Spring melon harvest is well under way and it is important to begin thinking about whitefly management in fall produce and melon crops. The first line of defense in avoiding whitefly issues in the fall produce and melon plantings is for PCAs and growers to be vigilant in their whitefly management program on cotton this summer. This is particularly important since there appears to be a large acreage of cotton being grown again this year. Before whitefly management begins in cotton however, it is important that whitefly populations be prevented from building up to large numbers in the spring melons that are currently being harvested or have recently finished. In surveying melon crops for CYSDV this spring, it became readily apparent that similar to last year, a large proportion of the spring melon acreage throughout the area was grown near cotton. In fact, our surveys show that on an area-wide basis more than 70% of the melon acreage this spring was planted either adjacent to or within a 1/4 mile of cotton (see 2011-2012 Melon CYSDV Survey). In the Gila Valley, about 84% of the melon acreage was grown adjacent to cotton, whereas in the Yuma Valley a little over 60% of the melon acreage is near cotton. Although whitefly numbers have been relatively light this spring, increased whitefly numbers have been observed over the past week in melons coinciding with higher temperatures and area-wide melon harvests. Thus, proper sanitation in spring melons is essential for avoiding unnecessary whitefly problems in cotton. It is highly recommended that melon growers quickly destroy plant residue as soon as possible following harvest. A delay in disking under melon fields following harvest can provide a large source of adult whiteflies that will readily disperse into cotton, especially when they don't need to fly very far. These whiteflies may also move into nearby weeds, many of which are hosts for the Cucurbit Yellows Stunting Disorder Virus (CYSDV). These plants also potentially extend the host-acquisition period for CYSDV. This may be important too since to date, CYSDV in spring melons incidence (albeit at non-economic levels) has been relatively high this year, particularly in the Dome Valley/ Wellton area. (see attachment).

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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.