2009 Annual Report
1a.Objectives (from AD-416)
To prevent alternate bearing, water stage fruit split, pre-harvest nut germination, and nutrient element problems limiting profitability; and to develop improved strategies for the control of pecan scab, and other diseases of foliage and fruit.
New funding ($89,280) will be used to expand current CRIS project objectives.
(1) Determine if the virulence of the scab fungus has changed in regards to the key cultivars being grown.
(2) Determine if cultural and spray practices are contributing to increased scab inoculum levels in the upper canopy of trees, and how these practices should be changed to reduce scab related losses.
(3) Assess scab susceptibility as if it interacts with rate of growth of host tissues and the secondary metabolites being produced by such tissues.
(4) Assess the impact of tree nutrition on the ability of pecan to tolerate or resist damage by scab organisms.
New funding $54,863 will be used to (1) develop improved strategies for control of pecan scab; and (2) develop improved strategies for the control of alternate bearing.
1b.Approach (from AD-416)
Problems will be addressed via development of strategies that regulate bearing using flowering regulators, fruit thinning, hedge pruning, and nutrient management. Fruit drop, split, and germination problems will be addressed via improved nutrient management. Disease control efforts will address strategies to improve spray coverage, efficacy of pesticides, and factors that regulate resistance or susceptability.
Resources ($89,280) will support ongoing research already taking place. Efforts will address the role of host plant nutritional status in relation to host resistance to scab; will access the possibility of changes in the virulence of the scab organism; will address how cultural practices are contributing to disease severity; and will investigate the role of secondary metabolites on scab.
Resources ($54,863) will support ongoing research to improve nutrition management, crop land management, control of alternate bearing, minimize fruit drop, and reduce scab susceptability of trees. Efforts will address improving plant nutritional status as a means of reducing tissue sensitivity to pecan scab.
Mouse-ear malady: The problems of “mouse-ear” and “orchard replant disease” are solved. To fully transfer technology, several research and trade articles were published. It was determined that high plant concentrations of Zn and/or Cu can trigger Ni deficiency. Trees have a high probability of being Ni deficient during the first few weeks of canopy development, thus, contributing to physiological and growth problems that limit profitability.
Water-stage-fruit-split: The problems of water-stage-fruit-split were partially solved. Information was reported in research journals as disseminated to farmers and extension specialists regarding usage of B and Ni to reduce incidence of water-stage-fruit-split in pecan.
Mechanical hedge pruning: Efficacy was demonstrated for mechanical hedge pruning strategies for the relatively low-light southeastern U.S. environment. One- or two-year cycle pruning is unlikely to be commercially efficacious, but methods using three or four-year cycles are likely efficacious, and offer a means of preventing tree crowding while increasing stability of alternate bearing.
High density hedgerows: Mechanical hedge-type pruning of young tightly spaced, high density (15 x 30 ft) orchards is not practical in the southeastern U.S. environment due to reversion to excessive vegetativeness.
Alternate bearing: Increasing auxins gibberellin concentrations in developing buds influenced return bloom. Endogenous phytohormones play a major role in alternate bearing, as well as that of resource reserves. Information on nitrogen management contributes to improving nitrogen usage.
Control of alternate bearing: Timely treatment of young trees with ethephon and prohexadine-Ca increases return bloom. The expense of using these in pecan appears to preclude commercialization.
Reducing vivipary: Vivipary can be reduced by reducing water stress and reducing nitrogen fertilization; and also by managing endogenous ABA (growth inhibiting phytohormone).
Chemical fruit thinner: Chemical thinning agents proved non-efficacious. An alternative approach targeted non-traditional agents with two exhibiting limited efficacy.
Pecan scab disease: Nickel possessed efficacy against scab disease; thus, supplementing fungicide sprays with nickel improves scab control while also improving nut yield and quality. Additionally, it was found that reducing volume and increasing speed of air-blast sprayers gave as good of control as the standard volume and speed; thus, farmers can reduce cost of spraying while protecting more trees in less time.
Phytophthora disease: Unsuitable weather conditions prevented field studies of phytophthora.
Shuck decline disease: Unsuitable weather conditions prevented field studies of shuck decline.
This project documents Specific Cooperative Agreements (#58-6606-5-246) with New Mexico State Univ., CRIS 6606-21220-011-03S)and SCA (#58-6606-6-175) with Univ. of Arizona, CRIS 6606-21220-011-04S, on "Western Pecan Research"; also, non-funded cooperative agreement, "Preventing Early-Season Fruit Drop," CRIS No. 6606-21220-011-05N with Georgia Pecan Farms, LLC. and ARS-Byron, Georgia.
Improved boron and nickel management reduces crop loss to water-stage-fruit-split: Crop loss to water-stage-fruit-split is a major cause for crop loss in certain pecan cultivars. Research found that the incidence of this form of loss is reduced by timely improvement of tree nutritional status for boron and nickel. The work demonstrates that orchard yield can be increased by improving tree nutritional status for boron and nickel.
Recovery and partitioning of nitrogen by pecan trees: Nitrogen management is a major, and increasing, cost for pecan farmers. Research found that trees maintained with adequate nitrogen nutrition derive the majority of the nitrogen used for annual growth from N stored from the previous season, and explains why trees require at least two years to respond to changes in nitrogen management. The results emphasize the importance of marinating an annual nitrogen fertility program for current and future production.
Identification of factors that lead to nickel deficiency in plants: The expression of nickel deficiency by plants is a mystery when plants and soils contain what appears to be plenty of nickel to satisfy crop needs. It was found that expression of nickel deficiency depends largely upon the relative concentrations of zinc and/or copper (i.e., Zn:Ni or Cu:Ni ratio) in crop tissues and organs; thus, affecting the biological availability of nickel for plant processes. This research demonstrates that nickel deficiency is probably more common for agricultural crops than widely thought and that excessive agricultural usage of Zn or Cu fertilizers can potentially trigger Ni deficiency. The work impacts crop production and fertilizer management strategies.