Abstract:
The non-insecticidal control strategies currently being implemented in South
African orchards for the control of codling moth, Cydia pomonella (L.) may be
hampered bywooden fruit bins being infested with diapausing codling moth larvae,
acting as a potential source of re-infestation. Key factors contributing to the
success or failure of an entomopathogenic nematode application were investigated
using the SF 41 isolate of Heterorhabditis zealandica in laboratory bioassays with
wooden minibins. Under operational conditions, an application rate of 100 IJs/mL
(LD9=102 IJs/mL) effectively controlled codling moth larvae in these bins, and
for further laboratory bioassays, the LD50 value of 18 IJs/mL (≈25 IJs/mL) was
identified as the discriminating dosage. Maximum mortality was attained when
bins were pre-wet for at least 1 min (>90% RH) and maintained at maximum
humidity (>95% RH) post-treatment for at least 3 days (LT90=73 h), to ensure
nematode survival and subsequent satisfactory infection of diapausing codling
moth larvae. Tarping bins achieved the desired high level of humidity required.
Furthermore, adjuvants (specifically Reverseal 10™) also improved an application.
The study conclusively illustrated that if all the above-mentioned conditions are
met, H. zealandica has the potential to successfully disinfest wooden fruit bins of
codling moth.
