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Mar 7, 2018Pest Activity in Late Produce Crops 2018Aphids: In the past two weeks, aphid populations remained relatively low due to the cooler weather we have experienced. However, with the weather expected to increase back into the 80’s for the next 10 days, PCAs should be on the lookout for foxglove and lettuce aphids on late season lettuce. Green peach aphids remain abundant on cole crops; we can find hundreds of aphids per plant on small cabbage and broccoli at the Yuma Ag Center (YAC). Because aphid species are inherently different in their susceptibility to insecticides, the proper choice of product is important for achieving adequate control. In my lettuce trials, to date Movento, Sequoia, Sivanto, and Beleaf have provided the most consistent knockdown and residual control of green peach and foxglove aphids.
Thrips: Similarly, thrips were becoming quite abundant until the cooler weather appeared. Over the past 2 weeks thrips numbers have actually decreased in trials conducted at YAC. However, if dry conditions prevail, PCAs should expect thrips numbers to rapidly increase with the warmer weather. They should also expect thrips adults to begin migrating into late season lettuce fields from recently harvested fields. This can often make chemical control of thrips populations very difficult, particularly in March, as thrips adults may continually re-infest fields following spray applications. See the Thrips Control Chart_2018 for more information.
Corn Earworm: We have had no reports of corn earworm larvae showing up in head lettuce from local PCAs. We are also not finding CEW on head lettuce plaots at YAC, in fact it is rare to find a cabbage looper or beet armyworm. However, we did have a pheromone trap spike last week in the Yuma Valley. Since, March and April are historically the time when spring lettuce tends to be infested heaviest by earworms, PCAs should consider intensifying their scouting efforts and begin tightening their spray intervals on the last remaining head lettuce fields. For more information see Corn Earworm Management on Desert Produce.
Diamondback Moth (DBM): Compared to this time last year, DBM is almost non-existent. We can still find larvae on older cabbage at YAC, but they are very low on younger plantings. The several PCAs I have spoken to recently have reported that DBM is not an issue on spring cole crops this year. Similarly, pheromone trap catches are down, particularly over the past 2 weeks (see DBM Trap Network). If larvae do become abundant in late cabbage, based on trials conducted this fall, all the key insecticide products (including diamides) used to control DBM larvae should provide control.
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
