TRICHOGRAMMA: BIOLOGICAL CONTROL FOR COTTON BOLLWORM
Introduction
Bollworm (Helicoverpa armigera Hubn.) is probably the most destructive pest of cotton. It is also a known pest in other crops. It is called fruitworm in tomato, earworm in corn, and budworm in tobacco. If left uncontrolled, bollworm could leave a cotton farmer with zero yield on his farm.
Controlling bollworm by chemical means alone is costly, that is besides the hazards it brings to man and the environment. The use of Trichogramma chilonis, or Tricons, is an alternative biological control measure that has been found to be effective against bollworm.
What is Trichogramma chilonis?
Trichogramma chilonis are small parasitoids that attack and kill the eggs of a variety of lepidoterous pests. In cotton farms, they particularly oviposit on and parasitize bollworm eggs.
Why use Trichogramma?
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Trichogramma parasitizes the eggs, thus killing bollworms and other lepidopterous pests before they could inflict damage on the host plant.
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The use of trichogramma reduces chemical spraying and preserves predators or natural enemies.
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They are host-specific, thus safe to use.
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They can establish well in tropical agro-ecosystem and can be integrated with other control measures.
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They are cheap and can be mass-reared cheaply and conveniently in the laboratory on unnatural hosts.
When and how frequent Trichogramma are released in the field?
Trichogramma can be released as pupae (about to emerge) or as emerging adults. Pupae are released late in the afternoon while the emerging adults shold be released early in the afternoon to achieve high parasitization rate. Release of Trichogramma commences at 45 DAP when bollworms are presumed to be depositing their eggs. This is done twice a week. The total number of application is eight times.
How are the parasitoids released?
During mass production, Trichogramma eggs are packaged in paper strips, thus the name Trichogramma strip.Trichogramma may be released by using halved empty coconut shell tied with a string and suspended from a bamboo pole or stick. A paper clip is tied inside the hollow of the empty coconut shell where the Trichogramma strip is to be hanged. The coconut shell is hanged at least 30 cm above the cotton plant canopy. Trichogramma can also be very conveniently released by clipping the strips at the lower side of the upper third leaf. Thirty minutes after emergence, the parasitoids actively search for their hosts.
At what rate are Tricons released?
Trichogramma are applied at a rate of 67,000 parasitoids or 30 strips per release at two releases per week.
How much does trichogramma strips cost?
Ready-to-release trichogramma costs PhP3.00 per strip.
Where can tricons be purchased?
Trichogramma can be purchased in Trichogramma Mass-Rearing Laboratories run by CODA, the Department of Agriculture or private entrepreneurs.