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United States Department of Agriculture

Agricultural Research Service

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The laboratory was established in 1970 to study production and protection problems of fruit and tree nut crops. It sits on a secured 1,200 acre research farm. The research staff is comprised of two interdisciplinary research teams, the "Prunus Research Team" and the "Pecan Research Team." Represented disciplines are plant breeding, tree physiology, horticulture, plant pathology, entomology, and nematology. Research problems addressed by the laboratory are national and international in scope and are focused on providing producers of Prunus and tree-nut crops with knowledge, strategies, and cultivars that enable sustainable husbandry. Research programs support the USDA-ARS national programs in Crop and Commodity Pest Biology, Control, and Quarantine, Integrated Crop Production and Protection Systems, Plant Diseases, and Methyl Bromide Alternatives. The Location is tasked with the responsibility for supplying knowledge, technology, strategies, and genetic materials to extension specialists, to other scientists, and to industry groups. Specific recommendations and extension related resources are available from extension specialists within each state.

The Location's research seeks to enhance the production, value, and safety of pecan, peach, nectarine, and plum crops; to enhance economic competitiveness of farm operations engaged in the production of these crops; and to ensure the successful contribution of these crops to the American economy.

Specific research is directed at developing:

Improved scion and rootstock cultivars for peach, nectarines, and plums

Husbandry strategies that minimize alternate bearing of pecan

Control strategies for production limiting arthropod, microbial, and nematode pests peach, pecan, and plum.

RESEARCH PROGRAMS

PECAN

ALTERNATE BEARING

A primary problem affecting U.S. pecan [Carya illinoinensis (K. Koch) Wangenh.] growers, brokers, retailers, and consumers is alternate bearing, often referred to as biennial bearing. Pecan trees naturally exhibit extreme biennial fluctuations in individual tree production and in nut quality characteristics. This fluctuation also occurs at the orchard, regional, and national level. Nearly all pecan cultivars exhibit this tendency. The instability of supply and quality causes major problems in the development of domestic and foreign markets and an attendant instability of revenue. The severity of biennial bearing is influenced by a multitude of biotic and abiotic factors that interact to influence the amount of stress experienced by trees and orchards. Research efforts focus on developing knowledge and strategies that minimize these stresses and their impact on trees to allow growers to maintain proper equilibrium between crop load and canopy photoassimilate production.

PRODUCTION LIMITING DISEASES

Pecan scab [Cladosporium caryigenum (Ell. Et Lang) Gottwald] is considered the most serious disease threat to pecan [Carya illinoinensis (K. Koch) Wangenh.)] production in the humid southeastern United States. Pecan scab control requires about nine applications of fungicide during the season beginning at bud break (early April) and continuing through mid August. The discovery by our laboratory of two new pathogens, a yet unnamed species of Phomopsis and Phytophthora cactorum (Lebert & Cohn) Schroeter, and the "rediscovery" of a third organism, Glomerella cingulata (Ston.) Spuald. & Schrenk, all of which are associated with late season fruit decline, have introduced new concerns for disease control. Recent discoveries indicating that the persistence of pecan fungicides was less than previously assumed and the curative properties were not effective under commercial conditions, have complicated the task of developing effective disease control. Thus, research efforts focus on the introduction and evaluation of new sprayer technology for fungicide application, developing knowledge of the pathogens and critical periods of susceptibility of the host, orchard management decisions to reduce tree stress, and disease control based on predicted criteria.

ARTHROPOD PESTS

Pecan [Carya illinoiensis (K. Koch) Wangenh.] production throughout the U.S. is adversely affected by certain insect and mite pests. In the southeastern U.S., the pecan weevil [Curculio caryae (Coleoptera: Curculionidae)] is the predominant pecan pest and yearly losses are substantial. Due to a scarcity of practical biological options for managing the pecan weevil, chemical options are relied upon. Chemical control of the pecan weevil and other serious nut-feeding pests leads to the destruction of natural enemies in the orchard and can result in outbreaks of foliar pests. Foliar pests, such as aphids and mites, contribute to decreased nut production across all pecan producing regions by inducing foliage to senesce early or by decreasing rates of photoassimilation. Research efforts focus on integrated pest management strategies which reduce broad-spectrum pesticide inputs while maintaining profitability to the grower. Biological control agents, cultural practices, and target-specific insecticides will be used in a comprehensive approach to pest management in pecan.

PEACH

SCION BREEDING

Peach growers need a series of varieties that are consistently productive and have commercial quality fruit to be competitive. To be productive a peach needs to bloom at the appropriate time for that area and set fruit every year. To be marketable, commercial fruit must be large, firm, red, round, and of good eating quality. Varieties must be available that ripen from mid-May until September. Varieties that are tolerant/resistant to diseases such as bacterial spot and brown rot are more economical to produce. This breeding program is designed to develop new varieties that improve on existing Southeastern peaches so that better fruit is available in the grocery store.

ROOTSTOCK BREEDING

The southeastern United States peach industry is faced with several formidable soilborne problems, chief among these are peach tree short life (PTSL), associated with the ring nematode, and Armillaria Root Rot (ARR). For the past several decades these two problems have been responsible for more than 85% of the tree deaths experienced throughout this industry. The cost of this premature tree mortality has been estimated at between $18 and $20 million in lifetime production losses each year on average. This program has identified several sources of resistance to both problems. Guardian rootstock [ Guardian Angel for Peach Trees ] was released in 1993 in cooperation with Clemson University . To date it has shown superior resistance to PTSL compared to standard commercial peach rootstocks and is now displacing these rootstocks in the commercial trade. Final evaluation of the first group of Armillaria resistant selections is approaching completion. Additionally, this program has identified rootstock candidates with a variety of commercially useful characteristics, including bloom delay (to avoid spring frosts) and dwarfing (to reduce tree management costs).

The peach shipping industry of the Lower Coastal Plain has long suffered from the lack of breeding programs specifically targeting their unique climatic requirements. As a result, current varieties fall short in both productivity and eating quality. This program (USDA, UGA and UFL cooperating) is taking a unique approach to variety development through the utilization of non-melting type germplasm normally used only in breeding programs for canning type peaches [ Pick a Perfect Peach ] . This germplasm softens much more slowly as the fruit ripens, allowing it to hang on the tree longer without compromising sufficient firmness for shipping. The end result is a substantially more mature piece of fruit with significantly improved eating quality for the consumer.

INSECTS AND MITES

Plum curculio (Conotrachelus nenuphar) continues to be the primary pest in peach orchards throughout the Southeastern U. S. and commercial control tactics rely heavily upon chemical insecticides. Additionally, other pests such as the peachtree borer (Synanthedon exitiosa), lesser peachtree borer (S. pictipes), and white peach scale (Pseudaulacaspis pentagona) are serious indirect pests that attack the trunk and scaffold limbs. Conventional control of these pests also relies upon chemical insecticides. Research efforts focus on integrated pest management strategies that target these pests. Biological (i.e., predators, parasitoids, and insect pathogens) and cultural (e.g., orchard floor management) control practices within peach orchards may help to reduce pesticide inputs. Additionally, mating disruption with encapsulated pheromone may prove beneficial for management of S. exitiosa and S. pictipes.

NEMATODES

Nematodes are a major problem on Prunus species, causing reduced tree vigor, premature tree death, and orchard replant problems. Research efforts focus on understanding nematode-tree interactions and on alternative approaches to chemical control. Research also addresses cover crops to suppress nematode populations and on developing nematode resistant germplasm.

PLUMS

CULTIVAR DEVELOPMENT

Plums, with their wide range in colors and flavors, are a popular fruit in the South. However, most varieties with good eating quality have less tree vigor and disease resistance compared to older, poorer quality varieties. The goals of the breeding program are to develop plums with healthy vigorous trees that produce large, firm, delicious fruit. Plums are needed that ripen from May until August. Although the current industry is mainly pick-your-own or local sales, there is good potential for industry expansion if a series of suitable varieties were available.


Last Modified: 10/11/2005
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