Almond harvest is well underway in California, and with it, the time for assessing the extent of damage by navel orangeworm (NOW) and other pests and pathogens arrives. Guidelines for best practices to assess crop damage from the 2021 season are provided in this article.
Image by Mando Perez.
Collecting samples before nuts are transported to the huller is beneficial to growers and Pest Control Advisors (PCAs) for multiple reasons. First and foremost, growers and PCAs can use the extent and source of nut damage to assess how their Integrated Pest Management program performed. Using this knowledge, growers can evaluate their IPM program and plan for any necessary adjustments heading into next season. Additionally, this data can be used to track block-by-block damage over the years and gain a better understanding of the areas of the orchard that tend to be most vulnerable to certain pests and diseases.
University 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 can 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 assessing 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 insects.However, damage from navel orangeworm tends to be the most extensive and noticeable. NOW larvae often feed in groups and extensive damage to the nutmeat results t, NOW produces excessive amounts of frass and webbing as they consume the nut.
Navel Orangeworm damage on sampled almonds.
Navel orangeworm damage tends to be quite distinctive, and as a result, growers are unlikely to mistake NOW damage for that of any 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.
Oriental Fruit Moth damage on sampled almonds.
Other forms of insect damage may be detected in almond harvest samples, although generally not as severe as navel orangeworm. For example, ants will hollow out the nut, leaving just the skin,and leaffooted bug feeding 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 program should be thoroughly evaluated and any available adjustments made to prevent future damage. A cornerstone of many IPM programs is pheromone-based mating disruption. Mating disruption products for NOW and other pests 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 and does not leave residue on crops. Suterra provides two mating disruption options for Navel orangeworm that are widely used by growers, aerosol Puffers® (available for conventional and organic production) and a microencapsulated sprayable formulation. If you have questions about Suterra, Integrated Pest Management or mating disruption, contact your local representative or send us a message online using this form.
Information provided herein does not constitute a recommendation. Always consult with your PCA to determine the best pest management practices and timings for your operation. Adhere to state and local regulations and the current pesticide label and check with your organic certifier.