By Daniel Palla, Technical Sales Representative, Trécé
The Navel Orangeworm is a significant pest in agricultural systems due to primarily feeding on the seeds of tree nuts, including almonds, pistachios, and walnuts. It also infests other crops like figs, but its most destructive impact is on nut trees. The larvae of the Navel Orangeworm tunnel into the nuts, feeding on the seeds and causing significant damage. This feeding reduces the nut’s quality and increases the likelihood of secondary infections, such as those caused by fungi like Aspergillus, which can produce harmful mycotoxins like aflatoxin.
The adult moths lay their eggs on the nut tree’s fruit, and the larvae hatch and burrow into the nut to feed. The feeding process creates holes that allow pathogens to enter, causing further deterioration. The presence of Navel Orangeworm damage can severely affect crop yields and quality, making it a major pest of concern for nut growers.
The Navel Orangeworm is resistant to pyrethroids, which are a class of synthetic insecticides commonly used to control a variety of pests. However, resistance to pyrethroids has been observed in Navel Orangeworm populations. The reasons for this resistance are multifaceted:
1. Genetic Adaptation: Over time, Navel Orangeworms have developed genetic mutations that help them metabolize or detoxify pyrethroids more effectively. These mutations have become more prevalent in populations exposed to repeated pyrethroid applications, leading to resistance.
2. Target Site Insensitivity: Resistance can also arise from changes in the insect’s nervous system, where the pyrethroid no longer binds to the intended target, preventing the insecticide from working effectively.
3. Overuse of Pyrethroids: Repeated reliance on pyrethroids without rotating to other classes of insecticides can select for resistant individuals, increasing the overall resistance within the pest population.
As a result of this resistance, pyrethroids are becoming less effective in controlling the Navel Orangeworm, making it necessary for growers to explore alternative pest management strategies.
Enter Winter Sanitation. This process refers to the practice of cleaning up and removing mummified or damaged nuts and other crop debris from the orchard after harvest. This is a critical step in managing Navel Orangeworm populations for several reasons:
1. Breaking the Life Cycle: Navel Orangeworms overwinter as larvae inside mummified nuts or other crop debris left in the field. By removing these sources of infestation, growers reduce the number of overwintering larvae that can emerge in the spring to reinfest the new crop.
2. Reduced Pest Pressure: By eliminating the places where Navel Orangeworms can survive during the off-season, growers minimize the initial population of moths that will lay eggs on the new crop. This reduces the overall pest pressure during the growing season.
Mating disruption is an integrated pest management (IPM) strategy used to prevent the Navel Orangeworm from mating and reproducing effectively. This is typically done by releasing synthetic sex pheromones into the air, which interfere with the male moth’s ability to locate a mate. The key reasons why mating disruption is important include:
1. Disrupting Reproduction: Mating disruption prevents males from finding females, which reduces the number of eggs laid on the crop. Fewer eggs mean fewer larvae to damage the nuts.
2. Reduced Chemical Use: By preventing mating, mating disruption reduces the need for chemical insecticides. This makes it an environmentally friendly option and can help slow the development of resistance to insecticides, such as pyrethroids.
3. Targeted Control: Mating disruption targets only the reproductive process of the pest, rather than the entire population. This reduces the likelihood of harm to beneficial insects, such as pollinators, and non-target organisms in the ecosystem.
4. Long-Term Effectiveness: Because mating disruption targets a fundamental aspect of the pest’s biology, it can be an effective long-term solution. When used in combination with other strategies, it can help sustain pest control efforts over multiple growing seasons.
5. Cost-Effectiveness: While the initial cost of deploying mating disruption may seem high, the reduction in chemical pesticide use and the potential for fewer pest outbreaks can lead to overall cost savings in the long run. Additionally, reducing the damage caused by Navel Orangeworms can lead to better crop yields.
