2013 Annual Report
Evaluations to determine the susceptibility of Mediterranean fruit fly to infest tomatoes of different ripeness stages were conducted. Results of this study will be used to determine host status at different stages of ripeness. Indeterminate, Beefsteak tomatoes that were already harvested were selected for ripeness stages according to the color classification requirement standards for grades of fresh tomatoes. Laboratory reared Mediterranean fruit flies were obtained from the Pacific Basin Agricultural Research Center’s rearing facility in Hilo, Hawaii. Three ripeness stages which showed at least 30% pink or red color and three ripeness stages of green, 10% or less of pink or red and 10 but no more than 30% pink or red were tested. Tomatoes were placed in wooden, screened infestation cages together with a cohort of gravid, female fruit flies. After 24 hours the tomatoes were removed and placed individually in plastic holding buckets. Buckets were checked at 11, 14 and 18 days after infestation. Results have shown that Medflies were more likely to infest and emerge from tomatoes with 30% or more pink or red coloring. These infestation studies were conducted to determine host status for this variety of tomatoes.
Forced infestation tests were conducted on both the red and green spectrum of tomatoes. Mediterranean fruit fly pupae were obtained from the Pacific Basin Agricultural Research Center’s rearing facility in Hilo, Hawaii. Pupae were allowed to emerge in 33 cm cube screened aluminum cages and given water, sugar and protein. Cages were held in a 12:12 L/D cycle, 75° F, 65% relative humidity (RH) insect holding room. Beefsteak tomatoes were obtained from Hamakua Springs Farm on the island of Hawaii. Six tomatoes (each average weight approximately 164g) were placed in a wooden infestation cage (61cm x 41cm x 32cm) containing 60 female med flies, ages 5-10 days old. Flies were allowed to infest tomatoes for 24 hours, at 77° F and 66.3% RH with a 12:12 L/D cycle. At the end of the infestation period the tomatoes were removed and placed in individual buckets (15cm high, 14.5cm diameter). Buckets were held in a fruit screening room. Three un-infested tomatoes were held as controls. Tomatoes were checked at 11, 14 and 18 days after infestation for pupae. Pupae were held until emergence. Emerged and un-emerged pupae were recorded.
Beefsteak tomatoes were selected from the red colored spectrum according to U.S. standards color classification requirements for grades of fresh tomatoes. Pink is classified as 30% but not more than 60% shows pink or red color. Light red is classified as more than 60% but less than 90% of the surface shows pinkish-red or red color. Red is classified as more than 90% of the surface shows a red color Further studies were also conducted on susceptibility of tomatoes with 30% or less of pink or red coloring. Beefsteak tomatoes were hand-picked and selected from the green colored spectrum according to US standards color classification requirements for grades of fresh tomatoes. Green is classified as a completely green surface with varying shades of green. Breakers are classified as a definite break in color from green to yellow, with no more than 10% pink or red. Turning is classified as 10 but not more than 30% definite change in color from green to yellow, pink and red combinations. Completely green tomatoes were rarely infested by medfly. Breakers and tomatoes classified as turning had higher infestation rates by Medflies.
A total of 270 tomatoes were infested. Out of the total numbers of tomatoes infested stages for each ripeness, these were the percentages of infestation for various ripeness of tomatoes based on color: pink 78%, light red 81%, red 90%, and green 60%, breaking 56% and turning 83%. The high infestation rates are due to the forced infestation by laboratory-reared flies in a confined area. The results showed less infestation on green and breaking colored tomatoes compared to tomatoes from the red color spectrum.