It seems at the end of every fall, I make the same comment “insect pressure this
season was the most unusual and unexpected I’ve experienced in a long while”. That’s
probably because I have a short memory. But, a quick look at both recent and historic
data on pest abundance recorded from our University of Arizona research plots and
areawide sampling/trapping suggests that insect pressure this fall was historically
low for some pests, while unusually heavy for other pests compared with previous
Pest Abundance on Desert Produce and Melon Cops in 2017)
Whitefly/CYSDV: Areawide, whiteflies in fall melons were at the
lowest levels we’ve measured over the past 11 years. Accordingly, CYSDV incidence
at harvest in cantaloupe fields was the lowest we’ve seen since the virus first
showed up in 2007. The virus incidence in over 32 melon planting was very low in
most fields, but a few hot spots were observed in Roll and Wellton in fields adjacent
to cotton and alfalfa. For the most part, whiteflies were similarly light in produce
crops with an occasional flare-up in some isolated areas.
Beet armyworm, cabbage looper and corn earworm: Pretty average
worm year in Yuma. Population abundance on untreated lettuce at the YAC this fall
was lower than last year, but higher than 2015. Activity appeared to slow down dramatically
in early November, even with the warm nighttime lows we experienced. Anticipated
more activity in to December. Corn earworm was very light.
Bagrada bug: The pest was almost non-existent this year. For a
third year, they were so light in my research plots that we were not able to conduct
any efficacy trials. Bagrada abundance in the past two falls has been the lowest
we’ve observed since the invasive stink bug first showed up in 2010. Similar trends
have occurred in California, and we’re not sure why?
Thrips: The western flower thrips pressure this fall was heavy,
but the pest was not as abundant as last fall. Our fall trials showed that they
averaged over 40 / plant in the non-treated checks, which translates into significant
damage to lettuce if not controlled. Similarly, bean thrips showed again in October,
but were only about half as abundant as they were in 2016. Nonetheless these numbers
cause significant scarring to seedling plants.
Flea beetles: Beetle activity at YAC was considerably lower than
last what we experienced last fall. In fact, we had difficulty getting any decent
flea beetle studies conducted. However, had reports of sustained flea beetle movement
onto lettuce (with significant feeding damage) from alfalfa and other sources earlier
in the fall.
Diamondback moth (DBM): Well DBM was obviously not a problem for
local desert growers in 2017. Did not receive a single report of difficulty in controlling
populations. Verimark Tray drenches performed well, as did conventional chemistries
(including Coragen, pyrethroids and Lannate). Research showed that transplants were
very clean this year, whereas migratory populations of DBM accounted for most of
the in-field populations. This was consistent with areawide Pheromone trapping that
showed DBM trap captures began following storms that occurred in early September.
At YAC, the DBM larval population on direct-seed broccoli was 2-3 times higher than
we’ve previously recorded; a result of migration. Larval number still remain moderate
(6 larvae/ 10 plants) in early December. Remember: DBM is usually a spring pest
in the desert, so keep your eyes open for larvae and damage on those late cole crops
and seed crops.
Name the Insect
Brown marmorated stink bug nymphs: Halyomorpha halys
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
Areawide Diamondback Moth Trapping Network
Click here to see results of DBM pheromone trap network.
Remember, When in Doubt . . . . . “SCOUT”