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Dairy Cow Reminders For January 2004

By Department of Primary Industries - 7th January 2004 - Back to News

Pastures

Long-term perennial rye grass pasture growth rates for January on dry land pastures in Gippsland are 12 to 17 kg DM/ha/day. These low growth rates reflect the lack of soil moisture as the limiting factor that reduces plant growth. Those on irrigated land rye grass pastures can expect an estimated growth rate of 30 to 40 kg DM per hectare per day. Irrigated paspalum pastures with adequate drainage may exceed the growth rates of ryegrass pastures during the hotter summer months.

Ryegrass leaf appearance rates for mid January can be quite variable due to rainfall, but is estimated to be between 10 to 15 days for each ryegrass leaf to emerge and extend to its full leaf length. Therefore, pasture rotations in January should be at least 30 to 35 days between each grazing.

Excessive daytime temperatures and dry conditions will suppress rye grass growth rates and leaf size, while very dry conditions may shut the plant down all together.

Only well managed and adequately irrigated pastures will respond to applications of nitrogen.

Cows

Select a paddock close to the dairy for those excessively hot days to reduce the cows walking distance in the hot afternoon sun.
Be proactive in managing heat stress on your herd, install shade cloth over part of the yard and operate yard sprinklers on hot days.
After the busy spring, mating season and hay harvest, some of the dairy shed record keeping has fallen by the way side. Update all your cow records and quality assurance (QA) information during January. Set aside one of those hot afternoons and spend it in front of the air conditioner entering all the backlog of data into the farm record system.

Young stock

Start to prepare for the pink eye season, get some treatment supplies on hand and avoid pastures with long dry grass and dusty conditions.
Carry out a faecal worm egg test to evaluate your worm control program.

Environment

Check your dams for blue green algae on a regular basis
It is a good idea to have more than one source of water for the farm just in case one system breaks down.

Risk Management

Have you updated your insurance policy to cover the hay in storage on the farm
Monitor the new season’s haystacks for excessive heat generated from storing damp hay rolls in sheds.

Summer Crops

Properly identify your turnip pests before you buy the insecticide
When strip grazing turnips, feed silage or another fibre source to the herd after the morning milking, but prior to turnip crop grazing to help balance fibre in the ration.

CHECK FOR DIAMONDBACK MOTHS

"Farmers should be continually checking their forage turnip crops for the caterpillar of the Diamondback Moth or Plutella," says Frank Mickan, Pasture and Fodder Conservation Specialist, DPI, Ellinbank. "If you have noticed small dark brown moths (male) with three diamond-shaped patterns aligned on its back or lighter tanned moths with less distinctive diamond patterns, then you have already missed the first complete cycle of the diamondback moth, also called the cabbage moth."

Many farmers in the South West of Victoria have already had to spray their brassica crops this summer. The diamondback moth has caused much of the damage seen this season. Similar damage is sometimes caused by the larger cabbage white butterfly.

Spraying is the only defence against Plutella currently, but unfortunately, insecticide resistance is developing within this species. To slow this down and to achieve a maximum kill each spraying, we must use the best insecticides and spraying techniques available.

There are only two families of chemicals available for Plutella control. These are the synthetic pyrethoids (SPs) and the organophoshpates (OPs). While the short withholding periods of the SPs are attractive, Plutella develops resistance to this family of chemicals quite rapidly, so avoid them if possible. Consider these rules when choosing which chemical to use:

· Only use insecticides registered for use in brassica forage crops;

· Use recommended rates (if it doesn’t work at the recommended rate, it may not work at a higher rate either, and instead can cause residues that are also illegal);

· Observe all grazing withholds as per the label. Some chemicals are registered for control of Plutella in horticultural situations, but have not been registered for use in forage turnips, ie those to be grazed by cattle, and so has no grazing withholding period stipulated.

It is important for you to consider the "10 Golden Rules" for spraying brassica crops:

1. Only spray when necessary - sprays also kill beneficial predatory insects.
2. Use softened water or rainwater if possible - hard or alkaline water can reduce chemical effectiveness so use immediately after filling the spray tank.
3. Use high water volumes, from 150 – 200 L/ha, to achieve the point of runoff. Good coverage with spray is essential, both above and below the leaf.
4. Consider using cone type nozzles for high volume, fine droplets.
5. Higher pressures and finer flat jet nozzles give small droplets, but take care with drift.
6. Use wetter/surfactant adjuvant as per insecticide label to ensure the chemical stays on the leaf. Brassica leaves are waxy, so water droplets bounce and roll off them readily.
7. Calibrate the boomspray properly to ensure the correct rate of insecticide is applied.
8. Spray in the evening - only the second and third stages of Plutella caterpillars are affected by spraying and these actively feed at night - plus there is less evaporation and UV degradation of the insecticide.
9. Monitor spray results and reinfestation. Sprays will not kill moths, eggs, very young (burrow into leaf) or very old caterpillars and pupae.
10. 10. Respray as necessary, perhaps after 10 –14 days at this time of year.

The life cycle of Plutella speeds up in the warmer weather taking about 14 days at 28 °C but slows down to 47 days at 15°C.

Chemical use is not the answer to controlling Plutella. In future, biological control agents such as parasitic wasps will be commercially available, and perhaps gene technology will contribute to our arsenal of control measures. In the meantime however, we must ensure that we make the most effective use of our current line of defence – insecticides.

Source: http://gippsland.com/

Published by: news@gippsland.com

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