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Showing posts from July, 2015

Sugarbeet crop update

Mohamed Khan, Extension Sugarbeet Specialist
Planting
In North Dakota and Minnesota, ideal planting time is in mid- to late-April so that plants can close rows by June 21 to maximize photosynthetic activity during long daylight hours for highest yields. The lack of snow and rainfall preceding and during early April resulted in growers being able to plant over 90% of their sugarbeet crop during April. However, inadequate soil moisture in many areas resulted in delayed emergence, and in some fields, uneven seedling emergence. Fortunately, several rainfall events in May and June have resulted in adequate moisture for the sugarbeet crop as well as recharging of the soil moisture content. May was relatively cool but since June 1, average daily bare soil temperature was over 55°F resulting in rapid crop growth. As such, most fields in Minnesota had a full canopy by the 4th of July.

Pest alert - Two-spotted Spider Mites in Soybeans

Bruce Potter, Bob Koch and Ken Ostlie.

In spite of the abundant rainfall and the relatively mild temperatures, some Minnesota soybean fields have populations of two-spotted spider mites (TSSM) at or near economic damaging levels and mites can be found at lower levels in others.

The downside of insurance insecticide applications for soybean aphid

by Robert Koch, Extension Entomologist; Bruce Potter, IPM Specialist; and Jeff Gunsolus, Extension Weed Scientist

For soybean aphid management, we encourage you to rely on scouting (actually getting into the field and looking at plants) and the validated economic threshold (average of 250 aphids per plant, aphids on more than 80% of plants, and aphid populations increasing) to determine when to apply insecticides for soybean aphid (see "Scouting for soybean aphid"). The threshold number of aphids is below the number required to cause yield loss and allows time to apply an insecticide before economic loss is incurred. However, you might be tempted to apply insecticides for soybean aphids at low population levels or without regard to the size of the aphid population in field, just in case you might have a problem. These "insurance" applications of insecticides can have negative impacts.

Refresher on scouting for and managing defoliating insects in soybean

by Robert Koch (Extension Entomologist), Tavvs Alves (Grad. Student), Anh Tran (Grad. Student), and Wally Rich (Junior Scientist)

As you begin scouting soybean fields for soybean aphid, you should also be on the lookout for other insect pests and the injury they can cause on the plants. One such group of additional pests is referred to as “defoliators” or “defoliating insects.” Defoliators are insects that eat the leaves of plants. In soybean, we can find a diversity of defoliators, including various beetles, caterpillars and grasshoppers.

Armyworms in Small Grains

We are receiving calls regarding armyworms in small grains in NW MN.

At this time they are small larvae (1/2"-3/4" long) and feeding in the lower foliage.  Scout for armyworms at grassy margins of the fields, low, weedy areas in fields or in lodged grain; populations are more likely to develop in these areas first.  Armyworms prefer the edges of leaves first and are messy, wasteful eaters.  They generally retreat during the day under soil and plant residue on the ground and feed more often beginning at dusk, it’s easier to scout for armyworm damage than the armyworms themselves.  Look for leaves that have been notched/cut, partially eaten leaf material on the ground, and small round pellets (armyworm frass, i.e. poop) near the base of the plants.

Consider applying insecticide if: there are 4-5 armyworm larvae per sq. ft., caterpillars are ¾ - 1 ¼ in. long, leaf feeding or head clipping is found, and parasites are not evident.  By the time armyworms are more than 1 ½ in long,…