The status of the silverleaf whitefly nymph can be gauged using a mobile phone lens attachment in conjunction with the NymphCheck app. Photo: CottonInfo

THE CottonInfo NymphCheck app is enabling growers and advisors to use a mobile phone image taken with the aid of a clip-on lens attachment to determine nymph viability in silverleaf whitefly in cotton crops.

The software is based on work by University of Southern Queensland researchers Dr Derek Long and Dr Alison McCarthy in partnership with Queensland Department of Primary Industries and CottonInfo IPM technical lead Dr Paul Grundy.

NymphCheck classifies nymphs as healthy and viable, or non-viable if parasitised, dead or empty cases.

A lens which clips on to a mobile phone is required when using the NymphCheck app. Photo: CottonInfo

The app works entirely offline and does not need an internet connection.

“When managing crops late in the season, please consider the silverleaf whitefly populations in your fields, and consult the silverleaf whitefly decision matrix, revised in 2024, to estimate your risk,” Dr Grundy said.

“Take advantage of the revised NymphCheck app that can help determine parasitism levels in your crop.

“The simplified sampling procedure now focuses on the presence/absence of nymphs in the mid canopy.”

From first open boll onwards, assessing nymph viability is a crucial component of ongoing silverleaf whitefly management decision-making.

During this period, assessment of nymph viability can determine the impact of parasitism, which can increase rapidly, and the efficacy of applied insecticides.

Determining nymph viability, particularly due to parasitism, can be difficult and requires magnification.

The impacts of this mortality can markedly reduce what might initially appear to be high numbers of nymphs and negate the need to spray or make a follow-up application.

Silverleaf whitefly was detected in Australia in 1994, and it first tested the industry when its numbers boomed in the Emerald district in Central Qld in the 2001-02 season.

Its resistance to broad-spectrum insecticides meant answers were sought from Arizona in the United States, which pointed to the need for a tightened sowing window and management across the region.

In 20025-26, silverleaf whitefly had become a problem in the St George district of south-west Qld too, by which time pyriproxyfen had become the cornerstone product for management of the insect.

Since then, alternative modes of action have been introduced, and an integrated pest management program has been adopted with local thresholds, greater reliance on natural enemies, and effective management of resistance.

The NymphCheck app is the latest tool growers can use to help keep silverleaf whitefly populations in check.

Source: CRDC Spotlight magazine