Abstract: The migratory grasshopper, Melanoplus sanguinipes (Fabricius) (Orthoptera: Acrididae), is one of the most important grasshoppers in western North America rangelands in Fort Collins, CO (USA). The laboratory bioassay trials were conducted to determine the specific effect of microbial insecticides and repellents for control of migratory grasshopper in Fort Collins, Colorado. In an initial trial, both Beauveria bassiana and spinosad treated foliage produced significant mortality to grasshoppers at 120 h post-exposure, with some more rapid mortality within 24 h when spinosad was used at a higher rate. Significant mortality from B. bassiana was first observed after 72 h, with the high rate (1 lb/100 gal concentration). In a second trial treatment with Bioneem, Trilogy (neem oil), and Garlic Barrier were also included all treatments caused significant mortality at 96 h, with significantly most mortality with B. bassiana and spinosad. At 192 h, B. bassiana and spinosad produced 100% mortality. In conclusion, Beauveria bassiana and Spinosad were effective microbial insecticide for reducing population density of migratory grasshopper in both laboratory bioassays trials. In addition, Bioneem had significant repellent effects on migratory grasshoppers.
Introduction
The migratory grasshopper, Melanoplus sanguinipes (Fabricius) is an economically important grasshopper distributed throughout North America (Gurney and Brooks, 1959). Methods of control have been predominately limited to the use of insecticide sprays. Unfortunately, applications of insecticides have resulted in large and immediate decreases in certain non-target arthropods (Pfadt et al., 1985; Quinn et al., 1991). Microbial insecticides and repellents reduce plant injury by migratory grasshopper and other species common to the northern Front Range of in Colorado (Demirel, 1998). One microbial insecticide that has been long considered for use as an insect control agent is Beauveria bassiana (Balsamo) Vuillemin (Hyphomycetes: Moniliales) that is being developed as a bioinsecticide of grasshoppers (Inglis et al., 1995) and many other types of insects (Anderson et al., 1989; Knudsen et al., 1990; James and Lighthart, 1994). Many of the dead grasshoppers treated with B. bassiana exhibited dark red coloration, a common symptom of B. bassiana infection (Marcandier and Khachatourians, 1987). Spinosad is a recently developed insecticide produced as fermentation product of by the soil actinomycete Saccharopolyspora spinosa. Spinosad has biological activity against a wide range of the insects including Lepidoptera, certain Diptera and Thysanoptera (Berard et al., 1994).
In laboratory and field applications of several commercial neem-extract formulations, Zimmerman et al. (1993) showed activity against eggs and larvae of elm leaf beetle, Xanthogaleruca luteola (Muller). These experiments showed that although neem was slower to display initial effects, it ultimately yielded a level of control comparable to that of many synthetic insecticides. In addition to azadirachtin there are many other biologically active chemical compounds derived from neem seed extracts (Schmutterer, 1990). Neem oil contains a complex array of biologically active compounds known as limonoids (tetranortriterpenoids) of diverse structural types (Ley et al., 1993). Pesticides using the azadirachtin-free neem oil fraction have been developed (e.g., TrilogyR) for control of certain arthropods and plant pathogens. For example, treatment with neem oil resulted in a reduction of eggs produced and increased incubation time for of the spider mite Tetranychus urticae (Koch) (Dimetry et al., 1993).
The purpose of this study was to determine the specific effect of microbial insecticides and repellents for control of migratory grasshopper in Fort Collins, Colorado (USA).
Materials and Methods
Laboratory Ingestion Trial I, 1997
Trials were conducted with adult migratory grasshoppers to determine susceptibility
to ingestion exposure to Beauveria bassiana Strain GHA (BotaniGard WP9702)
and spinosad (Conserve SC) in Fort Collins, CO (USA). Beauveria bassiana
Strain GHA (BotaniGard WP9702, MycoTech Corporation, Butte, MT) and spinosad
(Conserve SC, Dow AgroSciences, Indianapolis, IN) were applied to alfalfa leaves
with a series of 0.25 times dilutions that were reflecting labeled use rates;
BotaniGard WP9702 1 1b/100 gal; BotaniGard WP9702 0.25 1b/100 gal; BotaniGard
WP9702 0.0625 1b/100 gal; Conserve SC 0.4170 mL-1; Conserve SC 0.1043
mL-1; Conserve SC 0.0261 mL-1) and a water check. Adult
migratory grasshoppers were collected from alfalfa at the Horticulture Research
Center and Agricultural Research and Demonstration Center (ARDEC) of Colorado
State University northeast of Fort Collins, CO. Grasshoppers were then confined
8 per petri dish (100x15 mm), with 5 petri dishes used per treatment and maintained
at room temperature. Alfalfa leaves were dipped in the dilution of the various
treatments, allowed to air dry and then placed with grasshoppers. After the
originally treated alfalfa foliage was consumed, untreated alfalfa foliage was
used to maintain grasshoppers in all treatments. Mortality was assessed at 24
h intervals for six days following exposure. Data from trial was analyzed by
analysis of variance (ANOVA) with using the SAS software and means were separated
by using Student-Newman-Keuls (SNK) Multiple Comparison Tests (SAS Institute
Inc., 1990).
Laboratory Ingestion Trial II, 1997
This study expanded upon that of the previous experiment by including additional
treatments in Fort Collins, CO (USA). In addition to B. bassiana Strain
GHA (BotaniGard WP) and spinosad (Conserve SC), a garlic-derived insecticide/repellent
(Garlic BarrierR), neem oil (without azadirachtin) pesticide (TrilogyR)
and neem-derived crude extract (azadirachtin + neem oil) (BioNeemR)
were included. Treatments were applied at the following concentrations, reflecting
labeled use rates: BotaniGard WP 1 1b/100 gal, Conserve SC 0.0625% concentration
(8-fl oz/100 gal), Garlic Barrier 10% concentration (10 gal/100 gal); Trilogy
1.0% concentration (1 gal/100 gal) and BioNeem 2.5 concentration (2.5 gal/100
gal) and a water check as a control treatment. Adult migratory grasshoppers
were confined, 8 per petri dish (100x15 mm), with 6 petri dishes used per treatment.
Alfalfa leaves were collected from the Horticulture Research Center of Colorado
State University northeast of Fort Collins, CO. Treatments involved in dipping
alfalfa leaves, allowing them to air-dry and then feeding the leaves to the
grasshoppers. After the originally treated foliage was consumed, untreated foliage
was used to maintain grasshoppers in all treatments. Mortality was assessed
at 24 h intervals for two days and at 48 h during a subsequent interval, for
a 192 h total during this study. Data from trial was analyzed by analysis of
variance (ANOVA) with using the SAS software and means were separated by using
Student-Newman-Keuls (SNK) Multiple Comparison Tests (SAS Institute Inc., 1990).
Results and Discussion
Laboratory Ingestion Trial I, 1997
At 120 h, all B. bassiana and spinosad treatments produced significant
grasshopper mortality (Table 1). Effects were most rapid with
spinosad, which showed mortality effects at the higher rates during the first
evaluation. Spinosad at the highest (0.4170 mL-1) concentration was
caused significant mortality than water check treatments at the 24 h evaluation.
At 72 h, all of the spinosad treatments produced significantly greater mortality
than untreated check. At 96 h, the high rate of spinosad (0.4170 mL-1
concentration) showed 100% mortality. Significant mortality from the high rate
of the BotaniGard WP9702 formulation of B. bassiana Strain GHA was first
observed at the 72 h evaluation. At that time, mortality was 30%. At 96 h, mortality
was 57.5% compared to the untreated check. At 120 h (five days), mortality was
95% from B. bassiana at the 1 1b/100 gal rate; slightly lower (85%) mortality
was observed at this time from both the 0.25 1b/100 gal and 0.0625 1b/100 gal
B. bassiana rate. At 144 h (six days), all of the B. bassiana
concentrations showed up to 95% mortality in this trial. Several studies were
also conducted its use in control of grasshoppers. Laboratory spray tower trials
with B. bassiana have been conducted on fourth-instar migratory grasshopper
and larvae of the yellow mealworm, Tenebrio molitor L. (Marcandier and
Khachatourians, 1987; Moore and Erlandson, 1988; Khachatourians, 1992). At 10
days, mortality of grasshoppers treated with B. bassiana was 72.5%, significantly
higher than the mortality of the yellow mealworms and mortality of both species
receiving air and oil treatments (Brinkman et al., 1997). This is similar
to the laboratory trial results of Marcandier and Khachatourians (1987) who
observed, at 14-days post treatment, 90-100% mortality of grasshoppers after
being dipped in a distilled water suspension containing 2x107 conidia
per milliliter. However, there were no significant differences, compared to
the water check, observed at 144 h post exposure in this trial because of high
background mortality in the untreated check.
Laboratory Ingestion Trial II,1997
Effects were most rapidly observed with BotaniGard when produced significant
mortality effects at the highest rate during the 24 h evaluation (Table
2). This was significantly different when compared with the BioNeem treatment
and untreated water check. At 48 h, grasshoppers exposed to BotaniGard continued
to have the highest mortality when compared the other treatments. At 48 h, there
were no significant differences among the other treatments. At the 96 h evaluation
there was significant mortality from both BotaniGard and Conserve, compared
to other tested treatments.
| Table 1: | Leaf-dip bioassay using microbial insecticides for control of migratory grasshopper on alfalfa |
| z Numbers within a column not followed by the same letter are significantly different (p<0.05) by SNK | |
| Table 2: | Leaf-dip bioassay using microbial and repellent insecticides for control of the migratory grasshopper on alfalfa |
| zNumbers within a column not followed by the same letter are significantly different (p<0.05) by SNK | |
At 192 h, BotaniGard and Conserve produced 100% mortality. Brinkman et al. (1997) reported that at 10 days, mortality of grasshoppers treated with B. bassiana was 72.5%, a lower infection rate than was noted in this study. BioNeem (neem-derived insecticide) treatment also produced significant mortality at this time. Some early trials showed neem-derived insecticides capable of control of some insect species. For example, Heliothis virescens (Fabricius) larvae consumed less food, gained less weight and were less efficient at converting ingested and digested food into biomass (Barnby and Knocke, 1987). Population levels of chrysanthemum leafminer, Liriomyza trifolii (Burgess), were significantly reduced by neem-derived insecticides (Parkman and Pienkowski, 1990). Ascher et al. (1992) used the commercial azadirachtin-enriched formula AzatinR to successfully reduce nymphal populations of western flower thrips, Frankliniella occidentalis (Pergrande). Price and Schuster (1991) conducted field trials using neem and various synthetic insecticides to control population of the Bemisia tabaci (Gennadius) on poinsettia. There was no significant difference in grasshopper mortality resulting from exposure to the Garlic Barrier, Trilogy and untreated water check treatments.
The result of B. bassiana supported previous study and even caused significant mortality on the migratory grasshopper short period comparing with them. However, the using B. bassiana in the field condition was not success comparing with laboratory bioassay (Demirel, 1998). For this reason that the weather condition was very important factor to get a good result from B. bassiana treatments in field conditions. Spinosad was an effective as a bio-insecticide for reducing population density of grasshoppers in both laboratory bioassays and field trials (Demirel, 1998). In addition, the spinosad might be easy to apply for migratory grasshopper at home garden and organic farming. In this study also indicated that Bioneem had significant repellent effects on migratory grasshoppers. In addition, Trilogy and Bioneem had significant repellent effects on migratory grasshoppers and reduction of leaf area consumed in laboratory bioassays (Demirel, 1998). The Garlic Barrier did result in good mortality on the migratory grasshopper in laboratory condition. However, the other repellent insecticides of Hot Pepper Wax treatment was the most effective repellent insecticide for reducing leaf area consumption in the field (Demirel, 1998). In conclusion, using of the microbial and repellent insecticides might be important for control migratory grasshopper in home garden area in Fort Collins, Colorado. As a result, Beauveria bassiana and spinosad were effective microbial insecticide for causing mortality on migratory grasshopper in both laboratory bioassays trials. In addition, Bioneem had significant mortality on migratory grasshoppers.
Acknowledgements
This project was supported by Colorado Agricultural Experiment Station of Colorado State University, Fort Collins, Colorado.
ND was supported by the Ministry of National Education of Republic of Turkey.