The latest Arizona Vegetable Integrated Pest Management Update from the University of Arizona (UA) Cooperative Extension in Yuma, Ariz., released Sept. 21, 2011.

Insecticide pre-mixtures and insect management

By John Palumbo, UA Research Scientist and Extension Specialist

Insecticide pre-mixed products are currently available for the management of insect pests on desert vegetable and melon crops. These products offer growers and pest control advisers (PCAs) the convenience of two different active ingredients in the same formulated product.

Examples of pre-mixtures include Durivo, Vetica, and Brigadier. These pre-mix products contain combinations of active ingredients that PCAs have been using for many years (e.g., thiamethoxam, bifenthrin), as well as active ingredients recently registered (e.g., chlorantraniliprole and flubendiamide). In some cases, the pre-mixed products are available at reduced prices relative to tank mixing two individual products.

Users should consider which active ingredients are included in the ‘in-can’ mixtures, and at what rates these active ingredients are applied relative to the pre-mixed formulation. This is important.

First, the rates used for the pre-mixture should be within the recommended rates of the individual active ingredients necessary to control a particular insect(s). This may force PCAs to use high rates of the pre-mixture to achieve adequate control of multiple pests. Traditionally, this has been achieved through tank mixtures of two or more products; each at the recommended rates.

Second, although the active ingredients found in pre-mixes are of different chemical classes, one or both of the active ingredients may be the same as other products currently used in the same field.

PCAs should be careful not to inadvertently expose insect populations to the same chemical class (mode of action) by making repeated applications with products with the same mode of action. This is how insecticide resistance quickly develops.

To avoid this, be aware of the active ingredients in all products applied. For example, the pre-mixtures Durivo, Voliam Xpress, Voliam Flexi, and Vetica contain active ingredients with the same mode of action as Coragen and Synapse.

For more information on pre-mixtures, the active ingredients, and rate equivalencies, review this document: Insecticide Pre-Mixtures for AZ Vegetables and Melons.

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

Managing sclerotinia lettuce drop with fungicides

Managing sclerotinia lettuce drop with fungicides

By Mike Matheron, UA Extension Plant Pathologist

The successful management of any plant disease is achieved by focusing control efforts on one or more vulnerable stages in the disease or life cycle of the pathogen.

For lettuce drop caused by the fungi Sclerotinia minor and S. sclerotiorum, this point of attack centers on the fungal bodies called sclerotia. At crop maturity, sclerotia produced on infected plants are incorporated into the soil along with crop debris as the land is prepared for planting the next crop.

For the Sclerotinia fungi, sclerotia serve the same purpose as seeds for plants. That is they allow the organism to carry over in soil in a dormant state until conditions become favorable for germination and growth.

Over the last several years of research trials, traditional application of fungicides to the lettuce bed surface after thinning has provided at best about a 50 to 60 percent reduction in dead plants compared to plots without a fungicide treatment.

In a four-year comparison of fungicide efficacy when soil contained Sclerotinia minor, there were no statistically significant differences in disease reduction provided by the products Botran, Contans, Endura, Rovral, and Switch.

When soil contained Sclerotinia sclerotiorum, products that provided the highest and statistically equivalent levels of disease control were Contans, Endura, and Rovral.

Fungicide application to the bed surface prevents germination of sclerotia at or near the soil surface, but has little effect on sclerotia deeper in the soil profile. Ongoing research is focused on examining new chemistries and methods of application to soil with the goal of consistently increasing the level of Sclerotinia drop control above the 50 to 60 percent now achieved.

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

Vegetable herbicide registrations

Vegetable herbicide registrations

By Barry Tickes, UA Area Agriculture Agent

Few new herbicides have been registered for use on vegetables over the past 25 years. The increasing costs of pesticide development and registration combined with the high liability and relatively limited acreage of specialty vegetables are the major causes.

Efforts have instead been directed at finding new uses, application techniques, and formulations of older products.

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

Kerb: 10 years after 9/11

Kerb: 10 years after 9/11

By Marco Pena, UA research specialist

UA weed scientist and Area Agriculture Agent Barry Tickes has conducted several trials to determine the best application method of Pronamide herbicide (Kerb) in lettuce.

Tickes’ studies in 2000, one year before the 9/11event, demonstrated that when the product is applied after planting and before sprinkler irrigation in the low desert that it is often leached below weed seeds prior to germination. The result was lost efficacy.

In one experiment, Tickes stopped the sprinklers and sprayed plots with a CO2 backpack in the mud. This showed that Kerb applications should be delayed up to six days after starting sprinklers for late season plantings. This delayed application at the time required that aerial applications be made. With the terrorists attacks 10 years ago all air traffic was suspended.

PCAs asked if the product could be chemigated (sprinkler applied). Tickes conducted several trials in the Yuma area to answer this question.

Surprisingly the trials revealed that the product performed better chemigated than applied by air. Today, most Kerb in Arizona is chemigated and applied in delayed applications. This method is extensively used in California.

To review the data from this research, read Timing Kerb Applications in Lettuce and Evaluation of Kerb Applied by Sprinkler Irrigation to Lettuce both written by Tickes.

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