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  • Author or Editor: David T. Handley x
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A light frost in a field of strawberries (cv. Redchief) resulted in varying degrees of injury to blossom receptacles. Five injury categories were established: 1. No damage; 2. Brown discoloration only at the tip of the receptacle; 3. Brown discoloration over approximately 1/2 of the receptacle; 4. Brown discoloration over the entire receptacle; 5. Black discoloration over the entire receptacle. From each category four blossoms at anthesis were tagged and allowed to develop for 30 days. Blossoms with no visible injury on the receptacle developed normally. When browning was observed on the tip of the receptacle or on approximately 1/2 of the receptacle, various deformities developed, tending to be more pronounced in the latter category. Blossoms with brown or black receptacles generally died. Thus, expression of frost injury on strawberry blossoms in the field can vary greatly.

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Frost injury on strawberry flowers (cv. Redchief) was studied in a field over two seasons. During the first season, a light frost during anthesis caused varying degrees of injury to blossoms. Five grades were assigned to the blossoms according to the degree of injury observed. The resulting fruit malformations correlated to the severity of blossom injury, ranging from no development (blossom death) when flower receptacles were completely black, to slight dimpling when only a portion of the receptacle had been discolored. During the second season, a colder frost occurring at the bud stage caused generally greater injury to the blossoms. The range of injury was less variable, therefore only three grades were assigned to the blossoms. The resulting fruit malformation again related to the intensity of blossom injury. Frost has long been understood to kill unprotected strawberry blossoms. This study has shown that nonfatal frost injury to strawberry blossoms can result in a variety of fruit malformations which previously may have been attributed to other causes.

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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.

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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.

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Six strawberry (Fragaria × ananassa Duch.) cultivars known to vary in susceptibility to tarnished plant bug (Lygus lineolaris P. de B.) injury (apical seediness) were grown under three insecticide regimes including no spray, one spray and three sprays, to determine if differences in susceptibility could be used to modify chemical controls for this insect. The most susceptible cultivars harbored more tarnished plant bug nymphs than the least susceptible cultivars. Differences in injury among cultivars was greatest when no insecticide was applied. `Honeoye' and `Sparkle' had the least amount of apical seediness, followed by `Redchief', `Guardian' and `Kent'. `Mic Mac' consistently had the highest level of injury. When insecticide sprays were reduced, apical seediness did not significantly increase for cultivars exhibiting low susceptibility.

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Three strawberry fields in Maine where surveyed to determine what level of blossom injury was caused by strawberry bud weevil; whether different orders of blossoms were effected differently; and whether injury was influenced by the location of the plants in the field. Three strawberry fields which had no insecticide applications where surveyed. A sample of 200 inflorescences where examined in four different locations in each field. The number of inflorescences in a field that had injury from strawberry bud weevil varied from 10% to 64%. Most flower clusters showing injury had one bud girdled, but many had two or more buds girdled. The tertiary and secondary order buds had the highest levels of injury, while the primary and quaternary buds had the lowest levels of injury. Location of the plants in the field did not show any obvious effects on injury levels.

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Rowcovers applied to strawberries have documented value for increased earliness and yield. The effect of rowcovers on insect damage to strawberries was investigated in this study. Nonwoven rowcovers were applied over strawberries in the fall with and without malathion to determine their effect on tarnished plant bug (Lygus lineolaris) and strawberry bud weevil (Anthomonus signatus) injury over two harvest seasons. Rowcovers increased the “umber and weight of marketable fruit. Tarnished plant bug injury was reduced by the use of rowcovers in 1990, regardless of insecticide application. I” 1991, rowcovers reduced tarnished plant bug injury only when a fall insecticide was applied. Rowcovers increased the number of flower buds killed by the strawberry bud weevil where no insecticide was used in 1990, but had no significant effect on the number of buds killed in 1991. The effect of rowcovers on insect injury to strawberries appears to depend upon the overwintering habits of the insects, and the prevailing weather patterns during a given season.

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Some Maine tomato growers use unheated greenhouses or high tunnels to extend the short growing season. But, what varieties should growers choose? The objective of this trial was to test varieties of greenhouse and open field tomatoes to identify the best performers in high tunnels in terms of yield, quality, disease, and taste. Results showed that both open field and greenhouse varieties produced similar and acceptable yields of high quality marketable fruit. Open field varieties showed more disease than greenhouse varieties. There were some significant differences between individual varieties. Betterboy scored highest in sensory analysis, but lowest in yield/quality. Brilliante scored poorly on marketable yields, but well in terms of premium yields, quality, disease and taste. It may be well suited for direct marketing to repeat customers (e.g., farmers' markets). For commercial production Jet Star, Brilliante, Cobra, and First Lady II appear to be good choices based on overall scores.

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