Codling moth flight begins at similar time each season but regionally these dates vary from October 7th (North Island), October 21st (Nelson) and November 1st (Otago).
This date of first flight each season is called the BIOFIX point and represents the date at which egg-laying and population development commences.
Thereafter the rate of development of codling moth is controlled by temperature.
The total amount of heat required, between the lower and upper thresholds, for codling moth to develop from one point to another in its life cycle is calculated in units called degree-days (DD).
Codling moth has lower and upper development thresholds of 10oC and 31oC respectively. Below and above this range of temperature the eggs and larvae do not develop.
Using daily temperatures and the time taken for egg laying and development to proceed to egg hatch (120 DD from BIOFIX) allows the time of first egg hatch to be predicted.
This information allows growers in each region to accurately time the first insecticide for codling moth control even when spring temperatures are highly variable.
Please select the weather station closest to your orchard and watch daily during October-November for the correct timing of your first spray.
Applications should commence anytime from 80DD onwards depending on the time taken to complete a spray cover on your orchard and the weather outlook.
Applications timed to as closely as possible to the recommended date (just prior to 120DD) will be more effective and will also achieve the maximum period of any residual control provided by the insecticide.
Applications should therefore commence once the DD indicator turns green, yellow indicates highly recommended timing and red (>120 DD) means your timing is past the period of optimum control.
Please ensure that all first insecticide treatments are applied no later than 120 DD to ensure compliance with audited market access programmes.
Unusually warm temperatures in Hawke's Bay during late September resulted in a small amount of codling moth flight activity before the BIOFIX date this season but there has only been continuous flight since October 6th.
We are not proposing to modify the Hawke's Bay BIOFIX date (October 7th) that is based on 20 years of trap records to address this small amount of early flight.
However we do suggest that you take a conservative approach to timing your first codling moth insecticide application again this year - try and get this completed by about 100DD after the BIOFIX date this season.
Do not push the envelop with getting your first application on, it is much better to be apply this first insecticide a couple days early rather than be a day too late. In late October we can easily move from 100DD to 120DD with two warm days.
Warm September temperatures in Nelson are likely to have had minimal impact on codling moth development this season. The first codling moth was caught on October 16th so continuous flight is likely to be underway by the BIOFIX date.
The regional risk from codling moth in Nelson is also much lower than either Hawke's Bay or Otago.
The Nelson BIOFIX date (October 21st) is appropriate for this season but again, we would suggest that you do not push the envelop with getting your first recommended insecticide application on, i.e. aim for completion by 100DD after BIOFIX.
Warm September temperatures also advanced flowering in the district this season and may have had some impact on codling moth development.
We are monitoring codling moth development and first flight in Otago and will supply further updates at this site if activity is significantly earlier than normal.