Some agricultural pests are inevitable, and the most seasoned growers eventually learn that the best way to handle them is to strike a balance. This is certainly the case with citrus crops during bloom and pollination season.
For example katydids love citrus, especially mandarins and clementines. The insects tie their entire life cycles into citrus and other trees: from egg laying and nymph hatching on through adulthood, chewing various parts of crops including leaves, flowers and fruits. Katydid’s can mar cosmetic desirability and marketability of citrus, though they don’t pose a mortal threat to trees.
Most times when katydids are expected to emerge, growers can safely and easily turn to pesticides or other chemical management to keep them from damaging fruit. However, citrus bloom is a unique time. During bloom season many bees are present. During this time, however, chemical use is extremely prohibited to prevent hazards to bees. Still, katydids can sometimes deal quite a blow on the quality of blooms and thus the quality and quantity of fruit later. They are also liable to wait out later until the first fresh early fruits arrive.
Says Robert Fahey, Pest Control and Irrigation Specialist at FGS, “Precise timing is necessary to prevent the killing of bees in the orchard. Growers want to spray at night when bees are back in their hive.”
Some growers may wait for the end of bee pollination to fully manage pests. However, waiting too long can cut into precious time preventing populations from growing and becoming even more damaging once fruits have emerged. It’s a window of opportunity— but a very careful one to navigate. So, what options do growers have?
Assess potential damage
As blooms are emerging and before petal fall takes place leading to early fruits— the most vulnerable time for katydid damage for example— it benefits to first take a closer look and assess the true extent and presence of pests in all growth stages. According to the University of California Integrated Pest Management Program (UC IPM), you can identify this through noticing fresh leaf damage in the center of leaves as early as April in the Central Valley. This can give an idea of how quickly populations might increase, grow and pose a risk to crops in coming weeks. It’s very likely this prime time period for evaluating trees will overlap with bee pollination.
Identify the type of katydid nymphs present in your orchard
If they are predominantly Angularwinged katydids (Microcentrum spp), you may not have cause for alarm as these will not damage fruit. But if (according to UC IPM) you find more than one forktailed katydid— and on anywhere around 20 trees in your orchard, within 3 minutes of searching each— it is wise to move forward with a katydid management plan as soon as possible. Some management plans are most effective during this nymph stage and when populations are first noticed and caught early.
Hand removal, leaf removal and cultural control
With proper human resources, hand removal can put a dent into smaller katydid populations especially on smaller orchards during the pollination window. With proper manpower, it could help medium and larger size orchards. Another preferred approach is cultural control during this time, removing any dead or damaged citrus leaves on trees, old leaves with obvious katydid eggs attached (grey, ovate, and flat) and discarded leaves on the orchard grounds near tree bottoms or under canopy. These could harbor freshly laid katydid eggs.
Regular mowing (of both leaves and grasses as well), shredding, mulching, burning or composting of leaves far off-site of the orchard can help destroy future katydid hatches in the next cycle— hatches that could contribute to further damage in coming weeks as the citrus blooms. These methods will not harm or interfere with bee pollination however if accomplished in the evening or nighttime hours.
Release of natural predators
Encouraging the presence and increased populations of natural predators can be a help during this time. These include assassin bugs, spechid wasps, tachinid flies and some bird species. Some beneficial insect populations can be commercially purchased and timed for release during these periods. To sustain them, chemical-free buffers and wildlife areas may need to be established adjacent to your orchard for these investments to be effective and successful.
Evening applications of restricted chemicals only
Chemical applications can still be possible and effective with bees in the picture, and especially when katydid populations are anticipated to be severe and growing rapidly. Even a very small population of forktailed katydid nymphs, if left to their devices, can quickly expand into considerable damage.
If other preventative measures during the citrus bloom and pollination don’t appear to be working, chemicals such as Spinosad— a bacterium-based application that naturalliy biodegrades quickly— will not harm bees if applied wisely and correctly. If applied in the evening after bees have returned to their hives it poses little to no danger to them, and is still effective. Spinosad is often recommended as the highest level of acceptable chemical pest control under organic regimes, and is certifiable and usable on organic acreage. Spray of all areas of the plant where katydids may be present, especially on flowers and leaves. Young fruit is also acceptable to spray.
Dealing with katydids while maximizing fruit yields year after year while protecting pollination and boosting profits at the same time is tricky during the citrus bloom. But it’s not impossible— it just takes is a little foresight, finesse and know-how.