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Blueberry Maggot, Rhagoletis Mendax Curran I. Introduction

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Blueberry Maggot, Rhagoletis Mendax Curran I. Introduction Blueberry maggot, Rhagoletis mendax Curran I. Introduction: Blueberry maggot was formerly considered a race of apple maggot, R. pomonella (Marucci 1966). In some areas it is the most important pest preharvest. Was common in Canada in lowbush blueberries, but since 1960's has spread southward through most of mid-Atlantic states (Milholland & Meyer 1984). Blueberry maggot was found to be common in the southeastern U.S. by Payne & Berlocher (1995), where an important host is deerberry, Vaccinium stamineum L. To date it has not been reported as important in Virginia, but this may result from unidentified infestations. II. Biology: Pupae overwinter in the soil at a depth of 2.5-15 cm (Milholland & Meyer 1984). Development is resumed in spring. Adults emerge shortly before harvest, usually last week of May or first week of June in North Carolina, peaking in mid-June (Milholland & Meyer 1984). After a 7-10 day pre-oviposition period, females start ovipositing on large ripening berries. Larvae hatch in about 5 days, feeding in the pulp of fruit for about 2 weeks. Larvae then leave berries, enter the soil to pupate. This species is univoltine, but a small proportion of the population may remain in the soil for 2-3 years [however, Payne & Berlocher (1995) reported it to be more strictly univoltine than apple maggot]. "The highest populations...are generally associated with fields where soil moisture remains high enough throughout the summer (due to irrigation, high organic matter, or tall bushes that shade the ground) to prevent desiccation of the pupae. Pest populations also tend to increase following years when wet field conditions delay harvest and a cold winter breaks pupal diapause." (Milholland & Meyer 1984). III. Monitoring: Use sticky yellow traps with protein hydrolysate or ammonium acetate bait, at a placement rate of 2-4 traps per acre. Use of an action threshold of 3 adults per week (or 5 adults per field per week) gives lead time for control (Meyer 1986). Traps should be placed in the upper half of the canopy, halfway between the center and edge of the plant, with leaves and fruit cleared from about 8 inches of the trap. Gaul et al. (1995) reported on deployment of traps for R. mendax. The first captures were before the first blue-colored berry in 39 fields over 4 years. Seasonal captures were 1.8-fold higher when traps were protected from the wind, 1.7-fold higher when berries were < 3 m from the trap (compared with > 3 m), 4-fold higher in fields with berries compared with vegetative fields, and 3-fold higher when placed in sheltered locations. Captures were 6-fold higher in weedy sites relative to weed-free sites. Workers in Massachusetts also use red sticky spheres for blueberry maggot adults. IV. Control: Chemical control : Several pesticides are effective, including malathion, Guthion or Sevin (Meyer 1986). A short residue pesticide like malathion may be required because of proximity to harvest. Diazinon 50W (2 lb./A) or Imidan 50W (2 lb/A) are also effective. Get adequate coverage of the lower half of bushes. If ripe berries are already present, harvest before spray is applied. "Once a field reaches its treatment threshold, continue insecticide applications every 7-10 days until all unharvested fruit has dropped." (Meyer 1986). Gaul et al. (1995) reported that dimethoate reduced infestations to < 1 larva per liter of fruit when applied within 10 days of the first mature female captured. Trap captures of adults within 5 days after a pesticide application reliably predicted continued BM pressure in 20 fields with low (0-5) through high (> 20) prespray captures monitored for 2 years. Biological control : Marucci (1966) listed two braconids in eastern U.S.: Opius melleus Gahan, Opius ferrugineus Gahan. These attack larvae; in New Jersey 10-40% of maggots may be destroyed. But apparently this is not an important factor since wild berries are always heavily infested even during years of high parasitism. Host plant resistance : Early maturing varieties may escape infestation; later varieties e.g. `Blueray', `Jersey', rabbiteye types, tend to develop higher populations (Milholland & Meyer 1984). Cultural control : "If possible use a harvesting machine to harvest all remaining fruit; this eliminates oviposition sites and should reduce future populations. Following this strategy for several years will gradually allow growers to eradicate spot infestations of the blueberry maggot." (Meyer 1986)..
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