Early harvests are of primary
importance to muskmelon and honeydew growers, since the demand for
melons reaches its peak during early summer months, making grower
profits more lucrative. In order to ensure early harvests, the melons
need to be planted into the field in late winter or early spring
before last frost dates. Although research has demonstrated that
early planting of cucurbits can be achieved with transplants, plastic
mulches and rowcovers, early production of muskmelons is still limited
by cold air and soil temperatures at the time of transplanting.
Muskmelons are native to tropical and southern Africa and are very
susceptible to low temperatures. When exposed to near freezing temperatures,
cucurbits may develop symptoms of low temperature injury, consisting
of stunted growth, decreased yield, increased susceptibility to
pathogens, necrosis on the plant tissue, or the death of the plant.
In addition, melons are vulnerable to temperatures cycling between
almost freezing and optimal temperatures.
Although some research has been carried out to investigate the effects
of low temperatures on muskmelon growth, there is limited information
available on the effects of low temperatures imposed at transplanting
on muskmelon yield. In an earlier report, yield of ‘Athena’
muskmelon decreased linearly as seedlings were exposed to 2°C
with durations ranging up to 81 h. The objective in this study was
to determine the long-term effects of short-term cold stress at
transplanting on the yield of three commercially popular muskmelon
cultivars and one honeydew cultivar.
To simulate temperature alternations that may occur after field
transplanting, ‘Athena’, ‘Sugar Bowl’, ‘Eclipse’
muskmelon, and ‘Tesoro Dulce’ honeydew (C. melo) transplants
were subjected to 2 ± 1 °C (35.6 + 1.8 °F) in a walk-in
cooler and then to 29 ± 5 °C (84.2 ± 9.0 °F)
in a greenhouse before field planting. In 1998, transplants were
exposed to 2 °C for 9 to 54 hours, and for 9 to 81 hours in
1999. ‘Athena’ and ‘Sugar Bowl’ yielded
less early melons in both years, whereas ‘Eclipse’ and
‘Tesoro Dulce’ early yields were only reduced in 1999.
Total yields of ‘Athena’ decreased linearly in both
years with 10% yield reduction occurring with 12 to 21 hours of
cold stress. Total yields of ‘Sugar Bowl’ decreased
linearly in both years with 11 to 18 hours of cold stress causing
10% yield reduction in 1998 and 1999, respectively. Therefore, early
planting before last frosts of all these muskmelon and honeydew
cultivars should be done with caution since reductions in early
yields are highly probable.
