The latest Arizona Vegetable Integrated Pest Management Update from the University of Arizona (UA) Cooperative Extension in Yuma, Ariz. released June 14, 2011.

Sanitation and whitefly-CYSDV management

By John Palumbo, UA Research Scientist and Extension Specialist

With the spring melon harvest well under way, it is important to begin thinking about whitefly management in fall produce and melons crops.

The first line of defense in avoiding whitefly issues in fall plantings is for pest control advisers and growers to do a good job controlling whiteflies on cotton this summer. This may be particularly important since the cotton acreage has increased significantly this year.

However, before whitefly management begins in cotton, it is important that whitefly populations be prevented from building up to large numbers in the spring melons that are currently being harvested.

In surveying melon crops for Cucurbit Yellow Stunting Disorder Virus (CYSDV) this spring, it became readily apparent that 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 83 percent of the melon acreage this spring was grown either adjacent to or within a one-quarter mile of cotton (See Melon Survey). In the Dome Valley and Wellton, about 95 percent of the melon acreage was grown adjacent to cotton.

Although whitefly numbers have been relatively light thus far, increased whitefly numbers have been observed over the past week in melons coinciding with higher temperatures and area-wide melon harvests.

Proper sanitation in spring melons is critical to preventing unnecessary whitefly buildups 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 fields also potentially extend the host-acquisition period for CYSDV. Good news though - to date CYSDV incidence in spring melons has been relatively low this spring, and was most evident in the north Yuma Valley as shown in the 2011 Spring Melon CYSDV Survey.

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