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

Bagrada bug seasonal activity

By John Palumbo, UA Research Scientist and Extension Specialist

It's been quite a while since we've received any calls concerning Bagrada bugs on local cole crops. In fact, we haven't seen any adults in the cabbage and broccoli plots at the Yuma Agricultural Center (YAC) since late January. This is not surprising considering the cool weather.

These observations are consistent with our experiences last spring when we didn't find our first Bagrada bug on spring cabbage until mid-April. However, last week we found a large number of Bagrada bug adults and nymphs aggregating within a small planting (0.15 ac) of untreated canola at the YAC. The canola plants are past full bloom and filling seed pods.

The bugs can be found walking within the canola on the ground and feeding damage can be found on older leaves. We presume this population is a result of adult and nymphs that migrated into the canola in December when an adjacent block of infested broccoli was disked under.

This should serve as a warning as Bagrada bugs are known to be a major pest of canola and Brassica seed crops in Pakistan and India. Pest control advisers and growers should monitor seed crops closely as the crops begin to mature.

Pay particular attention to the cracks and crevices in the soil underneath plants and in the furrow. I am not sure they will be an issue on seed crops, but there is still much we don’t know about this new pest in the desert.

Contact Palumbo: (928) 928-782-3836 or [email protected].

Gray mold

By Mike Matheron, UA Extension Plant Pathologist

As we move into the late stages of the lettuce production season in the desert southwest, the appearance of Botrytis gray mold may become more evident. The appearance of fuzzy gray growth at the base of maturing lettuce plants is a sign that the fungusBotrytis cinerea is present.

The gray growth contains vast numbers of spores dispersed in the air. This fungus can survive in the field as sclerotia in the soil, as a pathogen on many different crop and weed plants, and on crop debris.

When cool temperatures and high humidity prevail, spores landing on senescent or damaged lettuce tissue will germinate and then grow into healthy plant leaf and stem tissue which can lead to plant collapse and death.

Lettuce plants can be predisposed to infection by environmental factors including frost or heat plus by the activity of other plant pathogens, including Bremia lactucae (cause of downy mildew),Rhizoctonia solani (cause of bottom rot), and the Sclerotinia species that cause lettuce drop.

Botrytis and Sclerotinia are related fungal pathogens. Fungicides effective against one are usually active against the other. Fungicide applications are most effective when plants are young and gray mold is not yet present. The efficacy of later applications to older plants is not known.

Contact Matheron: (928) 726-6856 or [email protected].

Weed laws

By Barry Tickes, UA Area Agriculture Agent

Weeds can spread by seed, the whole plant, or plant parts including tubers or stolens. Over half of the weeds that are common agricultural pests in Arizona have been brought into the state either intentionally or unintentionally.

The Federal Noxious Weed Act was passed in 1974 and the Federal Seed Act was approved in 1939 to help control the local, state, and national movement of weeds.

Arizona has a “Regulated and Restricted Noxious Weeds” law that lists noxious weeds that are prohibited entry into Arizona. It also lists the noxious weeds that are classified as “regulated” or “restricted” and designates the restrictions for each classification. These lists are compiled by the Arizona Department of Agriculture’s Plant Services Division.

The lists included here were last updated on May 1, 2006. Please see the species of Noxious Weeds here. Arizona also has an “Arizona Seed Law” that prohibits the sale of seed containing “Restricted” or “Prohibited” noxious weed seeds. The lists that appear in the following link were compiled by the Arizona Crop Improvement Association and were updated in 2008. You can download the document Arizona Restricted Noxious Weeds Seeds here.

In addition to federal and state laws, counties sometimes quarantine certain infested crops or seeds and some form “weed districts” that raise funds to accomplish this. The Arizona Crop Improvement Association has been designated as the official seed certifying agency in Arizona.

All seed they certify has been tested and is tagged with a label that lists the percent of noxious weed seed in a batch of certified crop seed. Purchasing certified seed insures growers that they are not planting weed seed, and this practice has been very effective.

On the other hand, the lists of prohibited, regulated, and restricted noxious weeds compiled under the state noxious weed law contain many weeds common throughout the state. Weeds including common purslane, burclover, field bindweed, field and southern sandbur, and puncturevine are listed as “prohibited” but are widespread throughout the Arizona cropland.

Laws that regulate the movement of weeds are well-intentioned and can be effective but are difficult to enforce. Practices aimed at preventing weeds from moving into an area and becoming established are probably most effective on a local basis. There are practices that growers and pest control advisors can implement in an attempt to keep weeds from invading their fields.

Contact Tickes: (928) 580-9902 or [email protected].

Minimizing spray drift

By Kurt Nolte, UA Agriculture Agent

Regardless of the type of application system and cost, selecting the correct type and size of spray nozzle is essential. The nozzle determines the amount of spray applied to an area, the uniformity of the application, the coverage of the sprayed surface, and the amount of drift.

Drift can be minimized by selecting nozzles that produce a large droplet spectrum while providing adequate coverage at the intended application rate and pressure. As all nozzles develop a range of droplet sizes, those that develop the least amount of fines are least drift prone.

Although nozzles have been developed for practically every kind of spray application, only a few are commonly used in crop protection product applications.

Contact Nolte: 928-726-3904 or [email protected].