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David T. Handley

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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David T. Handley

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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David T. Handley and James E. Pollard

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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Mark G. Hutton and David T. Handley

Twenty-seven green bell pepper (Capsicum annuum) cultivars were evaluated over three growing seasons in Maine. Each year, plants started in a greenhouse were transplanted into double rows on raised beds covered with black plastic mulch. Overall yields were low compared with similar experiments in other regions of North America and varied considerably from year to year. ‘Ace’ and ‘New Ace’ consistently produced the largest crops by both weight and number of fruit. However, both of these cultivars had undesirable characteristics of small fruit size (<150 g), few lobes (two-three), and thin fruit walls (<6 mm), limiting their commercial market potential. Other cultivars, including ‘Vivaldi’, ‘Patriot’, and ‘Socrates’, had significantly better fruit quality but very low or inconsistent yield. The results of this study demonstrate the current limitations for growing economically viable crops of bell peppers in regions such as Maine that have short growing seasons and a wide range of seasonal temperatures. Further, the data underline the need for the development of cultivars better adapted to these growing conditions.

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Mark G. Hutton and David T. Handley

Bell peppers (Capsicum annuum) are an economically important yet difficult to grow crop in northern New England. Yields of bell peppers can be increased through the use of plastic mulches; however, refinements are needed to make bell peppers a more viable crop in regions with short, variable growing seasons. The objectives of this study were to (1) compare the effects of black mulch with white inter-row much, reflective silver mulch, and standard black plastic mulched beds on bell pepper yield and quality and (2) compare the effects of two in-row plant arrangements [single rows at 12-inch within-row spacing (7260 plants/acre) and double rows spaced 18 inches apart with 18-inch in-row spacing (9680 plants/acre)] on pepper yield and quality. Treatments were factorial combinations of three mulch treatments and two within-row planting arrangements. Double rows produced more fruit by number and weight than single rows; however, fruit harvested from the double-row plots tended to be smaller than fruit harvested from the single-row plots. Mulch treatments significantly influenced total marketable yield and yield of cull bell peppers grown in Maine. The plots receiving the inter-row white mulch or reflective silver mulch treatment produced significantly greater yield than standard black plastic mulch treatment. The reflective mulch treatment produced significantly more cull fruit per acre compared with the white inter-row mulch and black plastic.

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David T. Handley and James E. Pollard

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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John J. McCue, David T. Handley and James E. Pollard

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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Tori Lee Jackson, Mark G. Hutton and David T. Handley

Corn earworm [CEW (Helicoverpa zea)] is one of the most important pests of sweet corn (Zea mays) in New England. Conventional management of this pest is achieved through repeated applications of chemical insecticides through the silking period. Organic growers, however, have few alternatives to prevent CEW infestation. Technology first developed in the 1930s and 1940s, using applications of mineral oil directly into the silk channel with an eyedropper, has been further researched in recent years using vegetable oils with and without pesticides, but pollination problems associated with these treatments have been observed. Several materials were evaluated for efficacy in controlling CEW populations and for phytotoxicity to the developing ear. Materials evaluated were corn oil, soy oil, carrageenan, corn oil mixed with Bacillus thuringiensis ssp. kurstaki (Bt), soy oil mixed with Bt, and carrageenan mixed with Bt. All treatments were compared with an untreated control. Treatments provided a range of 33% to 50% control of CEW infestation. The oil and Bt combinations provided some reduction in infestation compared with the untreated controls (33% vs. 100% infestation), but this level of control was inadequate for all wholesale markets and most direct markets. Additionally, oil-based treatments also caused significant injury to developing ears by reducing pollination quality, impacting the development of the kernels at the ear tip. This condition referred to as “cone-tip” is of concern since it may decrease marketability. The percent unmarketable ears due to cone-tips ranged from 0% to 13% for the untreated and carrageenan-based treatments. From 12% to 42% of ears were unmarketable due to the soy oil treatments. Corn oil treatments caused 10% to 50% cone-tips.

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David T. Handley, Andrew Wheeler and James F. Dill

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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Heather D. Bryant, Mark G. Hutton, David T. Handley and Mary Ellen Camire

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.