The latest Arizona Vegetable Integrated Pest Management Update from the University of Arizona (UA) Cooperative Extension in Yuma, Ariz., released April 18, 2012.

Whitefly management on spring melons

By John Palumbo, UA Research Scientist and Extension Specialist

It’s the time of the year to start thinking about managing whitefly nymphs on spring melons. It seems within the last week whitefly adults have become increasingly abundant on melons of all sizes.

As temperatures continue to increase, feeding damage from whitefly nymphs in the next several weeks 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, pest control advisers 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 loss a foliar insecticide treatment should be applied when a threshold of two adult whiteflies per leaf is exceeded. By timing sprays based on the adult threshold, immature populations should just be starting to colonize.

Applying foliar sprays at this stage in population development has been shown to significantly reduce the chance of yield and quality losses during harvest.

This threshold applies for the insect growth regulators Courier, Knack, and Oberon; the neonicotinoids including Assail and Venom; and synergized pyrethroids.

For more information, click on these links: whitefly management, thresholds, and insecticide efficacy.

Note, CYSDV is not generally known to limit yield 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.

When practical, it is advisable to keep whitefly populations low on spring melons. This will also prevent potential dispersal in cotton later in June and July.

Remember: “When in doubt - Scout.”

Contact Palumbo: (928) 782-3836 or jpalumbo@ag.arizona.edu.