Controlling Squash Bugs Now Can Reduce Next Year's Pest Problems!

 

 

Squash bugs were abundant in Oklahoma cucurbit crops during the 2003 growing season. Many of these crops have already been harvested although pumpkins, squash and some late-planted melons are still in the field.  Squash bugs can be found in large numbers in many areas.  For crops that are already harvested, squash bugs in these fields are reproducing on fruit and vines that remain in the field and are building up populations that will eventually leave fields to over winter in nearby areas.

 

Why be concerned about over wintering squash bugs?  There are several reasons.  Recent studies conducted at the Lane Agriculture Center have demonstrated that squash bugs are not only serious pests of squash and pumpkin, as was known a century ago, but are also important pests of other cucurbits important to Oklahoma farmers such as watermelon and muskmelon.  The damage that can result from squash bugs includes direct plant injury due to feeding on plants as well as effects that lead to vine decline later in the season.  Studies have also shown that squash bug feeding in itself is more detrimental to the growth and yield of watermelon than was previously thought.  Feeding by a single squash bug can result in the death of numerous seedling plants.   Over-wintering squash bug adults seek newly planted cucurbits in the spring.  The more insects allowed to over winter, the greater the potential for injury to next year’s cucurbit crops.

 Vines killed by Squash Bugs.

 

  Watermelon vine infected by yellow vine disease.

 

Cucurbit Yellow Vine Decline (CYVD) is a relatively new and serious disease of cucurbit crops that has been primarily a problem in Oklahoma and Texas.  However, we continue to observe a wide geographical expansion of the disease into eastern, mid-western, and western states. Squash bug has been demonstrated to be a vector of the causal agent and is known to 'carry over' through the winter the bacterium associated with this vine decline.  The necessity for controlling squash bug can be illustrated by a pumpkin crop grown in 2002 at Lane, Oklahoma that was devastated by CYVD and had large numbers of bugs present.  These insects that fed in this crop and then left the field to over winter were a potential hazard to crops planted early the next spring.

 

  Numerous squash bugs on pumpkin.

 

 

At present, there are large numbers of nymphs (immature squash bugs) in the field that will likely to develop to adults before winter and may become CYVD carriers by ingesting the bacteria from infected plants. In the next few weeks we will begin to see adult squash bugs migrating from fields and seeking hibernation sites.  Allowing this situation to occur in cucurbit production areas is not sound pest management!  An important component of integrated pest management (IPM) is to use a combination of practices to prevent pest populations from becoming an economic threat.  In this case, one aspect of the IPM approach is to prevent the build-up of over wintering populations.  Therefore, time is of the essence for controlling these pest populations before they leave the fields.

 

   Squash bug nymphs.

 

How can we control these late-season squash bugs?  Typically, squash bugs populations peak during August and September.  If fall cucurbit crops are still in the field, make sure that adequate chemical/cultural approaches are used to control squash bug numbers.  Once harvest is completed, prompt destruction of watermelon, squash, and pumpkin vines and fruit will prevent nymphs from developing and deprive adults from building fat stores necessary to survive the winter.  This may be accomplished by mowing and disking, a practice that is needed in preparation for the planting of winter cover crops.  Again, keep in mind that the insects you are growing now are likely going to re-visit your fields next spring and that a percentage of them may be carrying the bacterium associated with CYVD.  The numbers of squash bugs that show up next year is directly dependent on the management steps that are taken right now.

 

For more information on the management of squash bugs and other vegetable pests call your County Extension Office.     http://countyext.okstate.edu/