Fall armyworm can present a substantial threat to production of a forage crop for crawfish, whether it is rice or sorghum-sudangrass. Large populations of fall armyworms may invade the forage crop for a variety of reasons, the primary one being that their previous host has been harvested. This movement into the crawfish forage crop has typically been observed in areas where corn, grain sorghum or milo or other grass-type plants have been harvested near a rice field. Armyworms are not afraid to march across soil in search of a new plant to devour.

Fall armyworms have a distinct Y-marking on their head capsule which can be used to distinguish them from other species of caterpillars (photo 1). Armyworms damage forage crops by cutting down seedlings or defoliating plants. This damage can be extensive enough to require replanting (photo 2). To scout for armyworm damage, look for cut and ragged leaves and then for the armyworm caterpillars on the plants or in the whorls (photo 3). You can also scout for armyworms using a sweep net to brush across the surface of plants and catch armyworms(photo 4). Another sign is the presence of cattle egrets or other birds foraging in the field (photo 5). These birds will often flock to fields with insect infestations.

Because the crop you are trying to protect will soon be food for crawfish, it is important to avoid applying chemicals to that crop that could potentially kill crawfish. Most synthetic insecticides are highly toxic to crawfish. This is true because crawfish have physiology that is similar to insects. At this time, there are limited options for control of fall armyworm attacking a crawfish forage crop. It is possible that the fall armyworms will be controlled by natural enemies – such as parasitoid wasps, bacterial infections or diseases. Although, oftentimes the natural controls will not control the population quickly enough to avoid extensive crop damage.

If you are experiencing crop defoliation or plant loss from an armyworm infestation, the first option is the application of Bacillus thuringiensis (Bt foliar spray). It is important that Bt be applied to young caterpillars. First and second instar caterpillars are most susceptible to Bt (photo 6). A second option for rice is to flood the field for two to three days to drive armyworms up onto plants where they will be more susceptible to attack by predators such as birds. The flooding may also drown the armyworms. Be sure to avoid completely submerging plants which may cause plant mortality from the flooding. Flooding in young sorghum-sudangrass is not an option in most cases because fields cannot be flooded and drained quick enough to prevent crop failure or set back from water-logged soils. Finally, try to avoid planting a forage crop near a host field (milo, sorghum, etc.) that will be harvested soon.

So is insecticide use for control of armyworms a potential option? Crawfish in capped or sealed burrows are probably not exposed to insecticides used in foliar applications for control of fall armyworms but the potential impact of residues on crawfish health is not known. The insecticides Karate Z, Mustang Max, Prolex and Proaxis, labeled for use in controlling fall armyworms in rice, have label restrictions that state "Do not use treated rice fields for the aquaculture of edible fish and crustaceans." Other insecticides used to control fall armyworms in pasture and forage crops, including sorghum-sudangrass, include Sevin, Lannate and Tracer. Although the labels for these chemicals do not specifically state that the fields cannot be used for the aquaculture of edible fish and crustaceans, most have specific warnings as to their toxicity to aquatic invertebrates, which, of course, includes crawfish. Contact your local county agent if fall armyworms attack your crawfish forage crop. They can provide you with the latest information and best course of action for fall armyworm control.

It’s easy to notice the negative impacts of predators like birds and raccoons in crawfish ponds, but in many crawfish farms tremendous losses to other types of predators often go unnoticed. Trash fish like bullhead catfish (photo 7, also called mudcats or polliwogs) carp and green sunfish (photo 8, green perch, slick perch) find their way into many ponds. Some crawfish producers view fish in their ponds simply as a nuisance when harvesting, but it has been estimated that a single two-inch long green sunfish could consume the equivalent of a whole sack of crawfish over its lifetime if it began eating newly hatched crawfish shortly after fall flood-up.

Of course, trash fish are more common in ponds that are filled with surface water from canals and bayous, but they can become a serious problem even in ponds that are filled with well water. There is probably some truth to the common belief that birds can introduce fish into crawfish ponds on their feet or feathers, but the numbers are usually negligible. A more common path of entry for trash fish involves backflow of water up drains and into ponds when ditches and canals are filled from heavy rains or tropical storms. Many farmers may not realize how often this can occur. Larger fish also have a tendency to swim against a current all the way up a drain pipe. Producers can minimize the entry of fish through drain structures by installing grating over drain openings, but provisions should be made to remove the grating when needed to prevent clogging with vegetation or other debris.

Efforts to reduce, prevent or eliminate fish populations in crawfish ponds should focus on two key strategies. The first applies to ponds filled with surface water and it’s one thing we’ve all learned over the years: thoroughly screening (filtering) and breaking up the water as it’s pumped into the pond is critical (photo 9). The second strategy can be just as critical: drying or treating any standing water where fish (or their eggs and larvae) might be able to survive over the summer to repopulate in the fall. Examples include low spots within ponds (such as ditches along the interior of the perimeter levees), drainage ditches and canals around pond levees, and drain structures and pipes that remain filled with water.

If standing water cannot be dried out due to weather conditions or pond and drain designs, several options are available to eliminate any fish that may be present. The compounds registered as fish toxicants by the United States Environmental Protection Agency (EPA) include Rotenone, Calcium Hypochlorite, Sodium Hypochlorite and Antimycin-A. Rotenone and Antimycin-A are restricted use pesticides and their application requires an applicator’s license. In contrast, Calcium- and Sodium Hypochlorite are widely available. Calcium Hypochlorite is commonly used as a source of chlorine for swimming pools and Sodium Hypochlorite is found in household bleach. Not all of these products are registered specifically for use as fish toxicants, by any means, but some examples of such products that are registered include HTH granules and tablets, Tru shock tablets and many brands of bleach. A complete list of registered fish toxicants can be found on the internet at http://aquanic.org and search for "registered fish toxicants." Click on Guide to Drug, Vaccine and Pesticide Use.

Always wear the proper protective clothing and safety equipment (gloves, safety glasses, etc.) when treating water with fish toxicants. Since chlorine content will vary from one product to the next, start out with a small dose and try to confirm the death of any fish that may be present. Then bump up the dose if needed.

Working wetlands are impoundments used to farm rice, crawfish and finfish. In Louisiana, there is very little finfish farming so the bulk of the working wetlands involve rice and crawfish with crawfish most often being farmed in a rotation with rice and other crops. Over half a million acres of rice is cultivated in the state with around 175,000 acres devoted to crawfish. The crops complement each other as rice is a grown in spring, summer and early fall and crawfish are grown from late fall, winter and spring.

Louisiana’s working wetlands provide shallow water and moist soil habitat for about 100 waterbird species including pelicans, cormorants, anhingas, grebes, waterfowl, wading birds, marsh breed in our region or stop and "refuel" before moving northward to breeding grounds. So, too, is fall when the adult and young birds return and stop before flying onward to wintering grounds.

Birders with their binoculars and spotting scopes are becoming more and more visible enjoying their sport in our working wetland landscape. Most respect private property and birds from public right of way or ask permission to use headlands to get closer to concentrations of birds. As with hunters and fishermen, there are always "bad actors" who trespass without permission or block roadways. Birders, however, rarely, if ever, litter when birding.

• Mid-Fall into Winter. Small crawfish reach two to three inches in size and large numbers of wading birds, especially great egrets, snowy egrets, dark ibises and white ibis (photo 10) feed heavily in impoundments. These crawfish are the current season’s crop.
• Winter and Early Spring. Gulls and terns will often feed heavily on crawfish molting near the surface on vertical vegetation in deeper waters that are not accessible to wading birds. These crawfish are the crop for the current season.
• Winter into Mid-Spring. Cormorants, pelicans and coots can feed heavily on crawfish in deeper waters not accessible to wading birds. These crawfish are the current season’s crop.
• Mid- to Late Spring. Yellow-crowned night-herons (photo 11) feed heavily on the periphery and take crawfish from traps in deep water. These crawfish are both the current season’s crop and the next season’s brood stock.
• Spring and Summer when ponds are being drained. All wading bird species assemble in large numbers to feed on stranded prey including crawfish. Depending on production strategy these crawfish may or may not serve as brood stock for the coming season.
• Mid-late Spring and Summer when new ponds are being stocked. Wading birds may concentrate in large numbers, especially if water quality deteriorates and crawfish are clinging to vegetation near the surface, or are in shallow water near the perimeter levee, to gain access to atmospheric oxygen. These crawfish are the brood stock for the coming season.
• Any time that a pond loses water during production season and becomes very shallow, especially when vegetation is sparse. This can be the result of a levee break or evaporation. All wading birds assemble in large numbers to feed on the crawfish and other prey present. Computer simulations, based on food energy requirements of wading birds and observed bird densities in such systems, suggest that the crawfish crop could potentially be severely impacted within three days with water losses and exposure of the crawfish to avian predators.

This competition for food resources and loss of standing vegetation has, at present, an unknown impact on crawfish harvest in commercial ponds. However, by quantifying bird utilization of specific crawfish fields, one should be able to determine the amount of vegetation they remove that might otherwise be a food resource for crawfish. Experimental studies some years ago at the University of Louisiana Lafayette Crawfish Research Center and the LSU AgCenter showed that crawfish growth is reduced in the absence of standing vegetation and the presence of standing vegetation (cultivated rice) increased potential crawfish production by a factor of approximately three.

During cold and cool weather, cut fish is the bait of choice in crawfish traps. Great Blue Herons and Doublecrested Cormorants are notorious for stealing this bait from traps. Roughly one quarter pound of bait is lost [$0.08-0.10 per bait] and crawfish cease to enter traps because the bait is no longer present.

While all predaceous waterbirds can be expected to catch crawfish on outer trap surfaces and from the inside of traps, the Yellow-crowned night-heron is especially notorious for removing crawfish from inside of traps from mid-late spring. This action often dislodges traps as well or destabilizes the traps. An added problem is death of herons that fall into traps while removing crawfish. These birds invariably die because they become trapped long before the harvesters return to tend traps. Because the birds are protected by state and national statutes, the harvesters could potentially be cited for illegal take of the birds with serious legal ramifications.

Increase Water Depth – Increasing water depth can reduce wading bird pressure within an impoundment. However, diving birds including waterfowl and cormorants and those birds that take prey from the surface or near the surface are not deterred from feeding in deeper waters.

Increase Vegetation Density – All birds have greater difficulty in foraging in heavy vegetation.

Improve Trap Support Rods and Close Trap Tops– Birds dislodge traps constructed with support rods. Support rods can be lengthened. Alternatively, permanent support rods can be placed into impoundments.However, if not removed at the conclusion of a production season, permanent support rods can damage equipment and be safety hazards. Some farmers are now using flaps to cover open tops of traps. This prevents birds from removing bait and crawfish from traps. But, such covers create operational problems.

An argument can then be made that heavy waterbird predation in a high density crawfish system will reduce crawfish densities and enhance production of large, more valuable crawfish. Countering this argument, however, is the results of several experimental studies where crawfish populations were intentionally thinned during the production season, but little or no compensatory growth of the remaining crawfish was observed.

Another contrary argument could be made that many waterbirds consume insects and fishes which are found in crawfish ponds, and many of these insects and fishes consume numerous small crawfish. Thus, if birds eat other organisms that prey on juvenile crawfish, this could increase crawfish survival and potentially increase crawfish production, assuming the pond is not overpopulated with crawfish to begin with. However, this also has not been studied.

Agriculture’s Natural Resources Conservation Service (USDA-NRCS) to secure conservation program funding to support working wetlands as waterbird habitat. Recently, funds have been made available for "early" fall flooding of working wetlands for waterbird habitat in hopes that birds will use inland habitat rather than put themselves at risk to oiling as a consequence of the BP oil spill catastrophe. This is certainly a positive development. That representatives of the Audubon Society consider the crawfish aquaculture "landscape" to represent a potential "Important Bird Area" is an equally positive development. Furthermore, the inaugural Yellow Rails and Rice Festival in November 2009 in Jefferson Davis Parish represents a partnership between the conservation and farming communities to focus the ecotourism potential of our working wetlands.

Crawfish farming can be risky. Crop failure in individual production units (ponds/fields) is not an uncommon problem and many farmers counter this problem by spreading their farming operation over multiple fields. Conservationists should realize, however, that all fields, regardless of income derived from crawfish, provide wonderful habitat for all waterbird species.