Français

Script 72.9

Notes to broadcasters

Integrated pest management or IPM is the approach taken by organizations and farmers around the world to manage crop pests while protecting human health, the environment and economic viability. IPM systems use all available tools – cultural, biological, genetic and chemical – to ensure that pests are kept below levels that cause too much crop damage. IPM accepts that pests will cause some damage to crops, but attempts to keep the level of damage below that which will hurt farmers economically. An integrated approach tries to manage conditions on the farm so that the contribution of natural pest controls, such as weather and natural enemies (spiders, ladybirds, etc.), is maximized. Unlike organic farming, IPM does use low risk pesticides as a last resort. IPM is based on a thorough knowledge of the farming ecosystem, and of the pests it supports. It investigates the reasons why the pest is a problem, and, based on that knowledge, tries to discover what farmers can do – or in some cases stop doing – to manage the pest.

The following script is about an integrated pest management approach to controlling the diamondback moth (DBM), one of the major pests of brassica vegetables. It concentrates on simple actions that farmers can take to manage this pest. The diamondback moth is the most important insect pest on cabbage and other brassica crops [collards, kale (sukumawiki), cauliflower, broccoli, Ethiopian kale, canola] in the tropics. These and other vegetables are important sources of micronutrients, which are essential for a healthy diet. This is especially important in light of the spread of HIV/AIDS in Africa. A vegetable-rich diet can bolster the immune system and help it to fight against the disease. Most vegetable growers in Africa are women. When broadcasting radio programs that give advice on managing pests in vegetables, be sure to choose a time slot that will reach women farmers.

This script contains a lot of information. You may feel it is necessary to break it up into separate scripts or to broadcast different sections at different times. Alternatively, you could produce a series of programs, each highlighting a different method for controlling the diamondback moth.

Script

Host 1:
Good morning [afternoon, evening]. This is [name of host].

Host 2:
And this is [name of host]. Welcome to our show.

Host 1:
Today we’re going to talk about how to handle a very serious pest that’s probably attacking vegetables in your garden.

Host 2:
That’s right. But to start off, I have a question for our listeners: Which insect pest causes the most damage on crops in the brassica family – vegetables like cabbage, sukumawiki, cauliflower, collards, broccoli, mustard, and rapeseed? [PAUSE] It’s the diamondback moth. Congratulations if you guessed correctly. The diamondback moth got its name because the adult moth has three small whitish diamond-shaped marks that you can see when its wings are folded.

Host 1:
There are many reasons why the diamondback moth is such a serious pest. First of all, it reproduces quickly – in fact it can have up to 15 generations in a year in the tropics! And a single female can lay more than 400 eggs during its life. So there are a lot of new larvae and moths throughout the year. It’s the feeding by larvae that causes damage to plant leaves.

Host 2:
And even though it’s not a strong flyer, the adult moth can be blown by winds over long distances.

Host 1:
The moth has also become resistant to many pesticides, so it is not easy to control with insecticide sprays. In fact, one of the reasons the diamondback moth is such a big problem is that many of its natural enemies – the bugs that eat it – have been killed by some of the commonly used pesticides.

Host 2:
And diamondback moth is a serious insect pest of brassica vegetables everywhere in the world, not just in Africa.

MUSICAL BREAK.

Host 1:
Perhaps it would be interesting for our listeners to know a little about the life cycle of this pest.

Host 2:
Female diamondback moths lay tiny white eggs on the upper surface of plant leaves. Pale green caterpillars hatch from the eggs in about five to eight days depending on how warm it is. The caterpillars live for about two to four weeks and do a lot of damage by eating the leaves of brassica vegetables, their favourite plants. After two to four weeks, they pupate in a cocoon which is stuck on the under side of the leaf. The greyish-brown adult moths come out about five to ten days later. The moths live for 16 or 17 days, but do not feed on plants.

MUSICAL BREAK.

Host 1:
Now I’m sure our listeners would be interested in learning about how they can reduce damage to their vegetables from the diamondback moth.

Host 2:
We’re going to discuss four different methods.

Host 1:
The first method is called intercropping. Intercropping means growing two or more crops in the same field at the same time.

Host 2:
Some farmers have had success by planting two rows of Indian mustard between every fifteen rows of cabbage. It seems that the diamondback caterpillars love Indian mustard and would rather eat it than cabbage. Of course these farmers had to make sure that they kept mustard growing in the field at all times. Otherwise the caterpillars would move over to the cabbage plants.

Host 1:
Other farmers planted rows of beans or onions between their collard plants. And the caterpillar caused much less damage to the collards.

Host 2:
Still other farmers planted tomatoes between the rows of cabbage – one row of tomatoes and then a row of cabbage, and so on. The moths stayed away from both crops, perhaps because they didn’t like the smell of the tomatoes.

Host 1:
These combinations of plants may or may not work for you. The point is that you can try different combinations to find one that does work. Remember that it’s best to intercrop your main crops with something that you can sell or that provides food for your family.

MUSICAL BREAK.

Host 2:
That brings us to our second method for controlling this pest. Diamondback moths don’t like rain!

Host 1:
That’s right. Rain makes it hard for them to fly. And it makes it harder for them to lay eggs on leaves. Heavy rain can even knock the caterpillars off the leaves and drown them.

Host 2:
Farmers can take advantage of this in two ways. The first is to plant crops in the rainy season. But don’t try this if you live in an area where blackrot is a problem. Blackrot is a major disease of brassica vegetables. The second is to water plants from above – for example using sprinkler irrigation.

Host 1:
Some farmers have had success controlling the moth when they water their plants from above for five minutes every day at dusk. They do this for the first four weeks after planting.

MUSICAL BREAK.

Host 2:
Okay, that’s two ideas: intercropping, and planting during the rainy season or watering from above. The third thing we want to talk about is a botanical pesticide that is becoming more available and less expensive in some parts of Africa.

Host 1:
A botanical pesticide is a pesticide that comes from a plant, rather than from chemicals. Today I’m talking about a pesticide that is made from an extract from the seed kernel of the neem tree.

Host 2:
The neem tree is native to India, but it is now grown in many parts of Africa. Researchers found that spraying a water solution of the extract from the neem seed on cabbages is more effective against diamondback moths than many pesticides.

Host 1:
And the pesticide made from neem seed is much safer than most synthetic chemical pesticides. It won’t poison or kill people. And it won’t poison the natural enemies or the good bugs in your field.

MUSICAL BREAK.

Host 2:
So far we’ve talked about three methods you can try to control the diamondback moth: intercropping, planting during the rainy season, and applying a botanical insecticide made from seeds of the neem tree.

Host 1:
Of course there are many other methods, but today we’re going to talk about just one more. One other control against the diamondback moth is to look for brassica varieties with glossy leaves, and plant these varieties in your field. Scientists don’t exactly know why, but it seems that the young diamondback moth caterpillars don’t like plants that have glossy leaves as much as the waxy-leaved varieties that we commonly plant.

Host 2:
We should also mention that hand picking can be effective for controlling the diamondback moth. Especially if the infestation is low. But farmers must check their crops regularly to discover new infestations early.

SHORT PAUSE, AS MUSIC COMES UP, THEN FADES DOWN AND UNDER HOSTS.

Host 1:
There’s no magic to managing difficult pests like the diamondback moth. You have to do a lot of little things right, like the methods we’ve mentioned today.

Host 2:
And keep looking for new ideas. Talk to other farmers. They may have found other ways to control this pest.

Host 1:
But no matter what pest you are dealing with, here’s something that’s always true: the more you know about the pest, the better you can control it.

Host 2:
Absolutely. We know the diamondback moth likes Indian mustard, but doesn’t like tomatoes …

Host 1:
…so we plant rows of Indian mustard or tomatoes between our rows of cabbage.

Host 2:
And we know that the moth doesn’t like rain …

Host 1:
… so we plant our crops in the rainy season. Or water our crops from above.

Host 2:
And we know that the moth doesn’t like glossy leaves …

Host 1:
… so we plant varieties with glossy-leaves.

Host 2:
And we know the moth doesn’t like neem at all …

Host 1:
… so we spray our plants with an insecticide made from neem.

Host 2:
That’s right. First, you learn about the pest. Then, based on that knowledge, you plan how to control it.

Host 1:
This is [name of host] saying goodbye.

Host 2:
This is [name of host]. Goodbye. And good luck.

MUSIC FADES UP AND THEN OUT.

Acknowledgements

Notes on scientific names:

  • Diamondback moth – Plutella xylostella
  • Indian mustard – Brassica juncea
  • Collard – Brassica oleracea var. acephala
  • Cabbage – Brassica oleracea var. capitata
  • Cauliflower – Brassica oleracea var. botrytis
  • Broccoli – Brassica oleracea var. italica
  • Ethiopian kale – Brassica carinata L.

Information Sources

  • Facknath, S. “Integrated Pest Management of Plutella xylostella, an important pest of Crucifers in Mauritius.” University of Mauritius. In Proceedings of the Second Annual Meeting of Agricultural Scientists, Boname Hall, MSIRI, Reduit, Mauritius. Aug.12-13, 1997.
  • Integrated Pest Management: Safe and sustainable protection of small-scale brassicas and tomatoes. A handbook for extension staff and trainers in Zimbabwe. Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent, ME4 4TB, United Kingdom.
  • Said, M., and F.M. Itulya “Intercropping and nitrogen management effects on diamondback moth damage and yield of collards in the highlands of Kenya.” African Crop Science Journal. Vol. 11, No. 1, 2003: 35-42.
  • Charleston, D.S., and R. Kfir. “The possibility of using Indian mustard, Brassica juncea, as a trap crop for the diamondback moth, Plutella xylostella, in South Africa.” Crop Protection. Vol.19, 2000: 455-460.
  • Srinivasan, K., and P.N. Krishna Moorthy. <EM><A title=”Link opens a PDF document on another web site” href=”http://www.avrdc.org/pdf/90dbm/90DBM57.pdf” rel=external target=_blank data-mce-href=”http://www.avrdc.org/pdf/90dbm/90DBM57.pdf”>Development and Adoption of Integrated Pest Management for Major Pests of Cabbage Using Indian Mustard as a Trap Crop</A></EM>. Asian Vegetable Research and Development Center (AVRDC). AVRDC, PO Box 42, Shanhua, Tainan 741, Taiwan ROC. Tel: +886-6-583-7801, Fax: +886-6-583-0009, Email: <A href=”mailto:avrdc@avrdc.org” data-mce-href=”mailto:avrdc@avrdc.org”>avrdc@avrdc.org</A>.
  • Talekar, N. S., S. T. Lee, and S. W. Huang. Intercropping and Modification of Irrigation Method for the Control of Diamondback Moth. Asian Vegetable Research and Development Center (AVRDC). AVRDC, PO Box 42, Shanhua, Tainan 741, Taiwan ROC. Tel: +886-6-583-7801 begin_of_the_skype_highlighting FREE +886-6-583-7801 end_of_the_skype_highlighting, Fax: +886-6-583-0009, Email: avrdc@avrdc.org.
  • Neem knocks out diamondback moth on cabbage. Asian Vegetable Research and Development Center (AVRDC).
  • Ana M. Varela, A. Seif and B. Lohr (2003). A Guide to IPM in Brassicas Production in Eastern and Southern Africa. The International Centre of Insect Physiology and Ecology, Nairobi, Kenya.