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How to Control Algae in Rice Crops

Algae, or slime is a perpetual problem in rice

crops in Australia and elsewhere. In some years

it is so prevalent in the water that large slabs

of algae cover the surface, smothering the emerging

crop.

Algae is commonly present in irrigation water and

generally the rate which it multlplies is balanced

by natural degeneration. However, when the balance

is upset through increased sunshine or by the introduction

of extra nutrients, the rate of growth increases and the

algae blooms become a problem Algae Crop

.

Algae thrives where there are plenty of nutrients in the water and when plentiful sunlight encourages photosynthesis. The rice crop conditions of shallow water, fertilizer and sunlight create an ideal environment for the growth of algae. During the wet season, the conditions for algae growth are also enhanced

as the water from rivers, creeks and reservoirs used

on the crops, contain a higher level of background

nutrients.

What are the effects of algae?

The obvious signs of algal bloom - great slabs of algae

- are like the tip of an iceberg. Before is seen there

has been a lot of damage to the crop at its most vulnerable

stage of growth. The effects include:

Inhibition of seedling germination and vigour - Plant

pathologists suggest the possible effect of algae could

be greater than that of fungi on germination during early

growth of rice seedlings.

Uprooted seedlings - Respiratory and photosynthetic gases

become trapped in the filaments tangled around seedlings,

uprooting many seedlings which are not securely anchored.

Competition for nutrients - Slime lives and grows on the same

nutrients as rice seedlings. In a blooming population the sheer

numbers of algal cells are enormous and represent a severe drain

on the available nutrients.

Seedling knockdown and smother - When filaments of algae are

in huge numbers they smother and drown the emerged seedlings

and a tremendous amount of damage has already been done.

Remedial treatments will salvage the crop but it is obviously

better to avoid this damage before it happens. A good seedling

stand is essential for high yields.

Present Treatment

In most cases action on slime is only taken when filaments are

present in huge numbers. The treatments available are limited.

Generally farmers use water control or bluestone, both of which

are drastic answers to a problem where a lot of damage is already

done.

Precipitates very quickly - Copper sulphate is precipitated by

carbonate hardness, accumulating in sediment at the bottom of

the storage and rendered unavailable to control algae. In normal

water the free copper ions which are toxic to algae combine

rapidly with the carbonate ions and fall to the bottom as insoluble

copper compounds within an hour. Chelated copper (coptrol) is

stable in hard water and remains available to be absorbed from

the water by algae.

Is difficult to apply - Bluestone irritates the eyes and skin,

is very corrosive to equipment, is invasive in aircraft instruments

and is hard to spread evenly from the air.

Copper Sulphate (Bluestone)

Is affected by humic content - The greater the humic

content in the water, the quicker copper is tied up and

precipitated out. Decomposing plant matter in rice crops

is thus a major limiting factor in getting results from

bluestone.

contributes to livestock toxicity problems - Because so

much copper from bluestone precipitates out rapidly as

insoluble carbonates and hydroxides, copper build-up in

the soil and pastures is a continuing problem. Copper

toxicity in sheep grazing on sub clover, or where Heliotrope

or Paterson's curse (also known as salvation jane, blueweed,

purple bluegrass, and riverina bluebell) is present is well

known in the irrigation areas.

COPTROL IS THE ANSWER

Coptrol is a new generation algicide which is so safe

it is registered for use in human drinking water as well

as in rice crops.

Coptrol offers a new approach in the prevention and control of free floating and filamentous algae in rice.

Coptrol is a special kind of organic compound in which the copper is held so tightly that it cannot be "stolen" by contact with other substances. This means for killing algae much lower quantities of copper are needed when compared to bluestone. Thus preventing copper build-up in pastures. In addition Coptrol is much more effective

at killing algae. And far from being irritant and invasive,

all the components of Coptrol are specifically

exempt from scheduling under the Uniform Poisons

Standard of the *NHMRC. *National Health and Medicine

Research Council of Australia.

Coptrol is highly specific to algae and does not harm fish, plants of livestock, when used in accordance with label directions. Indeed part of the molecule is a nutrient and algae actively seek out Coptrol, which leads to their quick destruction.

COPTROL

is very stable and highly effective in controlling

algae

is a liquid and is easy to apply

is not corrosive to air craft or equipment

remains active in water longer

will not build up in the soil

Method of Application

Since Coptrol is a non-corrosive liquid it is extremely

adaptable in application. Unlike bluestone it can be

applied as a PREVENTATIVE treatment prior to or

immediately after sowing. It can:

Piggyback with herbicide and insecticides

flown on to aerially sown and drill sown crops

Be mixed with water and dripped in to water flowing

into bays

Be poured from banks directly into flooded bays.

Coptrol can also be used in these ways as a REMEDIAL treatment for green and brown slime (which is usually blue green algae discoloured by degenerating plant material or suspended soil particles).

Rates of use

Situation

Pest

Application

Critical Comments

Preventive

Aerial Sown Rice

Blue-green algae

2L per 1 ha ideal

condtions

For average water

depth up to 10cm

3L per 1ha for average

water depth 1 0-15cm

4L per 1ha when average

water depth exceeds

15cm

Apply 7-10 days after sowing as a sole spray or in tank mix with standard

herbicide treatments. When applied as a sole spray use not less than 20L

water per litre of Coptrol. (The effectiveness of this product depends

on its concentration). Use of lower rate in deepwater will inhibit results.

Remedial

Rice:aerial and drill sown

Blue-green algae

2.5L per 1ha

Use lower rates in shallow water when algal filaments first become apparent. Use higher rates in deep water and where alagal bloom is smothering emerging

rice seedlings.