New Locust Hatching Dates

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22 Aug 2010
By Nick McClelland

How can the predicted spring locust hatchings affect the hay market?

The autumn locust swarms in Eastern Australia caused much destruction to newly germinated canola and cereal crops as well as perennial pastures. With autumn now behind us the oncoming spring will provide the additional challenge of controlling the nymph infestation when eggs hatch.

Widespread swarm formation occurred in New South Wales, northern South Australia, northern Victoria and Southwest Queensland during early April after the fledging of the major nymph infestation during March. There have been three generations of population increase this locust season as a result of widespread heavy rainfall and favourable habitat conditions. Despite intensive control of the current generation in New South Wales, eggs laid in autumn will produce a further generation of high density nymphs next spring. Migration to the south during the first week of April brought many swarms into the Murray Valley and Northeast regions of South Australia, Northwest and North Central Victoria and the southern Riverina in New South Wales. Further southward migrations occurred in mid-April. High density autumn egg laying followed immigration into these regions, and has also taken place in other regions of New South Wales and Victoria. There have been many reports of damage to autumn fodder, vegetable, canola and cereal crops. The outlook is for swarm densities to decline during May and there is unlikely to be further significant long distance migration. A serious widespread nymph infestation is expected in New South Wales, northern Victoria and eastern South Australia during spring. The plague situation, where numerous regions across several member states are affected by high densities of locusts, could continue during spring and summer if there is a high level of nymphal survival in spring.

Forecast dates in the table are based on development models for known or possible adult populations and assume sufficient soil moisture for development after diapause. Dates are estimated from longterm average temperatures and indicate the start of the majority of the population entering the life stage. Any actual egg laying will vary from nominated dates and hatchings could extend for several weeks. Forecast dates will be updated regularly. Expect some variation around these dates as temperature affects egg development rate and early hatchings have occurred in recent years. This table is current at the time of printing however as temperatures change from the initial predicted model tables will be updated on the Australian Plague Locust Commission website at www.daff.gov.au/animal-plant-health/locusts.

What does this now mean for hay producers?

Many NSW hay producers in the Forbes region have had new cereal crops damaged by the autumn swarms, however most in NSW and Victoria did not have their cereal hay crops sown when the locusts arrived. Those with cereal crops will need to be wary of the timing in which eggs will hatch in their district and the potential for mature locusts to swarm from other districts. It would be well worth considering the option of making silage for your own livestock consumption or for trading short distances as the timing for harvest can be earlier than the predicted hatching dates. For hay production it is necessary for the head to emerge from the sheath before cutting and then allow for curing as well, in most districts the hatching dates are later than the timing of normal hay production.

As suggested by the APLC the hatching dates could be up to a fortnight earlier if a warmer than normal winter and spring eventuate. However if this scenario occurs hay producers may well be producing their hay a fortnight earlier as the season allows.

While the first cut of lucerne should be produced before the hatching dates subsequent regrowth would be expected to be vulnerable to locust damage. Both lucerne hay production and lucerne seed production in South East South Australia could be compromised.

It is imperative that planning and preparation is thorough to best deal with the hatchings when they happen. Time invested now in researching the control measures, ways to avoid crop damage, and harvesting alternatives may well pay dividends in the coming spring.

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