Organic-Allowed Insecticide Options for the Management of Six Major Insect Pests in Arizona’s Vegetable Crops

The diamondback moth (DBM), Plutella xylostella, is a significant insect pest of Brassica crops globally. A major outbreak a decade ago established it as a key pest of Brassica crops in Arizona. DBM larvae feed on leaves and marketable portions of all Brassica crops and can cause significant yield losses if not adequately managed. During an outbreak, the control of larvae and adults becomes a significant challenge, often requiring repeated insecticide applications. DBM has a strong tendency to develop insecticide resistance, with documented cases reported in populations from California. Some of these resistant populations have been introduced into Brassica-growing regions of Arizona (Calvin et al. 2024 & 2025). Thus, the adoption of IPM strategies, more specifically insecticide rotation, is strongly recommended for effective management of the pest.

There are limited organic insecticide options to control DBM. Based on studies conducted at the Yuma Agricultural Center (YAC), the most effective organic options for controlling DBM include XenTari, DiPel, Entrust, a tank mix of DiPel and Pyganic, or a tank mix of XenTari and Pyganic (Figs. 1 & 2). In fall 2024, XenTari, Dipel mixed with Pyganic, XenTari mixed with Pyganic, Dipel, and Entrust resulted in 70, 65, 59, 47, and 47% decrease in DBM larvae, respectively (Fig. 1). In spring 2025, Dipel, XenTari, Dipel mixed with Pyganic, and XenTari mixed with Pyganic resulted in the greatest reduction of DBM incidence, with 49, 46, 38, and 35% reduction, respectively (Fig. 2). Our studies further demonstrate that a rotation program consisting of XenTari followed by Pyganic, and then by Entrust, can provide DBM suppression comparable to that achieved with repeated application of XenTari (Fig. 3.)

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The beet armyworm (BAW), Spodoptera exigua, is a major lepidopteran pest of Brassica crops and leafy vegetables in Arizona. BAW has a wide host range, including asparagus, bean, beet, broccoli, cabbage, cauliflower, celery, chickpea, corn, cowpea, eggplant, lettuce, onion, pea, pepper, potato, radish, spinach, sweet potato, tomato, turnip, alfalfa, corn, cotton, peanut, safflower, sorghum, soybean, sugar beet, and tobacco crops. BAW also develops well on weeds such as lambsquarters, mullein, pigweed, purslane, Russian thistle, parthenium, and tidestromia. BAW larvae feed on both foliage and fruit of crops. Small larvae feed gregariously and skeletonize foliage. Large larvae are solitary, and they chew large holes in foliage. BAW may destroy entire stands of seedlings and can stunt the growth of young plants. When approaching harvest, BAW infestation can result in economic loss by damaging and contaminating harvestable plant portions. The pest can burrow into the head of lettuce or into the buds of Brassica crops (Kerns 2000).

The results from our trial at YAC showed that Xentari, a tank mix of Xentari and Pyganic, and Entrust were the most effective treatments for suppressing BAW (>80%). Other insecticides or insecticide mixes, including AzaDirect, Dipel, a tank mix of Dipel and Pyganic, Gargoil, Grandevo, Venerate, M-Pede, and PFR-97, also provided BAW suppression ranging from 30 to 50%, compared to the untreated control (Fig. 4).

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Flea beetles, Systena blanda, can be serious pests of vegetable crops. Unmanaged populations can lead to substantial crop losses and cosmetic damage, particularly to leafy vegetables and Brassica crops. Although several flea beetle species attack vegetable crops, the most damaging species is the pale striped flea beetle. This beetle has a very broad host range and is an important pest in all leafy vegetables, Brassica crops, carrots, beets, and cucurbits. They can also occur in field crops such as alfalfa, corn, cotton, sugar beets, and Sudan grass. Additionally, the pest can be found on several weed species, including purslane, lambsquarter, and pigweed. On leafy vegetables and Brassica crops, pale striped flea beetle adults cause most of the damage by attacking the emerging cotyledons of direct-seeded plants and the tender new growth of transplants during stand establishment (Palumbo 2024).

Organic insecticide options for the pale striped flea beetle are limited. Results from our fall 2024 trial demonstrated that Biolink (insect & bird repellent), a tank mix of Biolink and Pyganic, and a tank mix of Entrust and M-Pede provided 55, 51, and 46% suppression of pale striped flea beetle (Fig. 5). Multiple applications are required to enhance seedling protection.

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Whitefly, Bemisia tabaci, has a broad host range and can cause significant economic damage to several crops in Arizona, including Brassicas, melons, and cotton. Whiteflies feed on plant phloem by injecting enzymes and removing the sap, thereby reducing the plant's vigor. After digesting the sap, whiteflies excrete honeydew, which promotes the growth of black sooty mold, thereby reducing plant quality. In many crops, the damage caused by Bemisia tabaci is indirect, as the insect vectors numerous devastating plant viruses (Osborne 2016).

There are limited organic insecticide options for whitefly control in organic vegetable crops. Results from our fall 2024 trial demonstrated that M-Pede can provide 32 and 53% suppression of whitefly nymphs and adults, respectively, on Brassica crops. Other products, including Surround, Pyganic, and BotaniGard, can also provide marginal levels of whitefly suppression (Figs. 6 & 7). It is best to apply Surround and BotaniGard when the plants are small. Dense foliage prevents insecticide droplets from reaching the lower leaves, where most whiteflies are located on the plants, thereby reducing the efficacy of the products.

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The green peach aphid (GPA), Myzus persicae, is a polyphagous pest that feeds on over 40 plant families, including some ornamental plants, vegetables, and melons. It is a significant agricultural pest and pathogen vector globally. In Arizona, GPA is a common pest of lettuce, leafy greens, and Brassica crops. This pest can cause damage to these crops through direct injury, virus transmission, and contamination of harvestable portions of the crops (Palumbo 2000, Natwick et al. 2016). The green peach aphid is a sap-feeding insect that uses piercing-sucking mouthparts to extract plant sap. This feeding activity disrupts the plant's nutrient transfer, which in turn diminishes its overall vigor. After feeding, green peach aphids excrete a large amount of honeydew that sticks to the leaves, which allows black sooty mold to develop, affecting the plant’s photosynthesis and the quality of the harvestable portions (Capinera 2023).

Similar to other pests, there are limited organic insecticide options for managing green peach aphid in organic vegetables. In our trials at YAC, we found that Aza-Direct can provide a measurable (greater than 50% reduction) suppression of green peach aphids on broccoli (Fig. 8). However, M-Pede provided the greatest (>50% suppression) suppression of green peach aphids in lettuce (Fig. 9). We will continue to investigate to determine if it is consistent that Aza-Direct and M-Pede have variable performance when applied to broccoli or lettuce. Because Aza-Direct has delayed effects and works as a growth regulator (Calvin et al. 2021), it is recommended to apply it early in the season to allow the product sufficient time to work and enhance its efficacy.

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Western flower thrips (WFT), Frankliniella occidentalisis, one of the most economically important pests attacking vegetable crops in Arizona’s vegetable-growing regions. They are most important in head, leaf, romaine, and baby mix lettuces, cabbage, and spinach because of the cosmetic scarring they cause to leaves and contamination of harvested plant parts. Thrips are present season-long in leafy vegetables. However, they are usually most abundant during the spring as the temperature increases (Palumbo 2000).

Entrust can provide excellent (>90%) control of thrips nymphs and adults. In our studies, other bioinsecticides, such as Gargoil and Aza-Direct, also resulted in thrips suppression of approximately 40% and 50%, respectively (Fig. 10). In a rotation program, Aza-Direct and/or Gargoil can be applied at the beginning of the season when thrips populations are low, and thrips injuries are less problematic.

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• Entrust provides the best thrips suppression (>90%).
• Gargoil and Aza-Direct can provide 40 to 50% thrips suppression.
• Xentari, Dipel, Entrust, Dipel + Pyganic, or Xentari + Pyganic are the best options for Diamonback moth and Beet armyworm control.
• Aza-Direct provides a greater than 50% reduction of green peach aphid nymphs in broccoli.
• M-Pede provides greater than 50% reduction of green peach aphid nymphs in romaine lettuce.
• M-Pede performed best against whiteflies, but Surround, Pyganic, and Botanigard can also provide some level of suppression.

Calvin, W. and J. C. Palumbo. 2024. Chlorantraniliprole Resistance Associated with Diamondback Moth (Lepidoptera: Plutellidae) Outbreaks in Arizona Brassica Crops. Journal of Economic Entomology. toae212, https://doi.org/10.1093/jee/toae212 

Calvin, W., J. M. Beuzelin, O. E. Liburd, M. A. Branham, and L. Jean Simon. 2021. Effects of biological insecticides on the sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), in sorghum. Crop Protection. 142:105528. https://doi.org/10.1016/j.cropro.2020.105528 

Calvin W., M. N. Keith, and B. McGrew. 2025. Guidelines for Effective Management of Diamondback Moth in Brassica Crops. University of Arizona Extension Publication az2143. https://extension.arizona.edu/publication/guidelines-effective-management-diamondback-mothbrassica-crops 

Capinera, J. L. 2023. Green Peach Aphid, Myzus persicae (Sulzer) (Insecta: Hemiptera: Aphididae). https://edis.ifas.ufl.edu/publication/IN379 

Kerns, D. L. 2000. Mating disruption of beet armyworm (Lepidoptera: Noctuidae) in vegetables by a synthetic pheromone. Crop Protection. 19: 327-334.

Natwick, E. T., J. J. Stapleton, and C. S. Toddard. 2016. Agriculture: Cucurbits Pest Management Guidelines. https://ipm.ucanr.edu/agriculture/cucurbits/greenpeach-aphid/#gsc.tab=0 

Osborne, L. S. 2016. Bemisia: Biotype-Q or Biotype-B? https://mrec.ifas.ufl.edu/LSO/bemisia/bemisia.htm 

Palumbo, J.C. 2000. Management of Aphids and Thrips on Leafy Vegetables. University of Arizona, College of Agriculture and Life Sciences, Cooperative Extension, Tucson, Arizona. http://cals.arizona.edu/crops/vegetables/insects/aphid/aphidsandthrips.html  

Palumbo, J. C. 2024. Pale striped flea beetles in leafy vegetables and cole crops. VegIPM Update, Vol. 15, No. 16, Aug, 7, 2024