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Fall is a great season for baking, and if you have black walnut trees on your property, you can harvest your own delicacy every year in October. They may be a bit challenging to get into, but the tender, nutty morsels are well worth the effort because they will add a unique sweetness to your chocolate chip cookies and homemade cakes and pies. If you’ve got a problem with walnut caterpillars, however, your black gold can turn to black goo overnight, and you could end up with a pile of empty shells and disappointment as the fruit of all your labors. Here is an organic way to keep walnut caterpillars from feasting on your trees and nuts.
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Mix 3 qt. insecticidal soap and 1 qt. water, and put it into a bucket.
Walk around each walnut tree late in the evening and brush any visible caterpillars into the bucket manually. The larvae drop to the ground on the outer husks of the walnuts, so examine the perimeter of each tree around its trunk, and scoop any visible pests into the bucket. Use a ladder for hard-to-reach infested limbs.
Drop dark-streaked infected husks and shells into a vat of warm water, and remove dead maggots manually.
Hang a bug-zapper near your walnut trees in mid-summer, when the brown and yellow flies begin to lay eggs inside the walnut husks.
Purchase horticultural oil at your local gardening store, and spray the trees once you have removed the caterpillars by hand (see Resources below).
Cultivate any shells on the ground in the fall.
Always wear thick gloves when handling black walnut husks, as they contain a natural toxin that causes permanent staining on your skin and clothing.