[Edited_by_A._Ciancio,_C.N.R.,_Bari,_Italy_and_K.(Bookos.org)

IPM IN PECAN PRODUCTION
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Weed control is important and functions to: remove plants that compete with
the trees for nutrients and plants that provide food for kernel-feeding hemipterans;
and, to the preparation of the orchard floor for mechanical harvesting (Smith &
Carroll, 2004). Weed control initially consisted of disking and rolling the soil so that
the nuts could be collected from bare soil surface. This method made harvesting
easier but the harrow would often open a wound at the base of the trunk of each tree
and crown gall [Agrobacterium tumefaciens Smith & Townsend, Proteobacteria:
Rhizobiales: Rhizobiaceae] would infest the wounded trees and destroy a fair
portion of the root system. Growers shifted to a mowed surface between tree rows
with an herbicided strip along the tree row to prevent damage to the tree trunks.
Through the years the types of herbicides changed but the basic design remained the
same. Trees on land that is flooded part of the year along river systems or with flood
irrigation have either a bare soil surface maintained with herbicides or the annual
weeds are periodically mowed. In the last 30 years, growers have started an
integrated approach to weed control by seeding the orchard with various cool season
legumes. These are grown as intercrops in the mowed strip or as cover crops over
the entire orchard floor. The plants supply nitrogen and increase soil organic matter
and also enhance beneficial insects. In the last 5 years, growers have enhanced the
growth of the legumes by removing grasses during the winter and spring with,
sethoxydim, a selective herbicide.
Agricultural chemical usage in US pecan orchards varies considerably between
states and has increased significantly since the domestication of pecan began in the
early 1900s. Nitrogen fertilizer, pesticides and new cultivars have increased US
production per hectare. Pesticide usage is significant, for example, commercial
pecan producers currently use approximately 1/3 million kg of insecticide (active
ingredient) each season on 320,000 acres in Georgia and Texas (Smith, Harris, Lee,
McEachern, & Ree, 2002; Guillebeau, 2001). The most recent survey results
(USDA/NASS, 2000) indicate that approximately 69% of the US pecan acreage is
treated each year with supplemental nitrogen fertilizer, 67% is treated with
insecticides, 47% is treated with fungicides, and 44% is treated with herbicides.
2.1. Insect and Mite Pest Management in Pecan Orchards
The insect complex associated with pecan in native and improved systems includes
180 species of phytophagous insects and mites (Payne & Johnson, 1979; Harris,
1983) and each is associated by a diverse array of natural enemies (Tedders, 1985).
Insect management strategies range from total reliance on natural enemies to
intensive integration of chemical and biological controls (Table 1) (Dutcher et al.,
2003). The fruit and foliage in pecan orchards are susceptible to insect injury that
can result in economic losses for 7 months. Preventive cover sprays of insecticides
or miticides are not practical and the control of pecan insect and mite pests has
developed into a management scheme. Insects and mites and tree phenology are
monitored determine the abundance of the pests and the susceptibility of the tree to
injury. Direct control measures are applied when pest abundance exceeds an action
threshold and the tree is susceptible to injury. This prevents high costs, resistance,