An integrated pest management program includes both preventative and corrective actions to keep insect pests from causing crop damage in tree nut orchards. When economic realities come up against an IPM strategy, costs and value have to be weighed.
Drew Wolter, senior specialist in pest management at Almond Board of California, said the guiding principles of IPM look to uphold the three pillars of sustainability: environmental, social and economic. By nature, he said, economic viability is at the head of any sound IPM program, with prevention being the key step. Practices that do not just pay for themselves, but also help increase net profits for the grower, are all part of preventing crop damage in the orchard.
IPM programs need to be flexible and evolve to take into account changing environmental conditions and economic realities. The UCCE IPM programs found online are designed for specific crops and have been proven to significantly reduce pesticide use while protecting crop yields and quality.
Almond Board of California, California Pistachio Research Board and California Walnut Board, along with California Department of Pesticide Regulation, all provide funding for research in integrated pest management strategies.
The UCCE’s Sacramento Valley Orchard Source reinforces the economic aspect of IPM, offering growers a formula that takes into account the costs of a pest management strategy, value of the crop and damage using an equation where the economic injury level represents the target pest population density or where treating “pays.”
In the equation, cost of management is divided by crop value x damage x effectiveness of treatment.
When crop value decreases, the level of pest population tolerated increases in order to maintain economic balance.
Even with refined IPM systems, pest-related challenges in tree nut orchards continue. These include the introduction of invasive new insects, growth of tree nut acreage, integrating varieties, orchard spacing and irrigation with an IPM program.
Growers and farm managers considering cost saving strategies in their IPM programs should know the economic thresholds for insect pests and set priorities for pesticide applications, using timing for better efficacy to make the most of their investment.
Thresholds and Monitoring
UCCE farm advisor David Haviland in Kern County said knowing treatment thresholds and monitoring for pests and predatory insects can save management costs, but noted “less investment in management equals risk at harvest.”
“You need to monitor and sample to make good decisions,” he said.
Examples are spider mites and scale. Monitoring can reveal infestation levels and predator levels, giving a basis for a treatment decision. If predator populations are preserved, they can keep mite damage under control. Predators for other insect pests, including navel orangeworm (NOW), codling moth and plant bugs are less heavily relied upon for control.
Even though the initial investment in mating disruption is high, Haviland’s trials show a reduction of NOW damage in orchards where products are used. Cost is about equal to two spray applications, he said, but the orchard shape and location have to be a good fit.
Good orchard sanitation is the most cost-effective method of NOW control, but monitoring also plays a part in an IPM program. Sampling for infested mummy nuts in the orchard can allow for better decisions on early spray applications.
One of the first places to start, Sac Valley Orchard Source notes, is to use economic thresholds of pest levels when deciding any pest management method. Other noted strategies are elimination of unnecessary materials in the spray tank, spot treating pest outbreaks and prioritizing treatment locations and timing to achieve best results in areas of greatest need.
On the other hand, cost savings in management won’t be achieved if pesticide applications are not done properly. Sprayer calibration, sprayer speed appropriate for material and orchard size and volume to achieve adequate coverage are all important.
If timing of pesticide applications is off for the optimal stage to impact the target pest, cost of the application will not be recovered. Using below the label rate and not rotating chemistries to prevent resistance are not cost saving strategies, but rather add risk of crop damage.
Wolter said that orchard sanitation during the dormant season, for example, is proven to reduce NOW pressure for the following season. If sanitation is omitted or done poorly, growers may experience a wave of NOW flights during the following crop year. This not only leads to increased cost of management, but can also contribute to higher levels of crop damage, which will eat into net profits as the percentage of rejections at the processor increase.
In season management, tools that help maintain economic sustainability for growers stem from proactive practices including monitoring, trapping and use of pest prediction models. Wolter said that all of these tools feed into tracking pest pressure and developing economic thresholds for when to make chemical, biological or other applications. This strategy allows growers to move away from calendar-based application by understanding pest life cycles and quantifying when a management tool provides the greatest return on investment. By only treating when pest pressures approach a grower’s established threshold, the total number of in-season spray applications may be reduced.
Wolter said the same could be said for disease severity values, also known as DSV models. For example, the DSV model that has been developed for alternaria leaf spot provides growers with index values that have been assigned for a specific range of temperatures during a leaf wetness event. If followed correctly, growers will see that treatments are only needed if the accumulated index values over a seven-day period reach a value greater than 10. This reduces the total number of sprays that are normally done.
Cultural practices including site selection, variety/rootstock selection and thoughtful irrigation, and nutrient and chemical management may also mitigate future pest and disease challenges. Wolter said that good choices in cultural practices could go a long way in minimizing inputs within a season and across an orchard’s lifespan. Wolter said that proper orchard layout could improve air circulation and prevent disease. Providing habitat and minimizing broad-spectrum chemicals can increase the number of naturally occurring beneficial insects that provide a free control service. Thoughtful nitrogen management can help reduce severity of hull rot, Wolter added.
He noted that prevention-oriented IPM practices increase a grower’s insight into the dynamics of pests and diseases during that season. This provides the opportunity to reduce the total number of in-season spray applications and increase the options for managing pests and diseases while maintaining economic viability and reducing risks to human health and the environment.