Wide host range – Serpentine leafminer (Liriomyza huidobrensis)

Crops(s): Wide host range of plant species including onion, potato, brassica, beet, spinach, peas, beans and cut flowers

Disease(s): Serpentine leafminer (Liriomyza huidobrensis)

Guidelines:

1. The Serpentine Leafminer is a highly polyphagous pest of around 50 different plant families including many crops and weeds. Problems with Liriomyza typically result from the destruction of their parasitoids by excessive use of non-selective insecticides. Therefore, an Integrated Pest Management (IPM) approach should be adopted with focus on the preservation of beneficialarthropods and monitoring of pest populations, including:a. Monitoring via regular walk round of crops to determine presence of leafminers, including potential pest reservoirs in surrounding crops and weeds.
   b. Focus on areas exposed to prevailing winds and transport routes or unloading areas.
2. Liriomyza leafminers are vulnerable to a wide range of generalist parasitoid and predator natural enemies, even when introduced into non-endemic regions, thus broad-spectrum products such as Organophosphates, Pyrethroids and Neonicotinoids should be avoided where possible, or used at times to minimize impact on natural enemy population, such as the end of a growing season.
3. Larval stages should be targeted by products showing systemicity or good translaminar or locally systemic activity. This include Cyromazine, Abamectin, Cyantraniliprole, Chlorantraniliprole, Spinetoram, Spirotetramat (use for light infestations – suppression only).
4. Adult flies should be targeted by products with good residual and contact activity, including actives such as Abamectin, Cyantraniliprole, Chlorantraniliprole, Spinetoram.
5. When applying insecticides to this pest, key considerations should be given to:a. Apply insecticides only when needed based on economic damage thresholds (tbd);
   b. Use insecticides appropriate to the insect growth stage, eg. systemic and translaminar acting products are required for larval stages, and contact and residual activity is key for adults.
   c. Use a medium spray quality to ensure sufficient droplets cover the spray target to ensure the larvae ingest a lethal dose of insecticide;
   d. Use a well calibrated, functioning boom spray with appropriate water rate for the target crop to ensure optimum spray coverage;
   e. Use the recommended insecticide rates as stipulated on the relevant APVMA Emergency Use Permit;
   f. Inspect the performance of the insecticide 3-4 days after application. Always document the effectiveness of each insecticide application and never re-spray a failure with an insecticide with the same mode of action. Inform the permit holder, APVMA and agronomist of any spray failures.
   g. Resistance risk is increased where known incidences have been recorded internationally in Liriomyza species. This includes the following MoA groups: Carbamates (Group 1A); Cyclodienes/Organochlorines (Group 2A), Organophosphates (Group 1B); Pyrethroids (Group 3); Spinosyns (Group 5), Abamectin (Group 6) and Cyromazine (Group 17).
   h. When rotating between modes of action, take into account the resistance management strategies for other pests which may be present.
6. When using selected insecticides targeting the serpentine leafminer, the following resistance management strategy guidelines should be implemented:a. If the label allows and it is required for sustained pest management, use two sequential applications of any one Mode of Action (MOA) insecticide to span a single generation of Serpentine leafminer (~13-26 days at 20-30oC) and then rotate to a different MOA insecticide;
   b. Do not treat successive generations with products of the same MOA;
   c. The total exposure period of any one MOA insecticide applied throughout the crop cycle (from seedling to harvest) should not exceed 50% of the crop cycle;
   d. Abide by the individual label recommendation for maximum number of allowable applications per crop per season;
   e. Abide by individual label recommendation for the minimum reapplication interval and always use the full recommended label rates;
   f. Where possible, an Area Wide Management strategy should be adopted where the same MOA insecticides are used by all growers in the same time period; and
   g. As the industry learns more about how to manage this pest, this Strategy may be updated and regional-specific strategies may be developed. Check the CropLife Resistance Management website to ensure you are following the most up to date serpentine leafminer strategy.

List of active constituents approved for use under permits by the Australian Pesticides and Veterinary Medicines Authority (APVMA) as of January 2022

*Refer: CropLife Australia Expert Committee on Insecticide Resistance Mode of Action Classification for Insecticides
**Refer to the APVMA’s PubCris website (https://portal.apvma.gov.au/permits) to ensure permit is still active

Notes:

1. Life cycle prediction tool developed by Cesar: https://cesaraustralia.shinyapps.io/darabug2/
2. Hort innovation guidance document: 1303CR2_Management-guide_FINAL_150620.pdf (ausveg.com.au)
3. DPI factsheet: https://keys.lucidcentral.org/keys/v3/leafminers/key/Polyphagous%20Agromyzid%20Leafminers/Media/Html/Liriomyza_huidobrensis.htm
4. CABI datasheet, including information on natural enemies: https://www.cabi.org/isc/datasheet/30956#67C668C3-A81D-40A2-8D80-1A04AF7490B4