Russian wheat aphid exits advanced crops
LATE-sown crops, particularly those in the Riverland, have been hit by an infestation of Russian wheat aphid, according to SARDI researcher Maarten Van Helden.
In a mixture of trial crops in Loxton, Bool Lagoon and Roseworthy the aphid was found to be attacking young and drought-stressed crops, which as a result, stunted the crop’s growth.
But in crops which became well advanced, Dr Van Helden reported a reduction in RWA, likely due to the plant being “less attractive” to the aphid.
“Often the aphids are having an affect on the plant which cannot improve the feeding quality for the aphid,” Dr Van Helden said.
“If the aphid has not been present in high enough numbers the plant is taking over and growing through, becoming less attractive to the aphid.”
Dr Van Helden said at the three trial sites, crops were sown every month from April to July and crops that were sown late and had reduced growth had almost been completely attacked on nearly 100 per cent of tillers.
“We expected the aphid to build up on the April and May crops but that didn’t happen,” he said.
Dr Van Helden said based on the trials, sowing time was an important element of RWA risk.
Looking at crops across the Riverland and Mallee, Rural Directions consultant agronomist Richard Saunders said farmers were still learning how to combat RWA.
“Last year we had an amazing year and word is the rainfall washed the RWA off the plants,” he said.
“This year we haven’t had those rains and it’s been a lot drier and as a result the crops have been stressed.”
Mr Saunders said a number of farmers were using seed-treatment insecticide Imidacloprid to provide the crop some protection so it could “get away”.
Tarree Pastoral farm operations manager Josh Andrews reported RWA in his wheat and barley crops, but not as many as he had predicted.
“I thought we were going to have a lot of headaches being the second year having RWA, but I was surprised they weren’t as bad as I was planning for,” he said.
Mr Andrews said he treated later-sown crops with Imidacloprid, but earlier sown-crops were left untreated.