Trichogramma wasp
Trichogramma spp.
Role in the garden
A tiny parasitoid micro-hymenopteran of the eggs of pest lepidoptera: European corn borer (Ostrinia nubilalis), cabbage white (Pieris brassicae), codling moth (Cydia pomonella). The female lays her egg inside the host egg, which blackens and then yields an adult trichogramma instead of a caterpillar.
Activity period
May to September
How to attract / manage it
Effective mainly as a directed release: you buy cards containing host eggs parasitised by trichogrammas, to hang in the target crops at the time the pest lays its eggs. Producers: Biotop (Valbonne), Andermatt-France.
Practical guide
Where to find them
Practically invisible to the naked eye. Parasitised eggs blacken, a diagnostic sign: on the yellow cabbage-white eggs under a cabbage leaf, the presence of clusters of small black eggs = successful parasitism.
Sources
- Smith, S.M. (1996). Biological control with Trichogramma: advances, successes, and potential of their use. Annual Review of Entomology, 41, 375-406.
Favourite plants / resources
Related plant entries
Maize (corn)
A living stake for the Three Sisters, maize raises the vertical storey around which the whole planting is organised: its sturdy stalk carries the climbing bean, which fixes nitrogen and returns part of it to the soil for the following crops, while the squash spreads a living mulch across the ground that curbs evaporation and weeds. A heavy feeder and thirsty by nature, it calls for rich, deep soil, something a rotation with legumes helps to prepare. Its tall silhouette can also serve as a windbreak or cast light shade over lower crops that suffer in the heat.
Cabbage
A brassica with a long rotation: 4 to 5 years between two brassicas, 8 to 10 years after a clubroot attack (Réussir Fruits & Légumes, 2022), whose spores (Plasmodiophora brassicae) can contaminate the soil for up to 20 years (RHS). Very greedy (nitrogen, calcium, water). To be planted after a legume to benefit from the nitrogen.
Brussels sprouts
A late long-season brassica: occupies the soil from April to February. An excellent autumn and winter transition plant, to be earthed up for stability. Pinching out the head ('topping') in late August encourages the sprouts to swell evenly. Frost converts starch into sugars: the sweetest harvest is after the first frosts.
Cauliflower
Very greedy for nutrients and water, to be placed after a legume green manure or on a bed well amended with mature compost. Fold the outer leaves over the white curd to protect it from yellowing (sunlight), that's the natural 'blanching'.