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

ORGANIC INSECT AND DISEASE CONTROL FOR
Chenopods: Spinach, Beets and Chard
26 Organic Resource Guide
INTRODUCTION
Spinach, beets, and chard belong to the plant family Chenopodiaceae. There are very few crop
plants in this family, but many weeds, including common lambsquarters and oak leaf goosefoot.
The flowers of plants in this family are inconspicuous, greenish, and often arranged in
small clusters. Beets and chard are cool season crops that can tolerate frosts and light freezes.
Spinach is even hardier and tolerates temperatures as low as 15 o F. Beets and chard do well in
both warm and cool weather, but spinach will bolt under the hot temperatures and long days
of summer. There are some varieties of spinach that are somewhat bolt-resistant. While crops
in this family are related, the most important diseases are very crop-specific.
I. INSECT CONTROL__________________________________
APHIDS
The green peach aphid and black bean aphid are sometimes found on Chenopodiaceae crops;
however, aphids are not usually a problem in organic systems where broad-spectrum insecticides
are avoided. Aphid feeding can distort leaves, and aphids can transmit viruses from plant
to plant. Although they may appear at any stage, they are more of a concern later in the season,
when cucumber mosaic virus is more prevalent. Also, concern varies with market tolerance of
contamination with aphids in harvested crops. The largest concern is with spinach production
in high tunnels, where populations of aphids may explode quickly, and the infested crop may
harbor populations that could infest subsequent crops.
Cultural Control:
1. Row covers can protect plants if installed before winged aphids arrive, and they can
remain in place until harvest.
2. Aluminized reflective mulches may slow colonization of plants by winged aphids.
Direct seeding or transplanting through the mulch is recommended for maximum
protection
Materials Approved for Organic Production:
1. Soap provided poor control for green peach aphid, but studies with other species
showed five good, one fair, and two poor results. Ensure coverage of the parts of the
plant where aphids are located, especially the undersides of leaves and fruit.
2. Neem: Azadirachtin-based neem products may provide control.
3. Pyrethrin has not proven to be effective for aphids on spinach.
4. Beauveria bassiana may provide control.
FLEA BEETLES
There are several species of flea beetles that pose a risk to spinach, beets, and chard, including
the spinach flea beetle (Disonycha xanthomelas) and the pale striped flea beetle (Systena
blanda). Damage is most problematic in crops being marketed for greens; however, especially
when small plants are attacked, yield reductions or complete losses may be observed. Most
species overwinter as adult beetles and emerge in the spring. They feed on upper and lower
leaf surfaces, making small holes and, when present in large numbers, creating a shot-hole appearance.
These holes may become larger as the leaf grows.
Cultural Control:
1. Row covers are the most effective way to avoid flea beetles, but since they over winter
as adults in soil or crop debris, be certain to combine the use of row covers with crop
rotation.