Local Cropping Conditions

Environmental conditions continue to be dominated by exceptionally dry conditions. A few scattered showers have at least given an indication that precipitation is possible but the current situation is dire. Wide spread soaking precipitation is critical to salvage any hope for a non-irrigated spring seeded crop.

Area wheat continues to struggle due to harsh environmental conditions. Many fields were hayed, cut for silage or green chopped; which was the original plan in some cases but a salvage harvest due to freeze damage in others. Rumors of planting seed shortages have already started, it may be wise to monitor the situation closely. 

Planting operations continue at full speed in spring seeded crops, but currently in most if not all cases only irrigated fields have sufficient moisture to establish a crop. Early planted corn is up and growing . A few cotton fields have emerged while others have yet to be planted.. Sorghum planting will ramp up shortly.

Due to exceptional drought local signage has changed from "water on road" to ...

Thrips in Cotton

There are more than 5,000 species of thrips distributed worldwide.  The dominate species infesting cotton in the Northwest Plains of Texas is the western flower thrips (WFT) but onion thrips have out numbered WFT on occasion.

Thrips are relatively weak fliers but can drift long distances in the wind.  They have an extremely wide host range which includes many cultivated crops, ornamental plants and weeds.

Adult thrips (WFT) are winged slender straw colored insects 1/12 to 1/16 inch long.  The wings are fringed and held directly over the body when at rest.  Immature thrips look similar to the adult but are generally lighter in color and without wings. Thrips have rasping mouthparts which include a single mandible which the thrips uses to rupture host tissue then the exposed juices are consumed.

Adult and immature thrips on cotton.

Thrips may overwinter in several life stages including hibernating adults, larvae on winter plants or as pupae in the soil.  In early spring thrips begin reproducing on available host plants.  An adult female will live approximately 60 days during which time she will lay nearly 100 eggs.  Depending on species, reproduction may occur sexually or asexually.  The thrips life cycle progresses from egg to adult in 8 to 20 days depending on temperature.  Multiple generations are produced each year.

Both adults and immature thrips feed on leaves and in the terminal of cotton.  Leaf feeding will result in silvering of lower leaf surfaces.  Feeding on leaves which have not fully expanded will cause leaves to become distorted.  They will be cupped upward and severe infestations will cause the leaves to roll up similar to a clinched fist.  The total leaf surface area of the first 5 true leaves may be reduced as much as 50% when severe thrips pressure goes untreated.  Heavy thrips pressure may result in stunted plants, delayed fruiting and maturity, and terminal loss.  Under favorable growing conditions cotton may “outgrow” moderate thrips pressure.  Thrips damage is magnified by conditions which inhibit rapid seedling growth and development.  Cotton is generally no longer considered susceptible to thrips damage past the 5th true leaf stage.

Total thrips per plant and the presence of immatures must be obtained to make good management decisions.  A visual inspection of both upper and lower surfaces of leaves and the plant terminal of at least 10 random plants in several locations within a field should be conducted.  The total number of thrips per plant and percent immatures should be recorded.  Folded or damaged leaves must be unfurled and the terminal dissected to count hidden thrips.  Alternatively, plants can be “beaten” onto an 8 inch white paper plate or into a cup  and dislodged thrips counted.  This method is quick and easy but may not account for thrips embedded in folded leaves and the terminal.

Treatment thresholds for thrips in cotton are based on the number of thrips per plant, presence of immature thrips, and crop stage.  A suggested guideline for thrips management is one thrips per true leaf through the 5th true leaf stage.  If a residual insecticide, either soil applied, seed treatment, or foliar, application has been previously made the thrips population should contain immatures to justify a sequential foliar insecticide application.  The presence of immature thrips is an indication that the residual activity of a previously applied insecticide is beginning to break down. Under  poor growing conditions the action threshold should be reduced to 1/2 thrips/true leaf to avoid excessive damage.

Any production practice which stimulates rapid seedling growth and development will reduce cottons susceptibility to thrips damage.  In cases where thrips are a perennial pest preventative treatments, ie seed treatment insecticides are recommended.  Utilizing seed treatment insecticides will reduce the likelihood that foliar insecticide applications will be needed.  The reduction of early season foliar insecticides will conserve natural enemies as they begin to build.  A purely remedial (foliar) approach to thrips management will require intense management.  Frequent scouting and possible multiple foliar insecticide applications may be necessary to prevent undue thrips damage.  Once cotton has reached the 5th true leaf stage and is growing rapidly there is little chance that thrips feeding will impact yield.

Severe thrips damage to cotton.

2012 HPWD Winter Water Level Measurements

Winter water level measurements indicate an average decline of -1.87 feet in the groundwater levels of the Ogallala Aquifer within the 16-county High Plains Underground Water Conservation District No. 1 (HPWD) service area in 2012. This decline is 0.69 of a foot less than the -2.56 feet decline recorded during extreme drought conditions in 2011. The 10-year average change (2003-2013) was -0.89 of a foot while the five-year average change (2008-2013) was -1.40 feet. Each county in the water district had declining groundwater levels in 2012.  Locally,  groundwater levels changed -1.95 feet in Bailey County and -3.13 feet in Parmer County.

Early Season Thrips in Cotton

I have seen large numbers of thrips in wheat, which will likely move into adjacent cotton as the cotton emerges and wheat desiccates. Cotton will need to be monitored closely from emergence. The first week is critical in thrips management.

Act fast to prevent damage, insecticide applications made after visual damage occurs are too late to provide adequate protection. We are continuing to refine the thrips action threshold, which will take growing conditions into consideration  as well as the thrips numbers in the field. Insecticide applications for thrips  after the 5th true leaf are not warranted and should be avoided to protect beneficial arthropods. 

Acephate applied at emergence may be necessary if producers used no preventive insecticide seed treatments. Follow-up applications may be necessary, based on threshold (one thrips per true leaf under good growing conditions or one-half thrips per true leaf under poor growing conditions). If a preventive insecticide seed treatment is used, then subsequent insecticide application should be based on the same threshold, but the thrips population should include immature thrips, which is an indication that the seed treatment is beginning to lose effectiveness.  More drought and early season pest concerns in a Southwest Farm Press article by Ron Smith,  http://southwestfarmpress.com/cotton/drought-early-season-pests-concern-hp-cotton-experts

Heat Stress

Heat-related injuries can renderpeople helpless before they even realize they are in trouble. Depending on the severity—ranging from heat cramps, to heat exhaustion or heat stroke—heat stress may lead to a few hours or days of lost work time or to life-threatening injury. See the full story by Ron Smith, Southwest Farm Press, at http://southwestfarmpress.com/management/heat-stress-hits-quickly-may-be-deadly

Cotton Planting

Growers in areas with a short production season may want maximize the growing season by planting cotton as early as possible. Producers should plant according to soil temperature, not the calendar. If planted too early, a crop may suffer stand loss and cold temperature stress, which reduce yield potential. On the other hand, planting too late produces larger plants that are more vegetative and difficult to manage and are exposed to more late season risks. The optimum soil temperature for cotton planting is 65 degrees F at seeding depth at 8 a.m. for 3 consecutive days, with a favorable 5 day weather forecast. Temperatures of 60 degrees F are acceptable with a favorable forecast. However, planting in soils cooler than 55 degrees F will cause poor seedling vigor and seedling disease problems. It Also, consider delaying planting when the 5-day forecast predicts the accumulation of less than 25 heat units (DD 60s).

Wheat Freeze Injury

The overall wheat crop is in poor condition and has been subjected to harsh environmental conditions since the day it was seeded. Extreme to exceptional drought, high winds and extreme temperature swings have been the norm and have taken their toll on the area wheat crop.  Recently freezing temperatures have caused significant injury to area wheat; low temperatures reached potentially damaging levels on four occasions since March 25. The following table provides low temperatures in degrees F recorded at 4 local NOAA weather stations on dates where potentially damaging low temperatures occurred.

Date	Clovis	Friona	Muleshoe	MWR*
3/25	13	17	15	16
4/10	16	20**	21	23
4/19	n/a	19	20	19
4/25	15	20	20	20
*Muleshoe National Wildlife Refuge, **Mesonet data

Stem, head, and growing point damage as well as leaf burn has been observed. The following table outlines established freezing temperature injury thresholds as well as potential yield impact for wheat at current crop stages of area wheat.

Growth Stage	Temp (2 hours)	Yield Effect
Jointing	24oF	Moderate to severe
Boot	28oF	Moderate to severe
Heading	30oF	Severe

Inspection of growing points and stems are necessary to evaluate potential injury prior to heading. A normal, uninjured growing point is bright white to yellow-green and turgid; freeze injury causes it to become white or brown and water soaked in appearance. Injury to the lower stems in the form of discoloration, roughness, lesions, splitting, collapse of internodes, and enlargement of nodes frequently occurs at the jointing stage and the following stages after freezing. Severe stem injury can affect plant-water relations during the late season. Affected plants can suddenly dry down as evaporative demand exceeds the capacity of the stem to uptake water. Lodging of plants is the most serious problem following stem injury. The most apparent symptom in the heading stage is usually chlorosis or bleaching of the awns so that they are white instead of the normal green color. Freezing temperatures that injure the awns will usually kill the male flower parts.

English Grain Aphids

English grain aphids and bird cherry-oat aphids have also been observed in area small grains. Populations have ranged from low to relatively high. English grain aphids are usually green with black legs, cornicles and antennae and can be easily confused with greenbugs with out magnification.  Bird cherry-oat aphids are yellowish green to dark green to black with a reddish-orange area around the base of the cornicles. Both of these species suck plant juices while feeding but do not inject a toxin like greenbugs do. Chemical control of these aphids is rarely justified as they seldom cause yield loss but each field should be closely monitored. The aphids are normally controlled by many of the same predators and parasites that help control the greenbug.

Illustration Credit, NDSU

Greenbug Resistance to Insecticides

Greenbug resistance to registered insecticides can cause problems for small grain producers and could be carried over to greenbug management issues in sorghum. A few fields where control problems were observed have been tested using a method developed by Ed Bynum (E. D. Bynum, JR. and T. L. Archer, 2000.  Identifying Insecticide-Resistant Greenbugs (Homoptera: Aphididae) with Diagnostic Assay Tests, J. Econ. Entomol. 93(4):1286Ð1292 (2000)). This testing confirmed clorpyrophos resistant greenbugs in isolated spots.
 Surveys in 1990 in High Plains sorghum found insecticide-resistant greenbugs in most counties north of Amarillo. Resistant greenbugs will continue to develop and reproduce after an insecticide treatment; their reproductive potential is extremely high. Every effort should be made to apply insecticide only to fields where economic thresholds have been exceeded to reduce the rate of selection for insecticide- resistant greenbugs and reduced rates should not be used.

Greenbugs in Wheat

Greenbugs and greenbug mummies 

Greenbugs continue to persist in many wheat and other small grain fields. The threshold for greenbugs in wheat at this time of the growing season considering a grain value of $6.50 and a control cost of $12/acre is an average 3 greenbugs/tiller. Greenbugs suck plant juices and inject toxins into plants. These aphids are pale green, approximately 1⁄16 inch long, with a dark green stripe on their back.