Nightmare November, divine December?

With about half the normal rainfall in October and about a third of normal in November,  the silage harvest was, well, wanting.

NovRainfall

We’d barely gotten the last bale off the paddocks when, one Tuesday morning, Clarky sounded the alarm.

“You’d better get Marian straight down to paddock 19 to have a look,” he said.

Now, Clarky is the king of the understatement. Nothing from snake to bushfire seems to rattle the fellow so, when, he said, “straight down”,  I dropped everything to investigate.

It was an invasion. Marching from west to east were legions of centimetre-long army worms.

Army wormsSquare

A few of the voracious Army Worm larvae

Army worms are as destructive as a team of teenage footy players on grand final night. They descend en masse and literally eat everything in sight.

They weren’t anywhere to be seen the day before and were suddenly in plague proportions, crawling across the track, aloft on ryegrass stalks, wriggling along the rim of the trough.

A careful inspection of the paddocks revealed a heavy infestation from boundary to boundary. The choice was stark: spray or pray.

After a sub-par Spring, this was the last thing we needed. The caterpillars would very likely leave nothing for the cows to graze. On the other hand, spray is the method of last resort.

As the sun moves overhead, army worms retreat to the cool spaces at the base of the pasture, unseen and untouchable. Spraying has to be done at dawn or dusk and the chemicals are nasty, killing pretty much every living thing – good and bad – they touch.

We may not have an organic farm but we don’t like pesticides. It’s much better to let the beneficial insects, like the beautiful Glossy Shield Bug identified for me on Twitter by Dr Manu Saunders (@ManuSaunders), keep the nasties in check.

ShieldBug

Juvenile glossy shield bug (Cermatulus nasalis)

But when you have a plague like this following a Spring drought and a forecast game-changing big rain is on the way?

The Department of Ag reckons “spraying is recommended when the density of larvae exceeds 1 to 3 larvae per square metre”. That made me giggle nervously, given our infestation of “too many to count” per square metre. Reluctantly, yet desperately, I put in the call and quarantined the cows in a separate section of the farm.

Four weeks on and the worms have all but disappeared, continuing to flourish in just a couple of paddocks where excess leaf litter provided cover.

When the drenching December rain came, I was grateful I’d taken this path. With the army worms vanquished and drought broken, the cows were free to graze lush grass again.

While I hate using pesticides, I have a sneaking suspicion I’d better get used to it.

The Department notes:

“Major outbreaks occasionally occur across Victoria, particularly after periods of drought. There are many factors which may lead to an outbreak. They may arise from large invasions of moths which have bred in arid regions of New South Wales, South Australia or western Queensland. Alternatively, they may arise because of significantly less mortality of eggs and young caterpillars. Droughts appear to trigger outbreaks because of the adverse effects they have on the natural enemies of armyworms; these predators and parasites are much slower in recovering from a drought than are armyworms.”

As the climate becomes more volatile, we can expect wild swings in bug populations, too. Sorry, Tony, it’s not beneficial but, yes, I guess it’s just part of farming.

5 thoughts on “Nightmare November, divine December?

  1. Thank you again for another well written account of rural life. I really respect the fact that you are unwilling to use pesticides, but sometimes have to find a solution. Even in my own garden I am sometimes faced with these dilemmas; this year it the rabbits that have invaded, but we are unwilling to lay baits or have them die in agony, can’t shoot, and sometimes just feel like “Mr McGregor”, waving my rake and shouting threats that Beatrice Potter could not have even imagined. I am pleased that your worms are now under control.

    • Yes, the rabbits are another tricky one. The environmental devastation they can wreak is pretty unpalatable too.

  2. Oh no, poor you Marian. I feel your dilemma but am glad it seems to be sorted. But for me as an amateur entomologist, I’d love it if you could email me that pic of army worm grubs, or a close-up if you have one, and give permission for it to go on BLG’s website.

  3. I experienced an invasion of army worms many years back in the dairy country north of Brisbane. Some farmers sprayed but one farmer fertilised his paddocks instead. The grubs only went for the lush improved pasture then quickly moved on. I think that the farmer who sprayed had the right idea as his grass quickly grew again.

    • They’re an amazing sight, aren’t they, Roslyn? The army worms love soft pasture and will certainly clean it out very quickly, leaving only the stalks behind.

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