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Richard Llewellyn

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Above: Closeups of Anastatus. When running around on a leaf they are hard to tell from ants. Their wings may reflect some light and note the boomerang shaped clear section in the wings.

The problem

The current problem stems from the seasonality of supply of silkworm eggs used as a host for the wasps. The eggs we have been recently presenting to the wasps have been in the freezer since March and now seem to be past their “best by” date. The low yield of wasps we are getting means that we cannot efficiently and reliably produce enough wasps at present. We still have a fairly large culture but we need to maintain a large culture in anticipation of getting more fresh eggs from China in late February.

To mass rear insects on a commercial scale one needs a steady supply of suitable food or eggs for the natural enemy. Early in the HAL project we built up our fruit spotting bug culture and were getting about 3,000 bug eggs per week. This is good for research purposes but way short of what is required for a commercial product where we talk in the millions.

We then turned to using silkworm eggs imported from China. For many years, the Chinese have been rearing large numbers of a closely related species of Anastatus for release into lychees for control of lychee stink bug. Fortunately for the Chinese, the supply window of fresh silkworm eggs coincides with the optimum time slot to rear wasps for the the field so that they do not need long term storage. With fruit spotting bug we would like to make releases more evenly through the year so this means we must store the eggs, in various ways, for later use

What we can do

There are a number of things that we can do that should help us get around this problem - a combination of logistical changes as well as different handling and storage of the wasps in the rearing process. At this stage, it looks like we may end up with two major release periods per year: one from March to April and another from August to October. We aim to use a combination methods: eggs stored for up to a month but not frozen; frozen eggs using different packing materials and cold stored parasitised eggs. On the latter, we have some data already but we need to refine the process and run through it again when we get more fresh eggs in February. We are confident that by experimenting with different storage procedures and packing materials we can get around these issues.


It will take another 12 months before we know if we can resolve the rearing issues and whether it looks like it's successful enough for longer term commercial viability. There are plenty of good natural enemies out there but it's quite another thing to mass rear them efficiently and cost effectively, so that many growers can benefit from them, not just a few.

We’d like thank all those who have encouraged and supported this work and we hope that we can be back on track soon.

Before mounting an egg to insert their ovipositor, Anastatus females, check to see if “the coast is clear”, inspect the egg carefully, to see if its a suitable host and detect if another wasp has already parasitised the egg.

Next Blog:
April Update../../2014/4/7_ANASTATUS_UPDATE_APRIL_2014.html