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.

Powdery mildew

Powdery mildew

By Mike Matheron, UA Extension Plant Pathologist

Spring is a time of transition for agriculture in the desert southwest. Cool-season crop harvest is wrapping up while spring and summer crops are planted and grown.

This is also powdery mildew season.

Powdery mildew can develop on commercial crops, including wheat, melons, and landscape plants.

It is not too early to consider management options for powdery mildew on melons. The disease generally is favored by dry weather conditions, moderate temperatures, reduced light intensity, fertile soil, and succulent plant growth.

The overall risk of powdery mildew increases as more of these factors become established in a melon field. Dry weather conditions and fertile soil are givens in desert melon production fields.

Spores of the powdery mildew pathogen, Podosphaera xanthii, can germinate to initiate disease at temperatures ranging from 72 degrees to 88 degrees Fahrenheit; optimally at about 82 degrees. These moderate temperatures, reduced light intensity, and succulent plant growth become increasingly prevalent as the melon plantings grow rapidly during April and May.

Another factor to consider when determining powdery mildew risk is the inherent susceptibility of the melon cultivar grown. The varieties known to be very susceptible to powdery mildew will require implementation of a rigorous disease management program involving applications of fungicides with differing modes of action throughout the period of high disease risk.

On the other hand, melon varieties with moderate to high levels of genetic resistance to the pathogen will require less fungicide inputs. To achieve maximum levels of disease control, powdery mildew fungicide application programs must be initiated before the visible detection of the fungus.

Less than optimal but good levels of disease control can also be achieved by waiting to begin fungicide applications until no later than the very first sign of disease in the field. These initial infection sites are often on the underside of leaves so frequent and comprehensive examination of the melon planting is required.

Contact Matheron: (928) 726-6856 or matheron@ag.arizona.edu.

Botanical classification of crops

Botanical classification of crops

By Barry Tickes, UA Area Agriculture Agent

An increasingly diverse number of minor acreage specialty crops are grown in this region every year. Managing some of these crops can be difficult without local experience.

It is helpful to know what botanical family they belong to because crops in the same family often have similar growth habits, pest problems, and fertility requirements. There are almost no pesticides registered for some of these crops because of the limited acreage. The response to pesticides is often, but not always, similar to that of other crops in the same family.

Knowing the family they are in can often give you an idea of what to expect. Kerb, for instance, is generally safe to crops in the Composite family (lettuce, artichoke, and radicchio) but is harmful to crops in the Brassica family (broccoli, cabbage, and bok choy).

Contact Tickes: (928) 580-9902 or btickes@ag.arizona.edu.

'Luigi' - the jungle bug

“Luigi” - the jungle bug

By Marco Peña, UA Research Specialist

Have you seen all life stages of the Bagrada bug?

We followed the life of a male Bagrada Bug we called ‘Luigi” starting at the egg stage. We witnessed his eclosion (hatching) at the Yuma Agricultural Center.

We also captured on video his sclerotization which is when the cuticle of an insect is hardened by chemical agents and changes in color. When Luigi became an adult we introduced him to Luciana, a beautiful Bagrada female from Holtville, Calif.

Watch the biographical account of Luigi's life in the video: Luigi, The Jungle Bug.

Contact Peña: (928) 782-3836 or marcop@ag.arizona.edu.  

CLICK HERE to check our Veg IPM Video Archive