Spring officially arrived yesterday (Mar 20), and the produce season is quickly winding down. Lately I've been contemplating how the weather this past winter influenced pest pressure on our winter vegetables. There is no doubt that temperatures throughout Yuma County were considerably warmer this winter relative to last year, particularly during January and February. Based on my observations at the Yuma Ag Center, aphid and thrips numbers have been lower this year compared with what we typically see during this period. However, as I have noted in earlier IPM Updates, abundance of these two pests has varied throughout the region. Reports of heavy thrips pressure are still coming in from the Dome Valley / Wellton area, and a few more PCAs have indicated that they are finding Lettuce (red) aphids in late lettuce crops. Currently, thrips numbers are building exponentially on our late lettuce trials at YAC, but this is expected given our warm and dry growing conditions. Surprisingly, cabbage lopper, beet armyworm, corn earworm and diamondback moth numbers have been higher this spring than I can ever recall. This is likely a result of the warm spring nighttime temperatures, as well as the lack of sprays being needed for aphid and thrips in January and February. these condition would have provided ideal conditions for larval development and abundance. We’ve also found low numbers of adult whiteflies on late cabbage and early melons at YAC. Lack of freezing weather this winter may have increased their overwintering survival. We'll soon find out in a couple of months. Finally, I've had a number of reports of seed corn maggots attacking melons and cotton. The weather condition in general would not be considered especially conducive to maggot outbreaks, but many of the reports suggested that stand problems were found in fields where preventive insecticides were not used and the crops was planted into heavy crop residue or prepared with manure. Adult seed corn maggots are quite heavy at the YAC, but no stand problems have been noted to date. For a detailed summary of the winter weather data described above, please visit Winter Weather Conditions Yuma County.

Remember: When in Doubt-Scout.

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

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.