Terrie Greco, B.A.; HLT Dip.

What are Trichogramma wasps and how do they act as a natural pesticide in non-agricultural gardens?

This is my fourth blog in a series on beneficial insects after I presented an overview earlier last month.  I still want to remind you, yet again, of the value of beneficial nematodes, but that will be in about four weeks since then will be an appropriate moment to apply or reapply them, as the case may be. 

Today I am going to write about “trichogramma”, a very scientific sounding beneficial but one which can prove very useful in fighting pest insects, namely codling moths, fruitworms, borers, budworms, loopers, leafrollers and leaf tiers. Trichogramma are sold in cards that are very easy to place at strategic locations in the garden. 

Trichogramma is a tiny wasp that controls countless Moth and Butterfly pests; we still consider these beneficials the ‘new kid on the block’ in our own gardens, even though they have been used around the world for years in agricultural applications.

The species recommended for properties with fruit trees – commonly infested with a number of different caterpillar pests – is Trichogramma minutum.  This species is suitable for plants in which the lower branches are five feet or more above the ground.

Trichogramma wasps perform their duties in a most fascinating way.  The adult wasp detects egg masses of moths and butterflies on plants through chemical and visual cues.  Once a suitable ‘host’ is located, the female ‘drills a hole’ and inserts her own eggs into the pest eggs.  At the same time, venom is injected into the pest egg which breaks down the yolk and embryo into a liquid form.  Voilà – homemade soup all ready for the wasp larva to feed on when they hatch.  Mothers really do think of everything, don’t they?

The Trichogramma larva develops very quickly into adults from the comfort of their host egg.  Once they emerge as adults – they find a mate and carry on the family tradition.

As effective as they are – their short life span dictates that two or to three releases must occur over a period of time for good control. Most importantly – you need to identify the pests you want to control correctly before using any beneficial– after all – you want to use the most effective treatment to control your pests! 

And don’t worry about getting stung – they won’t bother you – in fact – you won’t even know they’re around.

Biofloris now sells these natural pesticides.  Just click here for more info or to order them.

Oh, and here’s a picture of what they look like: 

Trichogramma spp. – Trichogramma Adult Wasp

I got a lot of positive feedback on last week’s “Caterpillar Brigade” post.  I also received numerous emails requesting photographs.  So I put some together here for you:

Image 1 – Malacosoma americanum: Eastern Tent Caterpillar ‘tent’ Webs

Note that the Eastern Tent Caterpillar always produces a silken web in the forks of tree branches.  During the day, the caterpillar leaves the nest to feed and returns at night.  The nests grow larger as the caterpillars mature and need more room.  Constant home renovation!

Photo courtesy of John Himmelman, childrens author, illustrator and naturalist

Image 2 – Malacosoma americanum: Eastern Tent Caterpillar Egg Bands

Note that compared to the Forest Tent Caterpillar egg bands, the edges are more rounded.

Photo courtesy of Brian Kunkel, University of Delaware, www.bugwood.org

Image 3 – Malacosoma americanum: Eastern Tent Caterpillar Mature Larva

Note that the Eastern Tent Caterpillar has a white stripe down the back, blue spots on either side and plenty of hairs (setae).

Photo courtesy of David Cappaert, Michigan State University, www.bugwood.org

Image 4 – Malacosoma americanum: Eastern Tent Caterpillar Adult Moth 

Note  the white forewing stripes on Estern Tent Caterpillar compared to the darkish stripes on Forest Tent Caterpillar. The adult female of the Eastern Tent lays eggs in early to mid summer in a band around twigs.  The eggs over winter and hatch in early spring just before bud burst.  This pest prefers apples, crabapples and cherry trees.

Photo courtesy of John Himmelman, author, illustrator and naturalist

Image 5 – Malacosoma disstria: Forest Tent Caterpillar egg band on twig.  Pruning off the egg bands in spring will do much to reduce the population.  Compared to Eastern Tent Caterpillar egg bands, the edges of the egg band is square rather than rounded. 

Photo courtesy of Thérèse Arcand, Natural Resources Canada, Canadian Forest Service 

Image 6 – Malacosoma disstria: Forest Tent Caterpillar mature larva – This caterpillar can be identified by the white  ‘keyhole’ or ‘footprint’ shaped spots down the back and a blue stripe on either side of the body.

Photo courtesy of John Himmelman, author, illustrator and naturalist 

Image 7 – Malacosoma disstria: Forest Tent Caterpillar Female Adult – The adult female moth lays hundreds of eggs on a small band around tree twigs in mid-summer.  The eggs over winter and hatch in the spring.  Note the dark beige coloured wings with the two dark downward facingbands on the forewings.

Photo courtesy of John Himmelman , author, illustrator and naturalist 

Image 8 – Hyphantria cunea:  Fall Webworm Tents – Compared to the webs of the Eastern Tent Caterpillar, which are produced in the forks of trees, Fall Webworm forms silken tents at the ends of branches.  The larva feeds inside the tent, destroying all the foliage in the web before moving to another location on the tree.

Photo courtesy of G. Keith Douce, University of Georgia, www.bugwood.org

Image 9 – Hyphantria cunea:  Fall Webworm Larva – The larva are creamy white with prominent black bumps on the body, and extremely hairy.  If I were a bird – I would have trouble swallowing this caterpillar! 

Photo courtesy of John Himmelman , author, illustrator and naturalist 

Image 10 – Hyphantria cunea:  Fall Webworm Adult Laying Eggs – The adult female lays a large mass of eggs on the underside of leaves of White Ash, Birch, Willow – to name just a few hosts. The egg masses can easily be missed by a homeowner. The adult is either pure white or has a scattering of small brownish/black markings on the white wings.

Photo courtesy of H C Ellis, University of Georgia, www.bugwood.org

Image 11 – Hyphantria cunea:  Fall Webworm Adult –Portrait of a moth…you gotta love that face – and wait – is that hairstyle a mullet??? Joking aside – it’s an amazing photo of a moment in nature captured in time…

Photo courtesy of John Himmelman , author, illustrator and naturalist 

We are very grateful to John Himmelman for generously offering permission for the use of his moth photographs on our website.  John is a well known childrens author, illustrator and naturalist.  Check out his websites below!

http://www.connecticutmoths.com 

http://www.johnhimmelman.com 

http://www.ctamphibians.com