Updated February 2024 – In the world of commercial agriculture, one of more impactful phenomena is the occurrence of mummy nuts. This term, while whimsical in nature, refers to a serious issue that occurs in nut orchards, particularly in almonds, walnuts, and pistachios. In this month’s article, FarmSense will delve into what mummy nuts are, their significance in commercial agriculture sanitation, and the strategies employed to mitigate their impact. Let’s begin unwrapping the mystery of mummy nuts in commercial agriculture.
What are Mummy Nuts?
Mummy nuts is the name given to nuts that remain on the trees after the harvest season has ended. These nuts, for various reasons, fail to detach from their branches, leading to a range of consequences during the following season. The causes of mummy nuts can be multifaceted, including environmental factors, diseases, and inefficiencies in harvesting methods. Unlike their healthy counterparts, mummy nuts are characterized by their shriveled appearance and darker coloration, making them easily distinguishable. IPM Innovator Award winner and licensed pest control advisor, Cliff Kitayama, Ph.D., explained the following to us, “shriveled mummy nuts are usually caused by water stress or sometimes by a broken branch that creates a similar condition. These are typically referred to as “stick tights” and are extremely difficult to remove. Stick tights often maintain a tight seal and are not as easily accessible to insects.” Kitayama went on to explain, “pests like the navel orange worm (NOW) and the nitidulid sap beetle, tend to target mummy nuts that have a poor seal and good kernel as these create the best over-wintering environment.”
The Impact of Mummy Nuts on Commercial Agriculture
The presence of mummy nuts in orchards is not merely a cosmetic issue but poses significant challenges to commercial agriculture. One of the primary concerns is the propensity of these leftover nuts to harbor pests and diseases, which can then infect new crops during subsequent seasons.
One of the primary concerns around mummy nuts lies in the fact that they present not only a tempting food source, but also a cozy shelter and breeding ground for the dreaded navel orangeworm during winter months. Although it may seem as though commercial farmers wouldn’t be concerned with navel orangeworm infestations in nuts that will never be harvested, their presence can result in substantial damage to subsequent harvests. In fact, a recent report found that navel orangeworm infestations cost almond growers an average of $393/acre and $262/acre for pistachio farmers for winter sanitation and pesticides targeting this pest. This works out to 8% of almond revenues lost to navel orangeworms [source: Agri-Pulse & Giannini Foundation of Agricultural Economics].
In addition to the risk of infestations by pests like the navel orangeworm, mummy nuts can also be a source of fungal infections. Mummy nuts often become an ideal environment for fungal spore growth. The moist and nutrient-rich conditions of these unharvested nuts often foster the proliferation of fungi which, in some cases, can even spread to healthy nuts in the following season.
One such fungi, Aspergillus flavus, thrives in these neglected nuts and produces aflatoxins, potent toxins that pose health risks to both humans and animals. Aflatoxins are commonly found in agricultural commodities, including nuts, grains, and spices. Given the potency of aflatoxins, regulatory agencies have established acceptable presence threshold rules for agricultural goods. In the US, the FDA’s aflatoxin threshold in human foods is 20 parts per billion (ppb) and European Union aflatoxin tolerances are even lower across almost all food groups. This often leads to a large number of quality assurance and testing firms, as well as diligent efforts by processors, to remove any imperfect nuts. This is especially true for products destined for international export. If a shipment is rejected in port due to excessive aflatoxin presence, it must then be reconditioned and re-submitted for inspection. This translates to costly delays and possibly repercussions by regulatory agencies of the destination country.
The presence of aflatoxins not only impacts the quality and safety of the nut crop but can also lead to significant economic losses due to reduced marketability and regulatory issues. Circling back to the pest concerns, waste products and excrement left in mummy nuts by pests like the navel orangeworm also provide additional resources and nutrients which increases aflatoxin production.
Mummy Nut Management and Mitigation in Commercial Agriculture
Addressing the challenge of mummy nuts requires a multifaceted approach. Initially, farmers focus on optimizing harvesting techniques to ensure maximum removal of nuts from trees which results in leaving as few nuts behind as possible. This can involve adjusting the timing of harvests, fine-tuning mechanical harvesters, or employing labor and cost intensive manual methods to dislodge stubborn nuts.
Post-harvest orchard management plays an equally crucial role in mitigating the potential impact of mummy nuts. Farmers may use mechanical shakers to dislodge remaining nuts, manually remove them, or even utilize natural predators, such as birds, to assist in clearing the trees. Additionally, maintaining a clean orchard floor is essential to prevent pests and diseases from overwintering and affecting the next crop cycle.
Pest management is another critical component in controlling the impact of mummy nuts. Farmers employ sustainable integrated pest management (IPM) strategies, including monitoring pest populations, using pheromone traps, applying select targeted pesticides, and promoting the presence of natural predators. These efforts help keep pest levels in check, reducing the likelihood of infestation in both mummy nuts and new crops.
Technological Advances to Manage Mummy Nuts
As with most things, ongoing research and technological advancements will play a pivotal role in addressing the mummy nut issue in the future. Researchers are continually exploring disease-resistant tree varieties, developing more efficient harvesting technologies, and investigating biological control methods to manage pest populations.
In recent years, the significance of the mummy nut problem has garnered the attention of the tech community, resulting in new efforts to provide commercial farmers with new tools aimed at mummy nut detection and sanitation. Researchers at the University of California, Merced have developed a method that uses object detection software models to analyze crop photographs and determine mummy nut pressure. By identifying areas with high concentrations of mummy nuts, farmers can implement more targeted management efforts. Precision agriculture tools like this enable the application of treatments more accurately and efficiently, reducing waste and minimizing environmental impact. This method however, while promising, only provides intel pertaining to crops with a high density of mummy nuts.
In terms of mummy nut removal technology, companies like InsightTRAC have developed a novel approach to autonomous mummy nut removal. InsightTRAC has created a robotic mummy nut removal rover that can be operated 24/7 in almond orchards. This self-driving vehicle navigates almond orchards to identify mummy nuts. Once a mummy nut has been identified, the device removes it from the almond tree using one of four robotic turrets to fire a biodegradable pellet, knocking the mummy to the ground.
Economic and Environmental Considerations of Mummy Nuts
The economic implications of mummy nuts are considerable. Infestations and diseases originating from these nuts can lead to reduced yields, lower quality produce, and increased production costs. Farmers must invest in additional labor, equipment, and pest control measures to manage the issue, impacting their bottom line.
Moreover, mummy nuts pose environmental challenges. The need for increased pest control can lead to higher pesticide usage, affecting local ecosystems and biodiversity. By adopting sustainable management practices and leveraging technological advancements, farmers can mitigate these environmental concerns while maintaining productive and profitable orchards.
Although it is difficult to fathom that old, unharvested, and dead nuts can cause so many issues, the fact remains that mummy nuts have far-reaching implications for the commercial nut industry.
They present challenges in terms of pest and disease management, economic viability, and environmental sustainability. Through a combination of improved harvesting techniques, diligent orchard management and monitoring, integrated pest management (IPM), and the implementing new technology, farmers can more effectively address the issue. As research continues to advance, new strategies and tools will emerge to help farmers maintain healthy, productive orchards, ensuring the long-term success and sustainability of the commercial nut farming industry.