The Impact of Beauveria bassiana, Trichogramma, Bt Sprays, and Spinosad on the Lepiodpteran (Crambidae) Cereal Stalk Borer- The European Corn Borer (Ostrinia nubilalis)

The Impact of Beauveria bassiana, Trichogramma, Bt Sprays, and Spinosad on the Lepiodpteran (Crambidae) Cereal Stalk Borer- The European Corn Borer (Ostrinia nubilalis)

Summary

The research examined the effects of microbial control strategies and also Trichogramma pertiosum on the European corn borer (ECB), Ostrinia nubilalis. Our research which was conducted at the Northwestern Branch of the Ohio Agriculture Research and Development Center (OARDC), one of the fields’ research facilities owned by Ohio State University and located in Wood County Ohio, had 7 treatments. Each treatment had five replications making a total of 35 plots. The treatments included spinosad, an insect growth regulator from bacteria, the entomopathogenic fungus Beauveria bassiana, Trichogramma pretiosum, a type of wasps which parasitizes the eggs of Ostrinia nubilalis and foliar applied Bt spray, and two combinations of Beauveria bassianan and BT spray and Trichogramma pretiosum and Spinosad.

The infections by the European corn borer larvae on stalks of corn were very severe in all the control treatments for both 2006 and 2007. The Microbial treatments applied to the corn imposed various degrees of restraints on the European corn borer population. In all the parameters there was a significant difference between the control and other treatments with a P value of <0.001. In this research treatment 3 (Spinosad) emerged as the most effective biological agent in the control of the European corn borer. The results also showed that when the biological agents are used in combination as in treatment 6 (Beauveria bassiana with Bt spray) and Treatment 7 (Spinosad with Trichogramma pretiosum) they become more effective.

The results of the research done on the abundance and composition of the arthropods in the treatment plots clearly showed that different treatments applied to various plots had no effect on the distribution and composition of these arthropods. All the P values obtained by one way ANOVA were bigger than 0.005.

Possible desirable outcomes of the project would be an increased awareness of the alternative and potentially useful control strategies available for Ostrinia nubilalis. This research is relevant in boosting underutilized control strategies and increasing stakeholder adoption of integrated pest management practices and thereby reducing the use of conventional insecticides especially for organic farmers.

Objectives/Performance Targets

The proposed research had the following objectives:
1. To compare the efficacy of Bt spray, Dipel Beauveria bassiana, Trichogramma pretiosum, and Spinosad for the economic control of Ostrinia nubilalis.
2. Integration of natural enemies in developing sound management program for Ostrinia nubilalis.
3. The impact of these treatments on the abundance and composition of arthropods.

Accomplishments/Milestones

Parameters were established to determine the level and extent of damage to the stalks and corn by the European corn borer larvae. These parameters were: number of infected stalks per plot, the number of larvae found per stalk per plot, number of tunnels per stalk per plot, Length of tunnels per stalk per plot, number of infected cobs per stalk per plot and the yield per plot.

During mid August, 20 stalks of maize/corn were randomly (to void being bias) selected from each plot and were visually sampled for damaged stalks, Ostrinia nubilalis larvae per stalk, number of tunnels per plant, tunnel length per plant, and infected cobs recorded. Random sampling ensures that each member of the population has an equal and independent chance of being chosen as a member of the sample, but the selection of any member of the population must in no way influence the selection of any other member. During harvesting time, the total yield per plot was also noted in bushel (equal 8 gallons, it’s an old volume measure of cereals) per acre.

The calculated data were statistically analyzed by first doing Normality Test and then later statistical analysis using Minitab 14, one-way ANOVA and differences between parameters were obtained by using Tukey post-hoc comparison test.

Number of Infected Stalks

There was more damage or infiltration by the European corn borers in the stalks of corn in the treatment 1 (control plots) than in the other treatment plots. The control treatments had a mean of 17 infected stalks per plot, while the other treatments had much less than that. There was a significant difference between treatment 1 (the control) and the other treatments. One way ANOVA – (DF = 6, 28, F =14.73 and P value of < 0.001). There has been very little infection to the stalks of corn from treatment 3 (Spinosad) and treatment 7 (Spinosad and Trichogramma pretiosum) with a mean of 3.4 (±0.98 SE) and 4.8 (±1.2 SE) respectively of the sampled stalks.

The 2007 results are some how similar to the results obtained in 2006. There was no noticeable difference between the control and treatments number 2. But there was a significant difference between the control and treatments 3, 4, 5, and treatment 7 (One way ANOVA – DF = 6, 28, F = 9.83 and P value of < 0.001). There was more infection of the stalks in treatment 1 (control) and treatment 2 (Trichogramma pretiosum) with an infection mean of 20 (± 0.0 SE) and 19.6 (± 0.4 SE) respectively. The trend seems to be very similar with that of 2006.

Number of Larvae Per Stalk

The highest number of larvae per stalk was found in the control treatment followed by the treatment with Trichogramma pretiosum. The control treatment had a mean of 34.8, while the other treatments had less than that. There was a significant difference between treatment 3 and treatment 7 with the other treatments. One way ANOVA – DF =6, 28, F = 14.37 and P < 0.001. There were fewer larvae per stalk in treatment 3 (Spinosad) with a mean of 9.8 (± 0.58 SE) and treatment 7 (Spinosad and Trichogramma pretiosum) mean of 8.6 (± 1.86 SE) than in any other treatments.

The 2007 results were almost similar to the 2006 results. The highest number of larvae was found in the control treatments 1 (with a mean of 29.4) followed by the treatment 2 with Trichogramma pretiosum (mean of 25.8). There was a significant difference between treatments 3 with the other treatments. One way ANOVA – DF =6, 28, F = 7.03 and P < 0.001. There were fewer larvae per stalk in treatment three (spinosad) with a mean of 6 (± 1.48 SE) followed again by treatment 7 (Trichogramma pretiosum and spinosad) with mean of 10.8 (± 1.16 SE) than in the control treatment which had a mean of 25.8 (± 3.38 SE).

Number of Tunnels Per Stalk

There were more tunnels in the stalks of corn from both control plots (treatment 1) and plots with Trichogramma pretiosum (treatment 2) with a mean of 24.2 (± 3.8 SE) and 25.4 (± 2.44 SE) respectively). There was a significant difference between the treatment 1 (control) and treatments 3 and 7. One way ANOVA – DF = 6, 28, F = 9.09, and P = < 0.001. Treatments 3 with Spinosad and 7 Trichogramma and Spinosad had low numbers of tunnels (mean of 6.6 (± 0.4 SE) and 7.6 (± 7.6 SE) respectively) per plant compared to the rest of the treatments.

In 2007, there were more tunnels in the control treatment (treatment 1) with a mean of 44.8 cm (± 3.06 SE) followed by the treatment 2 with a mean of 36.6 cm (± 3.82 SE) than any other treatments. There were few tunnels in Treatment 3 (Spinosad) with a mean of 11.8 cm (±1.28 SE). There was a significant difference between treatment 1 (control) and treatment 3 (Spinosad). One way ANOVA – DF = 6, 28, F = 14.18, and P value of < 0.001.

Length of Tunnels

There was no significant difference between treatment 1 (control plots) and the treatment 2 (with Trichogramma pretiosum). Both treatments had long tunnels means of 32.6 cm (± 2.3 SE) and 32 cm (± 5.4 SE) respectively. However, there was a significant difference between treatments 1 and 2 and Treatments 3 (with Spinosad), 6 (Beauveria bassiana and Bt spray) and 7 (Trichogramma and Spinosad). One way ANOVA – DF = 6, 28, F = 6.96 and p = < 0.001. The shortest length of tunnels was recorded in treatment 7 (Spinosad Trichogramma) with a mean of 6.8 (± 1.7 SE) and also in treatment 3 (Spinosad) with a mean of 14 (± 3.3 SE).

In 2007, the longest tunnels were also in treatments 1 (control) and 2 (with Trichogramma) with a mean of 46 (± 1.9 SE) and 39 (± 3.86 SE) respectively. The shortest lengths of tunnels were in Treatment 3 (with Spinosad) with a mean of 12.4 (± 1.5 SE). There was a significant difference between the length of tunnels in Treatment 1(control) and the lengths tunnels of other treatments. One way ANOVA – DF = 6, 28, F = 15.88 and a P value of <0.001.

The Number of Infected Cobs

The highest infection on the cobs was recorded in treatment 1 (control) with a mean of 17.4 (±2.0 SE) and treatment 2 (with Trichogramma pretiosum) which had a mean of 13.4 (± 1.3 SE). There was no significant difference between treatment 1 (control) and treatment 2 (with Trichogramma pretiosum).
The lowest infection of the cobs was in treatment 3 (with Spinosad). There was a significant difference between treatment 1 and treatments 3, 4, 5, 6 and 7. One way ANOVA – DF = 6, 28, F = 7.08 and P < 0.001. There was also low infection of cobs in treatments 5 (Bt sprays) and 7 (Trichogramma and spinosad).

In 2007, the highest infection of cobs was in treatment 1 (control) with a mean value of 14.2 (± 0.73 SE) followed by the plots in treatment 2 (Trichogrammma pretiosum) with a mean of 11 (± 1.14 SE). There was no significant difference between treatment 1 and treatment 2. There was a significant difference though between treatment 1 and treatments 3, 4, 5, 6 and 7. One way ANOVA – DF = 6, 28, F = 20.19, with a P value of < 0.001. The lowest infection of cobs was recorded in treatment 3 (with Spinosad).

Yield

The yield was much lower in the treatment 1 (control treatment) with a mean of 124 (±18.8 SE) bushel per acre, than the rest of the treatments, followed by that of treatment 2 (Trichogramma pretiosum) with a mean yield of 157 (± 6.8 SE) bushel per acre. One way ANOVA – DF = 6, 28, F = 2.49 and P < 0.047. The highest yield was in treatment 7 (Spinosad and Trichogramma pretiosum) with a mean yield of 170 (± 10.4 SE) bushels per acre followed by that of Spinosad with a mean yield of 169 (± 5.9 SE) bushels per acre (Figure 8).

In 2007, the yield was slightly lower in treatment 1 than in the other treatments. In treatment 1 the yield mean was 163 (±4.6 SE) bushels per plot while in the other treatments the yield was higher than that. The highest yield was in treatment 3, with 181.4 (±1.7 SE) bushels per plot followed by treatment 7 with a mean yield of 178 (± 2.4 SE) bushels per plot. There was no significant difference between the yield in treatment 1 and the yield in other treatments. One way ANOVA – DF = 6, 28, F = 1.49, and the P value of 0.217.

Yield losses due to the European corn borers can vary from year to year according to the levels of infestation, and I think are generally unpredictable from one year to the next.
Yield losses are primarily physiological losses from reduced plant growth. Stalk tunneling results in shorter plants with fewer and smaller leaves. Movement of water and nutrients can be restricted over the entire kernel- filling period. During the period of kernel growth, there is between 5 and 6% loss in grain yield for each larva per plant. During corn development stage, the loss per plant is about 2 to 4% (Mason C. E. et. Al. 1996). Most yield losses can be attributed to the impaired ability of the corn plants to produce normal amounts of grain due to physiological effect of larvae feeding on the leaf and conductive tissues.

The Impact of These Treatments on the Abundance and Composition of Arthropods

Another research was also conducted to find out the arthropod predatory fauna and to assess the potential impacts these treatments could have had on the abundance and composition of arthropods in corn field.

Method

The random sampling process of insects started three weeks after the application of treatments. Movement through each plot was a random walk and the beat – stick method of sampling was used. The beat stick method equipment consisted of a cut broomstick approximately ½ m. in length and a home tray (where arthropods fell after gently beating the stalk of corn with a stick), a jar (1000cm3 in volume) with less than 100cm3 of ethyl acetate solution in it, and a net for trapping the arthropods. There were also a number of plastic bags. After opening and closing of the jar, the smell of the ethyl acetate could diminish and insects could take long before they died. During that time some of the arthropods could were put in plastic bags until I came back to the lab where I could refill the jar with new Ethyl acetate. This method of collection concentrated on free moving or flying arthropods. Any insect arthropod that was seen on the corn leaves, stalk or tassels was trapped by a net and after catching it was put in a jar containing ethyl acetate solution (which kills arthropods within few minutes). Some arthropods could fly away after falling on the tray and it was at that time that the net proved very essential because they could be trapped by the net and finally caught. During both years 2006 and 2007 identification of the arthropods was done in the lab when the whole process of sampling was over. Sampling arthropods was always done on days that were clear and dry and with a minimum temperature of at least 70 degrees Fahrenheit.

Results of Insect Sampling

During 2006 and 2007 sampling of insects was done in all the 35 plots. Most arthropods sampled from different plots with various treatments were in the order of Coleoptera (lady beetles Japanese beetles and Western corn root worm), Hemiptera (Sink bugs), Hymenoptera (bees), and Lepidoptera (Moth) and Orthoptera (Katydids and grasshoppers). The reason may be for having sampled few orders of arthropod could be that the changes in corn plants growth levels could have potentially affected the arthropod orientation and interaction with the plants, and not the microbial agents. For arthropods that feed on pollen (at that stage pollen had fallen off) the changed plants could for example offer less pollen as food source. A decrease in arthropod species availability would eventually affect other arthropod populations that fed on those arthropods from the decreased population. Bees need both suitable nesting sites and pollen plants (Gathmann et al. 1994). Parasitoids depend on spatially and temporally co-occurrence of hosts and nectar (Russell 1989). Some monophagous insect herbivores may spend their whole life on one host plant, feeding copulating and ovipositing (Zwolfer and Harris 1971; Tscharntke 1999), and may be these could be the ones that were sampled.

In both years the collection was dominated by the Western corn root worms in all the plots while the least were the bees and the moths. The following were the average insects that were sampled in all the plots. Analysis of variance (ANOVA) was used to determine if any significant difference occurred within the plots. The data were statistically analyzed by using Minitab 14, one-way ANOVA and differences between parameters could have been obtained by using Tukey post-hoc comparison test, but there were no significant differences between the control treatment and the other treatments.

The analysis showed no significant differences between the insects sampled from the control treatments and the other treatments. The P values obtained by one way ANOVA were greater than 0.005.

The number of western corn root worm was quite high in all the plots, Minitab 14: One way ANOVA – DF =10, 24. F = 0.77. P = 0.657.

Diabrotica Virgifera-Virgifera

Though there were more diabrotica virgifera-virgifera in treatment 1, mean 13 (± 1.6 SE) than in the rest of the treatments, there was no significant difference between the control treatments and the other treatments. The P value was greater than 0.005. One way ANOVA, DF = 6, 28, F = 1.37 and P value 0.261.

In 2007 there were more diabrotica virgifera-virgiferas caught in treatment 2, mean 3.4 (±1.1 SE) than in the other treatments and again there was no significant difference between the control treatments and the other treatments. One way ANOVA – DF = 6, 28 F = 1.94 and P value of 0. 109. The p value was greater than 0.005.

Popillia Japonica

The Popillia japonicas were relatively low in numbers in all the plots. Looking at the graph one would think that treatments 3 (mean of 0.00 (± 0.0)) and 4 (mean 0.0 (± 0.0)) had lower numbers than the other plots. There was no significant difference between the control treatments and the other treatments. One way ANOVA – DF =6, 28, F = 0.50 and P value of 0.803.

In all the treatments the Popillia japonicas were very few that were sampled. Although at a glance it appears as though were more Popillia japonicas in treatments 6 Mean of 0.6 (± 0.4 SE) and 7 Mean 0.6 (± 0.4 SE) compared to Popillia japonicas in treatment 1 and the others, there was virtually no significant difference between the control and the various other treatments. One way ANOVA – DF = 6, 28, F = 0.17 and the P value was 0. 984.

Coccinella Septempunctata, 2006

Plot 1 seems to have had a large mean of Coccinella septempunctata than other plots while plots 5 and 6 (treatments 5, and 6) appear to have had the lowest means 0.4 (± 0.2 SE) and 0.4 (± 0.2 SE) respectively. But One way ANOVA – DF = 6, 28 F = 1.54 and P value of 0.200. So there was no significant difference between the control treatments and other treatments.

In 2007 all the plots had the same number of mean 0.2 and there was no significant difference between the control treatments and other treatments. One way ANOVA – DF = 6, 28 F = 0.00 and p value of 1.000.

Euschistus Variolarius, 2006

Treatment 7 had the larger mean 1.8 (± 0.8 SE) than any other treatment while treatment 4 had the lowest mean 0.00 (± 0 SE). Despite all this difference in means, there was no significant difference between the control and other treatments. One way ANOVA – DF = 6, 28 F = 1.92 and the P value of 0.112.

In 2007, treatment 3 had the largest mean 1 (± 0.77 SE) while treatment 2 had the lowest mean 0.4 (± 0.2 SE). There was no significant difference between the control and other treatments. One way ANOVA – DF = 6, 28 F = 0.25 and the P value was 0.953.

The Ostrinia Nubilalis

In 2006, there was no significant difference between the control (treatment 1) and the other treatments. One way ANOVA – DF = 6, 28 F = 01.67 P value of 0.166.

In 2007 there was also no significant difference between the control and other treatments. The one way ANOVA – DF = 6, 28 F = 0.50 and P value of 0.803.

Melanoplus Femurrubrum, 2006

The mean in all the treatments was less than 1. There was no significant difference between the control and the other treatments. One way ANOVA – DF = 6, 28 F = 0.92 and P value was 0.496.

The highest mean 1.2 (± 0.7 SE) was found in treatment 3 while the lowest mean 0.0 (± 0 SE) was found in treatment 2. There was no significant difference between the control and other treatments. One way ANOVA – DF = 6, 28 F = 1.05 and the P value was 0.94.

Neoconocephalus Ensiger, 2006

In all the treatments the mean was less than 1. There was no significant difference between the control treatments and the other treatments. One way ANOVA – DF = 6, 28 F = 1.88 and P value of 0.121.

In 2007 the largest mean 2.8 (± 0.5 SE) was found in treatment 7 while the lowest mean 1 (± 0.3 SE) was in treatment 3. There was no significant difference between the control treatments and the other treatments. One way ANOVA – DF = 6, 28 F = 1.78 and the P value was 0.139.

Andrena Imitatrix, 2006

In 2006 all the treatments had a mean of less than 1. There was no significant difference between the control treatments and the other treatments. One way ANOVA DF = 6, 28 F = 0.83 and the P value was 0. 554.

The number of mean of Andrena imitatrix cresson in all the plots was low, less than 1. There was no significant difference between the control treatments and the other treatments. One way ANOVA – DF = 6, 28 F = 0.26 and the P value was P = 0.951.

So far the statistical analysis done regarding the abundance and composition of the arthropods in all the plots for both years, showed no significant difference.

The results clearly show that the different treatments applied to various plots had no effect on the distribution and abundance of these arthropods.

Impacts and Contributions/Outcomes

The results of this study indicated intensive destruction of stalks, lots of European corn borer larvae in the stalks, lots of tunnels, much infestation of cobs and a yield loss of corn in the control treatments. There was also a considerable infestation of the stalks by the European corn borer larvae, a good amount of larvae and a number of tunnels, and infected cobs which consequently affected the yield in the treatment with Trichogramma pretiosum.

The explanation for this is that in the control treatments there was simply the lack of control of the European corn borer in those plots. Whenever there is infestation of pests and control measures are not implemented, the results will be destruction of the crops resulting in decreased yield of the same.

In the treatment 2 (with Trichogramma pretiosum), it could be that: a) It is always difficult to contain the Trichogramma in the same plots. They are flying insects and are prone to wander around or fly away to distant places; b) There is a major limitation to the use of Trichogramma due to reduced efficacy under conditions of heavy rainfall, sunshine and high temperatures (J. Chihrane and G. Lauge, 1996). There was a week when the temperatures were over 90 0F during this research; c) In addition to reducing the efficacy of parasitism by Trichogramma, high temperatures cause male sterility and reductions in the rate of wasp emergence from the capsules.

The other treatments 3, 4, 5, 6, and 7 provided a considerable amount of control of the European corn borer in almost all parameters for both years and especially in the year 2007.
Throughout this research spinosad has emerged as the most effective biological agent in the control of the European corn borer. Treatments 3 in all parameters have shown the efficacy of spinosad in controlling the European corn borer larvae. The results also show that when the biological agents are used in combination as in treatments 6 and 7 they become more effective. Trichogramma when applied a lone as in treatment 2, tends to be less effective but when combined with spinosad as in treatment 7 becomes more effective. Again the combination of Beauveria bassiana and Bt sprays is more effective than when these agents are applied to plots singly. The general trend so far has been that these biological agents have impacted the European corn borers. The infections on corn have been very severe in all the control treatments while the different treatments have imposed various degrees of restraints on the European corn borer population. In all the parameters there has been a significant difference between the control and other treatments with a P value of <0.001.

While the tradition control methods of using insecticides are sometimes environmentally hazardous, and fail to control the European corn borer larvae when the larvae are in the tunnels, these novel(underutilized) biological control methods if extensively used would provide good control measures in an integrated pest management. They would provide farmers an economically effective and environmentally sound approach to the management of the European corn borers. This is so because one of the Biological agents, Beauveria bassiana by the help of its conidia would grow into the tunnel of the stalk develop into hyphae which proliferate and kill the larvae inside the stalk. Beauveria bassiana also has no preference as to its host’s stage in life; it will attack larvae and adults. A very unique characteristic is that it affects its host upon contact, unlike many other pathogens that need to be consumed to cause infection. Upon contact the pathogen kills the host from the inside out. It produces spores, known as conidia (asexual form), that directly infect through the outside of the insect’s skin; it then proceeds to germinate. From the spores it secretes enzymes that attack and dissolve the cuticle. It also produces Beauvericin, a toxin that weakens the host’s immune system.

This research finding is relevant in boosting underutilized control strategies and increasing stakeholder adoption of integrated pest management practices and thereby reducing the use of conventional insecticide. The results are good and relevant for increasing farmers’ adoption of Integrated Pest Management practices, reducing the use of conventional, broad-spectrum chemicals for Ostrinia nubilalis control and employing less environmentally harmful insecticides. By adopting less broadly toxic chemicals in pest management, control by natural enemies of European corn borer, such as Parasitoids such as Trichogramma pretiosum and microbial pathogens may be enhanced and this would in turn reduce the need for chemical controls and make row crop farming more profitable for the farmers.

The results of the research done on the abundance and composition of the arthropods in the treatment plots clearly show that the different treatments applied to various plots had no effect on the distribution and abundance of these arthropods. All the P values obtained by one way ANOVA were bigger than 0.005.

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