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Vegetable IPM Updates Archive
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Update on Bagrada Bug on Desert Cole Crops (May 29, 2019)
The bagrada bug first invaded desert cole crops in the fall of 2010. Outbreaks occurring in the first few years were quite disruptive, causing significant damage and excessive insecticide spraying. However, I think most would agree that bagrada bug population pressure has been relatively light the past few years. In fact, infestations last fall were as light as we’ve seen since the bagrada bug first occurred on desert cole crops at damaging levels. To document changes in the severity of bagrada bug infestations on direct-seeded and transplanted cole crops and the intensity of chemical management, we have annually surveyed growers and PCAs from Yuma, Maricopa and Imperial counties since 2010. We recently conducted our annual survey and results show that since 2010 the cole crop industry has experienced widespread bagrada bug infestations throughout the desert from September into November, although some years have been less intense than others. Last fall (2018) was one of the lightest years we’ve seen to date. Based on seasonal population abundance studies of adults infesting non-treated broccoli plants at the Yuma Ag Center (see graph below), bagrada bug infestations have been steadily decline since 2013. Estimates of stand losses from bagrada bug infestations at stand establishment in both direct-seeded and transplanted crops have decreased considerably over the past 9 years and were particularly low during the 2018 fall growing season. The lower losses reported in 2018 are due to the lighter bagrada pressure experienced last season. Plant injury, defined as plants with multiple heads, forked terminals, and/or blind terminals resulting from bagrada feeding, was the lowest recorded since 2010 for both direct-seeded and transplanted crops. These data suggest that PCAs have adopted effective management programs to protect seedling crops during stand establishment. Insecticide usage to control this pest was low in 2018, where the percentage of acreage treated was lower this season than in any previous year. Pyrethroids remain the primary product used for controlling bagrada bug adults either via chemigation or with foliar spray applications. Based on survey results, products that have ontact activity appeared to provide the most effective control against bagrada adults on both direct-seeded and transplanted cole crops. Results from the survey also showed that over half of direct seeded broccoli was treated with clothianidin (Nipsit) in 2017, but a significant decrease in the Nipsit acreage and number of PCAs using the product was reported in 2018. The PCA’s who did use Nipsit in 2018 reported that the product was extremely effective in controlling bagrada bug adults. Overall, the results of the PCA survey are consistent with results obtained in research trials conducted at the Yuma Agricultural Center over the past four years. A summary of the 2010-2018 survey results can be found in the following report: Nine Years of Bagrada Bug on Desert Cole Crops.



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