How successful you are often depends on not only what you are doing, but how well you are doing that practice. The same is true with using row cover netting to manage insect pests of cucurbits and the pathogens they transmit. While the goal is to use the netting as a barrier to exclude the pests, success can be hidden in the details. With this article, we would like to discuss some of those details we consider keys to using row covers effectively.

Manage pests on transplants before they get to the field. Transplants are started about four weeks before being planted in the field, during which time they can be attacked by cucumber beetles and other pests in the high tunnel or greenhouse. They may also spend a week or so outside to harden off before transplanting. It is important to keep these pests off the young transplants when they are most vulnerable. We have used netting for exclusion over trays of seedlings prior to transplanting.

Install row covers the day of transplanting. We can have intense cucumber beetle pressure in some years where we have seen them flying and landing on the transplants while on the wagon before they are set in the field. Our advice to growers is to not quit for the day until all of the newly set transplants are properly protected with row covers. For larger fields, this may mean setting plants over several days so that the exposure time is kept to a minimum.

Cover the planting hole in the plastic with compost. Holes in the plastic made while setting plants provide spots where weeds can flourish and compete with cucurbit crops. If we were not using row cover, it would be simple enough to have someone come through and pull those weeds a week or so after transplanting. But that is not practical with the row covers. When transplanting, we can have a second person to toss a handful of compost or media to cover the hole around the newly set plants. This eliminates the need to manage weeds around the base of the plants while under the row cover.

Sealing the perimeter of the netting securely. Cucumber beetles and squash bugs will probe the netting searching for places to get at the plants. For this reason, it is important to have the perimeter of the netting completely secured to keep them out.  This can be a bit trickier on the ends of the field that cross the raised beds or with uneven fields. We have used various ways to secure the edge including water-filled lay flat hose, paving stones, sand or rock bags, and even gravel-filled lay flat. It doesn’t matter what you use so long as the edge is sealed and the weight does not have sharp edges that can damage the netting.

Mend tears in the netting fabric promptly. It would be nice to have netting that is in the same condition as when it was used for the first time. But either during the season or in coming seasons large holes may appear, most often due to netting getting caught in equipment. It is important to repair these holes quickly either by mending the fabric for a permanent fix or using clamps temporarily seal the breaches. Sewing holes with UV resistant fishing line is a good long-term fix.

Reduce netting/soil contact. With woven netting, weeds can grow through the netting when in contact with the soil. While this may not be a problem during the season, it can be a problem when removing row covers, storing them for the winter, and reusing them.  Weeds growing through the row cover take time and labor to remove and increase the chance of tearing the fabric.  We have placed a narrow strip of reusable landscape or shredded mulch under the edge of the netting to prevent this issue. The perimeter of the enclosure will have landscape fabric below the netting and a weight on top of it to secure the edge..

Be able to recognize female flowers. All cucurbits plants have separate male and female flowers. The flowers are typically open just for one day and are exclusively insect pollinated. The male flowers often appear weeks ahead of when the female flowers are formed. It is important to recognize when the female flowers begin to open in order to provide pollination under the row cover. Pollination can be enabled by removing the row cover for two weeks, opening the ends, or by placing a bumble bee colony under the row cover. To recognize the difference between male and female flowers, look at the stem of the flower just below the flower itself. Female flowers will have a swollen stem below the flower which is the beginnings of the fruit. The stem of the male flower does not have this and has uniform thickness from the vine to the flower.

Monitor for aphids under the row cover. While the row covers are used to exclude insect pests and the pathogens they may transmit, they also exclude pollinators and natural enemies of other pests. Over the years we have seen increased problems with melon aphids when using row covers, as predators and parasitoids that normally keep aphid numbers low are not present under the row cover. So, we watch for aphids on the under sides of leaves and, if needed, purchase and introduce lady beetles under row covers.

These are some of the practices we use to help ensure the greatest benefit from using row covers with cucurbits. As you use row covers, you may find other tricks to make them easier to use or more effective. Keep an eye on the current cucurbit for more tricks of the trade, as we will share new innovative practices gleaned from our research trials, on-farm trials, and our advisory panel of growers.