Cold has effect on tobacco

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The past week could be described as a Blackberry Winter, the last (we hope) cold snap before summer. According to forecasts as of this writing (last Tuesday), next weeks temperatures are supposed to be below normal too. In addition to dampening our spring fever these temperature changes can have an effect on many things agriculture too. While livestock are not impacted by the change, crops can be depending on their stage of development.

Tobacco, being a subtropical plant, probably has the biggest potential to be affected by cool, cloudy days. There are two possible problems. One is cold weather stress that causes a constricted yellow section in leaves that were being formed in the bud area when the conditions occurred. These plants should recover but have problems with premature blooms and ground suckers.

A week of cloudy/cool weather can cause plants to set a bud prematurely. Plants that tend to be susceptible to this are plants that have six leaves or more. The low light, cool weather is similar to the approach of fall that also produces low light and cooler temperatures.

This triggers the tobacco plant to set a bud to produce seeds prior to cold winter temperatures. Once set, the bud will produce flowers on a stalk with a low number of strappy leaves. However, premature bloom might be avoided by providing some light at the right time.

A timer set to turn lights on for an hour or two can degrade the phytochrome that builds up during low light conditions. This prevents the greenhouse plants from receiving the signal to set a bud and avoids premature bloom. However, plants already set can also be induced once in the field and not much can be done.

Early blooming is different from premature bloom and has different causes. Plants will have normal leaf development, but with fewer leaves than a normal plant. Plants may top out at 14 or fewer leaves and the crop may be extremely irregular in bloom. Cool, wet soils after transplanting influence the availability of phosphorus for plant uptake. The result is shortened internodes or distance between leaves.

The first several leaves will be clustered at the bottom and will never make it to the barn. This makes the plant appear much shorter and reduces usable leaf numbers. However, cool, overcast conditions shortly after transplanting may induce blooms earlier than normal, but not as drastically as that of premature bloom.

Topping and suckering will be more difficult in such an irregular crop. Early blooming plants can be topped and treated with a fatty alcohol, Prime+ or Butralin until the rest of the crop catches up. However, in most cases once-over topping and sucker control treatment may make more economic sense, and produce the best return for the efforts made. Plants with lower leaf numbers tend to compensate by producing larger leaves

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