Hanna Y. Hanna

The flower structure of most commercial tomato cultivars assures self-pollination and virtually eliminates the opportunity for outcrossing. Pollen is shed within the individual flowers during blooming when there is a strong enough vibrating force, such as wind, to shake the plant and the flower. In the absence of naturally occurring wind in the greenhouse, tomato flowers have to be vibrated by some mechanical means, such as electric vibrators, air blowers or bumblebees, to release the pollen.

Currently, larger greenhouse tomato producers use laboratory-reared colonies of bumblebees to pollinate the crop. In smaller operations, however, bumblebee pollination is not a good choice. At any given time, opened flowers are too few in number to supply enough pollen for the foraging bees. As a result, bees visit opened flowers repeatedly, destroying the protective anther tube (the pollenproducing parts of the flower) and damaging the pistils (the female reproductive organs).

The majority of greenhouse tomato operations in Louisiana and other southern states are small. Thus, handheld electric vibrators or air blowers may be the best pollinating tools for these operations. This study was conducted to compare the effectiveness and economics of these tools as pollinators in small greenhouse tomato operations.

Studies were conducted in a 30-foot by 96-foot double polyethylene greenhouse at the LSU AgCenter Red River Research Station in Bossier City. Tomato varieties Caruso and Trust were raised in 15-gallon polyethylene bags filled with ground pine bark. Four tomato plants were planted in each bag in two parallel rows, and 30 plants of each cultivar were grown under the same conditions for testing the effect of each method of pollination on tomato yield and fruit characteristics.

Tomato plants in the blowerpollinated treatment were vigorously vibrated on Monday, Wednesday and Friday of each week. Vibration took place around noon using an Echo P.B.- 1000 air blower. Vibration started at the beginning of blooming and continued for 13 weeks. The blower was held approximately 15 inches from the tomato plant and directed toward the flower clusters as the operator walked between the tomato rows.

Flower clusters in the electric vibrator treatment were vigorously vibrated by touching the flower stalk for about two seconds. Pollination was conducted using a Dutch-made electric vibrator on the same days and time as the blower.

Two additional greenhouses having 640 plants each were pollinated for 13 weeks by the same persons using either tool to determine pollination time. Cost of pollination by either tool was calculated based on a 13-week period at $7 per hour per person.

Tomatoes were harvested from each treatment at the pink stage three times per week for 13 weeks, and plant yield was determined. Mean fruit weight and diameter were also determined on a sample of 10 marketable fruits collected at random around mid-harvest. Seeds were extracted from the sample fruits, and the mean number of seeds per fruit was determined.

Test results indicated vibratorpollinated plants of each variety produced greater marketable yield than did blower-pollinated plants. Within varieties, marketable yield was greater and yields of culls were lower with vibrator-pollinated plants. Fruit weight and diameter and the number of seeds per fruit were greater in vibrator-pollinated plants. Marketable yield of Trust was greater in the first year, but yield for Caruso excelled in the second year.

The time needed to pollinate 640 plants for 13 weeks was 7.13 person hours using the air blower and 11.75 person hours using the electric vibrator. Labor cost for pollination was $49.92 for the air blower and $82.25 for the vibrator. The yield reduction using the air blower for pollination was not offset by the savings in labor cost.

We conclude that smaller greenhouse tomato growers should use the hand-held electric vibrators to pollinate their crop for maximum fruit yield, size and profit.

Hanna Y. Hanna, professor, Red River Research Station, Bossier City, La.

( This article was published in the winter 2005 issue of Louisiana Agriculture.)