Vegetable Crops News

Biological Control of Squash Bug on Pumpkin?

Squash bugs are difficult to control no matter what method is used. There are natually occurring parasites that attack the bugs, but they never build up to large enough numbers to suppress squash bug populations. One such parasitoid, the scelionid wasp Gryon pennsylvanicum, parasitizes squash bug eggs. It may be useful in augmentative releases as part of a squash bug managment program.

Field releases of the wasp did reduce squash bug populations 4-fold on "Jack-O-Lantern" pumpkins in Kansas, but the pest population was still higher than on plants treated with insecticides, and this effect was delayed until late in the season. The yield of No. 1 pumpkins in the wasp-treated plots was 23-70% of that in insecticide-treated plots (there were no harvestable pumpkins in the untreated plots). Biological control alone does not appear to be an economically feasible management approach for commercial pumpkin growers.

The use of a resistant cultivar ("Green-Striped Cushaw"), which is most effective against early instar nymphs, also reduced the pest population, but it too was not as good as insecticide treatments. The yield of No. 1 pumpkins in the resistant cultivar plots was 11-77% of that in the insecticide-treated plots.

However, squash bug populations were even lower in resitant cultivar plots that also received wasps, and the yields from these plots were higher than either treatment alone although yield was still only 51-66% of that in insecticide-treated plots.

Combining these two alternative management tactics biological control and host plant resistance appears to have potential as an alternative to chemical control.

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