Aug 2, 2022Insecticide options for navel orangeworm IPM in almond – a recent trial summary
Navel orangeworm integrated pest management
Navel orangeworm (NOW) is one of the important pests that draws nut crop grower’s attention throughout the season.
Although the economic damage may not be significant every year, the unpredictability associated with this pest makes it difficult for growers and pest control advisors (PCAs) to relax some of their pest management practices. The current NOW integrated pest management (IPM) practices include: (1) winter sanitation to remove and destroy ‘mummy nuts’ before mid-March, (2) mating disruption product application at the beginning of the season to gradually reduce the NOW population, (3) timely harvest to minimize late-season infestations, and (4) 1-2 insecticide spray applications during hull split.
All of these methods are commonly used IPM practices and should be combined to achieve the best results. As insecticide is a part of the NOW IPM strategy, in the 2020/2021 seasons, we evaluated the efficacies of multiple insecticides against NOW using the previous season nut (i.e., mummy nut) strands as substrate. We used mummy strands to compare insecticide efficacy as conducting large field trials is not always feasible, especially when several treatments with multiple replications are needed. Almond mummy nut strands have been used to evaluate insecticide performance in several other NOW studies.
Insecticide efficacy trials – 2020/2021
The insecticide study was conducted using mummy nut strands that consisted of 20 mummy nuts glued to a strand cut from window screen material (Photo 1A). Fifteen to 20 mummy strands (20 replicates in 2020; 15 replicates in 2021) were used for each of the 11 insecticides and a water-treated control (Table 1).
All insecticide concentrations were prepared in water using the 100-gallon per acre rate. The strands were thoroughly dipped in two quarts (1.89 L) of the prepared insecticide solutions for 10 seconds, allowed to air dry for about 30 minutes, and deployed to the selected trees in an almond orchard (Photo 1B).
Two rows of a pollinizer variety (in 2020) or three rows of Nonpareil variety (in 2021) were selected in the orchard, and one strand of each treatment (Table 1) was hung in a total of 15 to 20 trees. Experiments were set up in mid-August of 2020 (targeting the 3rd NOW generation) and late April of 2021 (targeting the 1st NOW generation). The nut strands were left in the field for two weeks to provide enough time for female NOW to lay eggs. Once collected from the field, we carefully looked at the NOW larvae under a microscope, and the percent nut infestation for each strand was calculated and used for statistical analysis. One-way analysis of variance (ANOVA) was used to determine whether or not percent nut infestation was affected by the treatments, and the Tukey-Kramer honestly significant difference (HSD) was used to compare treatments.