Background

Anastatus is an egg parasitoid of fruitspotting bugs (FSB). That is, it uses the bug eggs to rear their own young. It is commonly found in Queensland (I found it in the backyard) and also found in Northern NSW.

The Anastatus wasp is about 4 mm long and could be mistaken for an ant. Its wings are held close to its body and it is constantly walking across leaves but unlike ants it hops and flies small distances. It flies more readily at temperatures over 23 degrees.

Field work to date shows that the Anastatus females are able to find both FSB and BSB eggs in dense foliage and are likely to move over 100 meters in a week in search of bug eggs.

Mass Rearing

We have found that we can mass rear this parasitoid using unviable silkworm eggs imported from China. This is the most practical way of mass rearing the large numbers of parasitoids required. However, there are various logistical issues with a 12 month lead time. We are required to order the eggs in October to be received in March–April. Then we present the eggs to wasps for parasitisation. At a certain stage of the wasp development we can move the eggs into cold storage for up to 6 months. On removal from cold storage the wasp continues its development in the egg until its ready to chew out. This will enable us to bridge the winter gap and to start releases in late August-September.

Fruit Spotting bugs

FSB breed outside crops on suitable host plants and then, as adults, fly into crops. They will also breed in crops not sprayed with insecticides and if the food is good. If you see bug nymphs they are breeding in the crop. If the crop is likely to be sprayed with a broad spectrum insecticide, the wasps will be best released along crop boundaries and close to known or suspected bug breeding areas around the crop. Boundary unsprayed buffer rows are ideal, also house gardens and nearby abandoned orchards.

Using chemicals

Chemical management of bugs can continue until such time as its deemed that bug pressure has dropped enough to reduce spraying. If broad-spectrum insecticides are not being used in the crop then wasps can be released in the crop also.

Reductions in broad spectrum insecticides will allow increases in predators of bugs especially spiders and some ants. Higher numbers of other un-economic insects will also enable a higher population of spiders which will in turn catch more bugs.

District wide benefits?

We don't know what the longer term local and district wide benefits of the Anastatus sp. releases might be. High levels of parasitism from local parasitoids have been observed latter in the season at some sites. This suggests the wasps are very capable given the right conditions. By making mass releases this should be more common and help to reduce overwintering bug populations. The more farms in an area making releases the more likely this is to happen.

About the trial sites

The initial spots for releasing Anastatus sp. will be boundaries of crops and nearby likely bug breeding grounds. This presents some difficulties in measuring activity of the releases of FSB egg parasitoids. Bug eggs are also hard to find in a crop let alone in areas surrounding crops.

This means that apart from highly observed research trials, we are going to have to rely on changes in FSB activity and damage levels as well as your farm practices to assess the impact of the Anastatus sp. releases.

Monitoring

Measuring Anastatus sp. activity directly is very difficult as bug eggs are hard to find and breeding sites are not necessarily within the crop. Unlike, for example with Trichogrammatoidea cryptophlebiae (MacTrix), where it is easy to collect eggs and determine the level of parasitism.

We will therefore need to rely heavily on the assessment of changing numbers of bugs over time as well as document changes in decision-making and management practices. To do so we will need participants in the trials to complete an initial questionnaire and one at the end of each season based on information collected through that season. This information needs to be collected in a similar way each season for that site.

Likewise, obtaining direct evidence of bug densities in the crop is not possible so damage caused by bugs in the growing season and damage at harvest (if appropriate) will be used for the assessment. We have standardised the methods for assessing damage and tried to keep it simple. See "Monitoring notes".

The monitoring protocol may differ a little from what you have been doing so have a good look at it and contact us if you have any questions.

Selecting sites suitable for the Anastatus trial

• Please consider the following:
• Site area up 1 to 5 hectares
• Bugs typically present every year and hots spot area within the crop is desirable
• Identifiable likely source/s of bugs adjacent to crop
• Good records of past damage levels at harvest
• Records of nut drop caused by bugs
• Observation of bugs numbers if available
• Spraying records, timing, products used and % of crop sprayed
• As project progresses a preparedness to not spray if presence of bugs was deemed low

Requirements for participation in the trials:

• Provide crop and site details and answer initial questionnaire
• Map of site including likely bug breeding areas and host plants
• Releasing wasps – around 10 releases per year (may be done by grower or consultant)
• Provide records of all your spraying once a year
• Monitoring nut drop or fruit or shoot damage and submitting your results via a web form
• Harvest assessments if appropriate
• End of season questionnaire