Impact of Diamondback Moth on Arizona Cole Crops: 2017 Survey Results
In Arizona, the diamondback moth (DBM) is typically considered a minor pest that occasionally builds up to damaging levels in the winter and spring. In most years, growers can easily control the pest with 1-2 well timed insecticide sprays. However, beginning in October 2016 outbreaks of an invasive DBM population occurred throughout all vegetable growing regions in Arizona and continued throughout the remainder of the spring growing season. Cole crops that were affected included broccoli, cauliflower, cabbage, kale, mizuna/arugula, Napa cabbage, bok choy, Brussel sprouts and Brassica seed crops. It was quickly determined that the source of the DBM populations originated from infested transplants grown in local desert greenhouses. Within weeks of transplanting, PCAs and growers found that they could not adequately control the DBM infestations. To further complicate the situation, it was later discovered that the invasive DBM population was very resistant to the anthranillic diamide insecticides that are commonly used to control Lep larvae. After the first transplanted fields began to harvest in November, several growers reported that seriously infested fields suffered significant yield reductions, and incurred extremely high control costs. By late December, DBM populations began to spread from the infested transplanted fields to direct-seeded crops throughout the region, causing further losses. By February, reports of infested broccoli, cabbage and cauliflower fields were routine. The DBM infestations experienced by Arizona growers in 2016-17 were not anticipated, and the resistant population that entered the desert caused serious losses in cole crops. It has been suggested that the DBM outbreaks this year were comparable in severity to the early sweetpotato whitefly outbreaks in 1992. In an attempt to document the impact of the DBM outbreaks on Arizona cole crops, we conducted a two-part survey of growers and PCAs from Yuma and Maricopa Counties in April 2017 to (1) estimate the severity of yield losses to DBM on direct-seeded and transplanted cole crops, and (2) the intensity of chemical management required to control DBM, and associated level of control provided by each insecticide product used. To download a copy of the survey results, please go to Impact of Diamondback Moth Outbreaks on Arizona Cole Crops in 2016-17.
In Arizona, the diamondback moth (DBM) is typically considered a minor pest that occasionally builds up to damaging levels in the winter and spring. In most years, growers can easily control the pest with 1-2 well timed insecticide sprays. However, beginning in October 2016 outbreaks of an invasive DBM population occurred throughout all vegetable growing regions in Arizona and continued throughout the remainder of the spring growing season. Cole crops that were affected included broccoli, cauliflower, cabbage, kale, mizuna/arugula, Napa cabbage, bok choy, Brussel sprouts and Brassica seed crops. It was quickly determined that the source of the DBM populations originated from infested transplants grown in local desert greenhouses. Within weeks of transplanting, PCAs and growers found that they could not adequately control the DBM infestations. To further complicate the situation, it was later discovered that the invasive DBM population was very resistant to the anthranillic diamide insecticides that are commonly used to control Lep larvae. After the first transplanted fields began to harvest in November, several growers reported that seriously infested fields suffered significant yield reductions, and incurred extremely high control costs. By late December, DBM populations began to spread from the infested transplanted fields to direct-seeded crops throughout the region, causing further losses. By February, reports of infested broccoli, cabbage and cauliflower fields were routine. The DBM infestations experienced by Arizona growers in 2016-17 were not anticipated, and the resistant population that entered the desert caused serious losses in cole crops. It has been suggested that the DBM outbreaks this year were comparable in severity to the early sweetpotato whitefly outbreaks in 1992. In an attempt to document the impact of the DBM outbreaks on Arizona cole crops, we conducted a two-part survey of growers and PCAs from Yuma and Maricopa Counties in April 2017 to (1) estimate the severity of yield losses to DBM on direct-seeded and transplanted cole crops, and (2) the intensity of chemical management required to control DBM, and associated level of control provided by each insecticide product used. To download a copy of the survey results, please go toIn Arizona, the diamondback moth (DBM) is typically considered a minor pest that occasionally builds up to damaging levels in the winter and spring. In most years, growers can easily control the pest with 1-2 well timed insecticide sprays. However, beginning in October 2016 outbreaks of an invasive DBM population occurred throughout all vegetable growing regions in Arizona and continued throughout the remainder of the spring growing season. Cole crops that were affected included broccoli, cauliflower, cabbage, kale, mizuna/arugula, Napa cabbage, bok choy, Brussel sprouts andBrassicaseed crops. It was quickly determined that the source of the DBM populations originated from infested transplants grown in local desert greenhouses. Within weeks of transplanting, PCAs and growers found that they could not adequately control the DBM infestations. To further complicate the situation, it was later discovered that the invasive DBM population was very resistant to the anthranillic diamide insecticides that are commonly used to control Lep larvae. After the first transplanted fields began to harvest in November, several growers reported that seriously infested fields suffered significant yield reductions, and incurred extremely high control costs. By late December, DBM populations began to spread from the infested transplanted fields to direct-seeded crops throughout the region, causing further losses. By February, reports of infested broccoli, cabbage and cauliflower fields were routine. The DBM infestations experienced by Arizona growers in 2016-17 were not anticipated, and the resistant population that entered the desert caused serious losses in cole crops. It has been suggested that the DBM outbreaks this year were comparable in severity to the early sweetpotato whitefly outbreaks in 1992. In an attempt to document the impact of the DBM outbreaks on Arizona cole crops, we conducted a two-part survey of growers and PCAs from Yuma and Maricopa Counties in April 2017 to (1) estimate the severity of yield losses to DBM on direct-seeded and transplanted cole crops, and (2) the intensity of chemical management required to control DBM, and associated level of control provided by each insecticide product used. To download a copy of the survey results, please go to
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.
We are on the final section of virus transmission. Virus transmission by insects is one of the most efficient and economically important transmission in agriculture. When you have insects in your crops, not only you are losing your crops because of feeding/chewing by insects, a lot of insects also act as a vector of plant viruses.
Seven out of 29 orders of insect feeding on living green land plants are vectors of plant viruses.
Insect transmit viruses in 4 distinct modes:
Non persistent transmission: The insects can acquire the virus in a matter if seconds/minutes and they are immediately viruliferous. The virus in retained in the stylet of the insect and are transmitted to the next plant the insect feeds on. The virus is retained in the vector only for few minutes and is lost after insect molting. Most viruses transmitted by aphids are non persistent. So when you see few aphids in your melon field and see cucumber mosaic virus symptoms 1-2 weeks later in your field, don’t be surprised. Aphids are efficient vectors, and since viruses are systemic it takes anywhere from few days to 2-3 weeks for the plants to show symptoms. Thus it is very important to manage insects in the field even if you don’t think the ‘pressure’ is not as high.
Semi-persistent transmission: The insects can acquire the virus in minutes/hours and there is no latent (incubation) period in the insect. The virus can stay in the insects foregut for hours and is lost after insect molting. Some species of aphids and whiteflies fall in this category. Example: Cucurbit yellow stunting disorder virus in melons transmitted by whiteflies.
Persistent circulative: Insects have to feed on virus infected plants for hours/days to acquire the virus and the virus has to incubate for hours/days in the insect. After insect can transmit the virus for weeks. Virus can be present in the vectors hemolymph but there is no multiplication of virus in the insect body. Vectors in this transmission includes: Aphids, leafhopper, whiteflies, treehopper.
Example: Beet curly top virus transmission by beet leafhopper
Persistent propagative: Insects have to feed on virus infected plants for hours/days to acquire the virus and the virus has to incubate for hours/days in the insect. After insect can transmit the virus throughout its lifespan. The virus can multiply in the vector system and often times the virus particles are also passed on to the insect offspring. Tomato spotted wilt virus is transmitted on persistent propagative manner by 9 different species on thrips.
Save the Date : 2024 Plant Pathology Workshop
When: August 29th 8AM-12 PM ( breakfast and Lunch provided by Gowan Company and BASF)
Where: Yuma Ag Center, 6425 W 8th Street
What will covered: Plant Pathology program Updates, past season field trial results (we
have some exciting results to share), Q&A to help better Plant pathology program,
Industry panel discussion for all your industry related questions! See you in few weeks!
Controlling Disease and Weeds with Band-Steam – Yuma Trials Show Good Promise
In previous articles (Vol. 11 (13), Vol. 11 (20), Vol. 11(24)), I’ve discussed using band-steam to control plant diseases and weeds. Band-steaming is where steam is used to heat narrow strips of soil to temperature levels sufficient to kill soilborne pathogens and weed seed (>140 °F for > 20 minutes). The concept is showing good promise. This past season, three trials were conducted examining the efficacy of using steam for disease and weed control in Yuma, AZ. In the studies, steam was applied in a 4-inch-wide by 2-inch-deep band of soil centered on the seedline using a prototype band-steam applicator (Fig.1). The band-steam applicator is principally comprised of a 35 BHP steam generator mounted on top of an elongated bed shaper. The apparatus applies steam via shank injection and from cone shaped ports on top of the bed shaper.
Trial results were very encouraging as the prototype applicator was able to raise soil temperatures to target levels (140°F for >20 minutes) at viable travels speeds of 0.75 mph. Steam provided better than 80% weed control and significantly lowered hand weeding time by more than 2 hours per acre (Table 1). Results also showed that Fusarium colony forming units (CFU) were reduced from 2,600 in the control to 155 in the 0.75 mph and 53 in the 0.5 mph treatments, respectively (a more than 15-fold reduction). A significant difference in Fusarium wilt of lettuce disease incidence was not found, however disease infection at the field site was low (< 2%) and differences were not expected. At 0.5 mph, fuel costs were calculated to be $238/acre which was considered reasonable and consistent with the values reported by Fennimore et al. (2014).
An unexpected finding was that plants in steam treated plots appeared to be healthier and more vigorous than untreated plots (Fig. 2). This trial is still in progress and it will be interesting to see if this improved early growth translates into increases in crop yield.
In summary, early trial results are showing good promise for use of band-steam as a non-herbicidal method of pest control. We plan on conducting further trials in this multi-year study. If you are interested in evaluating the device on your farm and being part of the study please contact me. We are particularly interested in fields with a known history of Fusarium wilt of lettuce and/or Sclerotinia lettuce drop that will be planted to iceberg or romaine lettuce.
As always, if you are interested in seeing the machine operate or would like more information, please feel free to contact me.
Acknowledgements
This work is supported by Crop Protection and Pest Management grant no. 2017-70006-27273/project accession no. 1014065 from the USDA National Institute of Food and Agriculture, the Arizona Specialty Crop Block Grant Program and the Arizona Iceberg Lettuce Research Council. We greatly appreciate their support. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
A special thank you is extended to Mellon Farms for allowing us to conduct this research on their farm.
References
Fennimore, S.A., Martin, F.N., Miller, T.C., Broome, J.C., Dorn, N. and Greene, I. 2014. Evaluation of a mobile steam applicator for soil disinfestation in California strawberry. HortScience 49(12):1542-1549.
Click link below or picture to see the band-steam and co-product applicator in action!
Carryover of Vegetable Herbicides to Wheat Grown in Rotation
Almost all the herbicides used on lettuce, cole crops and melons have restrictions on how soon wheat can be planted in rotation after they have been used. Experience has demonstrated, however, that safe intervals can vary considerably based upon many factors and are almost always much longer than they need to be. The most important factors are rate applied, irrigation practices and tillage. For example, when Kerb used to be banded at 2 to 4 lbs. per acre after planting and incorporated with furrow irrigation, it was common to see treated strips across wheat fields which followed. This is uncommon now that lower rates are Chemigated. We still see some Balan injury at ends of fields or in overlaps especially when sudan is planted. Wheat it not very sensitive to Prefar and carryover injury is uncommon.
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.
To contact John Palumbo go to: jpalumbo@ag.Arizona.edu
