Resource Guide for Organic Insect and Disease ... - Cornell University

HORNWORM (TOBACCO Manduca sexta, and TOMATO, Manduca
quinquemaculata)
Hornworms are large green caterpillars (Photo 7.8) that are common in warmer climates. They
are, however, becoming more and more common in the Northeast, especially in high tunnels
and greenhouses. They can consume considerable leaf tissue.
Cultural Control:
Scouting and hand picking the larvae works well because they are usually present in small
numbers. The caterpillars are well camouflaged; look for the large droppings beneath plants.
Materials Approved for Organic Production:
1. Bt kurstaki: There is a lack of research data, however growers report successful use.
2. Spinosad: One recent study showed good control.
POTATO LEAFHOPPER (Empoasca fabae)
Potato leafhoppers (Photo 7.9) do not overwinter in the Northeast but “leap frog” their way up
from southern areas each summer, arriving in very large numbers in some years and smaller
numbers in others.
The potato leafhopper favors alfalfa, beans, strawberries, and potatoes. It is a serious pest of
potatoes, as both adults and larvae suck plant juices. Their feeding causes curling, stunting,
and dwarfing, accompanied by a yellowing, browning, or blighting of the foliage, known
as “hopperburn” or tipburn (because the damage is first seen at the leaf tips) (Photo 7.9).
Once significant “hopperburn” is evident, the crop has already lost yield, so early scouting is
important.
Cultural Control:
1. Crop rotation is not effective, as leafhoppers do not overwinter in the Northeast, and
they can move large distances.
2. Some varieties are more tolerant. These include “Elba,” “Green Mountain,” some
russets, “Snowden,” “Ontario,” and “Katahdin.” “Red Norland” is very susceptible. More
information may be found in seed catalogues or through the local extension office.
3. Scouting and early detection are important because population levels vary greatly
from year to year, and successful control must start early.
Materials Approved for Organic Production:
1. Pyrethrum (recent trials have shown one good result).
2. Neem products: One recent study showed fair control. Please see the neem material
data sheet for a discussion of the different types of neem products.
3. Spinosad: Entrust is not effective against this pest.
TARNISHED PLANT BUG (Lygus lineolaris)
The tarnished plant bug (TPB) is a sucking insect (Photo 7.10) that feeds on flowers and buds
of eggplant, pepper, and tomato and causes flower drop, which greatly reduces yield in some
years. When there are large numbers of tarnished plant bug, feeding on leaves will cause
browning of the tips and edges, especially on potato and eggplant. This damage may be
mistaken for a disease or hopperburn (see above discussion of leafhopper).
Cultural Control:
1. Avoid mowing legume hay fields surrounding crops just prior to or during flowering of
solanaceous crops because such a disturbance will drive the TPB into the crops.
2. Floating row covers work well to protect buds and flowers on young plants and can
greatly increase early yield. They may not be practical for mid-summer use.
3. Practice good weed control; TPB seems to be more of a problem in weedy areas.
Materials Approved for Organic Production:
There are no proven, effective organic insecticides for TPB, although pyrethrums will reduce the
overall populations. Neem products are recommended for trial.
Organic Resource Guide 59