Northwest Plains Pest Management News Vol XI Issue 15

NWP Sorghum field nearing maturity

A fast and furious corn harvest continues, most of the area corn silage has been harvested and grain harvest
is  progressing rapidly. Reported yields have been variable but most reports have been encouraging. Some sorghum has been harvested but for the most part the area crop is just reaching physiological maturity. Harvest aid application decisions to prepare the area cotton crop for harvest are being deliberated.

At this point cotton harvest aid applications will be weather driven, as it is unlikely that significant heat unit (HU) accumulations to further develop fiber will occur. Using historical weather data from 1980-2010 only 14 total HU are expected in October (14 HU is less than one normal August day). For best results harvest aid applications should be made on warm sunny days with an extended outlook of warm conditions.

Some factors that increase the performance of harvest-aid chemicals include the following:

• Warm, calm, sunny weather
• Soil moisture relatively low but sufficient to maintain cotton plant without moisture stress
• Soil nitrogen levels relatively low
• Leaves active and uniformly expanded on plants
• Little or no secondary growth evident on plants
• Plants with a high percentage of open bolls that have shed some mature leaves

Conversely, some of the factors which negatively affect harvest-aid chemical performance include:

• Applications made under cool (below 60o F), cloudy conditions
• Prolonged periods of wet weather following treatment
• Plants in vegetative growth state with low fruit set
• Plants severely moisture stressed at time of treatment
• High soil moisture and nitrogen levels 
• Plants exhibiting secondary growth 
• Poor spray coverage

Harvest-aid product selection, tank mix partners and rates vary with environmental and crop conditions. The  “2013 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide” contains a set of tables which suggest harvest aid products based on crop and environmental conditions. The full guide can be viewed at http://goo.gl/WkxFz4

Cotton Update

The area cotton crop is extremely variable ranging from very good, to beat up but beginning to turn the corner, to just emerged due to late rains. The larger cotton is squaring, the square sets have been near 100% in observed fields. Squaring cotton should be closely monitored for square robbing pests. The cotton fleahopper can be a significant pest from 1st square to first bloom in Texas High Plains cotton.  Fleahoppers can easily disperse from wild hosts to cotton by flight.  The good news at this point is very few have been collected in local surveys sampling weeds growing in ditches and uncultivated land. Adult fleahoppers are yellowish green to almost off white and approximately 1/8 inch long with an oval flattened shaped body.  They have piercing and sucking mouthparts.  Nymphs, the immature stage, look similar to the adult but smaller and without wings.  Cotton fleahoppers, especially nymphs, have a somewhat translucent appearance.  Small black spots may also be present on the back, legs, and antennae.  Fleahoppers are very flighty and will rapidly move when disturbed. Both adult and immature cotton fleahoppers will feed on tender vegetation including terminal growth, leaf buds and small squares.  Pinhead sized squares are most vulnerable and will take on a blasted appearance 1 to 3 days after the feeding occurs.  High populations of fleahoppers may cause excessive square shed. Twenty five to thirty cotton fleahoppers per 100 plants and unacceptable square shed (90% square set during the 1st  week of squaring and 85% the 2nd week) is the established action threshold.

Adult cotton fleahopper, Monti Vandiver