Pecans are produced on about a million acres world wide and annual production usually averages 200 – 300 million pounds. Domestication of pecan began in the late 1800’s and much genetic potential remains to be capitalized upon. Wild pecans in Texas, Oklahoma, Arkansas, Louisiana, and Mexico are perfectly acceptable in the marketplace such that Texas production consists of about 55% wild and 45% improved in an average year as of 2005.
The pest complex associated with pecan in the New World derives from those aboriginal relationships that evolved before domestication and presently key pests are limited to that complex. The ability to identify them combined with a knowledge of their biologies will allow pest management decisions to be made in time to minimize damage.
History of pecan and factors affecting arthropod management:
Prior to 1800
1800 – 1900
1900 – 1930
1930 – 1940
1940 – 1950
1950 – 1960
1960 – 1970
1970 – 1980
1980 – 1990
Prior to 1800
Native Americans gathered and subsisted on pecans; early explorers and settlers readily adopted them to their diets.
1800 to 1900
Settlers thinned tree stands in native range leaving pecans and grass for grazing. Seedling orchards established in southeastern U.S. Grafting technology for pecan developed but not heavily implemented until end of century. Rail transportation results in shipment of nuts to urban markets.
1900 to 1930
Vegetative reproduction inundates southeastern U.S. with many selected varieties.
Bordeaux spray 3 – 10 times recommended for nursery trees to prevent scab but large orchard trees considered unreachable. Plant resistant trees like Stuart, Schley and Frotscher. Early harvest, sanitation, burning and Persian insect powder used for insect control.
1930 to 1940
Shelling machinery, transportation and consolidations of orchards into economic units increase marketability of pecans.
Expanded production of most popular varieties like Stuart met with increasing levels of pecan scab on previously resistant varieties. Rosette linked to foliar zinc deficiency; lead arsenate and nicotine sulfate recommended for insect control. Spray machinery expensive, labor intensive and rarely employed.
1940 to 1950
Tank mixing of nicotine sulfate with needed fungicides recommended as “cheap insurance.” Contract spray services expand with truck-mounted hydraulic sprayers. DDT used for pecan nut casebearer but aphids and mites appeared in epidemic numbers; toxaphene alone or mixed with nicotine sulfate controlled pecan nut casebearer without resurgence of aphids and mites.
1950 to 1960
Airblast speed sprayers become available; compared to hydraulic sprayers, cheaper speed sprayers allow single operator to spray same number of trees with one-fourth the water and still obtain better coverage. Effective and economical rosette, arthropod and pathogen control with conventional and newer chemicals resulted. Malathion adopted for pecan nut casebearer control. Chemical management of pecans became widespread.
1960 to 1970
Cyprex and then Du-Ter replaced Bordeaux for pecan scab control and new carbamates, organophosphates and systemics became available for arthropod control. Mechanization for pesticide application, pecan maintenance, harvesting and processing burgeoned along with explosion of chemicals and solutions appeared faster than problems. Chemical schedules became routine and screening for efficacy dominated research efforts.
1970 to 1980
Chemicals and Resistance
Carbaryl became chemical standard for pecan weevil management, phosalone for other arthropods, Benlate and Du-Ter for pathogens, and NZN or zinc sulphate + uran for rosette. First case of pesticide resistance in pecan was a pathogen (causal agent for pecan scab) to Benlate in 1975, followed by hickory scorch mite resistance to carbamates and organophosphates in 1979.
Synthetic pyrethroids introduced late in decade. Integrated Pest Management (IPM) philosophy develops and spreads across agriculture due to widespread pesticide resistance by arthropods, secondary pest outbreaks like aphids, mites and leafminers due to broad spectrum pesticides killing natural enemies and societal concerns about environmental pollution.
Pecan industry buffered from many of these problems because of the surfeit of chemicals for all pests and lagging problems of resistance due to remaining management diversity. Aphids were viewed as a major problem in El Paso Valley of Texas and increased reliance on natural control by predators and parasites resolved their problem.
Increased attention in pecan paid to developing economic thresholds of important pests, refining understandings of basic biologies to predict and manage pests, to identify and rely on natural enemies of pests and other IPM strategies. Pecan IPM programs initiated in Alabama, Georgia, Texas and elsewhere late in decade. Widespread expansion of new pecan plantings of a few varieties occurred in Southwest and Mexico inside and outside the native range epitomizing the drastic narrowing of genetic diversity in the natural pecan population compared to cultivated varieties.
1980 to 1990
Arthropod resistance to pesticides becomes widespread and Federated Pecan Growers declare aphids the most destructive pest in 1985, refuting the contention that the pecan industry had adopted IPM without the normal cycle of subsistence, exploitation, crisis, disaster and finally integrated control.
Modeling efforts and basic biological studies on pecan nut casebearer, pecan weevil, hickory shuckworm, pecan aphids, pecan scab and other pests began to be implemented into management programs.
Phosalone withdrawn from market in 1989.
Implications of continued transition from diverse native and seedling trees to increased genetic uniformity of vegetatively propagated varieties on ability to manage diseases and arthropods became ever more apparent, continuing a trend observed at least half a century earlier.