Historically, our Areawide Pheromone and Sticky Trap monitoring for insects was terminated around the first of April as the produce season ended. Beginning 4 years ago however, we continued our Areawide Trapping Network throughout the summer to collect trapping data from all 15 areawide trap locations year-round.  So why is this additional trapping data useful? For several reasons: 

1) Understanding the activity of some of our key pests when produce is not grown during the summer may give us an indication of what to expect as the fall produce season begins. This may be particularly helpful for predicting moth flights and whitefly flights in August-September coinciding with early transplanting and direct seeded crops.  Another example is keeping track of corn earworm which can unexpectedly show up near the beginning of fall harvests. 
 
2) Trapping for pests during the summer has shown us that 2 of our more important produce pests are not caught in traps during the summer. We presume this is due to the absence of brassica crops and weeds for diamondback moth, and high daytime/nighttime temperatures lethal to aphids. The fact that trap catches resume in the fall supports our conclusion that these pests are absent in the summer, only to reenter the desert via winds and/or transplants in the fall. And finally, 

3) It gives me something to do in the summer other than write reports and papers. 
So, visit the Areawide Summer Trap Network if you’re curious what our key pests are up to.

Tis the season for late blight in celery! 

Late blight of celery is caused by fungi Septoria spp. The disease is named late blight as it is mostly seen at the later in the growing season, but don’t be surprised if you see the symptoms in early season when the weather is conducive. Leaf spots are dark, circular to irregular in shape, and 3-10 mm in diameter. Dark colored fruiting bodies (pycnidia) of the fungus which form in the center of leaf spots give the spots a grainy appearance. In case of severe infection, large number of spots are formed and can significantly reduce yield. Sometimes, angular spots are seen as the symptoms are restricted by leaf venation. The stalk or petiole of the plants can also be infected and large number of pycnidia observed in the stalk. Pycnidia is basically huge amounts of asexual spores in dark fruiting bodies and are formed on the older lesions and their development is encouraged by moist weather.

The pathogen is seed borne but will survive in soil in decomposing celery tissue for months. Cool and wet weathers favor the disease. Temperatures below  75 F are conducive to disease formation. High humidity allows abundant production of spores and epidemics are initiated by splashing spores or by movement of spores by contact. Rain, heavy dew or fog, and sprinkler irrigation when temperatures are above 70°F encourage disease development; splashing water disperses spores and aids in spore germination and infection

 Acquiring clean seeds is the best management practice for the disease. Hot water treatments are effective but might interfere the germination percentage. Clean cultivation, not planting new crop next to the infected crop field, crop rotation, and fungicides can be used to manage the disease.  Avoid sprinkle irrigation after symptoms are observed. Copper sprays can be used in organic farming.

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! 

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.

Results of pheromone and sticky trap catches can be viewed here.

Corn earworm: CEW moth counts down in most traps over the last week; about average for early October.

Beet armyworm: Trap counts increased in several areas last week, and about average for early October.

Cabbage looper: Cabbage looper trap counts increased in most locations, but still below average for this time of the season.

Diamondback moth: Adult activity spiked 2 weeks ago, particularly in the Yuma and Dome Valleys, but down over the past week. Average for this time of season.

Whitefly: Adult movement increasing Tacna consistent with melon harvests; overall about average for early October.

Thrips: Thrips adult movement peaked 2 weeks ago but down ovr the past week, overall activity above average.

Aphids: Winged aphids beginning to show up the north Yuma and Gila Valleys; below average for October.

Leafminers: Adult activity increased significantly last week in several locations, above average for this time of season.