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

Fall Insect Activity Remains Erratic

Seems that insect pests in fall produce crops are like a box of chocolates, you never know what you’re going to get. And this year is particularly interesting. Whitefly pressure has been the lightest I’ve seen in several years. There are exceptions, particularly in areas near alfalfa and where cotton is still being defoliated. Bagrada bug has also been very light this fall, although we are now beginning to pick up a fair number in broccoli plots at the Yuma Ag Center (YAC). Not sure why the numbers are lighter this year, and why they are just now beginning to show up in numbers. I have had reports that they are also showing up in a few areas in Coachella Valley. On the flip side, flea beetle activity has been very heavy this fall and populations remain very active in some locations. At YAC, flea beetle activity remains heavy and can be found on all lettuce and cole crops of all sizes. Worm activity has been erratic this fall, but there are plenty of them around. Beet armyworm pressure was very heavy about 3 weeks ago, subsided a bit last week, and now are coming on heavy again. Egg masses can readily be found on lettuce and broccoli. Perhaps most surprising has been the unusually heavy cabbage looper pressure the past few weeks. We’re averaging 3-4 larvae /plant in many of our efficacy trials, and egg lays remain steady. Have also had reports of diamondback moth on transplants in some areas. We can only find them on low numbers on direct-seeded broccoli. The good news is that our trap counts show that corn earworm moth activity is very low -but definitely don’t forget about them as the head lettuce begins to fold in. With the warm weather expected to continue for the next week or so, I would not anticipate the worm pressure to let up much. Thrips have also been unusually active so far this fall, showing up a few earlier than normal. At the YAC, we’re picking up quite a few bean thrips (see image below) adults. The adults are heavily scarring up the plants, but can be controlled with Radiant and Lannate. It seems like they dispersed into the Yuma Valley following that low pressure system that moved through the area last week. Finally, we’ve been picking up winged-aphids in our trapping network for the past 3 weeks, a bit earlier than normal. I have observed winged cabbage aphid and cowpea aphids on lettuce, and although we’ve yet to find any green peach aphid winged adults, I observed this week a few green peach aphid nymphs colonizing broccoli at YAC. Given that cool weather and windy weather we experienced recently, this is not surprising. Crops treated with imidacloprid should prevent significant colonization on younger crops. But keep your eyes open for aphids on older cole crops, particularly where the imidacloprid residual may be declining.

Bean Thrips

NAME THAT PEST CONTEST VIPM_Update_Vol_7_Num_21_002.jpg
Purslane Sawfly

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

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Fusarium Wilt of Lettuce

On September 26th the first confirmed sample of Fusarium wilt of lettuce for the 2016-17 production season was received at the Yuma Agricultural Center Plant Disease Diagnostic Clinic. Since the first discovery of this disease in Arizona during the 2001-02 growing season, Fusarium wilt has been detected every year, usually from late September through early January. The initial visual indications of the disease are yellowing of one or more older leaves and stunting of infected plants. These symptoms are usually followed by leaf wilting and can culminate in plant death. The external root surface is not affected; however, a brown to black necrosis of the internal taproot and crown tissue will be apparent. Disease incidence can range from a few plants up to large areas or zones of infected plants within a field. Plants can become infected and display symptoms at any age, ranging from very young plants just after thinning to those ready for harvest. The symptoms of Fusarium wilt resemble two other lettuce disorders in Arizona, ammonia toxicity and the early stages of lettuce drop. To confirm disease identity, it is necessary to bring plant samples to the Plant Disease Clinic for analysis. Confirmation of disease identity is achieved by isolation and identification of the causal fungus, Fusarium oxysporum, f. sp. lactucae, from symptomatic root tissue. Disease incidence and severity are strongly affected by planting date and the type of lettuce grown. The main determinant of disease severity with respect to planting date is soil temperature. Research data demonstrate that lettuce planted in September can result in high levels of Fusarium wilt, whereas plantings in the same naturally-infested field started in mid-October or early December sustain moderately low and trace levels of disease, respectively. Of many crisphead and romaine varieties tested, crisphead varieties generally are significantly more susceptible to Fusarium wilt compared to romaine lettuce. There are also significant differences in susceptibility among romaine cultivars. The lettuce Fusarium wilt pathogen can survive in soil for many years, so minimizing the spread of infested soil both within and especially between fields is of paramount importance. Two field trials have been established this year in early September within growers’ fields to evaluate some current lettuce varieties, experimental lines, fungicides and biofungicides for potential efficacy in managing Fusarium wilt of lettuce. The objectives of these studies are to find promising genetic resistance or tolerance to Fusarium wilt within one or more tested lettuce varieties as well as to identify products that can help reduce the incidence and severity of the disease. For more information about Fusarium wilt of lettuce, you are invited to consult the publication entitled “Biology and Management of Fusarium Wilt of Lettuce”.

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Weed Science:

Pigweed Control in Lettuce

Pigweed is a summer annual weed that can persist into the winter and cause problems in early season lettuce. There are 4 species of pigweed here that are all common and widespread. Palmer Ameranth is probably the most common. It is very aggressive and can grow to 6 ft. in height or higher. It has distinctive white veins on the underside of the leaves. This is the one that has become resistant to glyphosate in many agricultural areas including central Arizona. Redroot pigweed is probably the second most common . It is shorter and has stiff spiny scales. The lower stems are often red in reddish Tumble pigweed is much different. It is shorter, grows low to the ground and has smaller leaves. The branches are sticky and break off when mature and tumble in the wind. Prostrate pigweed is similar to tumble pigweed but the leaves are even smaller and create mats on the ground. All of these species need to be controlled before they become well established. Of the three preemergence herbicides registered on lettuce, Prefar is the most effective and Kerb is the least effective on pigweed. Balan is between these two. Cultivation and hand weeding are the only options if these fail. Kerb is the broadest spectrum herbicide on lettuce but this is one broad leave weed that can be more effectively controlled with Prefar and Balan.

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Area wide Insect Trapping Network:

October 12, 2016

Our area-wide trapping network is up and running. The project is designed to measure the activity and movement of adult populations of a number of key pests. The project is being funded by the Arizona Iceberg Lettuce Research Council, and will hopefully provide an indication of when pest activity (e.g., corn earworm moth flights) is increasing based on pheromone/sticky trap captures. The data is not intended to indicate field infestations, as trap data is largely a reflection of adult movement. If nothing else, the data may make PCAs aware of increased pest activity in some areas and encourage intensified scouting in susceptible produce fields. The pests being monitored include: corn earworm, tobacco budworm, beet armyworm, cabbage looper using pheromone traps; aphids, thrips and whiteflies using yellow sticky traps. A total of 15 trapping locations have been established. Traps will be checked weekly and data will be made available in the bi-weekly Vegetable IPM updates. If a PCA or grower is interested in weekly counts, those can be made available by contacting us.
Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: Moth activity continues to decrease significantly in all trap locations over the past two weeks. Trap catches were very low in each trap.

Beet armyworm: Armyworm moths remain active across most locations with activity greatest Wellton and Tacna.

Cabbage looper: Cabbage looper activity remains steady in many trap locations, particularly in Dome Valley, Wellton/Roll and the Yuma Valley. Trap catches were considerably higher this last week as compared to this time last season.

Whitefly: Adults captures on sticky traps increased over the past two weeks, particularly in the Yuma Valley.

Thrips: Thrips movement is still occurring in some areas; highest in Dome Valley and Wellton) and overall compared to this time last year.

Aphids: Aphid flights are much higher this fall compared to this time last season. Unusually high numbers were trapped in the North Yuma Valley last week, coinciding with the high W-NW winds.

Leafminers: Adult activity is generally low in most locations, down from 2 weeks ago.
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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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