Hi all,
This week we are seeing exponential growth in several populations of common pests and some newly arriving pest & diseases that we should keep out eye out for in the coming weeks.
Basil Downy Mildew is being reported in the region, with confirmed occurrences in Western Mass and Rhode Island over the past week. BDM can severely affect basil plantings, and if left untended can lead to complete crop loss. The tell-tale sign of BDM is a gray coloring (from the developing spores) on the underside of basil leaves. It can sometimes look like soil has kicked up onto the bottom of the leaf. If you suspect that it is BDM, you can place the affected leaves in a Ziploc bag with a wet paper towel to increase the sporulation. You can often be alerted to a potential outbreak by yellow coloring between the veins on the topside of leaves.
A great resource for identifying, reporting, and managing BDM is the Ag Pest Monitoring Site for basil. In recent years, some resistant cultivars have been developed. These cultivars and information on them may be found on the monitoring site too. For those dealing with a current outbreak, prompt removal of affected plants will help to reduce the inoculum from infecting other plants. If you suspect that you are seeing BDM, please send us a message and/or send a sample to the Plant Diagnostic Clinic here at UVM.
Other important notes:
Thanks to the some of the recent larger storms in the regions, Fall Armyworm are being found in states just south of us (e.g. NY and CT.) Currently, numbers are low both in CT and NY, but it is likely that adult FAW moths will begin to move into our region soon.
Squash vine borer are being seen in traps being monitored in NH, CT, and MA. Though the current numbers being reported are low, as the next few weeks heat up, those numbers will certainly tick up. The primary sign of SVB is the wilting of squash plants in the summer heat. With a closer inspection, you can find tunneling within the vines at the base of the plant. Unfortunately, once wilting is observed, there is very little that can be done to save the plant. Exclusion netting can be useful for excluding moth from plantings, though this strategy is only useful prior to flowering and the need for pollinators. Well-timed applications, chemical and non-chemical (e.g. diatomaceous earth), near the base of plants during the early stages of flights can be useful. Traps with SVB lures can often provide growers with a good resource for timing controls for their specific farm.
Colorado potato beetle populations are exploding in potato plantings around the state. Here in Burlington we are seeing mix of small and large larvae within potato fields. This is prime time to apply any above-ground tactics to reduce the current population size. That window may close as the larger larvae begin to head down to the soil to pupate. Larger larvae tend to become pink or salmon colored just before they crawl down the plant to burrow into the soil to pupate. However, there is some evidence that entomopathogenic nematodes may be a useful tool (as a soil drench) for reducing the in-field populations during the pupation stage/process.
Squash bug adults and eggs are being found in increasing numbers throughout Vermont. Check on the underside of leaves for their meticulously placed golden brown eggs. Straw or hay mulch can exacerbate squash bug outbreaks, as they tend to provide the perfect habitat for the pest during the hot and dry times of the day. Row cover can also be useful prior to flowering. Like cucumber beetle, squash bugs tend to prefer maxima species of winter squash.
As always you can find more details on other pests and diseases at our pest and scouting website.
Cheers,
Vic
| Pest | Crop | Observations |
| Colorado Potato Beetle | Potatoes | Most populations in the region are now a mix of large and small larvae. Soon the larger larvae will begin their journey down the plant to pupate. |
| Flea Beetle | Most all brassica crops | We continue to see large populations of flea beetle. We are especially seeing sustained populations in cooler regions of the state in the Connecticut River Valley. |
| Imported cabbage worms | Brassica crops (Kale, Broccoli, Cabbage, etc.) | Cabbage whites are flying and laying eggs. We are now seeing larvae feeding damage in many brassicas. Diamondback moth are also being found in brassicas in both adult and larval stages. |
| Leek moth | Garlic | We are still not seeing adult moths in traps yet, suggesting that the second and generally most damaging flight has yet to occur. We’re primarily seeing larval damage and pupae in the upper canopy of allium plantings. |
| Potato Leafhoppers | Alfalfa | We have official reports of PLH in beans within Vermont. They will likely persist and cause harm in other crops as the season progresses. |
| Striped Cucumber Beetle | Squash/Cucumber | Beetles are being seen and reported in numerous cucurbit crops. Numbers are becoming substantial and damage is significant, especially in cucumbers and C. maxima varieties of winter squash. |
| Spinach/Beet leaf miner | Spinach, Swiss Chard, Beets | Very few reports of leaf miner damage. |
| Squash bugs | Summer and Winter Squash | We’re seeing a plethora of adults and eggs with summer and winter squash. Nymphs are yet to be seen in any significant numbers |
| Squash vine borer | Winter squash | Moths are being found in traps from around the region. Moths are likely beginning to mate and lay eggs in squash plantings. |
| Tarnished plant bug | Strawberries | We are seeing a high incidence of tarnished plant bugs in the region, especially in strawberries. Cat-facing and other types of strawberry deformation from the “sting” of the bug has been seen. |