PPDL Picture of the Week
October 3, 2016
Wenjing Guan, Assistant Professor, Department of Horticulture and Landscape Architecture, Purdue University
Greenhouse and high tunnel grown cucumber is a high value
crop. Any kind of deformed fruit can reduce the value. Disease or insect
damages weaken plants that can cause deformed fruit, but what is often
overlooked are the other factors not related to pest problems. This article
discusses the potential reasons that may cause cucumber fruit become deformed
in protected production systems.
1. Pollination. The same as many other fruit vegetables,
insufficient pollination can cause deformed cucumbers. However, in the case of
greenhouse grown cucumbers, majority of the varieties are parthenocarpic, which
do not need pollination. Interestingly, if pollination does occur, it can also
lead to deformed fruit.
2. Temperature. Cucumbers are best grown when
temperature is above 65 °F.
Lower temperature may affect flower bud differentiation and lead to development
of curved cucumbers (Figure 1). We observed this symptom happened more often in
early seasons in a high tunnel production system.
3. Water. Cucumbers require a
large amount of water. If water supply is insufficient or ununiform, fruit expansion
rate is inconsistent that can result in poor-shaped fruit (Figure 2 and 3). We
observed the symptom happened more often during hot summer. When temperature is
high, fruit develop fast and they are more susceptible to ununiform water
4. Mechanical injury. Growth of expanded cucumbers can be inhibited by
clips, strings, stems, and tendrils. All of them may result in deformed fruit
(Figure 4). Deformed cucumbers reduce the crop value. Severely deformed fruit
should be removed as soon as possible so plant energy can be allocated to a newly
developed cucumber fruit.