Control of Bagrada Bug with Insecticides

In our last update we published a report that summarized the impact of bagrada bugs on desert cole crops over the past 3 years. That report included a summary of insecticides that PCAs found to be most efficacious against adults on fall crops. As mentioned in that report, the survey results were consistent with efficacy trials that have been conducted in small plot broccoli trials at the Yuma Ag Center over the past three years. These replicated, experimental trials followed a standardized protocol which involved 2-3 applications made during Sep and Oct as broadcast applications delivered at 25 gpa and 40 psi and applied at 5-7 day intervals. Numbers of live bagrada adults and fresh feeding signs on 20 plants per plot were recorded at 1, 3 and 5 days following each application. An example of one of those trials from 2012 is the attached report Evaluation Of Conventional Insecticides For Control Of Bagrada Hilaris On Broccoli, 2012. Since 2010 we have conducted a total of 17 efficacy trials using this experimental approach to evaluate conventional, experimental and organic-approved insecticides against bagrada bug. A summary table for all the products evaluated in these trials can be found in the attached Bagrada Treatment Matrix Table. This summary lists products based on chemistry, the number of trials in which the product was evaluated, the knockdown control at 1 day after application (DAA) and residual control at 5 DAA. Products were categorized as providing Excellent to good control, Fair to marginal control and Poor to no control. Knockdown and residual control was based on both adult counts on plants and fresh feeding signs on new growth following each spray. In general, much like the survey results, the pyrethroids provided the most consistent knockdown and residual control, followed by Venom/Scorpion, Lannate, Lorsban, Assail, Belay and Actara. None of the new experimental chemistry provided consistently Good control, and most of the organically-approved products only provided marginal knockdown. We plan to continue evaluations of new insecticides as they become available for testing.

Remember: “ When in Doubt…… Scout”

Click picture to listen to John

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

Sudden Wilt and Death of Melon Plants

Temperatures are rising, melon plantings are maturing, and sudden wilt and death of plants in some melon plantings is occurring. What is causing this sudden collapse of plants? In the desert melon production areas of Arizona and California, symptoms of melon plant wilting and collapse usually can be attributed to one of four diseases; Charcoal rot, Fusarium wilt, Monosporascus root rot and vine decline, or Pythium sudden wilt. Each of these diseases is caused by a different soil-borne plant pathogen, so knowing what management options are available first requires accurate identification of the responsible pathogen. Charcoal rot, Fusarium wilt, and Monosporascus rot, which are caused respectively by Macrophomina phaseolina, Fusarium oxysporum, and Monosporascus cannonballus, are not effectively controlled by fungicides at this time. Preventative actions that may lessen the severity of these diseases include planting resistant melon varieties when available (for Fusarium wilt) and minimizing plant stress. Plant stress due to over- or under-irrigation can be managed; however, other crop stresses due to fruit load and hot temperatures are obviously beyond your control. The other disease mentioned was Pythium sudden wilt. Pythium, the pathogen that causes this disease, is a fungus-like soil-borne organism that can be managed by fungicides, such as mefenoxam. However, the difficulty in preventing extensive Pythium sudden wilt is that once this disease is initially identified in a field, rapid deployment of an effective fungicide treatment will protect noninfected plants but may not save plants already infected but not yet displaying sudden wilt symptoms.

Click picture to listen to Mike's update

To contact Mike Matheron go to: matheron@ag.arizona.edu.

Pigweed Identification and Glyphosate Resistance

The first case of herbicide resistance in Arizona has been documented. Bill McClosky, U of A Weed Specialist, has confirmed the resistance of Palmer Amaranth to glyphosate. A series of greenhouse tests were conducted in Tucson with seed that was collected in cotton fields in the Buckeye area where pest control advisers became concerned. This resistance was confirmed in Palmer Amaranth which is the most common pigweed species in that region. Pigweeds are some of the most common summer annual broadleaf weeds in the low deserts. Although they are often lumped together, there are 4 different species of pigweed that are common here and more than 10 species that occur as weeds in California and Arizona. Their growth habits and response to herbicides are similar. It is easy to identify them by physical characteristics but one species of pigweed can hybridize with another and become less distinguishable.

Palmer Amaranth (Amaranthus palmeri) is probably the most common pigweed species found in this region. It is very aggressive and fast growing and can become 6 feet tall or higher if uncontrolled. It has one thick stem and several lateral branches. The leaves are lance shaped, hairless and have distinctive white veins on the underside. It has flowering tassels that become stiff and spiny. This species has become resistant to Glyphosate in many parts of the county.

Redroot Pigweed (Amaranthus retroflexus) is probably the second most common pigweed species. It is shorter and the seed heads are smaller, in clusters and have stiff spine-like scales. It has leaf hairs on the margins and the veins are often reddish. The lower stems are often reddish. This species will hybridize with Palmer Amaranth and become less distinguishable.

Tumble Pigweed (Amaranthus albus) is very different from Palmers or Redroot. It grows lower to the ground and has many branches that turn upright. The leaves are much smaller and narrower. The numerous stems are light green rather than red. The seed heads are small, spiny and at the base of the leaves rather than in long terminal spikes. When mature, the branches are sticky, stiff bristles that break off at the ground and tumble with the wind.

Prostrate Pigweed (Amaranthus blitoides) is very similar to Tumble Pigweed but the stems are more prostrate, grow close to the ground and form mats. The stems and leaves are smaller and reddish rather than light green.

Click picture to listen to Barry

To contact Barry Tickes go to:btickes@ag.arizona.edu.

Bug Festival 2013

This year the insect enthusiasts and members of the BugGuide (bugguide.net) community will hold their annual get together at the Santa Rita Experimental Range (SRER) in Arizona on July 25 to 28, 2013. The SRER is located in Florida Canyon in the Santa Rita Mountains, in the heart of SE Arizona, one of the most arthropod-species rich areas of the United States. Located in the juniper-oak belt of this sky island the station provides easy access Florida, Madera and Montosa Canyon and to habitats ranging from dry grasslands to high elevation mixed conifer stands. The station is part of the experimental range of the University of Arizona. U of A Professor Wendy Moore, curator of the Insect Collection of the University of Arizona (UAIC), has been promoting the local insect collection (UAIC) as a museum for the public and has made many efforts to further public interest in insects, their ecology, and their natural history. She has been instrumental in the creation of the very popular Arizona Insect Festival and is actively supporting many citizen science projects. The BugGuide Members Gathering 2013 in Arizona will be an opportunity for established BugGguide members to finally meet each other or see each other again in an environment full of opportunity to find bugs, hike, black light, get sun burned, and mostly to enjoy each other’s company. This is also a chance for local bug enthusiasts and entomologists to take part in the trips we will be organizing and to meet some interesting people. We don't have a fixed program yet but on Friday afternoon we will set up several black lights and mercury vapor lights to attract beetles, moths and more. For more information please contact Dr. Margarethe Brummermann here

To contact Ta-I go to:huang@cals.arizona.edu.

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.