Aphid alert as populations grow

17 July 2001

Aphid alert as populations grow

By Tom Allen-Stevens

POTATO growers have been advised to keep a watchful eye on late season aphids after alarmingly high numbers were found in several crops over the UK.

Populations have been variable, however, and it is unclear what effect this weeks forecast unsettled weather may have on aphid numbers.

ADAS specialists, monitoring ware and seed crops across the UK, have reported numbers increasing rapidly in certain areas.

Populations of the Peach-potato aphid — virulent virus vectors — have more than doubled in the West Midlands in the last week.

Average numbers recorded remain below the spraying threshold of five per compound leaf, however.

The most dramatic increase has been seen in Norfolk, reports Syngentas web-based potato aphid tracker service, which uses data supplied by ADAS.

Average numbers of 33.6 Potato aphids per compound leaf have been recorded, posing a serious threat to yield and risk of false top roll, warns the service.

Predators have become more prevalent, but remain at much lower numbers compared to aphid population.

Fears are now rising that growers could be subjected to a late season build-up of aphid numbers, not seen widely since the 1996 season.

But these fears may be unfounded as more unsettled weather is set to sweep through many parts of the UK this week.

Many sites saw aphid numbers crash as a result of last weeks poor weather.

Growers are advised to check crops every two to three days and, where aphid numbers are rising quickly, treat to control population growth and migration.

Use of a specific aphicide, such as Plenum (pymetrozine) or Aphox (pirimicarb), is recommended so as not to affect predators.

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