With the desert produce season finally completed, now is a good time to reflect on pest issues from last fall. I think most would agree that bagrada bug population pressure were very low last fall. In fact, the lightest infestations we’ve seen since the widespread outbreaks in 2010 when the bagrada bug first occurred on desert cole crops at damaging levels. It has since become an established pest, though one might not have thought so this year. In an attempt to document 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, Imperial and Maricopa counties since 2010. We recently conducted our annual survey in April. 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 (2016) was the lightest year we’ve seen to date. Based on seasonal population abundance studies of adults infesting non-treated broccoli plants at the Yuma Ag Center (see graphs below), bagrada bug infestations in the fall 2016 were lower than what we had observed since the pest first showed up in the desert. Bagrada bug population abundance on non-treated broccoli plots have also been consistently declining since 2013. Estimates of stand losses from bagrada bug infestations at stand establishment in both direct-seeded and transplanted crops have decreased significantly the past 5 years, and were particularly low in 2016. The lower losses reported in 2016 are likely 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 also lower in 2016 compared to previous years. These data suggest that PCAs have adopted effective management programs to protect seedling crops during stand establishment. Insecticide usage to control this pest remains high, and the percentage of acreage was treated in 2016 was consistent with previous years. 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 contact 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 a large percentage of direct seeded broccoli was treated with clothianidin (NipSit) in 2016, and performed well in controlling adults and protecting stands. 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 2010-2016 survey results can be found in the following report: Impact of Bagrada Bug on Desert Cole Crops.

Name that Pest

Ground Beetle Larvae (Carabidae)

Areawide Diamondback Moth Trapping Network

In response to the recent outbreaks of Diamondback moth (DBM) , Plutella xylostella in Yuma, we have established a pheromone trap network designed to monitor the activity and movement of adult populations of DBM. PCAs have had difficulty controlling DBM in cabbage, broccoli and cauliflower since October. Traps have been placed in Roll, Wellton, Dome Valley, Gila Valley and Yuma Valley in locations where cole crops are presently being grown or in areas where infestations were known to occur this fall.

Click here to see results of DBM pheromone trap network.

Remember, When in Doubt . . . . . “SCOUT”

To contact John Palumbo go to:jpalumbo@ag.arizona.edu

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.