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16.3.1.1.4 Plant Density and Row Spacing
Plant density and row spacing are techniques that can be used to manage the micro-environment of
insects and pathogens. High plant densities and narrower rows can create a cooler, more shaded environ-
ment, which has been shown to reduce citrus rust mite (Muma 1970). Wide soybean rows provide a more
open canopy, which frequently results in higher densities of large larvae of Helicoverpa zea (Alston et
al. 1991). This may not be from any direct effect on H. zea, but may be a result of pathogens, such as the
fungus Nomurea rileyi (Farlow) Samson, which can provide more effective biological control of H. zea
in a closed canopy with higher humidity (Sprenkel et al. 1979).
16.3.1.1.5 Trap Cropping and Farmscape Influences
The basic concept of trap cropping is to provide a highly attractive crop in proximity to the main crop
so that pests move to the trap crop and spare the main crop. Insects that are in the trap crop can then be
managed as needed to avoid later movement into the main crop. This technique has been shown to be
effective in multiple systems (Hokkanen 1991, Shelton and Badenes-Perez 2006), and, yet, it rarely has
been implemented on a commercial scale. Reasons for the rare implementation generally are related to
logistical challenges of growing two crops in a field (e.g., herbicide compatibility, fertilizer requirements,
planting dates, harvest dates) and the cost of taking land out of production to grow the trap crop, which
may not have any market value. Stink bugs often prefer soybeans over cotton (Bundy and McPherson
2000) and prefer soybeans in the earliest maturing varieties. Therefore, a trap crop of early-maturing
soybean can help protect a field of later-maturing soybean (McPherson and Newsom 1984).
In contrast to trap cropping to reduce pest damage, the location of fields within a farmscape can
increase or minimize pest damage of generalist insect pests. In the southern United States, wheat dries
down at the same time corn is in its early vegetative stages. Chinch bug [Blissus leucopterus leucopterus
(Say)] can be found in maturing wheat (Triticum aestivum L.) at high densities but is seldom regarded
as a pest at this time, so it is not managed. However, as the wheat begins to dry due to maturation, it
becomes an unsuitable host for the bug, which then leaves the wheat. Young corn growing adjacent to
the wheat is a suitable host, and damaging densities of chinch bugs can be found on the outside rows
of corn planted beside wheat. Similarly, western tarnished plant bug, Lygus hesperus Knight, stays in
alfalfa adjacent to cotton (Sevacherian and Stern 1974, Godfrey and Leigh 1994) unless all the alfalfa
is mowed (Sevacherian and Stern 1975). Strategic arrangement of crops in the farmscape should seek to
minimize interfaces that facilitate movement of a pest from one field to the next. The farther an insect
needs to move to find a suitable host, the lower the likelihood it will find the host, which can be an effec-
tive cultural control strategy in itself.
16.3.1.1.6 Planting Date
Planting dates often are chosen for agronomic reasons, and planting before or after recommended plant-
ing dates can have a substantial economic cost. However, even within the recommended planting win-
dow, the choice of planting date can impact the likelihood of pest damage. Tarnished plant bug [Lygus
lineolaris (Palisot de Beauvois)] densities generally increase throughout the growing season, so earlier
cotton plantings require fewer insecticide applications and have less damage than later plantings (Adams
et al. 2013). Another aspect of planting date is how it compares to neighboring fields of the same crop.
For example, one of the most effective ways to minimize damage from Contarinia sorghicola is to plant
all the sorghum at the same time so that all plants flower at the same time (Young and Teetes 1977).
These midges only attack sorghum during pollination, so when all fields are pollinating at the same
time, no fields suffer much damage because the midges are spread over many sorghum plants. Therefore,
there are no opportunities for midges infesting an early-flowering field to complete a generation and then
attack a late-planted field.
16.3.1.1.7 Water Management
Water management consists of draining water away from, or adding water to, a crop. The agronomic
impact of water management is great, so using water management for pest management purposes is
a reasonable option only when it is consistent with other agronomic needs. Flooding has been used to