- Agronomic: corn
- Pest Management: biological control, botanical pesticides, integrated pest management
The results of this study indicated intensive infestation 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 infested 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 pretiosum 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 pretiosum 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 pretiosum, 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 general trend so far has been that these biological agents have increased the mortality of the European corn borer larvae. 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 non-target 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 non-target arthropods. All the P values obtained by one way ANOVA were bigger than 0.05.
Maize (Zea mays) or corn, together with wheat and rice are the major cereal crops grown around the world (at least by 53 countries) (FAO Stat.2001). It ranks third in production following wheat and rice. Maize is the world’s most widely grown crop in almost all tropical areas of the world, including the tropical highlands over 3000 m in altitude as far North as the 65th latitude to temperate areas. Because of different ecological conditions that exist between the temperate areas and the tropics, the insect vectors and their disease agents also are different under these different conditions (Tsai and Falk 1999). Maize is an extremely important crop grown in the United States, Europe and Africa for both human and livestock consumption. Of the various pests that attack maize/corn in Africa, the Lepidopteran stem /stalk borers are by far the most injurious, particularly the Chilo partellus (Rami Kfir. 2002, Youdeowi 1989). In the United States (Ohio, Minnesota, Iowa and other Corn Belt states), there are a number of pests that attack corn and the European corn borer-Ostrinia nubilalis (Lepidoptera: Crambidae) is one of the most destructive pests. It significantly affects growth and production of corn.
The European corn borer came to North America during the early 1900s, possibly in broom corn imported from central Europe (Hungary and Italy). It was found in the North Central States in 1921. It spread slowly from Southern Michigan and Northern Ohio. The European corn borer, Ostrinia nubilalis is the most damaging insect pest of corn throughout the United States and Canada. Losses resulting from the European corn borer damage and control costs exceed $1 billion each year (Mason et al. 1996, University of Minnesota 2002). During a 1995 outbreak, losses in Minnesota alone exceeded $285 million. A recent four-year study in Iowa indicated average losses of nearly 13 bushels per acre (826.3 kg/ha) in both first and second generations of European corn borer, for total losses of about 25 bushels per acre (1589 kg/ha).
Damage to corn from the European corn borer has increased in Europe in the last several decades. This increase may be due to environmental changes, the significant increase in monoculture corn acreage, the introduction of more susceptible hybrids, and the increased use of pesticides, which could be reducing predator/parasites populations. (Cordero. et al. 1998).
To avoid total loss of corn, insecticides are often used by farmers to control the European corn borer. The use of insecticides such as Lorsban 4E (Chloropyrifos), Intrepid 2F (Methoxyfenozide), permethrin (liquid Ambush or granular Pounce), lambda (cyhalothrin) and furadan (carbofuran) has been very common, especially before the larvae tunnel into the corn stalks. However, scouting for European corn borers, especially second generation borers is hard exercise and timing an insecticide application for maximum efficacy is difficult. Many producers did very little to manage European corn borers in Illinois and some Midwest States (Rice and Ostlie, 1997). But overuse of insecticides is not economically sound and is environmentally hazardous. For example diazinon has a very high toxicity on fish, bees and birds, while permethrin has a very high toxicity to fish, and on bees, and low toxicity to birds. In recent years, elevated awareness of the impacts of pesticide use on the environment and human health has resulted in efforts to reduce reliance on chemical control. Many countries have instituted more stringent regulations on pesticide manufacture, registration and use, thereby increasing the cost and decreasing the availability of these tools. The need for alternatives to pesticide use is very clear. A recent report by the U.S Congress, Office of Technology Assessment (U.S congress, OTA 1995) indicated that biologically based technologies such as biological control could be more widely used to solve pressing needs in pest management.
The research had the following objectives:
1.To compare the efficacy of Bacillus Thuringiensis (Bt) spray, Dipel Beauveria bassiana, Trichogramma pretiosum and Spinosad for the economic control of Ostrinia nubilalis.
2.To assess the impact of these treatments on the abundance and composition of non-target arthropods.