All/multiple crops: From dry to wet – many crops and locations have seen a significant swing in their environmental conditions from very dry a couple weeks ago to now nearly too wet. With this extra stress coupled with prolonged, heavy dews in the morning has a few more diseases showing up or at least getting better established.
Alliums: The fall flight of allium leafminer (ALM) will likely begin the first week of September. Growers intending to use exclusion netting should cover fall alliums by Labor Day ensuring that there are no gaps between the soil and the netting. Insecticides are most effective for managing ALM when applied 2-4 weeks after the beginning of the flight; keep an eye out for future updates on the start of ALM activity for timing applications. More information on the lifecycle and management of ALM can be found here.
Brassicas: More Alternaria leaf spot has shown up this week and will progressively get worse with these cooler temperatures and morning dews. Look for small black lesions that enlarge and appear as a “target board” or “bulls eye” surrounded by a yellow halo. Eventually, the middles will fall out of the spots leaving holes in the leaves. Alternaria will infect all of the different brassicas including Brussel sprouts, collards, broccoli, cauliflower and those brassicas being used for cover crops such as tillage radish and mustards. Heavy infection can lead to unmarketable heads are reduce overall quality. Often what happens is secondary organisms such as bacterial soft rots enter the wounds created by the Alternaria lesions and lead to quicker breakdown. Disk or plow under residues from harvested brassicas as soon as possible to reduce the risk of spreading spores into new plantings and maintain a 3 year rotation away from brassicas. Fungicides include chlorothalonil (Bravo) and many FRAC Group 3, 7 and 11 fungicides including Switch, Luna Sensation and Flex, Miravis Prime, Reason and others for example. Resistance to the FRAC 7 fungicide Endura (boscalid) has been documented in Western NY, so growers are encouraged to minimize the use of FRAC 7 fungicides. Consult Christy Hoepting’s Brassica Alternaria Fungicide Cheat Sheet for more recommendations. Organic growers can use Oso (polyoxin D zinc salt) for suppression. An example conventional fungicide program targeting alternaria on broccoli developed by Christy Hoepting can be viewed below.
Cucurbits: In the last week more and more pumpkin and fall squash fields have been showing stress from too much water, especially those with low spots – yellowing, loss of vigor and in some cases, vine collapse. Some of this can also be attributed to diseases such as Phytophthora capsici, which continues to show up across the region. Plectosporium blight is also quite prevalent in the region and is also starting to collapse some plants; labeled FRAC 11 fungicides containing azoxystrobin can be added to tank mixes for plectosporium management. For the most part, powdery mildew control does not appear bad in most areas, especially on those farms that initiated their fungicide programs at the right time. Maintain fungicide program until you are harvesting in order to maintain as much leaf cover as possible to prevent sunscald. There are also reports of cucurbit downy mildew (CDM) moving into pumpkins and winter squash in New Jersey, so including targeted CDM products (Orondis Ultra or Opti, Omega, Zampro) along with your powdery mildew materials will be important for later harvested blocks. If you have been including products for Phytophthora capsici, many of those products also control CDM. Here the links for the CPM fungicide table and the link to the CDM fungicides.
Nightshades:
Late blight continues to move around the Northeast, with spread reported in the southern tier of NYS and new this week, in Chittenden County, VT near the Clinton County, NY border. Growers are urged to maintain protective fungicide spray programs and scout regularly for early symptoms of this disease. Familiarize yourself with the symptoms of late blight and report suspected infections to your local extension specialists.
Another issue this week has been lots of fruit cracking and more rain checking. Fruit cracking usually occurs when we have fluctuations in water and temperatures and rain checking usually occurs when we have water that sits on the fruit for extended periods of time. This can be from dews or prolonged rainy periods. As the water sits on the fruit it creates small cracks in the skin leading to tiny scabs and what eventually becomes a leathery, rough appearance. This is most common in field grown beefsteak varieties and not so much where tomatoes are grown in high tunnels.
If you are a tomato grower and not a sweet corn grower or growing both, you might not be paying attention to the sweet corn trap catches, but you should be! Corn earworm (CEW) catches are on the rise which is important to be aware of as CEW is also a common pest of tomatoes know as Tomato Fruit worm (TFW). TFW or CEW create large holes or tunnels in tomato fruit. According to entomologists at Rutgers Cooperative Extension, “local pheromone trap catches approaching 20+ CEW per night may warrant preventive sprays for this pest”. The most effective insecticides are those same materials that are most effective in sweet corn – Coragen, Besiege, Lannate and Radiant (Entrust SC for organic growers).
Bacterial leaf spot continues to plague many of the pepper plantings, leaving some plants almost defoliated and exposing the fruit to sunscald. Maintain copper applications to try and keep as much foliage as possible to protect the fruit. To distinguish blossom end rot from sun scald, blossom end rot usually occurs near the blossom end of the fruit on the side of the fruit and is usually tan or black in color. Sunscald usually appears on the sun exposed side of the fruit and is white/creamy white in color. Maintaining even watering throughout the season, especially during early fruit set will help reduce blossom end rot and maintaining as much foliage by controlling bacterial leaf spot will help reduce sun scald. Some growers have also gone to staking their peppers similarly to their tomatoes. Instead of using 4’ tall stakes and doing a basket weave, they will use much shorter stakes and put them in on the sides of the pepper beds and run several strings down the outside of the beds. This helps keep the pepper plants from flopping out into the rows and exposing them to more direct sunlight. The plants tend to fall into the middle or each other and help cover the fruit.
Corn: The number of corn earworms (CEW) has risen quite dramatically in the last week so most of the attention this week is on silking corn. If there is any good news, the cooler days and nights should slow their development down a bit, but as we get later into the season and corn plantings become fewer, pressure ramps up even more! Most sites this week are on a 3-4 day spray schedule. Take a look at the trap catch table below and then look at the spray schedule table to see what your region’s spray schedule should look like.
