June 20, 2014 Tobacco Scouting & Crop Report
GENERAL CROP CONDITIONS
Scouting June 20th revealed rapid growth due to increasing temperatures and scattered rainfall that provided relief from drought stress. Growers report 0.5-3” of rainfall depending upon location. However, plant growth is still variable depending upon soil type and transplanting date. Thus, results of pest are likewise variable.
Tobacco Budworm (TBW) – Tobacco budworms were found in several fields scouted. Three fields were above threshold with two at 12% TBW and the other at 27% TBW. Size of the TBW ranged from 1/8th inch to 1 inch with most about ½ – ¾ inch. Several points are worthy of mention.
First, one of the fields with 12% TBW had approximately 30% of the plants with a visible button. When tobacco plants reach the button stage, TBW causes much less damage. Thus the TBW seldom causes significant yield loss after the tobacco plant reaches the button stage. In contrast, the other field with 12% TBW was treated with Belt® about two weeks ago and had less than 10% buttons. From a technical point of view, both fields are above threshold. However, the real issue is whether or not an infestation of 12% late TBW is worth treating this time of the year when plants are approaching button stage. Data suggest that it is not.
This particular situation demonstrates a valid concern as posted on last weeks scouting report. Simply put, preventative pesticide applications often fail, even when the pesticide has been shown to offer longer residual control, if the product is not directly applied to cover the entire plant. Too, as noted in the post, there are many variables that determine the actual length of residual control. In this particular field, Belt® was properly applied when the fields exceeded a TBW threshold. It provided excellent control of TBW. However at the time of treatment there were only about 12-18 leaves on the plant. At the June 20th scouting, there were 22-26 leaves per plant. This means that the new 8-10 leaves per plant did not have any pesticide applied to them. As such, these new leaves are susceptible to insect infestation.
This field also demonstrates another important point about scouting and pests. Some of the fields scouted this season have never reached or even approached a threshold for TBW. This one particular field, for whatever reason, has continually shown to have TBW. We may never determine what makes this field more attractive than others. However, we do need to note such for future management decisions. More to the point, some areas habitually have greater insect pressure.
The image to the left shows leaf tip wilting caused by stinkbug feeding. With wheat harvest underway and increasing temperatures, stinkbugs are migrating to find food sources. Tobacco is not normally a preferred host for stinkbugs but they can be found feeding on younger leaves. If enough feeding occurs on one leaf (stinkbugs pierce the midvein of the leaf and extract plant juices from the leaf), the leaf may show signs of wilting. Furthermore, extremely high temperatures can cause leaf scorch.
While discouraging to see, seldom do stinkbugs cause enough injury to warrant treatment. The image and discussion is simply to provide information noting occurrence of this type of damage. Any producer, scout, agricultural supplier or consultant finding such damage should scout for live stinkbug adults or nymphs. If active stinkbug feeding is excessive, please contact our office for assistance in evaluation of damage.
No other insect pest were noted during scouting unless you consider the constant bombardment of deer flies a pest!
TOPPING AND SUCKER CONTROL
Two fields scouted are approaching time for a contact application with 30-37% of plants with visible buttons. One field had 57% plants with visible buttons and thus contact should be applied as soon as possible. Other fields scouted were less than 25% button stage or still small enough not to warrant evaluation.
Sucker control products are either a contact type (alcohol), systemic (such as MH) or a contact-local systemic type (flumetralin products). Various products are available with varying types of alcohol content or alcohol type or inclusion of systemic products. Make sure to read the label prior to application to understand precisely what is applied. A summary (Table 7-7. Chemical Control of Sucker Growth from the 2013 Tobacco Information) of suckercide types, rates, precautions and remarks can be download by selecting the link above.
Contact solutions should be applied when 50-60% of the plants have a visible button. Apply when the humidity is low, plants are not wilted or wet and temperatures do not exceed 90oF. (Generally between 10 am – 6 pm). It is suggested to utilize a 4% solution of a C8-C10 alcohol product followed by a 5% solution C8-C10 alcohol product 3-5 days later (or for any subsequent applications). If a C10 alcohol product is used, apply as a 3% solution. A general rule of thumb is that effective contact applications usually chemically top 5-10% of the plants. When no chemical topping is evident after the initial application, then either the product solution was too weak or the product was applied too late to be fully effective.
All applications should be made with a total volume of 50 gallons per acre using three nozzles per row (TG3-TG5-TG3) at 20-25 psi at about 2.5-3.0 mph. Note that greater speeds (6 mph) utilizing TG6-TG8-TG6 has been shown to be effective. The primary point is to apply a high enough volume directly over the row to achieve stalk rundown of the product applied. For more information on nozzle selection, speed, calibration or suckercide application, download the Tobacco Information and refer to pages 97-115.
One last important note regarding sucker control is that sucker control has been directly linked to nitrogen (N) rates. Using a base N rate of 50-80 lbs/ac (with the higher application rate only on deep, sandy soils), sucker control ranged from 80-87% when proper N rates were applied. Higher N rates (16-50 lbs/ac above recommendations) resulted in 55-66% control. The point here is that if excessive N rates were applied, do not expect good sucker control from any product.
For more information on tobacco production or current topics, visit the NCSU Tobacco Growers Information web portal at http://tobacco.ces.ncsu.edu/
Belt® is a registered product of Bayer CropScience
The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the N.C. Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conform to the product label. Be sure to examine a current product label before applying any product.