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M.R. McDonald, M.K. Sears, T. Clarke, J. Chaput and S.A. Marshall

A new pest of leafy vegetables was responsible for considerable reductions in marketable yield of several late-season crops in the Holland/Bradford Marsh area (44°5'N, 79°35'W) of Ontario in 1999. The pea leafminer, Lyriomyza huidobrensis, was present in high populations (25/sweep) in fields of celery, Asian crucifer crops, and spinach during the months of August and September. The high populations were associated with extensive leaf mining of celery, root parsley, and edible dandelion. On other crops, including spinach and flat-flowering Chinese cabbage (Brassica chinenesis group var. utilis) damage consisted of stippling of the leaves, as a result of feeding and possibly oviposition, but no leaf mining. The stippling was extensive and rendered these crops unmarketable. An other Asian crucifer, Chinese broccoli (Brassica alboglabra) exhibited high numbers of stipples on the leaves, but very low numbers of mines. The leaves of red beets exhibited a low incidence of mines, not enough to affect yield. This is the first report of the pea leafminer affecting field vegetables in this area and causing crop losses. Pictures of the pest and symptoms of damage to the crops will be presented.

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M.D. White, D.S. Tustin, K.F. Foote, R.K. Volz, J. Stokes, J. Campbell, R. Marshall and C. Howard

ReTain™ is a plant bioregulator containing the active ingredient aminoethoxyvinylglycine (AVG), which inhibits the ethylene biosynthesis pathway. In 1997, the first efficacy studies on `Royal Gala' apple with ReTain™ were conducted under New Zealand conditions in Hawkes Bay. ReTain™ was applied 4 weeks before the anticipated start of harvest on `Royal Gala' at 850 and 1700 g·ha–1 with or without adjuvants. ReTain™ application delayed the onset of `Royal Gala' fruit maturation between 1 and 2 weeks, resulting in enhanced fruit size and fruit flesh firmness at harvest. The optimum response for delaying the onset of fruit maturation was achieved using ReTain™ at 850 g·ha–1 if applied in combination with a wetter. Fruit were also graded for fruit quality and air-stored at 0.5 °C. Fruit after 10 weeks of storage showed no difference in fruit flesh firmness, but all ReTain™ treatments had fruit with less yellow background colour compared with untreated fruit. In 1998, efficacy studies were undertaken in three geographical locations on `Royal Gala'. ReTain™ was applied at a rate of 830 g·ha–1 in combination with Silwet L-77 at 0.1%. All trees with the exception of `Royal Gala' grown in the Hawkes Bay had not received any ReTain™ previously. In all regions, seasonal changes in background color and starch pattern index were delayed by ReTain™ treatment. A concurrent delay of an increase in soluble solids concentration and retention of higher flesh firmness were also induced by ReTain™ treatment.

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B.B. Boynton, C.A. Sims, M.O. Balaban, M.R. Marshall, B.A. Welt and J.K. Brecht

Cantaloupes (Cucumis melo) in three separate trials were cut into 1-inch cubes and irradiated at 0, 0.25, 0.5, 0.75, 1.0, 1.25, or 1.5 kGy; 0, 0.1, 0.2, 0.3, 0.4, 0.5, or 0.7 kGy; and 0, 0.3, 0.6, or 0.9 kGy, respectively. They were then stored in air at 3 °C for up to 20 days, and respiration rate, measured as carbon dioxide (CO2) production, microbiological counts [total plate count (TPC) and yeast and molds], texture, and color were measured during storage. Respiration rates were initially higher in irradiated cantaloupe. After 8 days, respiration was similar between irradiated and control fruit. Irradiation moderated increases in respiration in a dose-dependent manner. Highest irradiation doses resulted in initial TPC reductions of 1.5 log compared to the non-irradiated controls, and also prevented the 2.5 to 3 log TPC increases seen in controls after 10 to 11 days of storage. Texture differed on day 1, when controls were most firm, but irradiation maintained greater firmness than controls after day 7. Irradiation of fresh-cut cantaloupe has potential for shelf life extension and for integration with modified atmosphere packaging systems.