Hi all,
With the mini-heatwave over the weekend a few insect pests have spiked in the area. Most of these insects have been causing some damage but have really hit their stride over the last week. The ones that have been most notable on the farms over the last week have been onion thrips, flea beetles (in eggplant) and Mexican bean beetles. We’ve discussed both of these pests in detail over the past couple of weeks. If you would like to refresh your memory on the life cycles or potential management tactics, just click on the hyperlinked names above for these pests or scroll through our website blog to reread the previous entries.
This week, we are focusing on several of the diseases that we are seeing in abundance on farms and have been reported to UVM’s Diagnostic Clinic.
From Ann Hazelrigg:
“Powdery mildew is on the rise in cucurbits. Fusarium crown rot at the base of stems was identified in high tunnel cukes where soil conditions were warm and wet. I also have seen this fungus cause a rapid collapse of squash in fields in hot mid to late summer following rain. The pathogen causes a rot right at the soil line even though roots may look fine. It can be hit or miss in fields.
I have seen more angular leaf spot in cucurbits this year than in years past. It is a bacterial disease that typically shows up earlier in the season because it is seedborne. Cucumbers seem to get a lot of leafspot problems and are hard to diagnose from just a picture. It is best to send in a sample if you want to know, because the pathogen can only be identified by looking for fungal fruiting bodies or bacteria under the microscope. Here is a good factsheet on leafspots from UMASS: Leaf Spot Fact Sheet
Bacterial wilt was diagnosed on yellow squash where cucumber beetle numbers were high earlier in the summer. Tomatoes are just showing the usual leafspot diseases with an isolated (hopefully!) incidence of late blight in Ontario. There is a fair amount of blossom end rot on some of the first ripe tomatoes. I have been hearing of blossom drop in high tunnels due to the recent high temperatures. Peppers are also showing blossom end rot on sides of the fruit. It is hard to tell the difference between BER and sunscald, but either way, the fruit is ruined!
Downy mildew is prevalent on some onions. This fungus-like organism will not infect the bulbs but can influence size if the plants die early. It shows up as lighter green patches on the foliage with purple-grey downy growth visible especially when conditions are moist or in the early morning. Cercospora and other leafspots are showing up on beets. Don’t forget that thrips and spider mites may explode in this hot dry weather.”
Also, in regards to late blight, Meg McGrath from Cornell Cooperative Extension wanted to be sure that growers in the region are aware of some late blight look-a-likes. “There are 2 other Phytophthoras that can cause leaf and sometimes stem spots that resemble late blight.: P capsici = Phytophthora blight (tomato) and P nicotianae (both hosts but more common on potato). They don’t occur very often. Key difference – these 2 don’t sporulate on these tissues like the late blight pathogen (won’t see the typical late blight fuzz when leaves are incubated in a plastic bag for a day), so they don’t move as easily, and they are not so destructive. I’ve got photos in my Photo Gallery: https://blogs.cornell.edu/livegpath/gallery/”
If you have any questions regarding diseases on your farm you can send Ann a picture of a problem first and then she can follow up if a sample is needed at ann.hazelrigg@uvm.edu
In addition, our research team is looking to collect wireworms from agricultural soils to assess some biological controls that we have been testing. If you have any fields with a history of high wireworm pressure, we’d love to come out to your farm and put out some traps to collect for our experiments. Please reach out, we’re happy to take them off your hands…err…farm.
| Pest | Crop | Observations |
| Colorado Potato Beetle | Potatoes | Adults are being found in mass right now, with a lot of late instar larvae too. |
| Flea Beetle | Brassica and Solanums | Flea beetles have rebounded in some areas. We’re seeing some high pressure in eggplant on some farms in Vermont. |
| Imported cabbage worms | Brassica crops (Kale, Broccoli, Cabbage, etc.) | Damage seems to be spotty in brassicas for most of the cabbage moths |
| Leek moth | Onion | The second flight of leek moth has begun! Adult moths are currently laying eggs in alliums. |
| Mexican bean beetle | beans | We have been documenting some pretty large outbreaks in beans these days. |
| Japanese Beetle | Potatoes, Beans, Basil, etc. | There has been a marked increase in Japanese beetle populations in various crops. |
| Potato Leafhoppers | Beans and Potatoes | Hopper burn, at the moment, is limited on the farms we are monitoring. Some pressure in potatoes but not too bad. |
| Striped Cucumber Beetle | Squash/Cucumber | Beetles are being seen and reported in numerous cucurbit crops. The field population for winter squash have been rather normal for this time of the year, tolerable levels for most good-sized plants. However, some extensive bacterial wilt is being seen on farms with higher pressure. |
| Spinach/Beet leaf miner | Spinach, Swiss Chard, Beets | Lear miner damage has been steady in the last couple of weeks. Most of the damage seen right now is a remnant of early infestations. |
| Squash bugs | Summer and Winter Squash | Nymphs are being found in high numbers in most squash plantings. Adults are still laying eggs too. |
| Squash vine borer | Winter squash | Moths are being found in traps from around the region. We have seen many moths in traps and flying around summer squash plantings. |
| Swede Midge | Brassicas | We are seeing pressure building in many brassica crops. Be sure to rotate out of any fields that are showing high pressure this season. Swede midge overwinter in the field as pupae. |
| Tarnished plant bug | Strawberries | We are getting a lot of reports of farms with very high TPB numbers, especially flower farms. |