Whitton, New South Wales

Sentinel 5 has completed a trial monitoring the presence of cotton & horticulture pests & pathogens at a commercial cotton […]

Sentinel 5 has completed a trial monitoring the presence of cotton & horticulture pests & pathogens at a commercial cotton grower property at Whitton in Riverina. iMapPESTS have collaborated with CottonInfo’s Kieran O’Keeffe, sharing our observations with local industry and cotton industry stakeholders.

Sentinel 5 features insect suction traps at 6- and 2- metres, a pathogen spore sampler, a weather station and onboard telemetry. Samples were collected over a 24 hour sampling regime, six days a week.

A shortlist of priority insects for cotton were targeted for identification and quantification from the 6-metre insect sampler by entomologists at SARDI. A shortlist of priority pathogens for broadacre were screened for their presence and prevalence over the course of the trial.

Insect samples from the 2-metre insect suction trap were analysed by Agriculture Victoria Research (AVR) using their insect metabarcoding approach.

Insect pests targeted

Green mirid (Creontiades dilutus)

Onion thrips (Thrips tabaci)

Green peach aphid (Myzus persicae)

Green vegetable bug (Nezara viridula)

Fungal pathogens targeted

Sclerotinia white rot (Sclerotinia minor &/ S. sclerotiorum)

Blackleg of canola (Leptosphaeria maculans)

Septoria tritici blotch (STB) (Zymoseptoria tritici)

Yellow leaf spot (Pyrenophora tritici-repentis)

Chocolate spot of fava bean (Botrytis fabae)

Botrytis grey mould (Botryitis cinerea)

Insect diversity at Whitton

The insect samples from the 2-metre insect suction trap onboard Sentinel 5 were sent to Agriculture Victoria Research (AVR) to report on the diversity of the insects captured during the trial using their insect metabarcoding approach.

Metabarcoding is a process that can screen for a large number of target species in a single sample. The metabarcoding process works by using a non-destructive DNA extraction, which results in a “DNA Soup”. Once the DNA soup is sequenced, the data is then compared to a reference database of all the identifiable insect species that might be present in the sample. The out provides a receipt of all insect present in the sample.

Thrips in early season Southern cotton

CottonInfo’s Kieran O’Keeffe has been collecting insect samples from Sentinel 5 since early November.

In summary, thrip numbers are now starting to decline and no mirids have been detected yet.

Initial spray decision strategies in a cool start year are justified but follow-up sprays when numbers are declining and the crop is growing out of damage are not warranted.

Note that thrips populations will naturally crash in the field at about 50 DAS. This is very typical and this natural decline provides the opportunity for plants to recover. Plants will recover from less severe damage often with no yield loss or delay. This has been shown in southern NSW trials over several seasons.

Early season insecticide spray applications may seem a cheap option at the time but it will have consequences and lead to a reduction in beneficial insect populations. Cheap and early can result in expensive sprays later.