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Whitefly populations have been present in unusually high numbers on melon crops
this spring. These large buildups are in part due to warm winter temperatures which
likely resulted in low adult mortality during the winter and increased biological
activity over the past 4-6 weeks. As temperatures continue to increase, feeding
damage from whitefly nymphs should be a concern on all melon types. Honeydew and
sooty mold contamination on fruit of cantaloupes, mixed melons and watermelons can
significantly reduce quality and marketability. Although whitefly numbers have been
low up to now, PCAs should not be complacent in their monitoring and sampling. With
the warmer weather, numbers are likely to increase rapidly in the next few weeks.
Our research has shown that to prevent melon yield and quality losses, a foliar
insecticide treatment should be applied when a threshold of 2 adult whiteflies per
leaf is exceeded. By timing sprays based on the adult threshold, immature populations
should just be starting to colonize and applying foliar sprays at this stage in
population development has been shown to significantly reduce the chance of yield
/ quality loss during harvest. This threshold applies for the IGRs (Vetica, Courier,
Knack, Oberon), and foliar applied neonicotinoids (Assail, Venom, Scorpion). (For
more information, go to these documents on
IPM and Whitefly Management,
Whitefly Action Thresholds and
Whitefly control Also, be aware of pollinators in or around melon
fields. I recommend carefully reading labels to determine the products bee safety
before applying any pesticide in melon fields, particularly when bees are foraging.
Note: Cucurbit Yellow Stunting Disorder Virus (CYSDV) is not generally known to
be yield limiting on spring melons. However, research to date suggests that fall
melons may be at greater risk of CYSDV infection when planted in areas where CYSDV
symptoms were found on late spring melons. Thus when practical, it is advisable
to keep whitefly populations low on spring melons. This will also prevent potential
dispersal in to cotton later in June and July.
Click picture to listen to John’s update To contact John Palumbo go to: jpalumbo@ag.arizona.edu |
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For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
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