Page Intro: Trichogramma spp.: T. brassicae, T. minutum, T. pretiosum, are Moth Egg Parasitoids capable of reducing caterpillar pests. On this page you will find a description, life-cycle info, benefits, drawbacks, scouting info, advisories, usages, beyond the page, and other good stuff such as ordering.
Description
These 0.9 mm. mini-wasps are very popular and very effective Lepidopteran egg parasitoids. Lepidoptera (lep-ih-DOP-ter-rah) is the name of the order to which moths and butterflies belong. The eggs of over 150 species assigned as members of this order can be parasitized by the Trichogramma spp.
- T. brassicae
- These shipped as pre-parasitized, ready-to-emerge grain moth eggs (Sitotroga cerealella) adhered to a card which is perforated into 30 squares, is the product of choice when targeting the eggs of moths whose larvae are pests of cole crops.
- T. minutum
- These are shipped in the same style and manner as T. brassicae, above, is the product of choice when targeting the eggs of moths whose larvae are pests in an orchard or tall crop setting. In this case, “tall crop” means one which is over the 8-10 foot range.
- T. pretiosum
- These are shipped in the same style and manner as T. brassicae, above, is the product of choice when targeting the eggs of moths whose larvae are pests in a field, greenhouse or short crop setting. In this case, “short crop” means one which is under the 8-10 foot range.
Application rate protocols for both of the Trichogramma spp. described above remain unchanged, the height of the crop in the case of these mini-wasps determines the proper species to choose. (For more info, see the Rates.)
Some popular hosts of these mini-wasps include the eggs of: the Gypsy moth; codling moth (Cydia pomonella); diamondback moth (Plutella xylostella); Oriental fruit moth (Graphiolitha molesta); tomato pinworms (Keiferia lycopersicella); cabbage loopers (Trichoplusia ni); imported cabbage worms (Pieris rapae); tent caterpillars (Malacosoma spp.); and many, many more, even the grossly damaging tobacco/tomato hornworms (Manduca spp.). [Intro]
Life-style
The Trichogramma spp., as parasitoids, work by laying eggs in the eggs of many Lepidopteran spp. as mentioned under Description, above. The adult wasps can lay up to 300 eggs each, parasitizing an equivalent number of soon-to-be destructive caterpillars, loopers and/or worms. [Intro]
The wasps’ larvae which hatch from the eggs, attack the moths’ eggs’ embryos from within (endoparasitism). Instead of pests hatching out, more mini-wasps emerge instead.
The life-span of these parasitoids is roughly 7 days in their immature stages, then up to 10 days as adults. With such an abbreviated life-cycle, these parasitoids can sometimes build up to 30 generations per year (many of which overwinter). The conditions for optimum performance will be between 70-85°F with a relative humidity of around 60%. But these are optimum conditions, and not necessarily a prerequisite of successful implementation. Please note, however, significantly cooler or warmer temperatures and humidity fluctuations may hamper reproduction and development a certain degree.
Benefits
These wasps are cheap, easy and effective. The cards that these parasitoids are supplied on, because they are perforated into squares, as previously mentioned, make even distribution a sure thing. There’s only one problem, see next… [Intro]
Drawbacks
Ants. They love the eggs and will rob them from the squares. Therefore creativity is sometimes necessary: stapling the squares to leaves, attaching them to a tree trunk and surrounding the small area with a sticky barrier product may help.
Another option is to pre-emerge the eggs. To do this allow the cards to remain in the bags in which they are shipped (expand the bags before resealing them) and wait for emergence, checking the bags at least once daily. When the first sign of emerged parasitoids is evident, then hang the cards and shake out the wasps in the bags. This will reduce the amount of time the eggs on the cards are exposed and threatened by marauding ants.
Another drawback is their difficulty to scout (see Scouting).
And, as mentioned before, the Trichogramma spp. have a wide host range. This means they can parasitize a great number of eggs belonging to a great number of species. These wasps are indiscriminate killers. And as much as this is good and convenient to the grower, it can be hazardous to nontarget organisms. Caution and awareness should be exercised when employing these awesome parasitic mini-wasps (see Advisories for more details).
Last drawback: you must really know the pest you’re dealing with. Timing is critical in many cases. The pests’ eggs have to be available, and one sure way to guarantee this is to know when they are being deposited. The Trichogramma spp. are only a preventive weapon, they can’t parasitize the pests’ eggs once they hatch into larvae. [Intro]
Scouting
Your hands are tied. Seeing these little wonders at work is normally out of the question. They’re just too small and quick. If you can find the moth eggs, you may be able to determine if they have exit holes from the wasps. The only other indicator is the reduction of the numbers of caterpillars upon their hatch, and [less] damage noticed shortly thereafter.
Some caterpillar pests are more difficult to control than others. This can be a drawback, especially if the tough-to-kill pest is a serious pest. The Gypsy moth is a good example of this. With no significant numbers of natural enemies (because this pest was introduced to the US from abroad), Trichogramma spp. may have a difficulty making an impact if used by themselves. Therefore the implementation of multiple Integrated Pest Management (IPM) resources is necessary. Unfortunately, this costs time and money.
Battling ants, which are a real threat to biocontrol when it comes to these wasps, is sometimes very difficult. It adds complexity to the would-be simple implementation of these parasitoids. [Intro]
Advisories
If you’re aware of an endangered species of moth or butterfly at your release site, the release should be curtailed, or at least minimized. These wasps are not long-range flyers, though, and thus your release doesn’t have to be too far from the wildflower meadow. Use common-sense, that’s all.
Now speaking of wildflower meadows, this points us towards an interesting topic: trap-crops. But not in the conventional sense. Normally trap-crops will harbor the good bugs and pests, but in the case of these pests, a trap-crop probably won’t lure them. Moth and butterfly larvae seem to be such specific feeders. You will, however, by using a close-range trap-crop, lure other natural enemies. I see caterpillars being dragged off by wasps, birds and bugs all the time. Don’t spray pesticides (Bacillus thuringiensis, Bt, etc. not included), and lure the good guys. These two steps can do an awful lot and may lessen the necessity of purchased-parasitoid use. [Intro]
Usages
Greenhouses and interiorscapes have employed these wasps successfully. Mainly, however, these parasitoids are used in field and row crops, orchards and gardens. [Intro]
Beyond the Page
The window of opportunity when eggs are available for parasitism can be short, depending on species. If you’ve missed your opportunity, perhaps not all is lost since spined soldier bugs, P. maculiventris actually like munching on caterpillars so they can play the role of phase two stand-in. You’ll also want to use some Bacillus thuringiensis or Bt against the larvae. [Intro]
Rates, Instructions, and Purchase
Need more information? Check out our release rates or our short-term storage, handling, and release instructions. You may also purchase T. brassicae, purchase T. minutum, or purchase T. pretiosum. [Intro]
