Continuing warm wet weather is bad news for kiwifruit orchardists battling the Psa-V infection.

Significant periods of prolonged wind and rain increase the likelihood of Psa-V infection by way of leaf wetness and physical damage.

A Kiwifruit Vine Health weather map available for growers only.

Protectant spray programmes need to provide sufficient orchard coverage, including all new growth with particular attention paid to ‘infection periods'.

An infection period is defined as a prolonged two to three days of leaf wetness.

NIWA has provided kiwifruit growers an air parcel streamline forecast tool, which is only available on the Kiwifruit Vine Health Incorporated website's grower-only pages.

The tool animates predicted weather events over two-day and six-day forecast periods compressed in time.

The forecasts enable growers to follow hourly wind-speed and direction.

They also show accumulated surface precipitation as a continuum or range between all New Zealand kiwifruit growing regions.

The animated forecasts show the upstream path of air flow from the ground – in conjunction with precipitation – that is, the air movement responsible for aerosol development and airborne bacterial spread.

The tool enables growers to view weather events impacting high risk areas and priority zones and to pinpoint the direction of potential aerosol flow out of these regions in response to these weather events.

Access to the information is available only to orchardists who are registered users of the KVH website.

In the December 1 KVH bulletin, the site is offering beginner guide drop-in sessions for growers not confident about accessing the website.

Since the revised KVH website was launched in August, KVH says visitor numbers have been increasing by the week.

The site now registers 6000 separate computers accessing the site each month with an average of 20,000 user visits and 100,000 page hits.

People from 45 countries are visiting the website.

The infection continues to spread.

Last week KVH received 21 new Psa-V positive results bringing the total of Psa-V affected orchards to 889.

The majority of infected orchards are in the Te Puke region, 748.

The other Psa-V orchards detected with infected vines are in Tauranga, 52, Whakatane, 42, Opotiki, 23, Katikati, 11, Waihi, 10, and Franklin, 3.

Thirty five per cent of New Zealand's kiwifruit hectares are on orchards with Psa-V positive results.

Fifty per cent of Gold hectares are on affected orchards; 32 per cent of Green.

Psa-V on a kiwifruit orchard near Pukekohe is confirmed.

Two other Pukekohe orchards are probably also infected.

A priority zone has been established around the affected orchards.

Permission for the use of the antibiotic spray KeyStrepto ended on December 1.

Actigard is approved for use beyond fruit-set for all kiwifruit varieties – for fruiting vines up to 70 days prior to harvest.