The latest Arizona Vegetable Integrated Pest Management Update from the University of Arizona (UA) Cooperative Extension in Yuma, Ariz. released May 1, 2013.

Spider mites on melons

By John Palumbo, UA research scientist and Extension specialist

Over the last several weeks, I have received calls concerning spider mites on melons. Two spotted spider mites, Tetranychus spp, are widespread on melon crops throughout the southwestern U.S.

In general, outbreaks are more common on watermelons than other netted and mixed melon varieties. However, problems can certainly occur on all melon types.

Hot dry weather can be favorable for mite infestations. Mite populations can increase dramatically. For example, mites can mature from egg to adult in about 37 days when temperatures average about 60 degrees F. At an average temperature of 86 degrees F. it only requires 7-8 8 days to complete the lifecycle.

Several natural enemies - including predatory mites and thrips, minute pirate bugs, and lacewings - play an important role in regulating mite populations below economically damaging levels. Predators can keep mite populations in check by feeding slowly on developing mite populations.

When temperatures become hot and dry, mites can quickly out run the predator population due to rapid reproduction.

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Good irrigation and fertilization management increases plant tolerance to mites. Although economic thresholds have not been adequately established for spider mites in the low desert, treatment with an acaricide is recommended when significant webbing is found on leaves and predatory mites and thrips are absent.

Effective miticides for melons include Agri-Mek, Oberon, Acramite, Fujimite, Zeal, and sulfur. If leafminers are present in the field, Agri-Mek is a good option.

If whiteflies nymphs begin to build on older leaves, Oberon may be an effective option.

For more information on mites and their management please visit:Melon Insect Pest Management in Arizona.

Note: A thank you to those who completed the lettuce crop losses surveys and Bagrada surveys. The information will be very useful. If not completed yet, please return the survey as soon as possible.

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“Remember, when in doubt - scout.”

Contact Palumbo: (928) 782-3836 or