In cucurbits, an application of ProGibb® plant growth regulator can stimulate vine growth, boost fruit set, and help the plants withstand disease-related problems.
ProGibb can help plants survive weather stresses as well. Cucurbits are very susceptible to cool temperatures in the spring, and may respond by shedding their flowers. An application of ProGibb before flowering and just after flowering allows the plant to better maintain its growth during stress caused by chilling temperatures.
Specifically in cantaloupes and watermelons, growers can make one application of ProGibb prior to bloom followed by two additional applications at intervals of 10-14 days. On cucumbers, up to four applications may be necessary.
Because cucurbit crops may set low crops due to insufficient pollen available at bloom time, an application of ProGibb at bloom increases the number of male flowers, making more pollen available to the female flowers. This effect is particularly helpful under cool weather – and poor pollinating conditions.
The PGR ReTain® (aminoethoxyvinylglycine, or AVG) is also used on cucumber, in gynoecious breeding line seed production. Why? Some varieties of cucumber utilized in these programs do not produce male flowers, and the phenomenon has been traced to natural levels of ethylene within the plant. Using ReTain inhibits this natural development of ethylene so the plant can be freed to develop male flowers, and self pollination of the female flowers can take place.
Seed producers use this process to increase the production of desirable cucumber seed stocks. In the field, they can use ReTain in one to four applications at 250 ppm to 500 ppm of active ingredient, from the early first leaf stage through the tenth leaf stage. The rate and frequency of applications will depend on the sensitivity of the individual inbred line to ReTain. If seed producers are unsure of the sensitivity of a specific gynoecious line to ReTain, they should conduct a preliminary test on a few plants to ensure proper performance. They will want to use the appropriate skip row technique to achieve the desired sex ratio of plants.