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- Author or Editor: James E. Pollard x
A tissue macerating factor and pectinesterase activity were found in extracts from ‘McIntosh’ apple (Malus svlvestris, L.) during development of internal breakdown. Pectinesterase activity increased significantly and activity of the tissue macerating factor decreased significantly accompanying development of internal breakdown; concentrations of both remained low throughout development of the disorder. With loss of fruit firmness, fruit tissue water potential decreased as a result of decreasing solute potential and decreasing pressure potential. The first component of fruit firmness to decrease, tissue rigidity, is believed to decrease as a result of hydrolysis of intercellular pectins. The second component, cell turgor, decreased due to an increase in permeability of cell membranes to water in the later stages of development of internal breakdown. Decrease in both components of fruit firmness appear to contribute to tissue softening accompanying development of internal breakdown.
Application of 2-chloroethylphosphonic acid (ethephon) to ‘McIntosh apples’ in late August significantly increased development of anthocyanins in fruit peel, shortening the time to harvest by approximately 2 weeks. At higher rates of ethephon, treatment with succinic acid 2,2-dimethyl hydrazide (SADH) prior to ethephon applications was necessary to maintain fruit firmness. 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) contributed to excessive fruit cracking on the tree and in storage. SADH treatments were more effective than 2,4,5-T treatments in reducing accumulation of ethylene in stored fruit. Ethephon 50 ppm with SADH was more effective in producing desired fruit color, quality, and abscission characteristics than was the higher concentration of ethephon with SADH and 2,4,5-T.
The tarnished plant bug (Lvgus lineolaris) is a serious pest of strawberries in North America, causing a severe malformation of the receptacle known as “apical seediness” or “buttoning”. Light and scanning electron microscopy were used to assess tarnished plant bug feeding on strawberries and to determine the nature of the injury. During early fruit development stages (anthesis to petal fall) the primary feeding sites were developing achenes. Feeding sites on more developed fruit changed to receptacle tissue, usually close to an achene. The “buttoning” malformation of strawberries associated with tarnished plant bug is most likely a result of the destruction of achenes during early fruit development stages. Feeding on receptacle tissue later in fruit development causes more localized damage, such as creases and indentations.
Greenhouse experiments were designed to study conditions affecting strawberry malformation caused by the tarnished plant bug (TPB). Duration of blossom exposure to TPB affected the type of malformation. Exposure at anthesis for 8 hours caused visible deformity. Exposure for 48 hours caused some apical seediness, the malformation most commonly associated with TPB. Continuous exposure to TPB usually caused blossom death. Increased exposure to TPB caused a higher percentage of nonviable achenes per strawberry. Some effects appeared to be cultivar-dependent. Honeoye strawberries were less likely to show apical seediness than Redchief strawberries, but were more likely to experience blossom death. Malformation was also affected by strawberry development stage at the time of TPB feeding. Feeding at prebloom caused blossom death. Feeding at petal fall or achene seperation resulted in fruit malformation, about half of which was apical seediness. Feeding at pink receptacle stage caused little visible damage.
Over-wintering strawberry (Fragaria × ananassa Duch.) plants under row-covers applied in early Fall 1983 through 1985, and removed in spring at first bloom, significantly increased production of marketable fruit. Spunbonded rowcovers of nylon or polyester were more effective than those of slitted polyethylene. In years when winter injury affected fruit production in noncovered controls, addition of a winter-protective mulch to rowcovered treatments in early December had no effect on fruit production, compared to rowcovered treatments without winter mulch. In years when winter injury was not a factor affecting production, addition of winter mulch to rowcovers nullified the rowcover effect on production. Accumulation of degree days (base 10°C) in soil and air in rowcovered plots was significantly greater than in noncovered plots. The rowcover effects influencing fruit production appeared to occur in winter and/or spring rather than in the fall.
Succinic acid-2,2-dimethyl hydrozide (daminozide) treatment reduced both N concentration (dry wt basis) and content (mg/fruit) of ‘Mcintosh’ apple (Malus domestica Borkh.) early in the growing season. Ca concentration was higher in treated fruits at the beginning and end of the growing season but, due to fruit wt reduction by daminozide, Ca content per fruit was not significantly different. Daminozide did not influence either concentration or content of P, K, Mg, Fe, Mn, or Zn. Concentrations of all elements examined decreased during the growing season while total content per fruit increased.
Two independent studies conducted in 1986-87 and 1987-88 provided evidence that rowcover-modified microclimate can enhance yield component development in strawberry (Fragaria × ananassa Duch. cv. Earliglow). Early autumn rowcover application in 1986-87 followed by removal at bloom increased mean diurnal temperatures and degree-day accumulation in autumn and spring compared with controls without rowcovers. For rowcovered plants, leaf growth continued longer in autumn and resumed earlier in spring, and more trusses and flowers were produced. In 1987-88, increased production of marketable fruit with rowcovers occurred in the absence of an increase in flowers and appeared to be primarily due to increased development of tertiary berries.
Field experiments were conducted to determine differences in vegetative development and fruit production of Fragaria × ananassa Duch. in response to high-density planting vs. spaced-runner bed establishment, fruiting of high-density plantings in the establishment year, spring vs. summer planting of dormant crowns, and removal of stolons in excess of those required for a specific plant density. Yields did not differ significantly between spring-planted plots established exclusively with densely planted dormant crowns (11 plants per m2) and those established under a spaced-runner system using 4 stolons per mother plant to achieve the same final plant density. In spring-set, high-planting-density plots, fruit production in the planting year was low and had no effect on vegetative development or 2nd-year yields. Summer planting resulted in high mortality rates for 2 of 3 cultivars. By October, surviving summer-planted crowns had numbers of leaves and branch crowns per plant equivalent to those planted in spring. Reduced stolon production in summer plantings resulted in poor establishment of spaced-runner beds, but had no effect on dense-planted beds. Summer planting reduced yields in both high-density and spaced-runner beds compared to spring planting. Successful bed establishment in the summer is dependent on cultivar and planting density. Removal of stolons increased yields and promoted further stolon initiation in spring plantings, but had no effect on summer plantings.