“The overall outlook for the Mallee region is a moderate to high probability of high numbers of nymphs developing and migrations occurring, whilst the Wimmera region can expect low to moderate probability of high numbers of nymphs developing in spring,” Agriculture Victoria said.
The department is urging farmers to prepare chemicals and management approaches.
Agriculture Victoria joined forces with the Australian Plague Locust Commission and conducted ground surveys in north-west Victoria in mid-May following reports of locust activity in late April.
Consistent low to medium densities of adult locusts were found.
Most of the sampled adult females were observed with eggs developing or signs of egg-laying occurring, although widespread egg laying could not be confirmed.
Above average rainfall in May in north-west Victoria means that some habitats should remain favourable for locust breeding with adequate soil moisture for eggs to develop.
Agriculture Victoria said this was despite the BOM forecast for below average rainfall and warmer winter temperatures from a developing El Niño.
Eggs are predicted to hatch in spring in Victoria from late September onwards, likely resulting in some high densities of nymphs.
The locust population increased substantially in autumn from previously low background levels to medium to high levels in inland eastern Australia.
Favourable habitat was established following heavy rainfall in February and March, while warm autumn weather encouraged southward and south-eastern migrations.
April rainfall was low, but above average rainfall in May contributed to suitable conditions for continued locust breeding.
The overall outlook is for some medium to high densities of nymphs hatching in the southern part of inland eastern Australia and a moderate to high likelihood of widespread infestation developing in spring.
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