Marie Curie's Cat: The Trouble With Squash

Squash, and indeed the whole Curcurbitacae family have long held deep fascination for me. This year, we had a very bad crop, indeed. This will be a sad, sad winter with nothing but store-bought curcurbits for the near future. Here is a pcture of the criminal who has wrought such destruction in my pumpkin patch:

adult phase Melittia cucurbitae

larval phase, late stage, heavy damage

larval phase

The squash vine borer (Melittia cucurbitae) is a day- active species of moth that attacks wild and cultivated varieties of squash. The moth is often mistaken for a wasp because of its movements, black wings, and bright orange scales. The females typically lay their eggs at the base of leaf stalks, and the caterpillars develop and feed inside the stalk, killing the leaf. They migrate to the main stem, and with enough damage to the stem, the plant may die. They also eat through the stem and into the squash or pumpkin, thus causing even more crop loss.

The squash vine borer lives in most North American states, except the Pacific coast (how unfair!) Southern states have two broods a year, and in the warm sothwest, we have a near perpetual state of infection from first frost to about May or June.

Pesticides are not effective after the larvae are inside the plant. I find this a VERY difficult pest to control. I try to avoid the pest by timing the production season to harvest before the pests can build up, or after they have peaked, but that all depends on yearly frost patterns.

Prevention includes bacillus thuringensis to kill the grubs, before they eat into the vines or fruit. An old gardener trick for vining squash and pumpkins is to cover the vine with earth at various points along its length, causing rooting at several points, and thus continuing to feed the developing fruit despite the loss of the original stem. After the vine has taken root at multiple points, the infected portion of the plant can be cut off, along with another inch where the larvae is eating into healthy tissue, without significant to the plant. Once larvae are eat into the stems, control must be quick. The first sign of the problem is wilting of the vine, and it is sometimes too late for control efforts at that point. Experienced gardeners watch the stems for signs of frass (grub poop) protruding from small holes, which indicates the presence of the larva inside. Some gardeners carefully cut the stem along its axis and remove the caterpillar before it does too much damage. Others use a stiff wire, a needle, or a toothpick to kill the borer without too much damage, believe it or not, this can really work! So, if you want gorgeous pumpkins like this, the organic way, you know what has to be done!

squash blossoms