1 and 6.2.1)). When there are large numbers of natural enemies, do not apply insecticides butcontinue monitoring. When natural enemy populations are low compared to the aphid population,consider localized sprays. See next paragraph. Also see section 4.8 on natural enemy efficiency.· Soap solutions (concentration of 0.5 % (5 g per liter)) kills aphids instantly. See section 4.11.6.· Botanicals such as neem solutions may control aphids. Good results are obtained from variouslocations. See section 4.11.4.· Biopesticides: see box below for an example from Bangladesh.Cabbage Ecological Guide - 200084
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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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Page 75 and 76: Major Cabbage Insect Pests5MAJOR CA
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Major Natural Enemies of Cabbage In
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Major Natural Enemies of Cabbage In
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Disease Ecology7.1 Plant diseases a
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Disease Ecology7.3 How diseases spr
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Disease EcologyThe disease triangle
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Disease Ecologygrowth malformations
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Disease Ecology7.8 Control or manag
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Disease Ecologycontaminated seeds :
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Disease EcologyTrichoderma species
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Major Diseases of Cabbage8MAJORDISE
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Major Diseases of CabbageRole of en
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Major Diseases of CabbageOnce there
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Major Diseases of Cabbage· Practic
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Major Diseases of Cabbage¤Points t
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Major Diseases of Cabbagespores wit
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Major Diseases of Cabbage¤Points t
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Major Diseases of Cabbagebut does n
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Major Diseases of Cabbage8.7 Downy
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Major Diseases of Cabbage8.8 Black
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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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