Maize, commonly known as corn, is one of the most widely produced staple crops globally. Maximizing yield presents a continuous challenge due to the pervasive threat of insect pests. These pests attack the plant at every stage of development, from the seed to the mature ear, directly threatening the potential harvest. This damage necessitates protective measures to ensure crop survival and productivity. This brings into focus the central question: Does the routine application of insecticides reliably translate into a profitable increase in corn crop yield?
Key Pests That Threaten Corn Yield
Insect pests threaten corn crops by attacking different parts of the plant throughout the growing season. Early-season pests primarily target the seed and seedling. Species like wireworms and seedcorn maggots hollow out seeds or tunnel into young roots and shoots. This early damage can lead to a reduced stand density, as damaged seedlings may die, lowering the final plant population per acre.
Other significant pests focus on the plant’s structure and reproductive parts. The corn rootworm, a destructive pest in continuous corn fields, feeds on the roots, impairing the plant’s ability to absorb water and nutrients and causing severe lodging. Stalk-boring insects, such as the European corn borer, tunnel into the stalk, weakening the plant and disrupting the flow of water and nutrients. Later pests, including the corn earworm, feed directly on developing kernels, causing yield loss and creating entry points for fungal diseases.
Evidence on Insecticide Efficacy and Yield
Whether insecticide use increases corn yield depends heavily on the actual level of insect pressure in the field. When pest populations are high, particularly from feeders like the corn rootworm, insecticides often provide a necessary yield increase. Studies show that when pests are present, insecticide applications can increase yields by an average of about 10.9 bushels per acre in most trials. This yield protection is financially advantageous, especially when commodity prices are favorable.
The benefit is far less pronounced, or nonexistent, when pest pressure is low. For instance, in fields where corn follows a non-host crop like soybeans, and corn rootworm pressure is minimal, applying an insecticide may result in no significant yield difference compared to an untreated control. In such cases, the cost of the chemical application adds to the expense of production without generating a return, decreasing overall profit. Insecticide application occurs through two main methods: as a seed treatment coating the seed for early protection, or as a soil or foliar application applied at planting or later in the season.
Measuring the efficacy of these treatments relies on the concept of the economic threshold (ET). The economic threshold is the specific pest population density at which the cost of applying a control measure is justified by the expected increase in yield, preventing economic loss. Treating a field when the pest population is below this threshold is deemed an unnecessary intervention because the yield gain will not cover the treatment cost. For many pests, calculations are used to determine the necessary density of larvae or egg masses per plant before a spray application is economically warranted. This data-driven approach shifts the focus from preventative, blanket spraying to targeted, profitable pest management.
Economic and Environmental Trade-offs
The decision to use insecticides involves balancing the potential for increased profit from yield protection against financial and ecological costs. Economically, the insecticide product and the application cost represent a significant investment. If the expected insect damage does not materialize, the treatment expense can reduce the net profit, especially in fields with low pest density where the insecticide does not pay for itself. Producers must accurately forecast pest pressure to ensure the treatment is a worthwhile financial expenditure.
The use of chemical controls carries two major environmental and biological risks. Repeated and widespread use of the same chemical classes can lead to the development of pest resistance, where the target insect population evolves to withstand the insecticide. This resistance renders the product ineffective over time, necessitating the development of new alternatives. The second risk involves the impact on non-target organisms, particularly beneficial insects. Insecticides are not always selective, meaning they can harm natural predators and parasites, which naturally help control pest populations. Eliminating these beneficial species can inadvertently lead to outbreaks of secondary pests.
Modern Integrated Pest Management Strategies
The modern approach to pest control moves away from routine insecticide use toward Integrated Pest Management (IPM). IPM is a holistic system that employs a combination of methods to maintain pest populations below economically damaging levels while minimizing risks to the environment and human health. This strategy begins with field scouting, which involves regularly monitoring fields to accurately identify pests and quantify their population levels.
Scouting provides the data necessary to determine if a pest population has reached the economic threshold, ensuring chemical controls are used judiciously only when needed. Cultural practices form a major component of IPM, including crop rotation, which breaks the life cycles of specific pests like the corn rootworm by removing their host plant. Farmers also select corn hybrids that are genetically resistant to certain insects, such as those that produce Bacillus thuringiensis (Bt) proteins. By combining biological controls, resistant crop varieties, and targeted chemical applications, IPM stabilizes yield and manages pests sustainably without sole reliance on insecticides.