740 Invasive Stink Bugs and Related Species (Pentatomoidea)
control several insects in crops that are tolerant of flooding. Cranberry, Vaccinium macrocarpon Aiton,
is tolerant of flooded conditions, but the low dissolved oxygen content in flooded soil of a cranberry bog
can provide 80–90% control of blackheaded fireworm, Rhopobota naevana (Hübner), within 9 days
(Cockfield and Mahr 1992). Use of insecticide to control cranberry fruitworm, Acrobasis vaccinii R i ley,
during the summer growing season was reduced by 70% after implementing a 4-week flood during the
spring in Massachusetts (Averill et al. 1997). Continuous flooding for up to 6 weeks killed many wire-
worms, Melanotus communis (Gyllenhal), in Florida (Hall and Cherry 1993). Mortality increased with
warmer temperatures. In other situations, sprinkler irrigation is sufficient to reduce pest populations.
Diamondback moth [Plutella xylostella (L.)] has reduced mating, dispersal, oviposition, and increased
larval mortality when fields are irrigated with a sprinkler (Talekar and Shelton 1993). On the other hand,
mosquito populations, many which develop in stagnant water, can be reduced by draining land that
would otherwise hold pools of water (Keiser et al. 2005).
16.3.1.1.8 Nutrient Management
Several insect species, including aphids (Aphididae) and Lygus lineolaris, are known to concentrate in
the most succulent parts of a field. Succulence may be a function of water management, but, often, it is
a result of nutrient management, particularly nitrogen management. Excessive nitrogen often increases
vegetative growth and makes foliage more succulent. This can increase the growth rates of insects such
as aphids (Duffield et al. 1997, Nevo and Coll 2001), resulting in larger populations. Some nitrogen is
essential for plant growth, but, often, there is a level where there is enough nitrogen to meet plant needs
without impacting pest densities.
16.3.1.1.9 Intercropping
Intercropping is growing two dissimilar crops in the same space at the same time. This was common
before agriculture became mechanized, but equipment limitations today prevent widespread use of this
cultural control in many situations. Advantages of intercropping include increased yields (Li et al. 2001),
reduced economic risk (Rao and Singh 1990), and improved non-chemical weed control (Liebman and
Dyck 1993). For insect pest control, intercropping can be effective by making it harder for the pest to
identify the crop, or the non-host plant may impede movement even after the pest arrives in the field
(Trenbath 1993). Two commonly used intercrops are mixtures of alfalfa and a grass. Potato leafhop-
per [Empoasca fabae (Harris)] is a major pest of alfalfa, but intercropping alfalfa with a forage grass
results in reduced densities of this insect (Roda et al. 1997a,b). Another pest impacted by intercropping
is the alfalfa weevil, Hypera postica (Gyllenhal). This weevil is a specialist of alfalfa, so fields that are
seeded with a forage hay experience reduced levels of damage by this insect (Roda et al. 1996). Because
both alfalfa and forage grasses can be harvested together, this intercrop is not hampered by mechanized
harvest.
16.3.1.1.10 Harvest Management
Harvest management can play a role in several ways. In concert with managing the proximity of a pest
source field with potential sink fields (farmscape influences), the timing of the harvest of the source field
can play an important role in the scale and timing of the pest movement from one field to another. In
some cases, harvesting a crop early can be an alternative to spraying for the pest and then waiting until it
is safe to harvest. Also, harvest management can be used to reduce pest damage by harvesting the crop
in strips, thereby keeping the pest in the current crop rather than forcing it out of the field to feed in a
nearby crop that is more easily injured by the insect. All of these management practices can be shown,
using Lygus hesperus in an alfalfa-cotton landscape as an example. This plant bug prefers to feed in
alfalfa but causes greater economic damage in cotton, so management strategies are designed to keep
it from moving into cotton. Harvesting alfalfa early is one strategy whereby the alfalfa is harvested on
a 28-day schedule rather than the more conventional 35-day schedule (Godfrey and Leigh 1994). The
bugs can infest and oviposit in alfalfa as soon as new growth has emerged. By harvesting on a 28-day
schedule, nymphs from the earliest-laid eggs cannot complete development to the adult stage, so the life
cycle is cut short, and there are few adults available to migrate to nearby cotton fields. An alternative to