1a. Objectives (from AD-416):
1. Identify components of systems approaches that would be useful in implementation of such an approach for e.g. tomatoes based on selected scenarios when pests such as fruit flies are found to be present. 2. Quantify to the extent possible how the different components such as application of low-prevalence, or poor host status might be used to mitigate risk to an acceptable level. Determine if in-field and/or post harvest mitigations (i.e. inspection, sampling, packaging, etc) can lower infestations. Identify data gaps and provide research as needed to improve information. 3. Assess systems using probabilistic models and/or point and range estimates to quantify overall risk of establishment in the importing country.
1b. Approach (from AD-416):
Our approach will be to use tomatoes that are poor hosts of tephritid fruit flies as the crop/pest model and develop a proposed systems approach that might allow affected growers to move their product outside a quarantine area. We will establish the parameters and components of a systems approach which would mitigate the risk associated with the quarantine based on established biologically-based concepts such as low pest prevalence, poor-host status, and/or less than probit 9 regulatory treatments. Finally we will assess the system to determine if the mitigation measures as identified in the systems approach would sufficiently mitigate risk using models and data developed from this project. The specific outcomes of this project would be to provide regulatory groups and the industry with specific information on how this new risk mitigation method could work in practice.
3. Progress Report:
This is a final report for project 5320-22430-025-09R. The goal of the agreement is to develop systems approaches for crops resulting in fruit fly quarantines in the U.S., which contributes to objective 4 of the in-house project, "Assess the efficacy and quality of laboratory-reared used in SIT and natural enemies for control of fruit flies and other tropical plant pests of quarantine significance, and determine factors limiting their effectiveness". 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.