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March 2nd 2014 Vegetable IPM Updates
Insect Management
Weed Science
Insect Management:

Impact of Bagrada Bug on Desert Cole Crops, 2010-2015

With the produce season finally finishing, now is a good time to reflect on pest issues from last fall. The bagrada bug, Bagrada hilaris, first occurred on desert cole crops at damaging levels in the fall of 2010, and has since become an established pest. 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 (2015) 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 graph below), bagrada bug infestations in the fall 2015 were lower than what we had observed since the pest first showed up in the desert. Estimates of stand losses from bagrada bug infestations at stand establishment in both direct-seeded and transplanted crops have decreased by more than 50% over the past 5 years. The lower losses reported in 2015 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 2015 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 2015 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. However, more neonicotinoid products (Venom) are beginning to be implemented into the PCAs IPM programs. 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 2010-2015 survey results can be found in the following report: Impact of Bagrada Bug on Desert Cole Crops, 2010-2015.


Name this Insect Pest. - Syrphid Fly

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

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Disease Resistance and Tolerance

An extremely valuable weapon in the battle to manage plant diseases may reside within the plant’s genetic composition. This genetic disease management tool is commonly referred to simply as disease resistance or tolerance. These names are often used interchangeably; however, the definitions of each term denote an important difference. Resistance is the ability of a plant to exclude or overcome the effect of a plant pathogen, whereas tolerance is the ability of a plant infected by a pathogen to grow without dying or sustaining serious injury or yield loss. Therefore, resistance focuses on infection prevention, whereas tolerance allows infected plants to grow without serious injury or yield loss. Disease resistance and tolerance are not all or nothing conditions. For example, resistance can range from its highest level, which is called immunity, through degrees of useful resistance, and finally to its lowest level, where a plant is highly susceptible to a particular pathogen. Also, resistance and tolerance usually are limited to one or at most a few diseases, and not broadly functional against many or all plant ailments. The mechanisms within plants that give rise to disease resistance and tolerance are many and varied, but usually are biochemical and/or structural in nature. Successful suppression of pathogen activity by a plant is tied to how a particular pathogen gains entrance into a plant to initiate disease and additionally how a plant defends itself from that infection. One key advantage of strong genetic resistance or tolerance is that this disease management tool will be active for the life of the plant, without any input by the grower. In contrast, disease management products such as fungicides may have to be applied several times so as to be in place over the entire growth period of the plant when disease is expected. Also, disease management provided by plant genetics often targets diseases for which no other known effective disease management tools are known. Building disease resistance or tolerance into plants is an ongoing activity of plant breeders, using classical as well as modern genetic manipulation techniques to achieve this goal.

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Weed Science:

Sudan Grass

Sudan Grass fits well here as a warm season annual crop that is low input, does the ground some good and can be rotated with a variety of winter annual crops. It is fast growing, competes well with weeds and can be helpful in reducing summer annual weed populations. Weeds can be a problem in Sudan grass, however, and herbicides are occasionally needed. Growth regulators like dicamba and 2, 4-D are registered on sudan but are volatile in the summer and can be hazardous to use. Contact herbicides like bromoxynil(Buctril) and carfentrazone(Aim) are also registered but only effective on small weeds and can cause leaf burn. Sudan is known to have a toxic effect (allelopathy) to some weeds. Unfortunately it can also to toxic to some crops as well. Toxicity to lettuce was tested and verified in the Imperial Valley several years ago. Toxicity was reduced when the Sudan residues were broken down and leached before lettuce was planted.
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Question to the IPM Team:

Skeleton Weed

VIPM_Update_Vol_7_Num_11_003.jpg The Yuma IPM TEAM was asked to ID this weed found at the Yuma Foothills.

Skeleton Weed (Eriogonum deflexum)

Thank you for your questions and comments!
We are happy to help!!
Skeleton Weed

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The Vegetable IPM Updates Archive page provides links to updates from previous weeks.

The Vegetable IPM Video Archive page contains a collection of educational videos from current research work in vegetable crops by University of Arizona Researchers.


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.

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