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

Bagrada Bug Management in the Desert

Bagrada bug adults generally begin to appear on direct seeded fields and transplants in early September. In fact, trials conducted on untreated broccoli plots at YAC have shown that mid-September has historically been the time that bagrada begin to show up in large numbers; peak abundance of bagrada bug has occurred from late September to early October (see graphs below). However, there has been a trend of lower bagrada bug abundance since 2012, and last fall was the lightest we’ve recorded bagrada populations since we started tracking them in 2010.
So far this season, we’ve yet to see a bagarada here at YAC, but reports of bagrada in commercial cole crops are beginning to trickle in from PCAs, albeit very few. Similarly reports out of Imperial Valley and Coachella suggest that populations are light there as well. So, what should a PCA expect for this season? Can’t say for sure, but don’t be complacent just because you’re not finding a lot of bagrada adults on your first few fields. It would be wise to assume they will eventually show up in some intensity in some of your acreage, and you should prepare for them accordingly. Here are a few management tips to consider. (1) We’ve learned through research that when monitoring for bagrada bugs at stand establishment PCAs should focus on fresh feeding signs on new plant tissue, and adults later in the day when they are most active. (2) Research in the field has also indicated that direct-seeded and transplanted crops are susceptible to bagrada bug infestations during stand establishment and up to the 6-leaf stage. Furthermore, it doesn’t take a large number of bagrada adults to cause significant stand losses or crop injury. In untreated plots, we have consistently observed significant damage (15-20% blind plants) to direct seeded plants during the first 7 days after emergence (cotyledon to 1-leaf Stage) with only finding an average of 1 bagrada adult / 6 row. (3) Thus, we recommend that if you readily find 5% or more of plants with feeding signs during stand establishment, control should be initiated immediately. This can include chemigation or aerial applications with pyrethroids. Contact insecticides such as pyrethroids, Lannate, and Lorsban should be used once stands are lined out and pipe is pulled. After stands are established and plant size increases up to the 2 leaf stage, or on tagged transplants, consider alternating to dinotefuron (Venom/Scorpion) for protecting plants from bagrada feeding. This neonicotinoid will also provide knockdown of adult whiteflies and nymphs. (4) Also, growers who planted with Nipsit (clothianidin), should begin to closely monitor for fresh feeding damage around 14 days after emergence. More information on bagrada bug management on fall cole crops can be found in: Bagrada Bug Management Tips for the Low Desert.




Name the insect pest that caused the damage to this cantaloupe leaf.

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

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Plant Produced Chemicals Help Keep Diseases in Check

Certain chemicals serve as indispensable tools in the continuing effort to minimize crop losses due to plant diseases. For example, active ingredients within fungicides help growers to manage diseases caused by many plant pathogens. Although often not recognized or appreciated, various substances formed by plants and present before infection help these plants defend themselves against potential plant pathogens. The level of defense can range from various levels of resistance up to outright immunity. Numerous chemical substances are present on the surfaces of plant parts such as leaves, stems, fruit, seeds and roots. Chemicals with antimicrobial properties include phenolic compounds, tannins and fatty-acid like materials. Experiments have shown that some of these compounds have an inhibitory action on certain plant pathogens. As an example, toxic exudates on leaves of a specific variety of sugar beet are present at a sufficient concentration to inhibit spore germination of certain fungal pathogens. Another compound in certain types of tomato plants was shown to impart resistance to powdery mildew by inhibiting spore germination. Additionally, proteins and enzymes on plant surfaces can inactivate pathogen enzymes that are essential for disease development. These preformed compounds, together with various types of structural plant disease defenses, often are responsible for what we recognize as resistance to diseases in plants. Even if these plant derived chemical and structural disease defense systems can not totally prevent disease, they along with disease management tools applied by growers contribute to the overall level of disease suppression obtained on a particular crop.

Plant Defenses: “Roman Tomato"

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Weed Science:

Common Purslane

Common Purslane is one of the most prevalent weeds in this region and it is also included on the “ Arizona Prohibited Noxious Weed” list. Prohibited noxious weeds are those that are prohibited from entry into the state. It is probably more widespread than any other weed in Yuma County and characteristically germinates from March through November but can be found almost year round. Purslane is very prolific and the small seeds float in irrigation water, blow in the wind and reproduce vegetatively from stems that have been cut. Adventitious roots can grow from the nodes of cut stems. Stems must contain nodes or they do not survive. A trial conducted by Steve Fennimore in California demonstrated that viable seed was produced on purslane plants that were uprooted 3 weeks after germination. The number of viable seeds produced increased every week for the 6 weeks of the study. He found that one plant can produce approximately 5,000 seeds. In our trials we have found that purslane can be controlled with herbicides during ground preparation if it is small. If it gets larger than about 4” in diameter, control gets increasingly difficult. The contact herbicides are normally very effective on small purslane and do not have any residual soil activity on the crop. Most of these are PPO inhibitors and include Paraquat, Aim, Shark, Sharpen Goal, GoalTender, ET, and others. Glyphosate can also be used and does not have soil activity.

Learn how to cook purslane:

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Real IPM
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Common Purslane: A Prohibited Noxious Weed!! VIPM_Update_Vol_7_Num_18_003.png
Cartoon: Juan Peña

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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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