Agriculture

Rain – the good, the bad and the ugly – AgFax

Ponds with rivers. Photo: LSU AgCenter

A few showers every now and then during the summer are usually good for crayfish brood because it keeps their burrows moist and improves survival. This summer got off to a dry start across much of southern Louisiana with below-average precipitation in May and June across Acadiana. By mid-July, the drought was over and most of the region received above-average rainfall.

At a time when farmers were stocking rice fields, the hot, dry weather did not create the best conditions for crayfish to survive. Even with thick rice paddies, the water in the fields was extremely hot.

The permanent ponds were not as severely affected by the dry conditions because the portable rivers had all of April, May and June to burrow into the soft silt on the banks of the ponds and were better prepared to survive the summer.

About the time the rice farmers were ready to start cutting rice, the daily rains began. This summer, however, the rains have been unusually spotty. By August, some locations recorded many inches of rain, while fields a few miles away received only a few tenths of an inch.

While summer rains are usually good for crayfish, heavy rains associated with storms from late August to mid-October can cause problems (see below). During the next three to four weeks, the drainage pipes should be installed so that they do not hold more than a couple of centimeters in the fields.

In harvested rice fields, shallow water will help start the decomposition of straw. This will also encourage ratoon growth and may reduce weed growth. Spreading fertilizers over the field further stimulates the growth of rice stubble.

Permanent ponds that have been planted with rice to feed the crayfish should be in pretty good shape this season. Recent rain has supported rice growth and may have reduced weed pressure by keeping flooding shallow.

However, some farmers with permanent ponds failed to prepare their fields and plant rice to feed the crayfish, and weeds took over. Weedy ponds can still grow crayfish, but may need to be managed a little differently.

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As a rule, ponds overgrown with weeds should be flooded in late October, when the temperature drops in the fall. Depending on the type of vegetation, they may need to be washed more often than would be necessary if only rice were present. Maintaining a minimum flood of 6-8 inches will be cheaper to flush than a pond with deeper water.

Weedy ponds often lack food in the spring. Fields with thick walnut-type plants will have very poor water for 10 days after flooding and will run out of food by January. As the spring warms, fields with lots of weeds or sedges may do better and even grow on them.

Indigo fields will have poor water quality in the fall as all the leaves sink into the water, but the stems provide some vertical structure for the crayfish to rise to the surface. Other vegetation, such as rushes or grasses, will provide a lot of biomass for the food web, but these plants can grow so densely that they create problems with harvesting and water movement.

Keep in mind that the flood guidelines for crayfish ponds have been developed around the natural peak spawning months of September and October. If a buried female lays her eggs in early September, the young take several weeks to hatch from her tail, and they may spend another month or two with her in the ground without any ill effects.

While this is happening, the female patiently waits in her burrow for nature’s signals that it is time to leave with her chicks. That’s why some people will tell you that rivers won’t come out until they hear thunder.

There are exceptions to all rules when it comes to crayfish, but based on years of research and observations in ponds across the state, it’s safe to say that farmers usually have the best success if they wait to flood their fields until temperatures drop to 80-85 degrees during the day and 60-65 degrees in the mornings.

This recommendation takes into account two main factors: 1) crayfish spawning regime and 2) dissolved oxygen management (remember, the colder the water, the more oxygen it can have). And… since vegetation also affects water quality, the forage crop also needs to be considered when deciding when to flood.

When we talk about rain, we have to admit that sometimes we can get too much of a good thing. Heavy rains from tropical storms and hurricanes often force females out of their burrows too early, especially if they are temporarily submerged under stormwater. As many Louisiana growers have learned over the years, holding back stormwater in an attempt to save these animals is usually not a good idea.

Losing cankerworms early won’t hurt your crop as much as keeping deep rancid water in the field. If you experience storm-related flooding in the coming weeks before temperatures drop, drain most or all of it as soon as the creeks drop into the surrounding drainage.

Remember that flooding a field in early fall (by pumping or holding back rainwater) does not mean that all females from the dams will emerge and release their young at that time. Most of the females haven’t even laid their eggs yet. Getting an early harvest requires two things: 1) healthy feed and 2) pumping power and management skills to measure and maintain adequate oxygen levels until temperatures drop.

Bait development

We were contacted by a company developing a new crayfish and crab bait. They did some preliminary tests in Louisiana and found that the lure has good water resistance, catch rate and retention characteristics, and is effective in cold temperatures. They are looking for partners to continue evaluating their bait this season and to discuss the commercialization potential of this product in the Louisiana crawfish industry. If interested, contact Didier Buston in stockdidees@gmail.com .

Cranes

For hundreds of years, whooping cranes were an iconic species on Louisiana’s prairies and marshes, but by 1950 there were not a single one left in our state. In 2011, a non-migratory flock was reintroduced to White Lake as part of a species recovery plan, and more birds were reintroduced in subsequent years. Since the reintroduction began, the number of whooping cranes in Louisiana has increased to approximately 80 individuals.

Now, a team of researchers at the LSU AgCenter has put together a short survey to examine knowledge, attitudes, and behaviors toward these special birds. Please consider participating in the survey and keep in mind that your privacy and anonymity are important and will be protected.

You can find a survey here. This AgCenter survey will not collect any personally identifiable information, and no individual responses will be shared with other organizations, only aggregate results.

https://www.agfax.com/2022/09/23/louisiana-crawfish-rain-the-good-the-bad-and-the-ugly/ Rain – the good, the bad and the ugly – AgFax

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