BUG JUICE
(Art Agnello ama4@nysaes.cornell.edu,
Entomology, Geneva)
There are many insects present in apple orchards that provide a benefit
to growers by feeding on pest species. It is important that growers be
able to recognize these natural enemies, so that they are not mistaken
for pests. The best way to conserve beneficial insects is to spray only
when necessary, and to use materials that are less toxic to them (see
Tables 8 & 12, pp. 37 and 44 of the 1999 Recommends). This brief review,
taken from IPM
Tree-Fruit Fact Sheet No. 18, covers the major beneficial insects
that are likely to be seen in N.Y. orchards, concentrating on the most
commonly seen life stages. Factsheet
No. 23, "Predatory Mites" reviews mites that are important predators
of leaf-feeding mites.
Cecicomyiid Larvae (Aphidoletes aphidimyza)
This fly (Family Cecidomyiidae) is an aphid predator, and overwinters
as a larva or pupa in a cocoon. Adults emerge from this cocoon, mate,
and females lay eggs among aphid colonies. The adults are delicate, resembling
mosquitoes, and are not likely to be seen. The eggs are very small (about
0.3 mm or 1/85 in. long) and orange. They hatch into small, brightly colored,
orange larvae that can be found eating aphids on the leaf surface.
This may be viewed here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig1.html
These predacious larvae are present from mid-June throughout the summer.
There are 3—6 generations per year. In addition to aphids, they also
feed on soft-bodied scales and mealybugs.
Syrphid Fly Larvae (Family Syrphidae)
The Family Syrphidae contains the "hover flies", so named because
of the adults' flying behavior. They are brightly colored with yellow
and black stripes, resembling bees. Syrphids overwinter as pupae in the
soil. In the spring, the adults emerge, mate, and lay single, long whitish
eggs on foliage or bark, from early spring through mid-summer, usually
among aphid colonies.
This may be viewed here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig2.html
One female lays several eggs. After hatching, the larvae feed on aphids
by piercing their bodies and sucking the fluids, leaving shriveled, blackened
aphid cadavers. These predacious larvae are shaped cylindrically and taper
toward the head.
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig3.html
There are 5—7 generations per year. Syrphid larvae feed on aphids,
and may also feed on scales and caterpillars.
Ladybird Beetles (Family Coccinellidae)
- Stethorus punctum - This ladybird beetle is an important
predator of European red mite in parts of the northeast, particularly
in Pennsylvania, and has been observed intermittently in the Hudson Valley
of N.Y., and occasionally in western N.Y. Stethorus overwinters
as an adult in the "litter" and ground cover under trees, or in nearby
protected places. The adults are rounded, oval, uniformly shiny black,
and are about 1.3—1.5 mm (1/16 in.) long.
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig4.html
Eggs are laid mostly on the undersides of the leaves, near the primary
veins, at a density of 1—10 per leaf. They are small and pale white,
and about 0.3—0.4 mm (1/85 in.) long. Eggs turn black just prior
to hatching. The larva is gray to blackish with numerous hairs, but becomes
reddish as it matures, starting on the edges and completing the change
just prior to pupation.
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig5.html
There are 3 generations per year in south-central Pennsylvania, with
peak periods of larval activity in mid-May, mid-June and mid-August. The
pupa is uniformly black, small and flattened, and is attached to the leaf.
- Other Ladybird Beetles - Ladybird beetles are very efficient predators
of aphids, scales and mites. Adults are generally hemisphere-shaped, and
brightly colored or black, ranging in size from 0.8 to over 8 mm (0.03—0.3
in.).
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig6.html
They overwinter in sheltered places and become active in the spring.
Eggs are laid on the undersides of leaves, usually near aphid colonies,
and are typically yellow, spindle-shaped, and stand on end. Females may
lay hundreds of eggs.
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig7.html
The larvae have well-developed legs and resemble miniature alligators,
and are brightly colored, usually black with yellow.
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig8.html
The pupal case can often be seen attached to a leaf or branch.
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig9.html
There are usually 1—2 generations per year. One notable species
that is evident now is Coccinella septempunctata, the sevenspotted
lady beetle, often referred to as C-7. This insect, which is large and
reddish-orange with seven distinct black spots, was intentionally released
into N.Y. state beginning in 1977, and has become established as an efficient
predator in most parts of the state.
Lacewings (Family Chrysopidae)
Adult lacewings are green or brown insects with net-like, delicate
wings, long antennae, and prominent eyes. The larvae are narrowly oval
with two sickle-shaped mouthparts, which are used to pierce the prey and
extract fluids.
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig10.html
Often the larvae are covered with "trash", which is actually the bodies
of their prey and other debris. Lacewings overwinter as larvae in cocoons,
inside bark cracks or in leaves on the ground. In the spring, adults become
active and lay eggs on the trunks and branches. These whitish eggs are
laid singly and can be seen connected to the leaf by a long, threadlike
"stem".
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig11.html
Lacewings feed on aphids, leafhoppers, scales, mites, and eggs of Lepidoptera
(butterflies and moths).
True Bugs (Order Hemiptera)
There are many species of "true bugs" (Order Hemiptera) such as tarnished
plant bug, that feed on plants, but a number of them are also predators
of pest species. The ones most likely to be seen are "assassin bugs" or
reduviids (Family Reduviidae),
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig12.html
and "damsel bugs" or nabids (Family Nabidae). These types of predators
typically have front legs that are efficient at grasping and holding their
prey.
Parasitoids
Parasitoids are insects that feed on or in the tissue of other insects,
consuming all or most of their host and eventually killing it. They are
typically small wasps (Order Hymenoptera), or flies (Order Diptera).
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig13.html
AND: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig14.html
Although the adult flies or wasps may be seen occasionally in an orchard,
it is much more common to observe the eggs, larvae, or pupae in or on
the parasitized pest insect. Eggs may be laid directly on a host such
as the obliquebanded leafroller,
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig15.html
or near the host, such as in the mine of a spotted tentiform leafminer.
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig16.html
After the parasitoid consumes the pest, it is not unusual to find the
parasitized larvae or eggs of a moth host, or aphids that have been parastized
("mummies"). Exit holes can be seen where the parasitoid adult has emerged
from the aphid mummy.
This may be views here: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig18.html
AND: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/FruitFS/Ben_fig19.html
Generalist Predators
There is a diversity of other beneficial species to be found in apple
orchards, most of which are rarely seen, but whose feeding habits make
them valuable additions to any crop system. The use of more selective
pesticides helps to maintain their numbers and contributes to the level
of natural control attainable in commercial fruit plantings. Among these
beneficials are:
• Spiders (Order Araneae): All spiders are predaceous and feed
mainly on insects. The prey is usually killed by the poison injected into
it by the spider's bite. Different spiders capture their prey in different
ways; wolf spiders and jumping spiders forage for and pounce on their
prey, the crab spiders lie in wait for their prey on flowers, and the
majority of spiders capture their prey in nets or webs.
• Ants (Family Formicidae): The feeding habits of ants are rather
varied. Some are carnivorous, feeding on other animals or insects (living
or dead), some feed on plants, some on fungi, and many feed on sap, nectar,
honeydew, and similar substances. Recent research done in Washington has
shown certain species (Formica spp.) of ants to be effective predators
of pear psylla.
• Earwigs (Family Forficulidae): Although these insects may
sometimes attack fruit and vegetable crops, those found in apple orchards
are probably more likely to be scavengers that feed on a variety of small
insects.
APPLE LEAFMINER
(Dick Straub rws9@nysaes.cornell.edu,
Entomology, Highland
As occurs most years about this time, I have recently received some
inquiries from Hudson Valley growers regarding considerable foliar damage
by a leafminer. The pest is neither the spotted tentiform leafminer nor
the apple blotch leafminer -- gracillariid species that are commonly found
in this region. The culprit, apple leafminer (Lyonetia speculella
Clemens), has been occurring sporadically here in isolated orchards since
1987.
Female moths oviposit in tender new foliage by piercing the undersides
of leaves and depositing single eggs inside the leaf tissue. The hatched
larvae form serpentine mines, which are visible as wavy brown lines on
the tops of leaves. As the larvae grow, they enlarge their mines into
brown blotches, within which they consume all of the tissue between the
upper and lower epidermis. Unlike other leafminers of apple, L. speculella
is characterized by frass (small black pellets) that is constantly expelled
on a silken thread from the mine by the feeding larvae. Just prior to
pupation, larvae spin cocoons, which are suspended by threads and resemble
a hammock. Apple leafminer probably has 4 to 6 generations per year in
southeastern New York.
Moreover, unlike our other leafminers, larval damage is confined
to the youngest foliage, particularly terminal leaves of vigorously growing
shoots. Root initials or water sprouts that are partially shaded are the
preferred sites for feeding and pupation. Severely mined leaves turn brown
and die; most such leaves drop off prematurely, thereby decreasing the
number of the most photosynthetically active leaves. The potential for
damage is greater in young orchards than in mature ones, and vigorous
trees usually sustain higher infestations than do less vigorous trees.
Populations normally do not achieve high abundance or cause critical
damage until the beginning of the harvest period of our earliest cultivars.
Insecticidal control of larvae or adults at this time may not be a reasonable
tactic because of the pre-harvest interval of most materials and, just
as importantly, because infestations do not damage fruit or cause premature
drop of fruit. Broad-spectrum insecticides typically used in cover sprays
(OP's) are unlikely to provide significant control of adults or larvae.
The optimum control tactic would be 1 or 2 sprays of either methomyl,
oxamyl, endosulfan or a pyrethroid at petal fall or 1st cover. Undoubtedly,
Provado at the same timing would also do some good. We consider that sprays
are necessary only on non-bearing trees where vigor is essential, or on
bearing trees that had high infestations the previous season.
End of this issue: Scaffolds 1999 Index
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