Using Insecticides to Control Whiteflies in Spring Melons (May 14, 2014)

I discussed whitefly management briefly in our last update (April 30th, Vol. 5, No. 9), but thought it might be good to revisit the topic now that daytime temperatures are consistently in the 90’s and whitefly populations have reached levels that require treatment in many fields. Several factors play a role in determining which insecticide(s) you may want to apply. If the grower applied a neonicotinoid at planting (e.g., imidacloprid) the soil residual is long gone and it is likely no longer providing control of adults and newly emerging nymphs. Thus, if whitefly population abundance is sufficiently high enough to justify control, a foliar insecticide is recommended. When nymphs can easily be found on the crown and mid-vine leaves, an IGR or IGR-like product is recommended. This would include: Vetica, Courier, Oberon, and Knack. None of these products will provide good adult knockdown, but if applied correctly, will eventually suppress adult populations by preventing the development of the nymphs within the field. Experience has shown that these products can provide 14-21 days of residual control of nymphs. Control of adults infesting plants from outside sources will require a different approach. A Vydate+bifenthrin or Danitol tank-mixture is an option, but will likely only provide adult knockdown, with limited residual control (3-5 d). Among the neonicotinoids, Assail and Venom/Scorpion have shown the most consistent residual adult control (7-10 d) in experimental trials and will also provide decent control of nymphs on treated leaves. Because neonicotinoids are used on many crops grown throughout the year be sure to consider resistance management statements on the label as well as the UA Cross-commodity Guidelines before you apply them. This brings up another factor that is important to consider – presence of pollinators in or near the field. Be sure to check the label carefully for the Environmental Hazards statement, specifically for language and restrictions on honey bee safety. In some cases, products can be used effectively and safely through application timing and rates, whereas in other cases, some products should not be used when plants are flowering and pollinators are actively working fields. You must read the label carefully. The proximity to harvest may limit your choices as well. The PHIs for whitefly products vary anywhere from 0-7 days. Also, the presence of worms near harvest may influence your choice of products. If you’re using a whitefly specific product (e.g., Courier, Oberon, Knack, Assail) you might consider adding a pyrethroid for cabbage looper control, or a Lep material (e.g., Intrepid, Coragen, Belt, Vetica) for control of both looper and armyworm. Visit these publications for information on products available for Whitefly Control on Melons and Lepidopterous larvae management