Almond harvest will be underway soon in California, and with it comes the time for assessing the extent of damage by navel orangeworm (NOW) and other pests and pathogens. Guidelines for best practices to assess this season’s crop quality are reviewed in this article.
Collecting samples before nuts are transported for processing is beneficial to growers and Pest Control Advisers (PCAs) for multiple reasons. Growers and PCAs can determine the extent and sources of nut damage to assess how their integrated pest management (IPM) program performed and plan for any necessary adjustments heading into the next season.
Additionally, information taken from in-field samples for early harvested varieties can guide whether additional treatments should be considered to protect later varieties in the current season. There is also the tremendous value of this data to gain a better understanding, block-by-block, and year-by-year, of the areas that tend to be most vulnerable to certain pests and diseases and the conditions that lead to increased pest pressure.
Established guidelines suggest obtaining a sample of at least 500 nuts per block, ideally from multiple sampling locations in different parts of the orchard. NOW and other pests often exhibit different levels of pest pressure in different areas of the block or orchard, so acquiring a sample fully representative of each block is important to accurately assess the damage. After acquiring the sample, nuts can be cracked open to begin looking for signs and sources of damage. If the nuts are not cracked immediately, they should be stored in a freezer.
Kernel damage in almonds may be caused by a variety of issues. However, damage from navel orangeworm is often distinguishable from that caused by other insects, diseases, and disorders. NOW larvae often feed in groups, and damage is recognizable by extensive feeding on the nutmeat and the copious amounts of frass and webbing they produce as they consume the kernel.
Navel orangeworm damage is quite distinctive, and as a result, growers are unlikely to mistake NOW damage for that of other common pests. However, NOW infestation can mask damage caused by other pests that cause less extensive damage, such as peach twig borer (PTB) and Oriental fruit moth (OFM). Both of these pests leave shallower channels in nuts and produce much less frass compared to NOW and no webbing.
Other forms of insect damage may be detected in almond harvest samples. For example, ants will hollow out the nut, leaving just the skin, and feeding by leaffooted or stink bugs will appear as dark spots or gumming of the almond kernel.
If harvest samples or grade sheets reveal economic levels of pest damage, the integrated pest management (IPM) should be thoroughly evaluated, and any available adjustments made to prevent future damage. For NOW, a foundation of the IPM program is pheromone-based mating disruption. Mating disruption products, for NOW, release synthetic copies of the species’ sex pheromone into the environment, inhibiting the ability of males to locate females and successfully mate. This results in reduced reproduction, fewer pests, and less crop damage.
Mating disruption is species-specific, does not leave harmful residues on crops, and is safe for the environment and beneficial species. Suterra offers two proven mating disruption solutions for navel orangeworm that are widely used by growers: aerosol Puffers® (available for conventional and organic production) and a microencapsulated sprayable formulation (CheckMate® NOW-F). If you have questions about Suterra, integrated pest management, or mating disruption, contact us, and we will connect you with one of our experts.