By E. VinjeTweet
Grasshopper Control with Modern Baits
Semaspore Bait, a Persistent Biological, and EcoBran for Quick Knockdown
How To Use
Modern baits provide lasting protection from grasshoppers one which:
* Kills grasshoppers at their source — the hatching beds — where they are concentrated, before they can migrate to your crop.
* Persists throughout the hatching and growing season and at least through the following year.
* Provides quick-kill of any survivors from the hatching beds or migrants from other areas which might threaten your crop.
Semaspore Bait (the Nosema locustae protozoa attached to wheat bran) is the bait which is applied to the hatching beds — grassy areas, particularly those with southern exposure and more-sandy soil. This biological agent is only toxic to grasshoppers, killing about half those in the hatching area, and infecting most of the remainder. These infected survivors (which eat little and lay few and infected eggs) are necessary to infect new hatchlings and migrants, through cannibalism — this provides the persistent protection. The disease also carries-over to the next year via the infected egg cases and infected cadavers which overwinter.
EcoBran (wheat bran carrying 2% carbaryl) is spread between the crop being protected and the hatching beds to quickly kill any grasshoppers which might make it out of them. EcoBran can be replenished conveniently, as necessary. Because of the low carbaryl percentage, EcoBran is not-toxic to grasshopper predators: birds, for example, and it doesn’t affect grasshopper parasites that don’t have chewing mouths. Providing a mowed area between the crop and the hatching bed also enhances crop protection by providing a natural barrier to grasshopper migration (there is no food and they are exposed to predators) and promoting EcoBran consumption.
Organic growers can use the above approach, substituting Semaspore Bait for EcoBran, and using more Semaspore, since it acts slower. For the conventional grower, who misjudges the severity of the grasshopper outbreak and finds grasshoppers in his crop, EcoBran also can be applied to the crop directly to control them. Both Semaspore and EcoBran are applied with the same spreader.
Why Semaspore and EcoBran
They are the cost-effective way to eliminate grasshoppers, because:
* They work: both are approved by USDA-APHIS for grasshopper control. Baits based on Nosema locustae were originally developed by the USDA. Semaspore and EcoBran have been tested extensively by US and other government agencies, and by universities in many countries.
* Semaspore provides enduring protection, necessary because grasshoppers hatch over about a six week period. Cannibalism also kills grasshoppers which migrate through the treated area. Semaspore carries over to the next year, as well. Modern chemicals won’t endure. Waiting until a crop is infested and then using chemicals won’t reduce the grasshopper migration from the hatching beds. They will simply replace those killed in the crop. Also, without treating the hatching beds, the grasshoppers will generally be back the next year.
* The Semaspore/EcoBran approach attacks younger grasshoppers, which are easiest to kill, Waiting until they infest a crop and using chemicals means the grasshoppers are older and harder to kill. Also, killing them in hatching beds reduces the competition for food there, which lessens the need for survivors to migrate to crops.
* The approach is inexpensive. It’s not necessary to treat the whole crop, just its boundaries and the neighboring hatching beds (or even just the hatching “hot spots” within them).
Other benefits from the Semaspore/ EcoBran approach:
* EcoBran provides positive control of “leakers” from the hatching beds, and it can be used on the crop itself if it should be infested.
* Semaspore is non-toxic, except to grasshoppers, and Debug is low-toxicity. Both are preferred for long-term protection since they have little or no effect on grasshoppers predators/parasites.
* Bran baits are easy to apply. Inexpensive spreaders are available, appropriate to different size areas, and airborne spreaders are easily modified to accommodate bran.
When To Apply
Apply Semaspore Bait when immature grasshoppers in hatching beds number 10/sq yd. The USDA believes 10 will damage rangeland (fewer for cropland). More than 20 may require repeat Semaspore treatments or more than the nominal 1 lb./ acre amount. Semaspore is used on young grasshoppers — when most are 3rd instars, which are 4 weeks old, 1/2 inch long, and have wing buds. It kills younger grasshoppers sooner, and more of them, but then fewer are left around to infect others. Semaspore alone is not recommended for 5th instars, nearly 1 inch, because they do damage before dying. EcoBran at 1.5 lbs. / acre kills young grasshoppers and a 3 lbs. per acre, adults.
Apply Semaspore and EcoBran when grasshoppers are eager to eat — sunny, warm days — and when rain isn’t expected for 8 hours (this insures the bran is eaten before it can be damaged).
How To Apply
Semaspore Bait and EcoBran are easily applied with applicators appropriate to the infested area — aerial application (we can identify aerial applicators near you or provide instructions for easy modification of airborne sprayers), pneumatic sprayers or seed broadcasters, and “whirlybird” spreaders or hand application. Hopper exits must be shut low, and agitators used to keep the bran flowing. We can provide sources for effective, inexpensive spreaders.
CROPLAND, NURSERIES, LAWNS AND GARDENS are generally not hatching areas. Here, Semaspore is applied to the surrounding hatching areas for persistent infection/killing of the emerging grasshoppers (young grasshoppers are generally still in the hatching areas). EcoBran is used around the periphery of the crops to control any grasshoppers that get to them. EcoBran and, perhaps, the Semaspore, may have to be replenished for severe outbreaks. Conventional growers can apply EcoBran directly to the crop, as well.
PASTURES AND RANGELAND also include the hatching beds. Here, field scouting will identify them (see GRASSHOPPER CONTROL FACTS), areas where the vegetation is heavier, and Semaspore should be applied to them. EcoBran may not be needed to provide protection in these areas, but for heavy grasshoppers infestations it can be added to speed protection.
How Do They Work
Semaspore Bait is the Nosema locustae spore fixed to wheat bran with a sweetener — both attract grasshoppers. After young grasshoppers eat Semaspore, they consume less within a week and in 2 weeks, sometimes longer, about 50% die with 50% or more of the remainder weak, infected, and eating 75% less. Survivors are necessary to spread the disease to new hatchlings and immigrants, through natural cannibalism, which provides the persistent protection. Also, if any of the infected should lay eggs, these will be reduced by 60-80%, and the egg pod infected to carryover the disease to next year. Infected cadavers also overwinter to infect next year’s grasshoppers. These results have been documented in numerous tests by the USDA and others.
Infected grasshoppers develop a very large number of the spores within them, so that the cannibalizing grasshoppers get a much greater dose than from the initial Semaspore application. Consequently, the disease acts faster on the cannibalizers. Also, when Semaspore is used, dead grasshoppers aren’t often seen — they’re eaten too quickly by the survivors. Instead, Semaspore effectiveness is evidenced by the steady decrease in grasshopper numbers, and by some infected, weak survivors which aren’t doing damage.
Semaspore infects at least 90 species of grasshoppers, the black field cricket, and some other crickets and locusts. However, it is completely non-toxic to anything else, not affecting humans, pets, and the over 250 natural grasshoppers enemies. Semaspore comes ready to use in 1, 5 and 50 lb. containers which can be stored up to 6 weeks in a cool, dry place — refrigeration extends shelf-life significantly.
EcoBran is very effective at grasshopper quick-kill, yet is environmentally sensitive, having little impact on grasshopper natural enemies. It affects insects having chewing mouth parts, primarily, and USDA studies have shown EcoBran to have no effect on the development of baby birds. It’s advantage over sprays is that grasshoppers seek the bait and consume the chemical directly, resulting in death at low chemical content.
EcoBran is formulated by treating wheat bran with 2% Sevin (Carbaryl), and it averages 75% kill with 24-48 hours — 90% under good conditions. EcoBran is best applied to young grasshoppers ( at 1.5 lbs. / acre), but also works well against those older (at 3 lbs. / acre).
Grasshopper Control Facts
* Grasshoppers hatch when temperatures reach 60-70 F., and hatching lasts 4-7 weeks, the rate increasing with temperature. Peak hatch may occur a month after it starts. The hatch is greater if the preceding fall was warm, dry and long, with more adults laying eggs longer.
* Grasshoppers generally mature through 5 “instar” stages into adults, each instar involving a molt. An instar lasts for about 10 days with adults formed after 50 days. If Semaspore is applied about the 3rd instar, it has time to work before damage becomes significant. Also, Semaspore slows grasshopper development as it slows their consumption.
* Half of adult grasshoppers are females which can lay 8 or more egg pods that contain 20-100 eggs each, and eggs are not affected by winter, generally, because of a diapause stage. For warm and dry conditions 200-400 eggs result for each female, and 8 grasshoppers / sq. yd. can, even with 75% mortality to originals and hatchlings, multiply into 50-100 / sq. yd. the next year. Treat them this year!
* Young consume 14 times as much per day as a 3rd instar; destruction increases nearly 2.5 times with each instar — early treatment is obviously more cost effective. Grasshoppers consume both dry and leafy forage with “eastern” versions tending more to leafy. Most seem to be attracted to sources of protein: e.g., bran and other grasshoppers. Semaspore increases cannibalism since it weakens grasshoppers, making them easier to catch.
* Ten adults / sq. yd. are economically damaging to rangeland, according to the USDA. Smaller numbers can damage cropland/gardens, depending on crop type and age. A classic study showed that 6-7 adults / sq. yd. on 10 acres of pasture ate as much as a cow.
* Grasshoppers don’t necessarily mature where they are born. Egg pods are laid in grassy areas where the sod is unbroken (fend rows, roadsides, grassy ditches) — such areas with sandier soil and southern exposure (warmer) are best for egg laying. Because of open and often broken ground, grasshoppers will leave a weedless grain field or cultivated garden (sometimes even an alfalfa field) and find a grassy area to lay eggs. When the hatch becomes too large to be supported by local vegetation, grasshoppers migrate to other food; e.g., the grain field or garden. Treating young grasshoppers in hatching areas when they are concentrated and easily killed, and before migration really begins to crops, is the best way to attack them.
* A relatively “clean” strip between a hatching bed and a crop will help slow grasshopper migration. Grasshoppers are reluctant to enter the strip because it has no food, and they are very exposed to predators. Also, the strip enhances DeBug’s kill because grasshoppers have no other food. A wider strip is better, especially if the adjacent hatching bed is large.
* A region which had a grasshopper problem in a previous year probably will also have an infestation the next year – the decline of the problem is generally gradual. Weather will affect the current year’s hatch, but USDA studies show that, on the average, much of the previous year’s problem is passed on to the next year.