Australian Truffle Pest & Disease Newsletter

How costly is invertebrate damage to truffles?

Trimming invertebrate feeding damage leads to lower yield and quality and takes more time to process

This truffle season we are again undertaking harvest assessments to quantify the economic impact of invertebrates. It is important to keep in mind that invertebrates not only affect the bottom line through direct loss of product from eating it. Their feeding damage can also:

• increase the risk of rot;

• lead to greater costs in the time taken to both clean and grade damaged truffle; and

• leads to downgrading of the product after feeding damage is removed.

For this assessment, we are visiting six orchards three times each over the course of the season as well as other orchards on one-off visits. At each harvest, we collect 50 truffles and sort them according to the depth at which they formed - exposed, shallow or growing deep in the soil. After washing, truffles are assessed for damage, which is attributed to the most likely pest, then graded according to industry standards. We are recording any downgrade in class due to invertebrate damage.

At the end of the season, the information from across all of the orchards visited will be combined with average truffles prices to give an estimate on the economic impact of invertebrates in orchards.

At this stage, we only have preliminary results available from the June harvest. Please note that because the results below come from a limited data source they might not clearly reflect the true pattern for the whole season. As the season progresses and more assessments are done any trends should become clearer. Look out for our presentations at the ATGA conference and further newsletter editions for a more complete set of results.

Exposed truffles have had much higher rates of damage than those growing lower in the soil profile

So far this season the level of damage to individual truffles is much greater in those that are exposed. There was an average of close to 9% of each exposed truffle being damaged, while less than 3% of each individual truffle growing at depth was damaged.

This result backs up what was found in previous seasons where there was a clear trend in the orchards with higher pest damage had higher levels of damage in their exposed truffles, see properties 2, 3 and 5 in the chart below.

Average levels of Insect damage across five orchards over the 2017 harvest

Interestingly this pattern of greater damage in exposed truffles appears to be apparent in orchards that routinely cover their truffles.

The higher level of damage in exposed truffles is reflected in the percentage of truffle that had to be trimmed. Across all of the orchards visited in June on average approximately 25% of each exposed truffle had to be trimmed off. This dropped to 15% for deep truffles.

On average exposed truffles required more trimming due to invertebrate damage compared to shallow and deep growing truffles

It will be interesting to see if this trend of greater damage on exposed truffles continues through the season and how damage levels change across the season.