When producing Zucchini squash, ending up with deformed, unmarketable fruit is a common challenge, especially during cool, rainy conditions. In many instances, this can be attributed to inadequate pollination, which can be caused by any number of reasons. A few of them are listed here.
Male flowers had not yet started to open
In young Zucchini, anthesis of female flowers can be seven to 10 days earlier than anthesis of male flowers. During this period the absence or shortage of pollen will have a detrimental effect on pollination, resulting in abnormal fruit development, or failure to develop. This usually affects the first three to four fruits produced on a plant.
Cool, rainy weather
During periods of high rainfall, the likelihood of inadequate pollination increases, caused by several effects that low temperatures and high rainfall have on the plant and on the pollination process. Changes in rainfall patterns can alter the timing of phenological phases, and rain increases the likelihood of pollen degradation and nectar dilution. Each will have a detrimental impact on the fitness of the plant, the pollinator or both. Such weather patterns can also impose energy constraints on the plant, or mechanically damage both plant and flowers. During cool weather and high rainfall, pollinating insects such as bees are also either less active or not active at all, which will also directly impact pollination efficacy.
Damage to flowers
If flowers are damaged prior to anthesis, the chance of inadequate pollination increases. Care should therefore be taken to not damage young female flowers prior to anthesis, when harvesting fruit from the plant, and especially when unskilled labour is used.
Absence of bees
Bees play a significant role in the pollination of plants. When bees do not visit flowers, pollination will therefore not be optimal. Low frequency of visitation can be caused by several factors, for example, industrial activity and development in the area that caused a reduction in the bee population; more desirable nectar available in surrounding areas, climatic conditions causing bees to become less active; or enclosed greenhouse structures.
Male to female flower ratio
Inadequate pollination can be further aggravated when the balance between the number of available male flowers versus the available number of female flowers is not balanced. Sex expression in plants can be affected by several factors, including photoperiods, temperature and nutritional status. The ideal production temperature for Zucchini squash is between 23°C and 29°C day temperatures and 15°C to 21°C at night. Low temperatures, especially cool nights, are detrimental to male flower formation and favour female flower development. In general, under cool conditions, female flowers will form first.
Starke Ayres has a wide range of Zucchini varieties to suit every growers’ specific needs. Visit our website www.starkeayres.com or contact your representative for more information on the products available.