Location: Southern Horticultural Research2009 Annual Report
1a. Objectives (from AD-416)
The objectives are to develop new and improved crop production practices and disease and insect control practices for ornamental, small fruit and other horticultural crops adapted to the U.S. Gulf Coast region. The developed management techniques are needed to minimize production losses and improve crop quality and yield for the purpose of increasing net income.
1b. Approach (from AD-416)
Identify and evaluate nutritional and cultural requirements, non-Apis pollination efficiency, insect pest problems, and plant disease problems to improve orchard establishment, human health benefit, crop yield, and post-harvest quality of fruit crops. Management techniques to be evaluated include planting systems, irrigation systems, fertilizer selection and timing, non-Apis bee colony establishment, suitability of bio-control organisms, pesticide selection and timing, cultivar selection, fruit handling, and post-harvest storage conditions. Identify and evaluate different organic substrates, insect pest problems, and plant disease problems to improve production options and crop quality of ornamental plants. Management techniques to be evaluated include irrigation and nutritional requirements of plants grown in different organic substrates, suitability of bio-control organisms, cultivar selection, pesticide selection and timing, pesticide application technology, disinfestant selection, and sanitation practices.
3. Progress Report
Small fruit physiology research progress determined nutraceutical components of barely ripe, fully ripe and over-ripe berries, initiated a storage study, and established a field fertigation study that is in progress. Additionally, a study utilizing composted poultry litter was initiated to determine organic and mineral fertilization on established muscadine grapes. Small fruit entomology research includes development of trap-nesting stations of the blueberry orchard bee in multiple states so adults are available for release in commercial blueberry fields, taxonomic identification of undescribed wasp species that parasitize gall midge, and improved culturing methods of lace bug so colony size and stages are available for insecticidal bioassays and screening plant resistance. Goal is to promote populations of beneficial insects, parasitoids of blueberry pests, and blueberry pollinators. Small fruit plant pathology research progress included identification of 19 Phytophthora cinnamomi isolates from blueberry roots, a method to screen blueberry resistance to Phytophthora root rot, planting of blueberry cultivars in a Phytophthora infested field, nitrogen fertilizer effects on muscadine diseases, bumble bee delivery of fungicides and biological agents to reduce blueberry flower blight, screened strawberry germplasm for resistance markers to anthracnose; and planted blackberry cultivars to evaluate rosette and orange rust tolerance. Ornamental horticulture production research progress included successful use of processed pine tree substrates for propagation and production of ornamental crops. Pine residual substrates require minimal nutrient modification to obtain plant growth comparable to pine bark. Further modification of whole pine substrates is required to increase root development of stem cuttings to levels obtained in pine bark. Commercial development, substrate availability and market costs have been discussed with potential substrate suppliers. Ornamental entomology research progress included a study at three locations evaluating media incorporated granular insecticides to control strawberry root worm (SRW) in containerized azaleas. Treatments were exposed to field populations of SRW and will be evaluated for SRW presence and damage. These treatments will be caged after one year’s exposure to evaluate efficacy of the soil incorporated insecticides. Control will include identifying sources and movement of SRW and improved application and timing of insecticides. Ornamental plant pathology research progress included finding that temperature has a greater influence than relative humidity on Rhizoctonia web blight on azalea in the nursery thus greater potential for judging when to apply a fungicide, that the pathogen can be eliminated from azalea stem cuttings used for propagation by hot water (122°F) submersion for 21 minutes, and that spore survival of a pathogen influences disinfestant usage. Control of web blight will require improvements in both fungicide timing and sanitation.
1. Effective biological control of blueberry gall midge from outside sources. Eighteen commercial blueberry farms from central to south Mississippi were surveyed for five parasitoid species that are crucial for keeping blueberry gall midge populations in check. Random arrays of 10 sticky traps per field did identify gaps in the protection afforded to farms by gall midge parasitoids. Three of the five wasp species made up about 95% of all gall midge parasitoids. However, farms having blueberry nurseries seem to lack these effective parasitoids. Our data indicate that these beneficial insects were inadvertently introduced to many Mississippi farms from an outside blueberry plant source. Farms that propagate and establish their own blueberries plants may have to introduce their own wasp populations. We have developed rearing protocols for one species of these wasps and expect to use it for augmentative biological control releases in farms with high blueberry gall midge densities.
2. Nitrogen fertilizer affects severity of anthracnose crown rot disease of strawberries. Anthracnose crown rot is a serious disease which often kills strawberries in the southern U.S. The influence of fertilizer on the severity of anthracnose crown rot was evaluated in three greenhouse studies which determined that anthracnose disease severity ratings and percent foliar nitrogen increased as nitrogen (N) fertilizer level was increased but were not influenced by phosphorus and potassium levels. In other experiments evaluating seven N sources at three levels, plants receiving 160 ppm N had higher disease severity ratings than plants receiving 0 or 40 ppm N. Among plants receiving 160 ppm N, those treated with calcium nitrate had the least disease. When N fertilizer is applied to strawberry plants as calcium nitrate, anthracnose crown rot severity should be less severe than when N is applied in ammonium forms. These results show that the form and rate of fertilizer may have a significant impact on the severity of diseases such as anthracnose crown rot of strawberry.
3. Elimination of Rhizoctonia from azalea stems used for propagation. The pathogen that causes web blight on azalea, binucleate Rhizoctonia, is carried on healthy appearing stems used to propagate next year’s crop. An ARS scientist in Poplarville, Mississippi, in cooperation with a Mississippi State University scientist developed methods that will eliminate Rhizoctonia species from azalea stems collected for propagation. Standard control approaches of dipping stems in disinfestants or fungicides were proven to be ineffective, but submerging stems in 122°C water for 21 minutes totally eliminated the pathogen from the stem with only minor damage that would not hinder rooting success. This is important for ornamental plant producers in the southeastern U.S. who grow azalea cultivars, as the pathogen annually damages about 30% of the cultivars commonly grown. This research is one component of an integrated control approach and a critical first step in minimizing the spread of this pathogen in the azalea crop. The control strategy will reduce crop damage, minimize fungicide usage, while improving crop yield potential. The same pathogen group causes similar disease problems on multiple other woody shrub genera, such as holly.
4. Control of foliar diseases in the greenhouse using hydrogen dioxide. Commercial ornamental plant producers commonly use products containing hydrogen dioxide that have an E.P.A. registration for application on plants, yet published efficacy data shows that products are ineffective. An ARS scientist in Poplarville, Mississippi, showed that hydrogen dioxide can control foliar disease in greenhouse produced ornamental crops. It was shown that hydrogen dioxide must be applied on plants a minimum of 3 to 5 times per week to prevent development of daylily rust. This information is important for ornamental plant producers since it provides knowledge about how to use an environmental friendly product to achieve disease control comparable to standard fungicide products. This research is one component of the planned development of a more comprehensive integrated control strategy, so ornamental plant producers can achieve better control of a multitude of pathogens on a range of diverse crops grown at a single facility.Marshall, D.A., Spiers, J.M. 2009. Establishment of Rabbiteye Blueberries in Poultry Litter. Acta Horticulturae. 810:723-728.