Eventful start to growing season

Eventful start to growing season

Our Wayne County Integrated Pest Management Program has been out scouting in the fields, high tunnels and orchards of commercial fruit and vegetable growers for about a month now. In the past month we have seen various weather extremes, major changes in crop progression and rapid arrival of some early season pests.

The weather extremes we have faced this past month induced some significant stress on both fruit and vegetable crops. To start the month out, we faced freezing temperatures and repeated frost concerns. Early in the month we also dealt with heavy rains and in some cases flooded fields and ponding water. The script has flipped as we are now dealing with above-average temperatures and dry conditions.

What we observed with the cooler temperatures and excess water was an overall slowdown in plant development and growth. Cooler temperatures and cloudy days really cut into the accumulation of growing degree days and restricted photosynthetic processes to a minimum.

The challenge with plant progression and development being slowed, in this case, actually got set up in March when we had two weeks of above-average temperatures. This abnormally warm period pushed some pest cycles up by about two weeks. Therefore, we have had slow-growing plants with a fairly active population of insect pests, setting up some challenges with insect pests feeding on young, stressed plants, slowly developing new growth or on blossoms and blooms.

Additionally, the freezing temperatures and frosts resulted in some blossom/bloom loss and damage such as frost rings on apples. Colder temperatures also result in limited activity from pollinators, so we are now seeing some of the effects from poor or incomplete pollination.

The hot and dry weather, generally speaking, is hard on fruit and vegetables this time of year, but more so on newly transplanted vegetable crops.

First off, these crops do not yet have a vigorous root system established to withstand drier soil conditions. The abundance of moisture earlier this month did not encourage plants to grow deep roots, down to where there is more consistent moisture. Shallow roots do not bode well in situations where soil moisture conditions rapidly change from excess moisture to dry. There are many of our area growers who use drip tape or other irrigation systems; however, there are cases where the irrigation systems are not yet set up to irrigate these early season crops.

The other challenge about sunny days reaching temperatures in the high 80s is transplanting. While these may seem like great days to plant your transplants, it is best to hold off and wait for either cooler temperatures in the evening or cloudy days.

This is especially important if the transplants are being planted into black plastic mulch. Under clear and sunny conditions, the black plastic mulch can exceed temperatures of 130 F. Temperatures like that will result in injury to the plant. Burns can occur on the stems, leaves and fruit, and even the roots can be damaged.

Stem girdling is a major problem with planting into black plastic mulch on hot days. This happens due to hot air that is trapped under the plastic being funneled out through the holes where the transplants or seedlings are planted. Stem girdling can then lead to plants being susceptible to wind damage. As you can see, planting on too hot of a day can result in compounding issues that can last for several weeks.

The one benefit of the sunny, warm days was it really encouraged rapid growth of a lot of our perennial crops or early seeded crops. The apple and peach trees really took off, and fruit size on these trees increased tremendously. Grape vines rapidly put on shoot growth, and strawberries put on many new blossoms, both of which quickly outnumbered the ones that had been frozen or frosted.

This is relieving to see and gives us hope that yields will not be significantly affected by the adverse weather conditions. Given some timely rains and stable temperatures, we should continue to see a lot of healthy-looking plants and good conditions for pollination and fruit development.

A return to warmer temperatures also brings favorable conditions for insect pests to make themselves known. In early planted vegetable fields, we are already finding some key insect pests at fairly high populations. More specifically, looking at cole crops (cabbage, broccoli, kale, et cetera), flea beetles have been out in force. Flea beetles also feed on beet greens, potatoes and many other crops.

Also on potato plants, we have been finding a significant amount of Colorado potato beetle adults. While we are finding the adults, they are not the ones who do the damage. The potato beetle larvae are the ones who cause major damage to potato plants. Where there are adult beetles, egg masses and larvae are soon to follow.

Another beetle vegetable growers are concerned with this time of year is the cucumber beetle. This beetle is problematic due to the fact it vectors a disease called bacterial wilt. The cucumber beetle feeds on cucurbit crops such as summer squash, melons and cucumbers. Young plants have a low tolerance to cucumber beetle feeding and are very easily lost due to bacterial wilt. Accordingly, it is important for growers, both home and commercial, to keep an eye on cucumber beetle populations and treat the plants if the number of beetles exceeds five beetles per plant.

Aphid populations can really take off during hot, dry spells, and we have found that to be true this past week or so. The aphids we are finding are feeding on crops such as apples, tomatoes and peppers. The feeding we observed in peppers was concerning due to the massive quantity of aphids feeding on the emerging leaves and growing point of the plant.

Feeding damage is not the only concern with this insect pest. Aphids also excrete honeydew, a sugar-rich and sticky substance. Honeydew can mold and result in sooty mold. While this mold does not directly infect the plant, it does affect the plant indirectly by restricting the amount of sunlight reaching the leaf surface.

Whether you are a large-scale commercial grower or just have a few plants in your backyard garden, regularly inspecting and scouting your plants will help you keep track of insect pest populations, diseases or other issues that may be negatively impacting your plants.

If you would like to receive free email updates and recommendations from the Wayne County IPM program about current happenings out in the field, you can visit u.osu.edu/waynecountyipm and click the subscribe tab at the bottom right of the page.

Frank Becker is an OSU Extension agriculture and natural resources program assistant and may be called at 330-264-8722.

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