Late Season Pests in Pumpkins and High Tunnel Tomatoes

Jerry Brust, IPM Vegetable Specialist, University of Maryland;

It is that time of the year again; as the season winds down some late season pests can come in and ruin what is left of a dwindling crop. In pumpkins it could be “rind worms” which are any number of caterpillar species that will feed on the outside of a pumpkin and scar the surface or penetrate into the rind. Either way it opens the pumpkin up to secondary infection and causes it to rot much sooner than it should. The other big pest is the squash bug, which will concentrate its numbers and feeding on the pumpkin fruit if the foliage goes down and is no longer there (Fig 1). The nymphs and adults can feed heavily enough that they will “deflate” a pumpkin or reduce its vigor (including the stem) by sucking all its juices out. Any of these pests can be easily controlled with an insecticide application like a pyrethroid; the difficulty is making sure to catch the problem before it becomes too late.


Figure 1. Squash bugs feeding heavily on pumpkin fruit because no vines are left in the field

In high tunnels there has been a surge of worms that have suddenly shown up in the past couple of weeks. As corn and natural hosts of the worm pests begin to shut down the moths are attracted to high tunnel plants that are green and still growing. I have seen hornworms, and yellow striped, beet and southern armyworms in high tunnel tomatoes where they tend to feed on the fruit when they become medium size or larger. Smaller larvae tend to stay on the foliage (Fig 2).



Figure 2. Large worms tend to feed on the fruit while small worms tend to feed on foliage, except for fruit worms, which will feed on the fruit when they are both very small and large larvae. They usually start feeding under the calyx or cap of the tomato as in Fig 3.


Figure 3. Tomato fruit worm feeding under calyx of tomato fruit

Tomato fruit worm, however will attack the fruit when the larvae are very small or large (Fig 3). As with pumpkin pests the tomatoes in high tunnels need to be watched carefully for the next several weeks until we have a frost or two. Bt products will work well as long as worms are small and not attacking the fruit, but other chemicals such as pyrethroids or Avaunt or SpinTor or Lannate will be needed if the worms are large or damaging the fruit.

I am conducting a study looking at tomato production inside a high tunnel (HT) compared with tomatoes just outside the high tunnel with the same number of plants and the same variety all planted on the same day in June. The HT tomatoes have been severely attacked by small and large larvae of several worm species with 40% of the tomatoes being damaged. (I am not treating the tomatoes in order to make the comparison.) However, just outside the high tunnel there have been few worms at all and almost no large worms with only about 5% of the tomatoes being damaged. I am not sure why the worms survive better in the high tunnel-temperatures have not been much different between the HT and outside until the last few days. I will be looking at natural enemies (both insects and disease) and the number of eggs laid by the female moths over the next few weeks to see if there are any differences with these factors.

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