UConn Extension Vegetable IPM Pest Message & Reports from the Farm, Friday June 17th, 2016 [Comments or answers in brackets/color are provided by Jude Boucher, UConn Extension] [I didn t receive any reports from the field this week from growers (hint, hint!) and pest levels on the farms I visited were at an all-time low for this time of year (that s good news!), so the message this week will be short and sweet. Early sweet corn that was previously under row covers is silking in the Valley.] Randy Rogowski, Laurel Glen Farm, Shelton, CT [reported by JB] Brassica crops were scouted and again this week we failed to find any caterpillars or damage. We found just a couple of second generation leaf miner eggs batches on the bottom of Swiss chard leaves. Leaf miners can attack chard, beets and spinach and also build up on many weeds, such as lambsquarter, nightshade, chickweed and plantain, if left uncontrolled. Effective control of the first generation helps reduce damage from second and third generations during the summer months. Scout your greens now for leaf miner eggs and treat if you find them to reduce the number of mines in the leaves, which the larvae make while feeding between the upper and lower leaf surfaces. Most products will require a second application in 7-10 days, an adjuvant to help the product work, and good coverage on the lower side of the leaves. There are a few systemic products that can control the pest without complete under-leaf coverage and for an extended period of time. Note that many products are only labeled for use on Swiss chard (see New England Vegetable Management Guide www.nevegetable.org ). Unless damage has been exceptional heavy, you may only need to control the miners on beets if you are selling the greens. Crop rotation to a field where greens were not grown the previous season can help reduce pest pressure, and row covers work well if the sides are buried and combined with crop rotation. The wasp parasitoid Diglyphus isaea can also help reduce the damage, especially if releases are timed with egg hatch and combined with other alternative methods. Top left: leaf miner eggs Bottom left: leaf miner maggot (removed from mine) Top right: leaf mines in spinach Bottom right: clean spinach under covers
Lars Demander, Clover Nook Farm, Bethany, CT [reported by JB] When I arrived, Lars had already controlled young Colorado potato beetles on his potatoes and adult striped cucumber beetles on his cucurbits with a single application of Sevin. Neither pest was present on his plantings this week. We talked about using a different product on second generation CPB or for the first generation next season for resistance management. Remember that CPB can learn to eat any insecticide in as little as 3 years or 6 generations according to the scientific literature. There are many effective insecticide groups that can control potato beetles (resistance groups 3, 4, 5, 6, 16, 22, 28, etc., see the NEVMG). He also showed me how he uses landscape cloth between his rows of black plastic for his melons to both control weeds and keep the fruit clean. I like this system because it allows water to penetrate into the soil within the planting. I once visited a farm where the grower had covered the entire surface with plastic both in-row and between rows. This controls the weeds on an organic farm, but the problem was that it created a lot of impermeable surface. In a heavy rain event the water flowed off his field and flooded his high tunnel below. I have also seen droughts so severe that growers just could not get enough water on their plants with trickle irrigation alone and had to supplement with overhead irrigation that could be a problem with an all-plastic surface. There are many organic farms where they use wide sheets of landscape cloth to cover the whole surface for high-value crops. This is a little more expensive but the material can be used for many years. I have always thought that the plants do not do quite as well on landscape fabric as they do on black plastic mulch some growers disagree with me but I m basing my opinion on many observations over many years. Anyway, I like Lars system of black plastic rows with landscape row-middles and thought you might like to try it. Plastic mulch for melons with landscape cloth between rows We scouted Lars unsprayed Brassica planting together and failed to find any caterpillars.
This is the time when onion thrips can become a problem, but Lars pointed out how by changing from black to reflective silver mulch 4-5 years back they had eliminated the onion thrips problem on the farm completely. He said they haven t had any thrips in 4-5 years. Silver, reflective mulch for thrips control on onions (you can also use landscape cloth between) They had just finished staking their tomatoes and, for the first time used rebar to stake half the field, which they thought would work out much better than wooden stakes because of their durability. I have seen rebar used for staking on other farms and, aside from the initial expense, they are right, and you never usually have to invest in stakes again. Tomatoes with wooden stakes (left) and rebar (right side of field)
Susan Mitchell, Cloverleigh Farm, Mansfield, CT [reported by JB] To control leaf miners Susan has been removing leaves that are infested with mines and larvae before the maggots drop to the ground to pupate and eventually produce summer generations. Despite her best efforts with the time available, she still has more mines than she would like. I recommended that she try applying row covers immediately after planting, and support the covers with wire hoops to prevent injury to the greens underneath. Susan and I scouted her Brassica planting and found just a single small imported cabbage worm the first one I have found all season! Only 10% of the plants were infested and the threshold is 20%, so no treatment was needed and we will scout again next week. Note: some organic growers use a threshold of 50% infected plants or higher, depending upon what they think their market can bear. UConn s Brassica thresholds of 20% for heading plants and 10% for leafy Crucifers were created for wholesale production and the demands placed on growers by the regional market or retail supermarkets. Earlier Susan had a moderate infestation of cutworms in her onion bed. She controlled them with Dipel directed to the base of the plants and hole in the plastic, and scattered some Seduce to provide residual control. It worked well and she lost far fewer plants than she had expected based on the number of caterpillars she was finding. Josh Bristol, Bristol s Farm Market, Canton, CT [reported by JB] Tomatoes they found more early blight lesions during the week and continued to remove lower leaves with signs of early blight. I recommended that he start a fungicide program alternating between copper and DoubleNickel on a 7-10 day basis. Sweet corn Josh and his dad hilled some of their plantings of sweet corn. They buried all the weeds on some of the younger plantings, but had to do some hand weeding where they were unable to completely cover some of the larger weeds in the oldest plantings. The wet weather the previous week kept them out of the oldest plantings a little too long and the weeds got a little too tall. For younger plantings, they tried using the tine weeder, as I had suggested last week, for blind cultivation at the white-thread stage (pre-emergence) and spike stage of the corn. One planting they did a little past spike stage and found the tine weeder was a little tough on the corn when it actually had leaves on the plants. Once the corn has leaves it is better to switch to a rolling cultivator, set less aggressively, so that it doesn t throw soil into the row. They are just learning the art of when to tine and rolling cultivate and when to hill, but are getting it down. We found just a couple of European corn borer larvae in his oldest planting. Josh also used the reflective aluminum mulch on his onions to control thrips and is harvesting his early Brassica plantings which were never sprayed and are free of caterpillars. On cucumbers he used row covers until the first flowers, then uncovered the plants and sprayed with Entrust when the cucumber beetles invaded. He still had some white scarring on the first fruit. Rotating the cucurbit crops up to his back field on the hill, may help reduce the size of the attack next year. We found some first and second Colorado potato beetle larvae on his potato planting. Time for an Entrust or Mycotrol application. Azadiractin may also help control this stage for organic farms. Don t
forget your cultural controls for this pest, crop rotation - the farther the better, plastic lined trench trap or trap crop between the overwintering hedgerow and new crop, flaming, mulching with straw, and hand picking on small plantings. Also, remember that potatoes can take 20% defoliation without reducing yields so you don t need to kill every beetle in the field to have managed them well. Potato leaf hoppers are just getting started so be sure to scout your potatoes and beans this week. Feeding by PLH can cause hopperburn and dramatically reduce yields or even kill plants. Collin Burson, Pinecroft Farms, Somers, CT [reported by JB] Sweet corn Their first field consisted of three plantings of corn. The first pre-tassel stage planting in E. Windsor had been sprayed for borer at mid-whorl. We found only 4% of the plants infested with live caterpillars in that planting and zero in the second and third planting. At a second field in Somers, the oldest planting in the late-whorl stage had 10% of the plants infested, while two younger planting at mid-whorl stage were still completely free of caterpillars (0%). Since all these plantings were below the 15% infested plant threshold for pre-tassel and 35% for mid-whorl stage, none of the corn required a treatment. We ll scout again next week. We set ECB traps up next to his pepper field to monitor the end of the first generation moth flight and watch for the second generation in late July or August, which can cause severe damage to pepper pods/yields. Owen Jarmoc, CT Valley Growers, Enfield, CT [reported by JB] All cucurbit fields were free of cucumber beetles. There were some plants that were killed by the extreme winds of the past week and some pepper plants girdled by the heat of the plastic - when the plants were touching the plastic at transplanting. He is re-setting lost plants this week. Brian Kelliher, Easy Picking Orchard, Enfield, CT [reported by JB] Bean plants, especially the more delicate yellow bush beans, had lower leaves that were scorched, yellow and puckered, and plants were stunted. He had been using a fertilizer with a trace of boron in it. My experience is that any boron added to beans will cause these toxicity symptoms, and you can sometimes have it occur even when following another crop that required extra B be applied the previous season (i.e. Brassica). Brian will try feeding the beans through the drip line with calcium nitrate to see if the plants grow out of the problem. That s all for this week. The next IPM pest message will be sent on Friday afternoon June24 th.