Apple, one of the most valuable fruit crops in the USA, is attacked by many pests. The apple maggot fly (AMF), Rhagoletis pomonella, is a key insect pest in the Northeast. To control AMF, growers typically apply up to three broad-spectrum insecticide sprays to the entire orchard. Foliar sprays target the adult stage. No management options are currently available to kill larvae and pupae of AMF in the soil. Entomopathogenic nematodes (EPNs) have been evaluated as biological agents against many pests. For AMF, two EPN species, Steinernema carpocapsae and S. riobrave, are good candidates. If EPNs prove to be effective at killing the immature stages of AMF in the field, then growers would have another integrated pest management (IPM) tool, which could lead to reductions in insecticide use against AMF in support of more sustainable apple production. In this project, I will evaluate the effectiveness of S. carpocapsae and S. riobrave against the soil-dwelling stages of AMF in three commercial apple orchards. As part of my professional formation, I will be involved in outreach activities with support from UMass Extension. My outreach plan includes one fact sheet, one peer-reviewed research article, one field day at the UMass Cold Spring Orchard, and presentations at regional and national conferences. This project will inform and potentially impact the decision-making of at least 250 apple growers within and outside Massachusetts. Extension and educational outcomes will increase grower knowledge and likelihood of adoption of EPNs to control immature stages of AMF.
The research objective of this project is to evaluate the virulence of the entomopathogenic nematodes (EPN) Steinernema carpocapsae and S. riobrave in commercial apple orchards. In this research I will test each EPN at two different doses of EPN application (high = 200 Infective Juveniles (= IJs) per cm2, and low = 50 IJs per cm2), and water only as control (no EPNs).
In the previous research by Pinero et al. 2019 with plum curculio (another apple key pest), they proved that these two nematodes are highly effective to plum curculio in the apple orchard condition. Therefore, if these two nematodes show to be highly effective for apple maggot fly larvae and pupae, we kill ‘two birds with one stone’.
The purpose of my project is to evaluate two promising entomopathogenic nematode (EPN) species to control larvae and pupae of AMF, potentially leading to more sustainable management of this key apple pest. If my results are positive, growers may reduce insecticide use against AMF because they will have a low-cost biological control tool that is not currently available to control AMF.
Apple is one of the most valuable fruit crops in the USA. In fact, the most recent data in the US value of utilized non-citrus production apple place in the second in the nation with 4.94 billion tones just after grape (USDA NASS, 2019). In New England, Massachusetts rank first with an average value of utilized production approximately 31 million /year (USDA NASS, 2019). In eastern North America, apple maggot fly (AMF), Rhagoletis pomonella (Diptera: Tephritidae), has been ranked as a key pest of apple. If left uncontrolled, it will bring economic damage at about 30-70% or even 91% out of total production (Prokopy et al. 2003). To maintain AMF populations below economic damage, apple growers depend on applying broad-spectrum chemical pesticides to the entire orchard. Inevitably, it influences the biological community such as beneficial arthropods, including many species of predators and parasitoids that biologically suppress several pests, as well as wild pollinators such as bees and syrphid flies in the orchard ecosystem. Pesticides also influence the functioning of agricultural soils, while their leaching to surface and produce a threat for the provision of the water resource and for the functioning of aquatic systems (Putten et al. 2006).
For many years, apple growers in Massachusetts and other New England states have supported apple IPM. They are likely to adopt ecologically-based IPM tools and strategies if those options are economically feasible and effective. However, in recent years the bulk of research and extension efforts related to fruit pest management has focused on evaluating newer chemistries that could replace the use of broad-spectrum insecticides, and research aimed at developing alternative IPM methods for arthropod pest has decreased substantially. I believe research in the area of biological control of apple pests is needed. A survey of 88 commercial apple growers from Massachusetts and Rhode Island was implemented by Dr. J. C. Piñero (project advisor) in mid-April 2018. Survey results revealed that for 32% of the growers AMF is the most damaging pests in apple orchards. Most growers indicated that more IPM-oriented research is needed.
Update report: 1/15/2021
Laboratory experiment process:
I have not run laboratory experiment yet.
Field experiment process:
This is the first progress report of project titled “Evaluation of entomopathogenic nematodes for biological control of apple maggot fly in commercial apple orchards”.
For this experiment listed below, instead of two entomopathogenic nematodes, we evaluated a single species. Steinernema. riobrave (purchased from Arbico Organics).
To get apple maggot fly (AMF) larvae for the experiment, 2,500 infested fruit was collected. Fruit were placed in groups of 100 each, under each of 25 emergence cages (1 x 1 x 1 m) during the first two weeks of August (Figure 1). In September 2020, we applied infective juveniles of S. riobrave and water as control in 4 commercial apple orchards (Cold Spring Orchard and Sentinel Farm, both located in Belchertown, MA; Red Apple Farm, located in Philliston, MA; and Small Ones Farm, located in Amherst, MA). At each orchard, we established four 1m2 areas and applied S. riobrave to two areas under the apple tree. The other two areas received water. Then, we placed 35 AMF pupae on the soil (inside each of the four 1 m2 areas per orchard). To protect pupae against predators, we covered the pupae with plastic containers (Figure 2). In December 2020, we went to the orchards to collect the released pupa. The pupae recovered were transported to the laboratory in labeled containers and they were transferred to an insect-rearing chamber. The pupae are being incubated at a constant temperature and once the adult AMF emerge we will record the number of adults emerging according to treatment (Figures 3 and 4). In the spring 2021, we will apply Galleria menollella larvae to the same treated areas (16 square meters across all 4 orchards) to determine whether the EPNs survived the winter.
EPNs: Steinernema carpocapsae and S. riobrave will be purchased from Arbico Organics (https://www.arbico-organics.com/category/beneficial-nematodes). Before doing my main experiment, I will execute a preliminary laboratory experiment to verify the condition and the virulence of the two EPN species. In this process, 10 larvae of Galleria mellonella (Lepidoptera: Pyralidae), a highly sensitive host, will be exposed to S. carpocapsae and S. riobrave for 24 hours (I will have proper replications). The insect host will be purchased from Amazon. Then, the mortality rate of G. mellonella larvae will indicative of the virulent effectiveness of these two species before applying them against AMF.
Sources of AMF: The first experiment will be done at the UMass Cold Spring Orchard using infested apples with AMF scarring. Apples will be collected in unsprayed sections of orchards and in areas where abandoned trees exist. Fruit will be collected during early July of 2020.
For the second experiment (to be done at two commercial orchards), I will use a powerful lure (AMF blend) to attract AMF to specific trees. Those trees won’t be sprayed with insecticides. This will result in greater fruit infestation by wild AMF.
Field Experiments: The first study will be conducted in one unsprayed section of the UMass Cold Spring Orchard. Five treatments will be evaluated: (1) S. riobrave high dose (200 IJ cm2), (2) S. carpocapsae high dose, (3) S. riobrave low dose (50 IJ cm2), (4) S. carpocapsae low dose, and (5) control which will receive water only. Each treatment will have 5 replicates, for a total of 25 experimental units.
To get AMD larvae for the experiment, I will collect 2,500 infested fruit. Fruit will be placed in groups of 100 each, under each of 25 emergence cages (1 x 1 x 1 m see picture – taken for plum curculio research) in early or mid August.
All emergence cages will be placed under the shade of the apple tree in the row. The EPNs will be formulated according to label directions and then they will be applied according to the dosage of the specific treatment using one gallon of water per cage. To prevent emerging AMF adults from escaping, the edges of the emergence cages will be buried, and a capturing cone/device will be placed on top to capture adult AMF. The cages containing infested apples and EPNs will remain under the shade of apple tree over the winter/spring in order to be influenced and exposed to EPN. Once adult AMD start emerging, I will record the number of adults the following summer (2021).
For the second field experiment, I will use natural infestation of apples in three commercial orchards (on-farm research). Two AMF lures (purchased from Great Lakes IPM) will be placed within the canopy of 4 trees per orchard (= 12 trees total). When the fruit drop to the ground, I will count how many apples have AMF scars, and then I will separate those apples in 5 groups. Each group will receive one of the 5 EPN treatments described above. Emergence cages will be placed on top of the fruit, and the edges will be buried. This on-farm experiment will be done in cooperation with three growers, and the main objective is to show growers how this experiment is done, and the results the following year. One field day will be done in the summer of 2021 to show other growers the results of this project.
Soil moisture will be recorded at the UMass orchard on a sample of 8 cages, for 12 months. Weather (rainfall, temperature) will be recorded using a weather station that is already in place at the UMass orchard and at one of the commercial farms.
Data analysis: The numbers of AMF adults that emerged inside each cage with different treatment and control will be compared statistically using an Analysis of Variance (P = 0.05).
Education & Outreach Activities and Participation Summary
The product of this project will include the following: one fact sheet, one extension document, one peer-reviewed publication, one poster presentation at the 2021 New England Vegetable and Fruit Growers Conference (Manchester, NH), and one oral presentation in the student competition section of the annual meeting of the Entomological Society in America (Denver, CO, 2021). I will also present the results of this project at the annual Field Day of the UMass Cold Spring Orchard (Belchertown, MA). The fact sheet will discuss biological control of AMF using EPNs and it will be posted on the UMass Extension Fruit program website. My results will be properly analyzed, and one manuscript will be prepared for submission to an entomological journal. My Extension activities will be supported by UMass Extension staff, and I expect my findings to reach 250 apple growers within and outside Massachusetts.