The old saying that an ounce of prevention is worth a pound of cure
is probably a conservative estimate. That sure is the case when it comes
to managing insects, weeds and diseases on vegetable farms, and especially
on organic farms, where the cures (read: organic pesticides) tend to be
relatively few, and relatively expensive.
End-of-season pest prevention comes in several flavors: sanitation,
crop rotation, record keeping, and soil stewardship. None of these may
seem mouth-watering (because they don’t generate cash in the near term)
but delayed gratification can be a good thing. Next year, and in years
to come, you’ll reap the rewards of a good management menu this fall.
Sanitation means cleaning up the fields and greenhouses. Plowing,
disking or otherwise incorporating residues to speed their decomposition
in the field can limit the ability of many insect pests to over-winter.
Sanitation can also reduce the amount of time that some insect pests have
to store up winter food by feeding on crop residues. Removal or turning
under rotting fruits and foliage can prevent some diseases from proliferating,
too. If weeds are present, putting them down before they set seed makes
good sense. Many annual weeds can produce tens of thousands of seeds per
plant if allowed to mature.
In greenhouses and high tunnels, sanitation provides an added benefit.
Not only can over-wintering sites for pests be removed, but a clean greenhouse
does not leave any food sources for insects that emerge in the early spring
when inside temperatures rise but annual crops are not yet present.
Crop rotation is a valuable cultural management technique for both
insects and diseases, and to some extent, weeds. Start your rotation right
after a crop is done in the fall by rotating into a cover crop. A winter
cover crop does more than just prevent soil erosion; it can help suppress
the growth of winter-annual weeds, and its presence promotes biological
activity, which helps speed the decay of disease organisms while enhancing
Before this growing season becomes a distant memory, be sure to make
a map of your fields and the location of your crops, so you can effectively
move things around over the next few years. In my observation, crop rotation
is one of the weakest areas of management, even among talented, experienced
growers. It’s usually a seat-of-the-pants affair. Very few growers have
a systematic plan for rotating their crops. Those that do often developed
it in response to a serious soil-borne disease like Phytophthora!
When planning your rotations, keep in mind that the distance between
this year’s and next year’s location of the same crop can have a strong
effect on how much insect control you get. While further away is better,
even a short rotation distance will help in most cases compared to going
back in a field with the same crop. Of course, that only applies to pests
that overwinter, like Colorado potato beetle and European corn borer. Pests
that fly in from afar won’t be affected by rotation.
When rotating for diseases, especially soil-borne diseases, greater
distances between fields from year to year can help, too, by lessening
the movement of spores via wind and water. It will be your job to limit
the movement of soil and spores via machinery when preparing fields in
the spring. Consider power-washing equipment in-between its use in well-separated
While winter cover crops are important for soil management, they
aren’t without a down side. If you are going to plant into cover-cropped
field in the early spring, get the cover crop residue incorporated about
a month prior to planting to reduce problems from seedcorn maggots. The
adult of this pest prefers to lay its eggs in areas with high organic matter,
and rotting vegetation in a freshly tilled field will be more attractive
to the flies.
In addition to making a map of your fields and crops for rotation
planning, it’s also a good idea to do some fall field scouting and make
a weed map. A quick scouting can help locate and identify weed problems
that may become expensive if they get out of control, and it can provide
information that will help you design a weed management program for next
Sometime this fall, walk through all your fields and note the following
information: How much weed pressure is there now, and was the pressure
earlier this year? As you look over a whole field, note the location of
weeds. High populations of weeds in the crop rows may be an indication
that cultivation equipment needs adjustment, or cultivation needs to be
done earlier or more frequently. What species of weeds are present – if
you cannot identify them take samples or digital pictures and send them
to an Extension specialist. Identifying weeds is key to designing a management
strategy based on how they grow and when in their life cycles they are
Weeds like yellow nutsedge, hedge bindweed, and quackgrass are spreading
perennials, which have underground parts that can spread throughout whole
fields. Because these weeds can be very damaging, and are difficult to
control, they are worth nipping in the bud with aggressive and timely cultivation.
The best time to control perennial weeds is in the fall. All perennial
weeds have storage structures (tap roots or rhizomes) below ground that
enable these plants to survive winter and regenerate the following year.
Fall tillage of perennial weeds will kill top growth, which stops the production
of winter ‘food’ by photosynthesis, and fragments the storage organs, weakening
the plant. It may not kill the weed, so frequent tillage for a period of
time may be required to destroy regrowth and prevent re-establishment.
In addition to perennials, keep an eye out for annual weeds that
are new to a field or are suddenly increasing in numbers. Some annual weeds
can be very difficult to control if allowed to gain a foothold. Hairy galinsoga,
for example, thrives under cultivated conditions, and can become widespread
on a vegetable farm rather quickly after arriving. Identifying it early
and working to eradicate it while you still can, using hand-removal if
necessary, is key to saving headaches down the road.