Diamondback Moth (DBM)
Common Name | Scientific Name | Geographic Distribution | Recognition and Diagnosis | Host | Biology and Ecology | Damage and Importance
Sampling and Economic Thresholds | Control Strategies
- English: Diamondback Moth (DBM)
- Spanish: Plutella, Palomilla de Dorso Diamante (DDM), Rasquiña
- Plutella xylostella (= maculipennis) (Curtis) (Lepidoptera: Plutellidae o Yponomeutidae)
- World wide. It is important as a pest in the lowlands in the tropics and subtropics. In temperate zones, DBM cannot survive the winter. It colonizes the crucifer growing regions at the end of the growing season, or by seedlings that come from subtropical areas.
- DBM live on several crucifer plants. They are a frequent pest of cabbage, broccoli, cauliflower, rape, and tsunga. For control practices, it is important to remember that mustard and other crucifer weeds are alternate hosts.
- The life cycle can be completed in one to two weeks, depending on the temperature. In the tropics, the life cycle is shorter in the lowlands than in the mountains. DBM is a serious pest in the dry season, but heavy rain washes out the larvae. Some countries recommend not planting crucifers in the dry season because this pest is so difficult to control.
- DBM caterpillars are detected by visual observations of the plant. Adults can be detected by the use of pheromone traps.
- Where to sample: For commercial purposes, the whole plant should be examined. Pay special attention to look for small caterpillars under the leaves in the basal part of the plant. Damage or holes in the leaves are not a good predictor of the caterpillar population.
- Economic threshold: In small cabbage plots (.25 ha) in Honduras, it is recommended to sample at least 60 plants and the action threshold is 1 caterpillar per plant. For broccoli and cauliflower at the vegetative stage, the plant can support 30% defoliation. At harvest time, an infestation level of 1 caterpillar per head is the action threshold.
- Biological control: There are several enemies that help to control DBM. For example, in Honduras, the parasitoid wasp Diadegma insularis (Hymenoptera: Chalcididae) can control up to 40% of the caterpillars when there is a limited use of synthetic pesticides. In Asia, the parasitoid Diadegma semiclauson has been used on a semi-commercial basis for control of DBM caterpillars.
- IPM practices:
- Planting season
- It is preferable to plant cabbage in the rainy season when the population of DBM is deterred by the rain.
- Sprinkle irrigation may reduce the number of caterpillars in the field. If it is applied at dusk, it may limit the activity of adults.
- Plot location
- It is better not to have multiple planting dates in the same area because the older plots will serve as inoculum of DBM for the new plantings. If you need to have several planting dates, plant the younger crop into the direction of the prevailing winds to make it harder for the moths to fly into new plantings.
- Seed-beds should be distant from old plantings and new plots to be planted. It is very important that cabbage seedlings are clean of DBM before transplanting to the field. On several occasions, attacks of DBM start with seedlings that are infested with DBM.
- Remove unharvested plant parts
- At harvest time, it is important to cut and, if possible, remove all plant materials that are not harvested. DBM can survive in plant residues and migrate to the next plot.
- In some areas, farmers inter-crop cabbage with other cole crops or crucifer weeds that are more attractive to the DBM than cabbage. These inter-cropped plants should be monitored with more frequency than the main crop and require control of the DBM before it can be passed to the main crop. Unattended trap crops can generate large populations of DBM. Special care is needed to manage these crops to use them as part of a control practice.
- In some areas, it is recommended to plant small plots of cabbage between other crops that are not susceptible to the DBM. The idea of inter-cropping is that DBM moths will have more difficulty in finding new crops when they are camouflaged between other non-susceptible crops.
- Pesticide resistance problems
- DBM has developed resistance to the bacterial pesticide, Bacillus thuringiensis, var. krustaki in areas where it is in heavy use, leaving farmers without a useful pesticide.
- Pesticide recommendations
- Because of severe pesticide resistance problems with DBM around the globe, it is very important to use pesticides as little as possible in an IPM program. You need to contact the local authorities for the specific pesticides to use in your country. It is recommended to make a pesticide screening study to find the best pesticides to use in rotation between the different pesticide families. Remember, you must use only pesticides that are legal to use for this pest and crop in your country.
- Spray techniques
- Cabbage plants contain large amounts of wax in the surface of the leaves. This wax makes it very difficult for pesticides to stay on the leaf surface. It is recommended to use spreader stickers to increase pesticide coverage and persistency. The majority of DBM caterpillars live under the leaf surface. For this reason, it is very important to have an excellent pesticide coverage under the leaves. Hydraulic nozzles are the best to use with backpack or tractor sprayers. The use of electrostatic sprayers improves pesticide coverage and reduces pesticide use.
- Andrews K. L. 1984. El manejo Integrado de Plagas invertebradas en los cultivos Agronómicos, Horticolas y frutales en la Escuela Agrícola panamericana. Zamorano Press.
- Shelton A. M., A. Turner, D. Giga, P. Wilkinson, E. Zitzanza, and D. Utete (1995) Diamondback Moth. Zimbabwe Horticultural Crops Pest Management. NYSAES, Geneva NY. 2 pp.
- For more information regarding this publication, contact Alfredo Rueda (email@example.com). You may also contact one of our collaborators in your geographic region who may have more specific technical information on the topic.
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- In most cases, farmers and practitioners are the real innovators in pest management. If you have made an improvement or a new system to control this pest we will be happy to publish it here. Please send a description of your discovery to Alfredo Rueda (firstname.lastname@example.org ).
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