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What to expect after release

The wasps will disperse from the cards and go in search of nutborer eggs to parasitise. Dispersal is slower in the dense foliage of a mature plantation than in a moderate spaced younger crop.

As mentioned in Release and Strategies the object of the regular release is to get some of the early laid eggs parasitised. This is difficult to measure at the time as the density of nutborer eggs is very low. However, experience over the last few years in trial sites and commercial releases has shown that some of these early eggs are parasitised so that when nutborer eggs are more easily found (1 or 2 per 100 nuts) some of these are usually parasitised.

Monitoring for nutborer and Trichogramma takes some practice so if you don't have the time to learn and do it yourself, we suggest you employ a crop consultant. Finding moderate to high levels of parasitism can save a lot of spraying and easily covers the cost of the consultant.

As Trichogramma build up in a crop there are various tell-tale signs that will alert the crop scout. Firstly, the appearance of black eggs and then black eggs with escape holes. Corresponding with the increase in the black eggs will be a decline in the number of hatched viable eggs.

However, many eggs found while monitoring may be parasitised but have not had time to go black which takes about 5 days. "Not black" eggs should be collected and grown out to see if they go black (and not thrown on the ground wasting this useful information). This process will give a more accurate idea of parasitism.

See Monitoring for details.

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Near fresh nutborer egg

Parasitised egg with wasp escape holes