| STINK
BUGS
Support
for the release of commercially obtained predators is primarily
anecdotal and theoretical; there is little, if any, scientific
documentation supporting the value of releasing bought
insects. Releasing predatory insects does NOT guarantee pest
control, NOR replace scouting, threshold adherence and other
good Integrated Pest Management (IPM) practices. Growers going
into bio-control need to have realistic expectations that
the method may not do the job alone. "Use is not discouraged,
but a realistic expectation of the potential benefits is needed"
Dr.
Gary Hein, Univ. of Nebraska Extension Entomologist.
Although
early green peach aphid populations are not high enough to
attract natural populations of predators, these same predators
also feed on Colorado potato beetle which usually appear earlier.
Therefore, early release of predators for Colorado potato
beetle control may delay the need for early season green peach
aphid control and allow fewer and later insecticide applications
against aphids.
In
the absence of stink bugs, lady beetles and other predators
after insecticide application, green peach aphid populations
often flare up in potato fields.
The
new transgenic clones of potato varieties would not affect
the predatory insects since they do not feed on foliage nor
do they have the gut chemistry to be affected by the Bt genes.
Two-spotted
and spined soldier stink bug (Perillus bioculatus and Podisus
maculiventus) are specialist predators of beetle larvae, especially
CPB. Other prey include cutworms and armyworms. They
are found throughout North America, and I've often seen the
adults sucking blood out of CPB larvae in potato fields. Other
larval prey of importance to potato production are the European
corn borer and cabbage looper. In Washington potato fields,
released stink bugs reduced CPB populations by 50%. They are
available commercially as adults; I found sources in Massachusetts,
New Hampshire and Ontario. Cost, however, may be prohibitive
for large scale addition to natural populations.
Life
Cycle -- The adult overwinters and, in spring, each female
lays a thousand eggs. The eggs hatch into nymphs (not larvae)
several days later. The nymphs feed on pest larvae, grow and
form a hard shell. After reaching their final size, they become
reproductive adults and lay eggs. There are 2-3 generations
per season.
Appearance
-- Adults are about ½ inch long and have a broad shield-like
body. The name comes from the release of a strong, unpleasant
odor when adults are disturbed. The spined soldier stink bug
adult is tan to pale brown with prominent spurs at the "shoulders"
behind the head. Two-spotted stink bugs are usually yellow
or red with a black "Y" on the back and two black
spots on the "shoulders." Eggs are deposited in
tight clusters of 20-30 on leaves and twigs. They are gray,
cream or gold colored and are barrel-shaped. Young nymphs
are red and black, and round instead of shield-like. As they
grow, they become marked with yellow-orange, black and cream
bands and patches. Nymphs are wingless but disperse in search
of prey. Both adults and nymphs have beaks used for stabbing
prey larvae and extracting the insides.
Pesticide
Tolerance -- Stink bugs are more susceptible to organophosphates
and carbamates (Furadan, Sevin, etc.) than their prey but
less susceptible to pyrethroids. In general, all natural insect
predators are sensitive to insecticides and will be reduced
dramatically.
Flowering
Plants -- As will be noted several times, the adult of
many beneficial insects also feed on nectar and pollen. So,
it's helpful to have wild flowers along fence rows and in
the general area. This helps keep adults in the area looking
for prey. For instance, flowering dandelions are a heavily
used pollen source for lady beetles in late spring around
potato fields. There are commercially available artificial
foods and honeydew substitutes to enhance lacewing populations.| |
