Hi all,
With a long stretch of wet weather being predicted for the region, along with cooler conditions, disease incidence is likely to increase in many crops. It is important to be pruning any diseased foliage and keeping airflow between plants and rows to reduce the likelihood of disease outbreaks.
Along with an increased probability of disease, storms originating from the south can also carry some unwanted pests up this way. One of the major pests that is transported up to Vermont each year are potato leaf hoppers. Although PLH is not hardy enough to overwinter here in Northern New England, PLHs hitchhike on the winds of storms to the region and quickly establish themselves for the season in alfalfa, beans, potatoes, strawberries, and various other crops. Our team is yet to detect PLH in any of the crops that we are scouting, but considering the frequency of storms and historical arrival dates, I would expect to see them very soon.
This is all to say that it is a good time to start scouting for the PLH adults and small green nymphs. Tapping or brushing plants is one way to check crops for adults (they’ll jump/fly when disturbed), but you’ll need to look on the underside of leaves to find the wingless nymphs. Because nymphs are often the most damaging life stage, early detection is critical. Once the characteristic “hopperburn” symptoms appear, the damage cannot be reversed. As soon as we begin finding PLH in our scouting network, we’ll be sure to let you all know.
The good news with the cooler temperatures and consistent rains is that many insect pest populations have been slower to build this season (e.g. onion thrips). This may allow for a bit of favorable asynchrony between pests and their crop hosts. With any luck, crops may be a bit more hardy and larger to provide some amount of tolerance in the face of pest feeding.
One pest that does not appear to have been slowed by the cooler weather is striped cucumber beetle (SCB). We continue to see high populations throughout the region and are receiving reports from growers struggling to keep adults in check. While both conventional and organic insecticides can provide effective control, cultural practices remain an important part of management. Exclusion netting, resistant or tolerant varieties, and physical feeding deterrents such as kaolin clay (e.g., Surround) can help suppress populations and reduce feeding injury prior to flowering. Recent research on cucurbit susceptibility in the Northeast revealed the following ranking from most susceptible to least: bitter gourds, winter squash (C. maxima), cucumbers, summer squash, cantaloupe honeydew, butternut winter squash, watermelon.
Though cucurbit plants can often withstand a fair amount of foliar feeding by striped cucumber beetles (SCB), it is important to remember that these beetles are also vectors of bacterial wilt. In most cases, the transmission of bacterial wilt is a greater concern than the feeding damage itself, as infected plants can rapidly wilt and die.
Interestingly, though SCB are vectors of bacterial wilt, transmission of the bacterium does not typically occur directly from feeding and saliva deposition. In reality, the highest concentration and viability of bacterial wilt is found in the frass deposited by beetles as they feed. Infection primarily occurs when frass comes into contact with feeding wounds on the plant. In theory, removing heavily damaged leaves and beetle frass may reduce opportunities for infection, although this is unlikely to be practical on a large scale. Rain might help!
Furthermore, bacterial wilt tends to wane later in the season. This may be because older cucurbit plants are less attractive to beetles, possibly due to changes in plant chemistry. Mature plants may also be better able to tolerate infection than young plants. As a result, bacterial wilt symptoms may develop more slowly or be less severe in older, larger plants.
In recent years, our team has evaluated a mass-trapping approach for managing striped cucumber beetles in squash production systems. While this strategy has shown promise in other regions, our trials have not yet produced consistent results. Maybe it is us! That said, we’d love to continue to refine the approach and would welcome opportunities to collaborate with growers interested in testing mass-trapping systems on their farms.
Quick notes from the field:
- Leek moth populations in the region are mostly in the cocoon stage, so a new flight will be on the horizon. Check your scapes, they love to feed on them
- First squash vine borer capture in NH, we are yet to see any in VT. More on this next week.
- CPB in VT are bad in most solanums, a bunch of growers are combining trap cropping with flaming + delayed planting.
- Low numbers of corn earworm and European corn borer picking up in MA, NH, PA
As always, our website for the scouting reports can be found here. In addition to the pests reported here, our website also has a more comprehensive list of pests. The list also documents the progression of many common pests as they emerge throughout the season.
For detailed management information about these pests, as well as a comprehensive guide to current production and pest management techniques for commercial vegetable crops, check out the New England Vegetable Management Guide. And, as always feel free to reach out to us if you have any questions.
| Pest | Crop | Observations | ||
| Colorado Potato Beetle | Potatoes | CPB larvae are feeding and impacting crops! Late instars make up most of the populations | ||
| Spinach/Beet leaf miner | Spinach, Swiss Chard, Beets | Very limited. Seeing few mines. | ||
| Striped Cucumber Beetle | Squash/Cucumber | Beetle populations are really large on many farms. | ||
| Flea Beetle | Broccoli/ Kale | Pressure is consistent but less than the beginning of the season | ||
| Three-lined potato bug. | Tomatillos | They are being reported in region the distribution is still spotty | ||
| Mexican bean beetle | Beans | Still limited to one or two farms at the moment | ||
| Leek Moth | Onions/Garlic | Mostly still in pupal stage, new flight to begin soon | ||
| Spotted Wing Drosophila | Berries | Still are yet to find any adults in our traps. | ||
| Swede Midge | Brassicas | Midges have been trapped but no damage has been seen. Likely to begin seeing damage over the next couple of weeks be sure to check sprouting broccoli | ||
| Squash Vine Borer | Cucurbits | Trapping of a few adults in NH | ||