Argentine Stem Weevil this summer
In 1986 Michael Gibian completed research on Argentine Stem Weevil (ASW) as part of his BScAgr degree.
Since then the ASW life cycle has been studied in Australia during insecticide registration work by Syngenta and Bayer.
In summary we can confirm:
• Over the past 30 years the period over which ASW poses a threat has widened from about 3 months to 6 months as the climate warms.
• Egg laying, which used to commence in early September, now starts in July with larvae found at Avondale Golf Club as early as 5 August after a bifenthrin application.
• Larvae live for an average 41 days, starting their feeding inside the stem before breaking out, migrating to the soil and then feeding on the root system. Their life cycle shortens with increasing temperatures, so numbers can exponentially increase toward late January.
• Larvae do the majority of damage. The presence of adults is only a concern because they will mate and reproduce.
• Adults have not been found to fly so their dispersal is by foot.
• Larvae numbers peak on different greens at different times.
Argentine Stem Weevil Treatment Considerations
It is very clear that the ASW is becoming tolerant, if not resistant, to many currently available chemistries. If you have evidence of failing control, consider Entemopathogenic Nematodes. The newer generation of combination products target adults and larvae simultaneously such as QUALI-PRO TWISTER. Target larvae control with SPINNER, a highly systemic and fast acting insecticide. Round out a complete program with SENTINEL, TEMPO XTRA, TETRINO and MONARCH.
It is most critical given the issues raised above to start control early (August at latest) with adulticides such as SENTINEL (Bifenthrin) or TEMPO XTRA. Adulticides should be rotated.
Throughout the year, larvicide applications should start early September with a program that covers both adults and larvae.
The threat from ASW is increasing. The program intensity and product mix of your program will depend on the threat ASW currently pose. There are a growing number of golf courses where insecticide control is failing so check larvae and adult numbers regularly, starting now. Don’t be panicked by high adult numbers provided the larvae number is low. Rotate insecticides and look to a program approach that alternates between chemical groups.