Hi all,
It looks like a very similar pattern to last year, with July bringing hot and dry conditions following a wet May and June. As we mentioned last week, this can be a mixed bag for pest and disease pressure. While hot and dry weather may slow the development of some diseases and insects, prolonged heat and drought can increase stress on crops. Extreme weather of any kind can also lead to unexpected or difficult to diagnose problems. Heat and drought stress can lead to symptoms that may mimic insect feeding or disease. That makes our job as scouts a bit more complicated, but we’ll still be out there each week doing our best to help identify issues and keep you informed.
After several weeks of encouraging growers to scout their beans and potatoes for potato leafhoppers (PLH), we saw several small outbreaks in beans on a couple of diversified vegetable farms this past week. This is a bit later than the past couple of years but falls in line with the general arrival time observed over the past decade. Although we are only seeing them in beans at the moment, potato leafhoppers have an extensive host range, feeding on more than 220 plant species, including both cultivated crops and non-cultivated or weedy species. The majority of these hosts (close to 62%) belong to the legume family, so perhaps they should really be called the bean leafhopper!
As mentioned previously, each spring potato leafhoppers migrate from their overwintering areas in the southeastern United States to northern regions of the U.S. and eastern Canada. Once they arrive and establish in bean and potato plantings, they typically complete two generations during the growing season. Interestingly, they begin preparing for their return migration rather early here in the Northeast. Previous studies have estimated that adult females begin preparing for their journey south as early as mid-August. At that point, female leafhoppers leave cultivated fields, stop laying eggs, and begin hitchhiking on favorable weather systems back to their overwintering regions in the Southeast.
While nonchemical controls for potato leafhoppers are most effective before they arrive and become established, growers with bean plantings that can be covered with insect exclusion netting may be able to delay or reduce infestations. Once a population is established in a crop, several conventional insecticides provide very effective control. For organic growers, field research suggests that pyrethrin- and neem-based products can reduce potato leafhopper pressure.
In addition to potato leafhopper, our team has uncovered several swede midge outbreaks in brassicas across the Champlain Valley and central Vermont, including Washington County. Swede midge is one of the more frustrating brassica pests, as it can decimate a crop if an outbreak coincides with the early stages of head formation in broccoli, cauliflower, and even Brussels sprouts. In recent years, we have noticed that many growers have begun planting sprouting broccoli as an alternative to heading broccoli. Unlike heading broccoli, swede midge damage to sprouting broccoli does not typically result in a complete loss of marketable yield, as the plants continue to produce side shoots and florets even after the growing tip has been damaged. This appears to be a good adaptation strategy, and we’ve heard positive things from several growers who have adopted this approach.
That said, anecdotally, we have been observing much higher levels of swede midge damage in sprouting broccoli plantings than in heading broccoli when scouting farms growing a diversity of brassica crops. Despite the increased damage, however, growers still seem to be harvesting respectable yields from these plantings. It makes us wonder whether sprouting broccoli could be functioning as a trap crop in these scenarios. It’s an intriguing possibility, and one we’d like to explore next season, if any farmers are interested?
Important notes from the region:
- Still are yet to see any spotted wing drosophila (SWD) on any of the farms that we monitor. We expect to see them soon.
- Sqaush bugs are beginning to pick up steam in summer squash plantings.
- Onion thrips are around but populations, in general have been spotty across fields. We’ll see if this pattern continues with the dry heat that is on the horizon.
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.
Finally, we would also like to acknowledge that funding for this year’s scouting program has been generously granted by VVBGA and the USDA Transition to Organic Partnership Program
Cheers,
vic
| Pest | Crop | Observations | ||
| Potato Leafhoppers | Beans | Seeing mostly adults and few nymphs. | ||
| Colorado Potato Beetle | Potatoes | All life stages are being seen on farms. | ||
| Spinach/Beet leaf miner | Spinach, Swiss Chard, Beets | No reported damage these days.. | ||
| Striped Cucumber Beetle | Squash/Cucumber | Beetle populations are really large on many farms. | ||
| Flea Beetle | Broccoli/ Kale | Very low | ||
| Three-lined potato bug. | Tomatillos | High pressure in most areas. | ||
| Mexican bean beetle | Beans | Still limited distribution. | ||
| Leek Moth | Onions/Garlic | Second flight is under way and egg laying is occuring | ||
| Spotted Wing Drosophila | Berries | Still are yet to find any adults in our traps | ||
| Swede Midge | Brassicas | We have seen several outbreaks in sprouting broccoli and red Russian kale. | ||
| Squash Vine Borer | Cucurbits | Numbers are picking up in traps | ||
| Squash Bug | Summer squash | Nymphs are starting to be seen in high numbers | ||
| Onion thrips | Onions | Still low pressure! | ||