Rob Wilson, with the University of California in Tulelake, Siskiyou County, also talked of seed treatments and in-furrow treatments. He said products with Sepresto and spinosad provided superior protection against maggot damage compared to Lorsban.

Among herbicides that Wilson found effective were Goal Tender to control weed seedlings and slow growth of larger weeds at early stages in crop development, and Decathal at planting;

For thrips control, Eric Natwick, UC farm adviser in Imperial County had this advice: Don’t plant onions near small grain crops, overhead irrigation may help suppress thrips populations, control thrips before the early bulb stage, randomly sample entire onion plants by pulling leaves apart and sample at least five plants from four separate areas of a field.

Natwick said it is important to rotate pesticides with different modes of action to avoid target pests developing resistance. He said results of studies on Torac use on larvae appear to be similar to effects of Radiant.

Some insecticides may knock down populations of thrips but also take out beneficials that can lead to increased populations later, said Steve Orloff UC county director with Siskiyou County. He found Movento with Lannate to be the most effective treatments.

Orloff said researchers remain puzzled about why there is considerable year-to-year variation in the pressure from thrips.

Richard Smith, a UC farm adviser for Monterey County, said a material called Zeus shows promise for controlling nutsedge when used as a pre-emergent. He said post-emergent applications are phytotoxic to onions.

Andre Biscaro, a UC farm adviser in Los Angeles County, described a software program called CropManage that can be used to give nitrogen and watering recommendations.

He noted that onions require frequent irrigation because they have shallow root systems and high sensitivity to mild water stress. Researchers plan to monitor three onion fields this year using CropManage, which draws on data on Soil Water Tension and from the California Irrigation Management Information System (CIMIS).

Garlic rust, which caused severe damage in the 1990s in California, is still out there – perhaps in a new form. That’s the word from Steven Koike, UC farm adviser in Monterey County.

Koike said crops need to be monitored closely for disease occurrence, along with weather conditions. He said it’s possible that today’s garlic rust – which can affect onions as well as garlic – is a different strain. Earlier studies showed it did not affect leeks, but today it does. Koike is studying whether materials used to control it remain effective.

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