The 2012 ASHS Annual Conference

Rowcovers have been used primarily to extend the growing season in temperate climates, however, in tropical and perhaps subtropical areas rowcovers have been used with other purposes. The most important benefit of rowcovers in temperate areas is the increase in temperature and protection against light freezes which enhances growth early in the season. This is particularly beneficial in vine crops such as sweetpotato and cucurbits. Spun-bonded rowcovers can be used in sweetpotato to enhance production of certified propagation material early in the spring. Similarly, rowcovers allows early harvest and higher yields in cucurbits, however, there is an additional outcome of using rowcovers. Since it does not allow pollination until it has been removed, rowcovers delay fruit set allowing the plant to grow larger and produce more female flowers by the time of rowcover removal. Consequently, the plant bears more fruits, but they may become smaller than without rowcover.  In contrast, other attributes such wind protection, insect/disease barrier, and reduced stress are more important in tropical and perhaps subtropical areas.  In the U.S. Virgin Islands, spun-bonded rowcovers are used in vegetable crops production mainly for protection against insects, but additional protection against virus transmission is taking place.  A benefit of rowcovers that has been overlooked is the role on plant–water relationships. Maximum air temperature under the rowcover can reach 45 to 50 °C in calm sunny days suggesting extreme stress, but it seems that plants are not affected. This may be explained by the fact that evapotranspiration under the rowcover is reduced significantly allowing the plant to tolerate high temperatures and grow larger. Therefore, rowcover appears to reduce water stress also providing more favorable conditions for plant growth.