Location: Tropical Crop and Commodity Protection Research
Project Number: 2040-43000-018-002-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2020
End Date: Jul 31, 2022
Objective:
1. Evaluate the efficacy of ethyl formate and phosphine fumigation against different developmental stages of Bactrocera dorsalis and Anastrepha suspensa.
2. Confirm the suitability of using A. suspensa as a surrogate of B. dorsalis.
3. Evaluate the efficacy of fumigation on different developmental stages of B. dorsalis and/or A. suspensa in papaya.
4. Evaluate the impact of treatments on fruit quality.
Approach:
Objective 1: ARS-Hilo will rear B. dorsalis on artificial diet and APHIS Miami will establish an A. suspensa colony on artificial diet. ARS-Hilo and APHIS-Miami will use exactly the same experimental method, treatment conditions, and protocols for ethyl formate and phosphine fumigations except on different pests. Fumigation will be conducted in 1 cu ft. chambers at 25°C. On average 100 eggs, 1st instar larvae, 2nd instar larvae, 3rd instar larvae, or pupae transferred onto new diet will be tested for each trial. After sealing the chamber, fumigant will be introduced into the fumigation chambers using gas tight syringe at the scheduled doses. At the completion of fumigation, the fumigation chamber will be opened and aerated for 1 hr. Then the treated specimen will be moved to a growth chamber (25°C, 75% RH). Mortality of egg, larvae, or pupae will be determined by evaluating egg hatch, larval survival, and adult emergence, respectively. The fumigant concentrations in chambers will be measured using GC-FID immediately after introduction and immediately before the treatment completion.
Objective 2: ARS-Hilo and APHIS-Miami will compare treatment efficacy data from Objective 1 for B. dorsalis and A. suspensa. A. suspensa will be considered as a suitable B. dorsalis surrogate for fumigation treatment if it is equal or more tolerant to the tested fumigants than that of B. dorsalis.
Objective 3: In the case A. suspensa is a suitable surrogate for B. dorsalis, APHIS-Miami will conduct efficacy trials of ethyl formate using A. suspensa on papaya produced in Florida. In the case A. suspensa is not a suitable surrogate for B. dorsalis, ARS-Hilo will further conduct efficacy trials of ethyl formate and phosphine treatment using B. dorsalis on papaya produced from Hawaii. Fruits will be infested artificially or naturally with B. dorsalis or A. suspensa. Eggs will be allowed to develop into larval or pupal stages. Egg, larval and pupal stages of flies in fruit will be treated at the doses for 99 or 99.9% mortality calculated for the most tolerant life stages determined in Objective 1, and evaluated for the mortality as described in Objective 1.
Objective 4: Ethyl formate sorption to papaya will be calculated. Papaya will be fumigated at the doses determined to effectively control the most tolerant life stages of B. dorsalis or A. suspensa as described in Objective 1. After treatment, fruits will be stored at 10°C and its weight and color parameters of each fruit will be measured at 0, 1, 2, 3, and 4 weeks post treatment. Colors of each fruit will be measured on surface using a spectrometer for luminosity, chroma, and hue angle. A penetrometer will be used to measure the firmness of the cut surfaces of each fruit.
